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User's Guide for the AMS/EPA Regulatory
Model (AERMOD)
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EPA-454/B-24-007
November 2024
User's Guide for the AMS/EPA Regulatory Model (AERMOD)
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Quality Assessment Division
Research Triangle Park, NC
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Notice
Mention of trade names, products, or services does not convey, and should not be interpreted as
conveying official EPA approval, endorsement, or recommendation. The following trademarks appear in
this guide:
Microsoft Windows is a registered trademark of the Microsoft Corporation.
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Preface
This User's Guide for the AMS/EPA Regulatory Model (AERMOD) provides user instructions for
the AERMOD model. The technical description of the AERMOD algorithms is provided in a separate
AERMOD Model Formulation document (EPA, 2024a). Additional resources provided by the USEPA
that may be helpful with respect to the application of AERMOD can be accessed via the Support Center
for Regulatory Atmospheric Modeling (SCRAM) website at https://www.epa.gov/scram.
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Contents
Section Page
1.0 Introduction 1-1
1.1 How to use the AERMOD manuals 1-1
1.1.1 Novice users 1-1
1.1.2 Experienced modelers 1-1
1.1.3 Management/decision makers 1-2
1.2 Overview of the AERMOD model 1-2
1.2.1 Regulatory applicability 1-3
1.2.2 Basic input data requirements 1-3
1.2.3 Computer hardware requirements 1-3
1.2.4 Dispersion options 1-4
1.2.5 Source options 1-4
1.2.6 Receptor options 1-5
1.2.7 Meteorology options 1-5
1.2.8 Output options 1-6
1.2.9 Source contribution analyses 1-7
2.0 Getting started - a brief tutorial 2-1
2.1 Controlling input and output files 2-1
2.1.1 Description of AERMOD input files 2-1
2.1.1.1 Input control file 2-1
2.1.1.2 Meteorological data files 2-2
2.1.1.3 Initialization file for model re-start 2-2
2.1.2 Description of AERMOD output files 2-2
2.1.2.1 Main output file 2-3
2.1.2.2 Detailed error message file 2-3
2.1.2.3 Intermediate results file for model re-start 2-3
2.1.2.4 Maximum value/threshold file 2-4
2.1.2.5 Sequential results file for postprocessing 2-5
2.1.2.6 High value summary file for plotting 2-6
2.1.2.7 TOXX model input files 2-6
2.1.3 Controlling file inputs and outputs (I/O) 2-7
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2.1.3.1 Controlling I/O on PCs 2-7
2.2 Description of keyword/parameter approach 2-8
2.2.1 Basic rules for structuring input control files 2-9
2.2.2 Advantages of the keyword approach 2-11
2.3 Regulatory default modeling options 2-12
2.4 Setting up a simple control file 2-13
2.4.1 A simple industrial source application 2-15
2.4.2 Selecting modeling options - CO pathway 2-15
2.4.3 Specifying source inputs - SO pathway 2-18
2.4.4 Specifying a receptor network - RE pathway 2-22
2.4.5 Specifying the meteorological Input - ME pathway 2-23
2.4.6 Selecting output options - OU pathway 2-24
2.4.7 Using the error message file to debug the input control file 2-28
2.4.8 Running the model and reviewing the results 2-32
2.5 Modifying an existing control file 2-40
2.5.1 Modifying modeling options 2-40
2.5.2 Adding or modifying a source or source group 2-40
2.5.3 Adding or modifying a receptor network 2-40
2.5.4 Modifying output options 2-41
3.0 Detailed keyword reference 3-1
3.1 Overview 3-1
3.2 Control pathway inputs and options 3-2
3.2.1 Title information 3-2
3.2.2 Dispersion options 3-2
3.2.2.1 DFAULT option 3-6
3.2.2.2 ALPHA options 3-7
3.2.2.3 BETA options 3-8
3.2.2.4 Options for capped and horizontal stack releases 3-8
3.2.2.5 Output types (CONC, DEPOS, DDEP and/or WDEP) 3-10
3.2.2.6 Deposition depletion options 3-10
3.2.2.7 NO2conversion options 3-10
3.2.2.8 FASTAREAand FASTALL 3-12
3.2.2.9 Urban transition and NOURBTRAN option 3-13
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3.2.2.10 SCREEN mode 3-14
3.2.2.11 SCIM 3-14
3.2.2.12 Deposition Options 3-15
3.2.2.13 Definition of seasons for gaseous dry deposition 3-16
3.2.2.14 Definition of land use categories for gas dry deposition 3-17
3.2.2.15 Deposition velocity and resistance outputs 3-18
3.2.2.16 Remove displacement height from RLINE wind profile 3-19
3.2.3 Low wind parameters 3-19
3.2.4 Building downwash options 3-21
3.2.4.1 ORD building downwash options 3-22
3.2.4.2 AWMAbuilding downwash options 3-24
3.2.5 Input parameters forNCh conversion options 3-26
3.2.5.1 Specifying ozone concentrations for PVMRM, OLM, TTRM/TTRM2, and GRSM
options 3-29
3.2.5.2 Specifying NOx background concentrations for the GRSM option 3-33
3.2.5.3 Specifying the ambient equilibrium NC^/NOx ratio (PVMRM, OLM, TTRM/TTRM2)
3-38
3.2.5.4 Specifying the default in-stack N02/N0X ratio (PVMRM, OLM, TTRM/TTRM2,
GRSM) 3-38
3.2.6 Averaging time options 3-39
3.2.7 Performing multiple year analyses with MULTYEAR option 3-40
3.2.8 Urban modeling option 3-42
3.2.9 Specifying the pollutant type 3-43
3.2.10 Modeling with exponential decay 3-43
3.2.11 Flagpole receptor height option 3-44
3.2.12 Plume Rise from Aircraft Emissions 3-44
3.2.13 To run or not to run 3-45
3.2.14 Generating an input file for EVENT processing 3-46
3.2.15 The model re-start capability 3-47
3.2.16 Processing for particulate matter (PM) NAAQS 3-48
3.2.16.1 Processing for fine particulate matter (PM-2.5) 3-48
3.2.16.2 Processing for particulate matter of 10 microns or less (PM-10) 3-50
3.2.17 Processing for 1-hour NO2 and SO2 NAAQS 3-51
3.2.18 Debugging output options 3-52
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3.2.19 Detailed error listing file 3-54
3.3 Source pathway inputs and options 3-55
3.3.1 Identifying source types and locations 3-55
3.3.2 Specifying source release parameters 3-60
3.3.2.1 POINT, POINTHOR, and POINTCAP source inputs 3-60
3.3.2.2 VOLUME source inputs 3-61
3.3.2.3 AREA source type 3-63
3.3.2.4 AREA source inputs 3-63
3.3.2.5 AREAPOLY source inputs 3-67
3.3.2.6 AREACIRC source inputs 3-68
3.3.2.7 OPENPIT source inputs 3-69
3.3.2.8 LINE source inputs 3-71
3.3.2.9 RLINE source inputs 3-71
3.3.2.10 RLINEXT source inputs 3-73
3.3.2.11 BUOYLINE source inputs 3-78
3.3.2.12 SWPOINT source inputs 3-81
3.3.3 Specifying gas deposition parameters 3-83
3.3.3.1 Source parameters for gas deposition (dry and/or wet) 3-83
3.3.3.2 Option for specifying the deposition velocity for gas dry deposition 3-84
3.3.4 Specifying source parameters for particle deposition 3-85
3.3.4.1 Specifying particle inputs for Method 1 3-85
3.3.4.2 Specifying particle inputs for Method 2 3-86
3.3.5 Specifying Emission and Output Units 3-87
3.3.6 Source input parameters forN02 conversion options 3-88
3.3.6.1 Specifying in-stack N02/N0X ratios by source for PVMRM, OLM, TTRM/TTRM2,
and GRSM 3-88
3.3.6.2 Specifying combined plumes for OLM 3-89
3.3.6.3 Specifying ambient NO2/NOX ratios for the ARM2 option 3-90
3.3.7 Modeling NO2 increment credits with PVMRM 3-91
3.3.7.1 Increment consuming and baseline sources 3-91
3.3.7.2 Calculating increment consumption under the PSDCREDIT option 3-92
3.3.7.3 Specifying source groups under the PSDCREDIT option 3-93
3.3.7.4 Model outputs under the PSDCREDIT option 3-95
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3.3.8 Background concentrations 3-95
3.3.8.1 Defining background concentration sectors 3-96
3.3.8.2 For applications that include sector-varying background concentration the minimum
sector width allowed is 30 degrees and warning messages will be issued for sector
widths less than 60 degrees. Sector-varying background concentrations will be
selected based on the flow vector, i.e., the downwind direction, based on the wind
direction specified in the surface meteorological data file. During periods of
specific wind directions, the associated user input sector-varying background
concentrations will be applied to the entire modeling domain (i.e., all
receptors).Specifying the background concentration 3-96
3.3.8.3 Specifying background concentration units 3-100
3.3.9 Specifying building downwash information 3-100
3.3.10 Specifying urban sources 3-105
3.3.11 Specifying variable emission factors (EMISFACT) 3-105
3.3.12 Specifying an hourly emission rate file (HOUREMIS) 3-108
3.3.13 Adjusting the emission rate units for output 3-112
3.3.14 Including source data from an external file 3-113
3.3.15 Using source groups 3-113
3.3.16 Specifying platform downwash information (POINT, POINTHOR, POINTCAP sources
ONLY) 3-115
3.3.17 Specifying highly buoyant point sources for HBP option (POINT, POINTHOR,
POINTCAP sources ONLY) 3-117
3.3.18 Specifying aircraft sources (AREA and VOLUME sources ONLY) 3-117
3.4 Receptor pathway inputs and options 3-118
3.4.1 Defining networks ofgridded receptors 3-119
3.4.1.1 Cartesian grid receptor networks 3-119
3.4.1.2 Polar grid receptor networks 3-123
3.4.2 Using multiple receptor networks 3-127
3.4.3 Specifying discrete receptor locations 3-127
3.4.3.1 Discrete Cartesian receptors 3-127
3.4.3.2 Discrete polar receptors 3-128
3.4.3.3 Discrete Cartesian receptors for evalfile output 3-129
3.4.4 Including receptor data from an external file 3-130
3.5 Meteorology pathway inputs and options 3-131
3.5.1 Specifying the input data files and formats 3-131
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3.5.2 Specifying station information 3-133
3.5.3 Specifying the base elevation for potential temperature profile 3-133
3.5.4 Specifying a data period to process 3-134
3.5.5 Correcting wind direction alignment problems 3-135
3.5.6 Specifying wind speed categories 3-136
3.5.7 Specifying SCIM parameters 3-136
3.5.8 Specify the number of years to process 3-137
3.5.9 Specify turbulence treatment options 3-138
3.6 Event pathway inputs and options 3-139
3.6.1 Using events generated by the AERMOD model 3-140
3.6.2 Specifying discrete events 3-141
3.6.3 Including event data from an external file 3-141
3.7 Output pathway inputs and options 3-142
3.7.1 Selecting options for tabular printed outputs 3-142
3.7.2 Selecting options for special purpose output files 3-145
3.7.2.1 MAXIFILE 3-146
3.7.2.2 POSTFILE 3-148
3.7.2.3 PLOTFILE 3-149
3.7.2.4 TOXXFILE 3-151
3.7.2.5 RANKFILE 3-153
3.7.2.6 EVALFILE 3-154
3.7.2.7 SEASONHR 3-155
3.7.2.8 MAXDCONT 3-157
3.7.2.9 MAX DAILY 3-159
3.7.2.10 MAXDYBYYR 3-159
3.7.3 EVENT processing options 3-160
3.7.4 Miscellaneous output options 3-160
4.0 References 4-1
APPENDIX A. Functional keyword/parameter reference A-l
APPENDIX B. Explanation of error message codes B-l
B. 1 Introduction B-l
B.2 Output message summary B-2
B.3 Description of the message layout B-3
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APPENDIX C. Description of file formats C-l
C. 1 AERMET meteorological data C-l
C.2 Threshold violation files (MAXIFILE option) C-3
C.3 Postprocessor files (POSTFILE option) C-4
C.4 High value results for plotting (PLOTFILE option) C-5
C.5 TOXX model input files (TOXXFILE option) C-l
C.6 Maximum values by rank (RANKFILE option) C-8
C.7 Arc-maximum values for evaluation (EVALFIL option) C-9
C.8 Results by season and hour-of-day (SEASONHR option) C-l 1
C.9 Source group contribution for ranked averaged maximum daily values (MAXDCONT).. C-12
C. 10 Daily maximum 1-hour values (MAXDAILY) C-15
C. 11 Maximum daily 1-hour concentration by year (MAXDYBYYR) C-l7
APPENDIX D. Overview of AERMOD revisions in version 24142 D-l
APPENDIX E. Glossary E-3
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Figures
Figure Page
Figure 2-1. Example Input File for AERMOD for Sample Problem 2-14
Figure 2-2. Example Input control file for Sample Problem 2-27
Figure 2-3. Example Message Summary Table for AERMOD Execution 2-30
Figure 2-4. Example of Keyword Error and Associated Message Summary Table 2-31
Figure 2-5. Organization of the AERMOD Model Output File 2-33
Figure 2-6. Sample of Model Option Summary Table from an AERMOD Model Output
File 2-36
Figure 2-7. Example Output Table of High Values by Receptor 2-37
Figure 2-8. Example of Result Summary Tables for the AERMOD Model 2-39
Figure 3-1. Relationship of Area Source Parameters for Rotated Rectangle 3-65
Figure 3-2. Definition of DCL for RLINEXT sources. Dashed lines represent lanes of a
roadway with an offset (DCL) from the median (solid line) 3-75
Figure 3-4. Definition of DCLWALL for RLINEXT sources. Dashed black lines represent
roadway sources and dashed orange lines represent barriers with an offset
(DCLWALL). The solid line in the right-hand panel represents the median 3-76
Figure 3-5 .Fixed Stack location with respect to Building and Wind Flow Orientation 3-83
Figure 3-6. Schematic Diagram Identifying New Building Data for Prime Downwash 3-104
Figure 3-7. New platform parameter figure with correct parameter definitions. Adapted
from Petersen (1984) 3-116
Figure B-l. Example of an AERMOD Message Summary B-2
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Tables
Table Page
Table 3-1 Summary of Deposition Options 3-16
Table 3-2. Implemented N02 Conversion Options by AERMOD Source Type 3-28
Table 3-3. Summary of Suggested Procedures for Estimating Initial Lateral Dimensions
oyo and Initial Vertical Dimensions ozo for Volume and Line Sources 3-62
Table A-l. Description of Control Pathway Keywords A-2
Table A-2. Description of Control Pathway Keywords and Parameters A-5
Table A-3. Description of Source Pathway Keywords A-20
Table A-4. Description of Source Pathway Keywords and Parameters A-22
Table A-5. Description of Receptor Pathway Keywords A-30
Table A-6. Description of Receptor Pathway Keywords and Parameters A-31
Table A-7. Description of Meteorology Pathway Keywords A-34
Table A-8. Description of Meteorology Pathway Keywords and Parameters A-35
Table A-9. Description of Event Pathways and Keywords A-37
Table A-10. Description of Event Pathway Keywords and Parameters A-3 8
Table A-ll. Description of Output Pathway Keywords A-39
Table A-12. Description of Output Pathway Keywords and Parameters A-40
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1.0 Introduction
This section provides an overall introduction to the AERMOD model and to the AERMOD user's
guide. Some suggestions are offered on how various users would best benefit from using the manuals.
Additionally, an overview of the model's applicability, range of options, and basic input data and
hardware requirements are provided. The input file required to run the AERMOD model (commonly
referred to as the control file) is based on an approach that uses descriptive keywords and allows for a
flexible structure and format.
1.1 How to use the AERMOD manuals
The AERMOD model user's guide has been designed to meet the needs of various users with
differing levels of experience with the model. This section describes briefly how users can benefit from
using the manual.
1.1.1 Novice users
Novice users are those with limited exposure to or experience with the AERMOD model. They
may be new to dispersion modeling applications in general, or new to the AERMOD model and therefore
unfamiliar with the keyword/parameter approach utilized for the input file. These users should review the
remainder of this Introduction to gain an overall perspective of the use of the AERMOD model,
particularly for regulatory modeling applications. They should then focus their attention on Section 2.0,
which provides an overview of the types of input and output files and setting up an input file that
illustrates the more commonly used options of the AERMOD model. Section 2.0 provides a basic
description of the input file structure and explains some of the advantages of the keyword/parameter
approach to specifying modeling options and inputs. Section 3.0 then provides a more detailed and
complete reference of the various options for running the model.
1.1.2 Experienced modelers
Experienced modelers have considerable experience in applying the AERMOD model in various
situations. They should have basic familiarity with the overall goals and purposes of regulatory modeling
and with the scope of options available in the AERMOD model. Experienced modelers who are new to
the AERMOD model will benefit from first reviewing the contents of Section 2.0 of this guide, which
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provides a basic orientation to the structure, organization, and philosophy of the keyword/parameter
approach used for the input control file. Once they have a basic grasp of the input file structure and
syntax rules, they will benefit most from using Section 3.0 of this volume as a reference to learn the
overall capabilities of the model, or to understand the mechanics for implementing specific options. The
information in Section 3.0 has functional organization with detailed descriptions of each of the individual
keyword options by functional pathway. Once they are familiar with the keywords, they may find the
functional keyword reference provided in APPENDIX A useful to quickly review the proper syntax and
available options/parameters for a particular keyword.
Experienced modelers may also need to refer to the description of model formulation for
AERMOD (EPA, 2024a) to gain a more complete understanding of the technical basis for the AERMOD
model.
1.1.3 Management/decision makers
Those involved in a management or decision-making role for dispersion modeling applications
will be especially interested in the remainder of this section, which provides an overview of the model,
including its role in various regulatory programs, a brief description of the range of available options, and
basic input and output data and computer hardware requirements needed to run the model. From this
information, they should understand the basic capabilities of the AERMOD model well enough to judge
the suitability of the model for specific applications. They may also want to review the overview
provided in Section 2.0 to learn about the nature and structure of the input control file to better review the
modeling results.
1.2 Overview of the AERMOD model
This section provides an overview of the AERMOD model, including a discussion of the
regulatory applicability of the model, a description of the basic options available for running the model,
and an explanation of the basic input data and hardware requirements needed for executing the model.
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1.2.1 Regulatory applicability
The U.S. Environmental Protection Agency (EPA) maintains a Guideline on Air Quality Models
(EPA, 2017b), hereafter, Guideline, which is published as Appendix W to 40 CFR Part 51 (as revised).
The Guideline provides the agency's guidance on regulatory applicability of air quality dispersion models.
In general, regulatory modeling applications should be carried out in accordance with a modeling protocol
that is reviewed and approved by the appropriate agency prior to conducting the modeling. The modeling
protocol should identify the specific model, modeling options, and input data (e.g., meteorology, emission
source parameters, etc.) to be used for a particular application.
1.2.2 Basic input data requirements
One of the basic inputs to AERMOD is the control file which contains the selected modeling
options, as well as source location and parameter data, receptor locations, meteorological data file
specifications, and output options. Another type of basic input data needed to run the model is the
meteorological data. AERMOD requires two types of meteorological data files that are provided by the
AERMET meteorological preprocessor program (EPA, 2024e). One file consists of surface scalar
parameters, and the other file consists of vertical profiles of meteorological data. These meteorological
data files are briefly described later in this section, and in more detail in Sections 2.0 and 3.0. For
applications involving elevated terrain effects, the receptor and terrain data will need to be processed by
the AERMAP terrain preprocessing program (EPA, 2018) before input to the AERMOD model.
1.2.3 Computer hardware requirements
The current version of the AERMOD model was developed within the Microsoft Windows
operating system (Windows) and has been designed to run on Windows PCs within a Command-prompt
using command-line arguments to initiate a model run. The amount of storage space required on the hard
disk for a particular application will depend greatly on the output options selected. Some of the optional
output files of concentration data can be rather large. More information on output file products is
provided in Sections 2.1 and 3.7.
The AERMOD model includes a wide range of options for modeling air quality impacts of
pollution sources, making it a popular choice among the modeling community for a variety of
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applications. The following sections provide a brief overview of the options available within the
AERMOD model.
1.2.4 Dispersion options
Since the AERMOD model is designed to support the EPA's regulatory modeling programs, the
regulatory modeling options will be the default mode of operation for the model. These options include
the use of stack-tip downwash and a routine for processing averages in cases of calm winds or missing
meteorological data. The model also includes various non-default options (e.g., suppress the use of stack-
tip downwash, deposition modeling, NO2 conversion, special processing for low wind conditions, and
disable the date checking for non-sequential meteorological data files, to list a few). The latter option
listed is needed to facilitate model evaluation. The AERMOD model also includes a non-default
screening mode added specifically for integration with the AERSCREEN model interface (EPA, 2021).
The user can specify several short-term averages to be calculated in a single run of the AERMOD model,
as well as request the overall period (e.g., annual) averages.
1.2.5 Source options
The model is capable of handling multiple sources, including point, volume, area, open pit, and
both buoyant and non-buoyant line source types. AERMOD models non-buoyant line sources as
elongated area sources or a series of volume sources. If elongated area sources are used to represent a
narrow non-buoyant line source, the user can specify a line source in the control file, and the input
required to define the source is simplified from the typical input required for an area source.
The buoyant line source algorithm from the Buoyant Line and Point Source (BLP) model
(Schulman and Scire, 1980) has been incorporated into the AERMOD model beginning with version
15181. Several source groups may be specified in a single run, with the source contributions combined
for each group. This is particularly useful for PSD applications where combined impacts may be needed
for a subset of the modeled background sources that consume increment, while the combined impacts
from all background sources (and the permitted source) are needed to demonstrate compliance with the
National Ambient Air Quality Standards (NAAQS). The model contains algorithms for modeling the
effects of aerodynamic downwash due to nearby buildings on point source emissions and depositional
effects on particulate emissions.
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Source emission rates can be treated as constant throughout the modeling period, or may be
varied by month, season, hour-of-day, or other optional periods of variation. Variable emission rate factors
may be specified for a single source or for a group of sources. The user may also specify a separate file of
hourly emission rates for all source or some subset of sources that are included in a model run.
1.2.6 Receptor options
The AERMOD model has considerable flexibility in the specification of receptor locations. The
user has the capability of specifying multiple receptor networks in a single run and may also mix
Cartesian grid receptor networks and polar grid receptor networks in the same run. This is useful for
applications where the user may need a coarse grid over the whole modeling domain, but a denser grid
over the area of maximum expected impacts. There is also flexibility in specifying the location of the
origin for polar receptors, other than the default origin at (0,0) in x,y, coordinates.
The user can input elevated receptor heights to model the effects of terrain above (or below) the
stack base elevation and may also specify receptor elevations above ground level to model flagpole
receptors. There is no distinction in AERMOD between elevated terrain below release height and terrain
above release height, as is with earlier regulatory models that distinguished between simple terrain and
complex terrain. For applications involving elevated terrain, the user must also input a hill height scale
along with the receptor elevation. To facilitate the generation of hill height scales for AERMOD, a terrain
preprocessor, called AERMAP, has been developed (EPA, 2018).
1.2.7 Meteorology options
The AERMOD model utilizes a file of surface boundary layer parameters and a file of profile
variables including wind speed, wind direction, and turbulence parameters. These two types of
meteorological inputs are generated by the meteorological preprocessor for AERMOD, which is called
AERMET (EPA, 2024e). Both meteorological input files are sequential ASCII files, and the model
automatically recognizes the format generated by AERMET as the default format. The model will
process all available meteorological data in the specified input file by default, but the user can easily
specify selected days or ranges of days to process.
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1.2.8 Output options
The basic types of printed output available by AERMOD are:
Summaries of high values (highest, second highest, etc.) by receptor for each different
combinations of averaging period and source group;
Summaries of overall maximum values (e.g., the maximum 50) for each averaging period
and source group combination; and
Tables of concurrent values summarized by receptor for each combination of averaging
period and source group, for each day of data processed. These "raw" concentration values
may also be output to unformatted (binary) files, as described below.
The summaries of high values by receptor and summaries of maximum values can be output for
one or more groups of sources and individual sources in the same model simulation. In addition, when
maximum values for individual sources are output, the user has the option of specifying whether the
maximum source values are to be the maximum values for each source independently, the contribution of
each source to the maximum group values, or both.
In addition to the tabular printed output products described above, the AERMOD model provides
options for several types of file output products. One of these options for AERMOD is to output an
unformatted ("binary") file of all concentration values as they are calculated. These files are often used
for special postprocessing of the data. In addition to the unformatted concentration files, AERMOD
provides options for several additional types of file outputs. One option is to generate a file of (X, Y)
coordinates and design values (e.g., the second highest values at each receptor for a particular averaging
period and source group combination) that can be easily imported into many graphic plotting packages to
generate contour plots of the concentration values. Separate files can be specified for all the averaging
period and source group combinations of interest to the user.
Another output file option from the AERMOD model is to generate a file of all occurrences when
a concentration value equals or exceeds a user-specified threshold. Again, separate files are generated for
only those combinations of averaging period and source group that are of interest to the user. These files
include the date on which the threshold violation occurred, the receptor location, and the concentration
value.
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AERMOD includes options for two types of output files that are designed to facilitate model
evaluation. One type of file lists concentrations by rank, where only one value per date is included. This
file may be used to generate Q-Q (quantile) plots of results, where values from different models and/or
observed data are paired by rank. The other type of output file provides arc maxima results, along with
detailed information about the plume characteristics associated with the arc maximum.
Finally, there are output options specifically for comparing model results to the 24-hour PM2.5,
1-hour NO2 and 1-hour SO2 NAAQS. The forms of these standards are based on averages of ranked
values across years which complicates their evaluation, especially the 1-hour NO2 and SO2 standards
which are based on ranked values from the distribution of daily maximum 1-hour averages.
1.2.9 Source contribution analyses
In air quality dispersion modeling applications, the user may have a need to know the
contribution that a particular source makes to an overall concentration value for a group of sources. This
section provides a brief introduction to how these types of source contribution (sometimes referred to as
source culpability) analyses are performed using the AERMOD model. More detailed information about
exercising these options is provided in Section 3.0.
The AERMOD model provides the option of specifying source groups for which the model
calculates high values independently. However, users may often have to run the model a second time
selecting only specific days where the high values occurred and setting up each source in its own source
group to obtain source contribution results. An EVENT processor has been incorporated into AERMOD
to simplify this task when required. Also, special processing and output options, mentioned above, are
included that are specific to determining source contributions with respect to the PM2.5, NO2 and SO2
standards.
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2.0 Getting started - a brief tutorial
This section provides a brief tutorial for setting up a simple application problem with the
AERMOD model, which serves as an introduction for novice users to the AERMOD model. The example
illustrates the usage of the more commonly used options in the AERMOD model. A more complete
description of the available options for setting up the AERMOD model is provided in Section 3.0.
The example problem presented in this section is a simple application of the AERMOD model to
a single point source. The source is a hypothetical stack at a small, isolated facility in a rural setting.
Since the stack is below the Good Engineering Practice (GEP) stack height, the emissions from the source
are subject to the influence of aerodynamic downwash due to the presence of nearby buildings. The
tutorial guides the user through selection and specification of modeling options, specification of source
parameters, definition of receptor locations, specification of the input meteorological data, and selection
of output options. Since this discussion is aimed at novice users of the AERMOD model, general
overviews of input and output files, as well as control file keyword/parameter approach, is provided first.
2.1 Controlling input and output files
This section describes the various input and output files used by the AERMOD model and
discusses control of input and output (I/O) in the Microsoft Windows PC environment. Much of this
discussion also applies to operating the model in other environments.
2.1.1 Description of AERMOD input files
The two basic types of input files required to run the AERMOD model are: 1) the input control
file containing the modeling options, source data and receptor data, and 2) the meteorological data files
including a file of surface parameters and a separate file of multilevel parameters. Each of these is
discussed below, as well as a third file type that may be used to initialize the AERMOD model with
intermediate results from a previous run.
2.1.1.1 Input control file
The input control file contains the user-specified options for running the various AERMOD
model (with a default filename, AERMOD.INP), includes the source parameter data and source group
information, defines the receptor locations, specifies the location and parameters regarding the
2-1
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meteorological data, and specifies the output options. Details regarding the keywords and parameters
used in the input control file are provided in Section 3.0, and APPENDIX A.
2.1.1.2 Meteorological data files
The input meteorological data is read into the AERMOD model from two separate data files, one
corresponding to surface (scalar) parameters, and the other corresponding to multi-level profiles of data.
The meteorological data filenames and formats are specified within the input control file using the ME
SURFFILE and PROFFILE keywords. The AERMOD model accepts meteorological data that has been
preprocessed by the AERMET meteorological preprocessor program (EPA, 2024e). The data are read
from formatted ASCII files of hourly sequential records.
2.1.1.3 Initialization file for model re-start
The AERMOD model has an optional capability to store intermediate results to an unformatted
(sometimes called binary) file for later re-starting of the model in the event of a power failure or user
interrupt. This unformatted file may, therefore, be used as an input file to initialize the model. This option
is controlled by the SAVEFILE (saves intermediate results to a file) and the INITFILE (initialize result
arrays from a previously saved file) keywords on the CO pathway.
When initializing the model for the re-start option, the user specifies the name of the unformatted
results file on the INITFILE keyword. The default filename used if no parameter is provided is TMP.FIL.
2.1.2 Description of AERMOD output files
The AERMOD model can produce a variety of output files, including a main file of model results,
an unformatted file of intermediate results for later re-start of the model (AERMOD only), and several
output data files for specialized purposes. These files are described below.
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2.1.2.1 Main output file
The AERMOD model produces a standard output file of model results called AERMOD.OUT, by
default, unless a unique name is provided by the user when AERMOD is executed at the command
prompt. The contents and organization of this file are shown in Figure 2-5. This file includes a
duplication of the contents of the input control up unless 'NO ECHO' is encountered in the input control
file. The contents of the input control file will be duplicated in the output file up to the place in the file
where 'NO ECHO' is specified. The contents of the input control file beyond 'NO ECHO' will not be
duplicated in the output file. A summary of control file setup messages and a summary of the inputs
follow the echo of inputs. The input summary includes a summary of modeling options, source data,
receptor data, and meteorological data, following the same order as the pathways in the control file. If
model calculations are performed, then the model results are summarized next. The content and order of
the model result summaries depend on the output options selected. Following the detailed model results
are summary tables of the high values for each averaging period and source group. The final portion of
the main output file is the summary of messages for the complete model run.
2.1.2.2 Detailed error message file
The user may select an option for the model to save a separate file of detailed error and other
messages, through use of the CO ERRORFIL keyword. The format and syntax of these messages is
described in APPENDIX B. The order of messages within the file is the order in which they were
generated by the model. The file includes all types of messages that were generated.
2.1.2.3 Intermediate results file for model re-start
The AERMOD model has an optional capability to store intermediate results to an unformatted
(sometimes called binary) file for later re-starting of the model in the event of a power failure or user
interrupt. This unformatted file may therefore be used as an input file to initialize the model. This option
is controlled by the SAVEFILE (saves intermediate results to a file) and the INITFILE (initialize result
arrays from a previously saved file) keywords on the CO pathway.
When saving the intermediate results for the re-start option, the user specifies the name of the
unformatted results file on the SAVEFILE keyword. The user has the option of specifying a single
filename, two filenames (for alternate saves), or specifying no filename. The default filename used if no
parameter is provided is TMPFIL. If a single file is used, then the intermediate results file is overwritten
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on each successive dump, with the chance that the file will be lost if the interrupt occurs during the time
that the file is opened. If two filenames are provided, then the model also saves to the second file on
alternate dumps, so that the next most recent dump will always be available.
2.1.2.4 Maximum value/threshold file
The user may select an option for the AERMOD model to generate a file or files of concentration
values exceeding a user-specified threshold. The OU MAXIFILE keyword controls this option. The user
may select separate files for each averaging period and source group combination for which a list of
threshold violations may be needed. Each file includes several records with header information
identifying the averaging period, source group and threshold value, and then a record for every
occurrence where the result for that averaging period/source group equals or exceeds the threshold value.
Each of these records includes the averaging period, source group ID, date for the threshold violation
(ending hour of the averaging period), the x, y, z and flagpole receptor height for the receptor location
where the violation occurred, and the concentration value.
The structure of the threshold violation file is described in more detail in APPENDIX C. Each of
the files selected by the user is opened explicitly by the model as a formatted file. The filenames are
provided on the input control file command. The user may specify the file unit on the MAXIFILE card
through the optional FUNIT parameter. Please note, when specifying the FUNIT 1 to 32 are reserved for
input/output files, internally computed file units range 100 to 730, and the following are reserved for
debug files: 731, 931, 932, 933, 937, 938, 939, 941, 8837, 8932, 9937, 9938, 9939, 9940. Therefore, to
ensure there will be no file conflicts, it is recommended that user-specified units begin at a large integer
value such as 10,000 and increment by one. If no file unit is specified, then the file unit is determined
internally according to the following formula:
IMXUNT = 100 + IGRP*10 + IAVE
where IMXUNT is the Fortran unit number, IGRP is the source group number (the order in which the
group is defined in the control file), and IAVE is the averaging period number (the order of the averaging
period as specified on the CO AVERTIME card). This formula was developed for up to nine source
groups and up to nine short-term averaging periods, therefore the range of possible internally generated
file units for MAXIFILE is 100 to 199.
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2.1.2.5 Sequential results file for postprocessing
The user may select an option for the AERMOD model to generate a file or files of concentration
values suitable for postprocessing. The OU POSTFILE keyword controls this option. The user may
select separate files for each averaging period and source group combination for which postprocessing
may be needed. For each file requested, the user has the option of specifying whether to use unformatted
files suitable for postprocessing or to use a plot format which could allow for importing the x, y
concentration files into a graphics package for plotting. For the unformatted file option, each file consists
of sequential unformatted records of values at each receptor location for every averaging period
calculated. For the plot file format option, each file consists of formatted records listing the x-coordinate,
y-coordinate and concurrent concentration values for each receptor and for all averaging periods
calculated. For certain applications, these files may become quite large, and should only be used when
needed, especially when using the plot format.
The structure of both types of postprocessing file is described in more detail in APPENDIX C.
Each of the postprocessing files selected by the user is opened explicitly by the model as either an
unformatted or a formatted file, depending on the option selected. The filenames are provided on the
input control file command. The user may specify the file unit on the POSTFILE card through the
optional FUNIT parameter. Please note, when specifying the FUNIT 1 to 32 are reserved for input/output
files, internally computed file units range 100 to 730, and the following are reserved for debug files: 731,
931, 932, 933, 937, 938, 939, 941, 8837, 8932, 9937, 9938, 9939, 9940. Therefore, to ensure there will be
no file conflicts, it is recommended that user-specified units begin at a large integer value such as 10,000
and increment by one. If no file unit is specified, then the file unit is determined internally according to
the following formulas:
IPSUNT = 200 + IGRP* 10 + IAVEfor short-term averages
IAPUNT = 300 + IGRP* 10 - 5 for PERIOD averages
where IPSUNT and IAPUNT are the Fortran unit numbers, IGRP is the source group number (the order in
which the group is defined in the control file), and IAVE is the averaging period number (the order of the
averaging period as specified on the CO AVERTIME card). This formula will not cause any conflict with
other file units used by the model for up to 9 source groups and up to 9 short-term averaging periods. This
formula was developed for up to nine source groups and up to nine short-term averaging periods,
therefore the range of possible internally generated file units for POSTFILE is 200 to 299 or 300 to 385
for PERIOD averaging periods.
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2.1.2.6 High value summary file for plotting
The user may select an option for the AERMOD model to generate a file or files of the highest
concentration values at each receptor suitable for importing into a graphics package in order to generate
contour plots. The OU PLOTFILE keyword controls this option. The user may select separate files for
each averaging period, source group and high value combination for which a plot file may be needed.
Each file includes several records with header information identifying the averaging period, source group
and high value number of the results, and then a record for each receptor which contains the x and y
coordinates for the receptor location, the appropriate high value at that location, and the averaging period,
source group and high value number.
The structure of the plot file is described in more detail in APPENDIX C. Each of the plot files
selected by the user is opened explicitly by the model as a formatted file. The filenames are provided on
the input control file command. The user may specify the file unit on the PLOTFILE card through the
optional FUNIT parameter. Please note, when specifying the FUNIT 1 to 32 are reserved for input/output
files, internally computed file units range 100 to 730, and the following are reserved for debug files: 731,
931, 932, 933, 937, 938, 939, 941, 8837, 8932, 9937, 9938, 9939, 9940. Therefore, to ensure there will be
no file conflicts, it is recommended that user-specified units begin at a large integer value such as 10,000
and increment by one. If no file unit is specified, then the file unit is determined internally according to
the following formulas:
IPLUNT = (IVAL+3)* 100 + IGRP* 10 + IAVE for short-term averages
IPPUNT = 300 + IGRP* 10 for PERIOD averages
where IPLUNT and IPPUNT are the Fortran unit numbers, IVAL is the high value number (1 for FIRST
highest, 2 for SECOND highest, etc.), IGRP is the source group number (the order in which the group is
defined in the control file), and IAVE is the averaging period number (the order of the averaging period as
specified on the CO AVERTIME card). This formula was developed for up to nine source groups and up
to nine short-term averaging periods, therefore the range of possible internally generated file units for
PLOTFILE is 400 to 499 or 300 to 385 with the use of PERIOD AVERTIME.
2.1.2.7 TOXX model input files
The user may select an option for the AERMOD model to generate an unformatted file or files of
concentration values exceeding a user-specified threshold for use with the TOXX model component of
TOXST. The OU TOXXFILE keyword controls this option. The user may select separate files for each
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averaging period for which a threshold violation file may be needed. Each file includes several records
with header information identifying the title, averaging period, threshold value, and receptor network
information, and then records including every occurrence where the result of any source group for that
averaging period equals or exceeds the threshold value. Records are also output that identify the
averaging period (hour number of the year), source group number and receptor number corresponding to
the concentration values.
The structure of the threshold exceedance file for use with the TOXX model component of
TOXST is described in more detail in APPENDIX C. Each of the files specified by the user is opened
explicitly by the model as an unformatted file. The filenames are provided in the input control file. The
user may specify the file unit on the TOXXFILE card through the optional FUNIT parameter. Please
note, when specifying the FUNIT 1 to 32 are reserved for input/output files, internally computed file units
range 100 to 730, and the following are reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941,
8837, 8932, 9937, 9938, 9939, 9940. Therefore, to ensure there will be no file conflicts, it is
recommended that user-specified units begin at a large integer value such as 10,000 and increment by
one. If no file unit is specified, then the file unit is determined internally according to the following
formula:
ITXUNT (IND AVE) = 300 + INDAVE
where ITXUNT is a Fortran array that stores the Fortran unit number for each output file specified and
INDAVE index reference for the ITXUNT array representing the averaging period based on the order
each averaging period is specified on the CO AVERTIME card.
2.1.3 Controlling file inputs and outputs (I/O)
2.1.3.1 Controlling I/O on PCs.
The main input control file and the main output print file are specified internally by AERMOD as
AERMOD.INP and AERMOD.OUT by default, respectively. The user has the option to provide
command-line arguments when executing the model at the command prompt to specify a user-defined
input control input filename and main output filename. When using the default names of AERMOD.INP
and AERMOD.OUT, a standard command line to execute the AERMOD model might look something like
this:
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C:\>AERMOD
where the command prompt has been given as "C:\>", but may look different on different systems, or may
include a subdirectory specification. Refer to Section 2.4.8 for details on specifying user-defined
filenames when running AERMOD from the command prompt.
2.2 Description of keyword/parameter approach
The input control file for the AERMOD model makes use of a keyword/parameter approach to
specifying the options and input data for running the model. The descriptive keywords and parameters
that make up this control file may be thought of as a command language through which the user
communicates with the model what he/she wishes to accomplish for a particular model run. The
keywords specify the type of option or input data being entered on each line of the input file. An
individual line or record in the control file is often referred to as a "card" throughout this manual and is
commonly identified by the primary keyword associated with the information entered on the record. The
parameters following the keyword define the specific options selected or the actual input data. Some of
the parameters are also input as descriptive secondary keywords.
The control file is divided into five functional "pathways." These pathways are identified by a
two-character pathway ID placed at the beginning of each line of the control file. The pathways and the
order in which they are input to the model are as follows:
CO - for specifying overall job COntrol options;
SO - for specifying SOurce information;
RE - for specifying REceptor information;
ME - for specifying MEteorology information;
EV - for specifying EVent processing;
OU - for specifying OUtput options.
2-8
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Each line of the input control file consists of a pathway ID, an 8-character keyword, and a
parameter list. An example of a line of input from a control file, with its various parts identified, is shown
below:
Column: 12345678 9012345 678 901234567 8 901234567890
CO MODELOPT DFAULT CONC
I Parameters
I ~ 8-Character Keyword
2 Character Pathway ID
The following sections describe the rules for structuring the input control file and explain some of
the advantages of the keyword/parameter approach.
2.2.1 Basic rules for structuring input control files
While the input control file has been designed to provide the user with considerable flexibility in
structuring the input file, there are some basic syntax rules that need to be followed. These rules serve to
maintain some consistency between input files generated by different users, to simplify the job of error
handling performed by the model on the input data, and to provide information to the model in the
appropriate order wherever order is critical to the interpretation of the inputs. These basic rules and the
various elements of the input control file are described in the paragraphs that follow.
One of the most basic rules is that all inputs for a particular pathway must be "grouped within that
specific pathway" and occur in the excepted order, i.e., all inputs for the CO pathway must come first,
followed by the inputs for the SO pathway, and so on. The beginning of each pathway is identified with a
"STARTING" keyword, and the ending of the pathway with the "FINISHED" keyword. Thus, the first
functional record of each input file must be "CO STARTING" and the last record of each input file must
be "OU FINISHED." The rest of the input control file commands will define the options and input data
for a particular run.
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Each record in the input control file is read into the model as a 512-character image beginning
with version 09292. The information on each input image consists of a "pathway," a "keyword," and one
or more "parameters." Each of these "fields" on a line in the control file command must be separated
from other fields by at least one blank space. To simplify the interpretation of the control file command
by the model, the control file must be structured with the two-character pathway in columns 1 and 2, the
eight-character keyword in columns 4 through 11, followed by the parameters beginning in column 13
through the end of image, limited to 512 characters. For most keywords, the order of parameters
following the keyword is important ~ the exact spacing of the parameters is not important as long as they
are separated from each other by at least one blank space and do not extend beyond the 512-character
limit. The example of a control file command from the CO pathway shown above is repeated here:
Column: 123456789 012 345 678 901234567 890123 45 67890
CO MODELOPT DFAULT CONC
I 1 ğ Parameters
~ 8-Character Keyword
2-Character Pathway ID
Alphabetical characters can be input as either lower case or uppercase letters. The model
converts all character input to upper case letters internally, except the title fields and file names to be
discussed later. Throughout this document, the convention of using upper case letters is followed. For
numeric input data, it should be noted that all data are assumed to be in metric units, i.e., length units of
meters, speed units of meters per second, temperature units of degrees Kelvin, and emission units of
grams per second. In a few instances, the user has the option of specifying units of feet for length and the
model will perform the conversion to meters. These exceptions are the input of receptor heights for
elevated terrain and the specification of anemometer height since these values are often more readily
available in feet than in meters.
Certain keywords are mandatory and must be present in every control file, such as the
MODELOPT keyword shown in the example above which identifies the modeling options. There are
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also keywords that are optional and are only needed to exercise specific options, such as the option to
allow for the input of flagpole receptor heights. Some of the keywords are repeatable, such as the
keywords to specify source parameters, while other keywords may only appear once. The keyword
references are provided in Section 3.0 and APPENDIX A.
With a few exceptions that are described below, the order of keywords within each pathway is not
critical. For the SO pathway, the LOCATION keyword must be specified before other keywords for a
particular source, and the SRCGROUP keyword must be the last keyword before SO FINISHED unless
the PSDCREDIT keyword is specified on the MODELOPT card, in which case, SRCGROUP is replaced
with the PSDGROUP keyword. For keywords on the SO pathway that accept a range of source IDs, the
source parameters specified by those keywords will only be applied to the sources already defined and
will exclude any sources that are specified latter in the input file.
The PARAMETER ILEN FLD is used to specify the maximum length of individual fields on the
input control file command and to declare the length of all filename and format variables. This
PARAMETER is currently assigned a value of 200 beginning with version 09292 and is in MODULE
MAIN1 in MODULES.FOR.
2.2.2 Advantages of the keyword approach
The keyword approach provides some advantages over the type of input file used by other models
that require formatted input of several numeric switches. One advantage is that the keywords are
descriptive of the options and inputs being used for a particular run, making it easier for a reviewer to
ascertain what was accomplished in a particular run by reviewing the input file. Another advantage is that
the user has considerable flexibility in structuring the inputs to improve their readability and
understandability if they adhere to the few basic rules described above.
Some special provisions have been made to increase the flexibility to the user in structuring the
input files. One provision is to allow for blank records in the input file. This allows the user to separate
the pathways from each other, or to separate a group of images, such as source locations, from the other
images. Another provision is for the use of "comment lines," identified by a "**" in the pathway field.
Any input image that has "**" for the pathway ID will be ignored by the model. This is especially useful
for labeling the columns in the source parameter input images, as illustrated in the example problem later
in this section. It may also be used to "comment out" certain options for a particular run without deleting
the options and associated data (e.g., elevated terrain heights) completely from the input file. Because of
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the descriptive nature of the keyword options and the flexibility of the inputs it is generally much easier to
make modifications to an existing input control file to obtain the desired result.
Another reason for improved "user-friendliness" is that detailed error-handling has been built into
the model. The model provides descriptions of the location and nature of all the errors encountered for a
particular run. Rather than stopping execution at each occurrence of an input error, the model will read
through and attempt to process all input records and report all errors encountered. If a fatal error occurs,
then the model will not attempt to execute the model calculations.
2.3 Regulatory default modeling options
The regulatory default option is controlled from the MODELOPT keyword on the CO pathway.
As its name implies, this keyword controls the selection of modeling options. It is a mandatory, non-
repeatable keyword, and it is an especially important keyword for understanding and controlling the
operation of the AERMOD model. Unless specified otherwise through the available keyword options, the
AERMOD model implements the following default options:
Use the elevated terrain algorithms requiring input of terrain height data;
Use stack-tip downwash (except for building downwash cases);
Use the calms processing routines;
Use the missing data processing routines; and
Use a 4-hour half-life for exponential decay of SO2 for urban sources.
Note that beginning with AERMOD version 18081, the 4-hour half-life is included by
default for SO2 urban sources for regulatory default applications and non-regulatory
applications.
The parameters used to specify options on the MODELOPT keyword are character strings, called
"secondary keywords," that are descriptive of the option being selected. For example, to ensure that the
regulatory default options listed above are used for a particular model simulation, the user would include
the secondary keyword "DFAULT" on the MODELOPT input. Upon initial execution, the model reads
the control file to identify any conflicts in the options specified. In most cases, the model will issue an
error message to inform the user of the conflict and abort before the simulation begins. For regulatory
modeling applications, it is strongly suggested that the DFAULT switch be set to ensure the regulatory
default options listed above are used and non-regulatory options are not used.
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In addition to the default regulatory options listed above, AERMOD includes several other
regulatory options that are application dependent and are required to be set explicitly by the user in the
control file. Most of these can be set with the use of secondary keywords associated with the
MODELOPT keyword. The MODELOPT keyword is described in more detail in the Section 3.2.2.
Throughout this user's guide, there has been an effort to clearly distinguish regulatory options that are
required to be set by the user and can be used simultaneously with the DFAULT keyword from non-
regulatory options that cannot be used along with the DFAULT keyword. These non-regulatory options
are sometimes referred to as "non-DFAULT" options since they cannot be used along with the DFAULT
keyword.
2.4 Setting up a simple control file
This section goes through a step-by-step description of setting up a simple application problem,
illustrating the more commonly used options of the AERMOD model. The example problem is based on
a simple industrial source application. The input file for AERMOD for the example problem is shown in
Figure 2-1. The remainder of this section explains the various parts of the input file for the AERMOD
model and illustrates some of the flexibility in structuring the input file.
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CO
STARTING
CO
TITLEONE
A Simple
Example Problem
for the
AERMOD-
-PRIME Model
CO
MODELOPT
CONC FLAT
CO
AVERT IME
3 24 PERIOD
CO
POLLUTID
S02
CO
RUNORNOT
RUN
CO
FINISHED
so
STARTING
so
LOCATION
STACK1
POINT 0.0 0.0 0
0
so
SRCPARAM
STACK1
500.0 65.00 425
15
.0 5
so
BUILDHGT
STACK1
36*50.
so
BUILDWID
STACK1
62.26 72.64
80
80
86.51
89.59
89
95
so
BUILDWID
STACK1
87.58 82.54
75
00
82.54
87.58
89
95
so
BUILDWID
STACK1
89.59 86.51
80
80
72. 64
62.26
50
00
so
BUILDWID
STACK1
62.26 72.64
80
80
86.51
89.59
89
95
so
BUILDWID
STACK1
87.58 82.54
75
00
82.54
87.58
89
95
so
BUILDWID
STACK1
89.59 86.51
80
80
72. 64
62.26
50
00
so
BUILDLEN
STACK1
82.54 87.58
89
95
89.59
86.51
80
80
so
BUILDLEN
STACK1
72.64 62.26
50
00
62.26
72. 64
80
80
so
BUILDLEN
STACK1
86.51 89.59
89
95
87.58
82.54
75
00
so
BUILDLEN
STACK1
82.54 87.58
89
95
89.59
86.51
80
80
so
BUILDLEN
STACK1
72.64 62.26
50
00
62.26
72. 64
80
80
so
BUILDLEN
STACK1
86.51 89.59
89
95
87.58
82.54
75
00
so
XBADJ
STACK1
-47.35 -55.76
-62
48
-67.29
-70.07
-70
71
so
XBADJ
STACK1
-69.21 -65.60
-60
00
-65.60
-69.21
-70
71
so
XBADJ
STACK1
-70.07 -67.29
-62
48
-55.76
-47.35
-37
50
so
XBADJ
STACK1
-35.19 -31.82
-27
48
-22.30
-16.44
-10
09
so
XBADJ
STACK1
-3.43 3.34
10
00
3.34
-3.43
-10
09
so
XBADJ
STACK1
-16.44 -22.30
-27
48
-31.82
-35.19
-37
50
so
YBADJ
STACK1
34.47 32.89
30
31
26.81
22.50
17
50
so
YBADJ
STACK1
11.97 6.08
0
00
-6. 08
-11.97
-17
50
so
YBADJ
STACK1
-22.50 -26.81
-30
31
-32.89
-34.47
-35
00
so
YBADJ
STACK1
-34.47 -32.89
-30
31
-26.81
-22.50
-17
50
so
YBADJ
STACK1
-11.97 -6.08
0
00
6.08
11. 97
17
50
so
YBADJ
STACK1
22.50 26.81
30
31
32.89
34 . 47
35
00
so
SRCGROUP
ALL
so
FINISHED
RE
STARTING
RE
GRIDPOLR
POL1 STA
RE
GRIDPOLR
POL1 ORIG STACK1
RE
GRIDPOLR
POL1 DIST 175. 350. 500
1000.
RE
GRIDPOLR
POL1 GDIR 36 10 10
RE
GRIDPOLR
POL1 END
RE
FINISHED
ME
STARTING
ME
SURFFILE
AERMET2.
SFC
ME
PROFFILE
AERMET2.
PFL
ME
SURFDATA
14735 198 8 ALBANY,NY
ME
UAIRDATA
14735 198 8 ALBANY,NY
ME
SITEDATA
ME
PROFBASE
0.0 METERS
ME
FINISHED
OU
STARTING
OU
RECTABLE
ALIVE FIRST-SECOND
OU
MAXTABLE
ALIVE 5 0
OU
FINISHED
Figure 2-1. Example Input File for AERMOD for Sample Problem
2-14
-------
2.4.1 A simple industrial source application
For this simple tutorial, an application is selected involving a single point source of SO2 that is
subject to the influences of building downwash. The source consists of a 50-meter stack with a buoyant
release that is adjacent to a building. It is assumed that the stack is situated in flat terrain in a rural setting.
A polar receptor network will be placed around the stack location to identify areas of maximum impact.
2.4.2 Selecting modeling options - CO pathway
The modeling options are input to the model on the Control pathway. The mandatory keywords
for the CO pathway are listed below. A complete listing of all keywords is provided in Section 3.2 and
APPENDIX A
STARTING -
TITLEONE -
MODELOPT -
AVERTIME -
POLLUTID -
RUNORNOT-
FINISHED -
Indicates the beginning of inputs for the pathway; this keyword is
mandatory on each of the pathways.
A user-specified title line (up to 68 characters) that will appear on each
page of the printed output file (an optional second title line is also
available with the keyword TITLE TWO).
Controls the modeling options selected for a particular run through a series
of secondary keywords.
Identifies the averaging periods to be calculated for a particular run.
Identifies the type of pollutant being modeled. At the present time, this
option has no influence on the results.
A special keyword that tells the model whether to run the full model
executions or not. If the user selects not to run, then the control file will be
processed and any input errors reported, but no dispersion calculations will
be made.
Indicates that the user is finished with the inputs for this pathway; this
keyword is also mandatory on each of the other pathways.
2-15
-------
The first two keywords are self-explanatory. As discussed above in Section 2.3, the MODELOPT
keyword on the CO pathway is pivotal to controlling the modeling options used for a particular run. For
this example, we intend to use the regulatory default option, and have specified for the model to output
concentration values. After the first three input records our input file will look something like this:
CO
STARTING
CO
TITLEONE
A Simple Example Problem for the AERMOD-PRIME Model
CO
MODELOPT
CONC FIAT
Note that the title parameter field does not need to be in quotations, even though it represents a single
parameter. The model simply reads whatever appears beginning in column 13 out to a length of 200
characters of the TITLEONE card as the title field, without changing the lower case to upper case letters.
Leading blanks are therefore significant if the user wishes to center the title within the field. Note that in
the output files, only the first 68 characters of TITLEONE are printed. Note also that the spacing and
order of the secondary keywords on the MODELOPT card are not significant. A MODELOPT card that
looked like this:
CO MODELOPT CONC FLAT
would have an identical result as the example above. It is suggested that the user adopt a style that is
consistent and easy to read. A complete description of the available modeling options that can be
specified on the MODELOPT keyword is provided in Section 3.0.
For this example, the average values are calculated for 3-hour and 24-hour and the full period that
is modeled. The control file might, therefore, look similar to this after adding two more keywords:
2-16
-------
CO
STARTING
CO
TITLEONE
A Simple Example Problem for the AERMOD-PRIME Model
CO
MODELOPT
CONC FIAT
CO
AVERTIME
3 2 4 PERIOD
CO
POLLUTID
S02
Note again that the order of the parameters on the AVERTIME keyword is not critical, although the order
of the short-term averages given on the AVERTIME keyword will also be the order in which the results
are presented in the output file. The order of the keywords within each pathway is also not critical in
most cases, although the intent of the input control file may be easier to decipher if a consistent and
logical order is followed. It is suggested that users follow the order in which the keywords are presented
in Section 3.0, in APPENDIX A, and in the Quick Reference, unless there is a clear advantage to doing
otherwise.
The only remaining mandatory keywords for the CO pathway are RUNORNOT and FINISHED.
We will set the RUNORNOT switch to RUN for this example. If a user is unsure about the operation of
certain options or is setting up a complex control file to run for the first time, it may be desirable to set the
model NOT to run, but simply to read and analyze the input file and report any errors or warning
messages that are generated. Once the input file has been debugged using these descriptive error/warning
messages, then the RUNORNOT switch can be set to RUN, avoiding a possible costly waste of resources
generating erroneous results. Even if the model is set NOT to run, all the inputs are summarized in the
output file for the user to review.
Our complete control file for the CO pathway may look something like this:
CO
STARTING
CO
TITLEONE
A Simple Example Problem for the AERMOD-PRIME Model
CO
MODELOPT
CONC FIAT
CO
AVERTIME
3 24 PERIOD
CO
POLLUTID
S02
CO
RUNORNOT
RUN
CO
FINISHED
The following set of control file options has a more structured look, but it is equivalent to the example
above:
2-17
-------
CO
STARTING
TITLEONE
A Simple Example Problem for the AERMOD-PRIME Model
MODELOPT
CONC FIAT
AVERTIME
3 24 PERIOD
POLLUTID
S02
RUNORNOT
RUN
CO
FINISHED
Since the pathway ID is required to begin in column 1 (see Section 2.4.8 for a discussion of this
restriction), the model will assume that the previous pathway is in effect if the pathway field is left blank.
The model will do the same for blank keyword fields, which will be illustrated in the next section, Section
2.4.3.
In addition to these mandatory keywords on the CO pathway, the user may select optional
keywords to allow the use of receptor heights above ground-level for flagpole receptors, to specify a
decay coefficient or a half-life for exponential decay, and to generate an input file containing events for
EVENT processing. The user also has the option of having the model periodically save the results to a
file for later re-starting in the event of a power failure or other interruption of the model's execution.
These options are described in more detail in Section 3.0 of this volume.
2.4.3 Specifying source inputs - SO pathway
Besides the STARTING and FINISHED keywords that are mandatory for all pathways, the
Source pathway has the following mandatory keywords:
LOCATION - Identifies a particular source ID and specifies the source type and
location of that source.
SRCPARAM - Specifies the source parameters for a particular source ID identified by a
previous LOCATION card.
SRCGROUP - Specifies how sources will be grouped for calculational purposes.
There is always at least one group, even though it may be the group of
ALL sources and even if there is only one source.
Since the hypothetical source in this example problem is influenced by a nearby building, we also
need to include the optional keywords BUILDHGT and BUILDWID in our input file.
The input file for the SO pathway for this example will like the following:
I STARTING I
2-18
-------
LOCATION
STACK1
POINT
o
o
o
o
O
o
SRCPARAM
STACK1
500.0
65 . 00
425.
15 . 0
5.0
BUILDHGT
STACK1
50 . 00
CJl
o
o
o
CJl
o
o
o
CJl
O
O
O
CJl
o
o
o
50
00
BUILDHGT
STACK1
50 . 00
50 . 00
CJl
o
o
o
50 . 00
50 . 00
50
00
BUILDHGT
STACK1
50 . 00
50 . 00
CJl
o
o
o
50 . 00
50 . 00
50
00
BUILDHGT
STACK1
50 . 00
50 . 00
CJl
o
o
o
50 . 00
50 . 00
50
00
BUILDHGT
STACK1
50 . 00
50 . 00
50 . 00
50 . 00
50 . 00
50
00
BUILDHGT
STACK1
50 . 00
50 . 00
50 . 00
50 . 00
50 . 00
50
00
BUILDWID
STACK1
62.26
72 . 64
80.80
86.51
89.59
89
95
BUILDWID
STACK1
87 .58
82.54
75 . 00
82.54
87 .58
89
95
BUILDWID
STACK1
89.59
86.51
80.80
72 . 64
62.26
50
00
BUILDWID
STACK1
62.26
72 . 64
80.80
86.51
89.59
89
95
BUILDWID
STACK1
87 .58
82.54
75 . 00
82.54
87 .58
89
95
BUILDWID
STACK1
89.59
86.51
80.80
72 . 64
62.26
50
00
BUILDLEN
STACK1
82.54
87 .58
89. 95
89.59
86.51
80
80
BUILDLEN
STACK1
72 . 64
62.26
CJl
o
o
o
62.26
72 . 64
80
80
BUILDLEN
STACK1
86.51
89.59
89. 95
87 .58
82.54
75
00
BUILDLEN
STACK1
82.54
87 .58
89. 95
89.59
86.51
80
80
BUILDLEN
STACK1
72 . 64
62.26
CJl
o
o
o
62.26
72 . 64
80
80
BUILDLEN
STACK1
86.51
89.59
89. 95
87 .58
82.54
75
00
XBADJ
STACK1
-47.35
-55.76
-62.48
-67.29
-70.07
-70
71
XBADJ
STACK1
-69.21
-65.60
-60.00
-65.60
-69.21
-70
71
XBADJ
STACK1
-70.07
-67.29
-62.48
-55.76
-47.35
-37
50
XBADJ
STACK1
-35 .19
-31.82
-27 .48
-22.30
-16.44
-10
09
XBADJ
STACK1
-3 .43
3.34
10 . 00
3.34
-3 .43
-10
09
XBADJ
STACK1
-16.44
-22.30
-27 .48
-31.82
-35.19
-37
50
YBADJ
STACK1
34 .47
32 . 89
30.31
26.81
22.50
17
50
YBADJ
STACK1
11 . 97
6.08
0.00
-6.08
-11.97
-17
50
YBADJ
STACK1
-22.50
-26.81
-30.31
-32.89
-34.47
-35
00
YBADJ
STACK1
-34.47
-32.89
-30.31
-26.81
-22.50
-17
50
YBADJ
STACK1
-11.97
-6.08
0.00
6.08
11 . 97
17
50
YBADJ
STACK1
22.50
26.81
30.31
32 . 89
34 .47
35
00
SRCGROUP
ALL
FINISHED
There are a few things to note about these inputs. First, the source ID (STACK1 in this example)
is an alphanumeric parameter (up to 12 characters) that identifies the inputs for different keywords with a
particular source. It is crucial that the source be identified with a LOCATION card before any other
keyword references the source, since this identifies the source type (POINT in this case), and therefore,
which parameters the model will allow. See Section 3.3.1 for a complete list and descriptions of the valid
source types. If the effects of elevated terrain were included in this analysis, it would be important to
specify the source base elevation above mean sea level (MSL) on the LOCATION card. For this
example, the source base elevation is 0.0 meters MSL.
Another thing to note is that since the model uses direction-specific building dimensions for all
sources with downwash, there are 36 building heights and 36 building widths entered on the appropriate
keywords, one value for each 10-degree sector beginning with the 10-degree flow vector (direction
toward which the wind is blowing) and continuing clockwise. Since the user could not fit all 36 values on
a single record, the pathway, keyword, and source ID were repeated as many times as were necessary. In
this case there were six values given on each of the six lines for each of the building dimensions. There
could have been fewer or more lines if exactly 36 values were entered before starting with a new
keyword. Since the building height was the same across the sectors (fairly realistic for the height but not
2-19
-------
for widths, unless the structure was circular), there is a short cut available for specifying numeric input in
the control files for the model. The user can specify "repeat values" by entering a field such as "36*50.0"
as a parameter for the BUILDHGT keyword. The model will interpret this as "36 separate entries, each
with a value of 50.0," and store the values in the appropriate arrays within the model. Since the model
must identify this as a single parameter field, there must not be any spaces between the repeat-value and
the value to be repeated.
The final keyword before finishing the SO pathway must be the SRCGROUP keyword (unless
the PSDCREDIT keyword is specified on the MODELOPT card, in which case SRCGROUP is replaced
with the PSDGROUP keyword). In this example, since there is only one source, we have taken advantage
of a short cut provided by the model by specifying a source group ID (which may be up to eight
characters) of ALL. Whenever this card appears in an input file, it will generate a source group with a
source-group ID of ALL, consisting of all sources defined for that run. The sources do not have to be
explicitly identified. In a run involving multiple sources, the user may specify multiple source groups by
repeating the SRCGROUP keyword. The use of the SRCGROUP card is explained in more detail in
Section 3.0.
Using some of the formatting options discussed above, the SO pathway for this example may
look like this, with the same result as above:
2-20
-------
SO STARTING
LOCATION
STACK1
POINT
o
o
o
o
o
. 0
** Point Source
QS
HS TS
VS
DS
** Parameters:
SRCPARAM
STACK1
500 . 0
65.0 425.
0 15. 0
5.0
BUILDHTS
STACK1
36*50
BUILDWTS
STACK1
62.26
72 . 64
80
80
86. 51
89.59
89. 95
STACK1
87 . 58
82.54
75
00
82.54
87.58
89. 95
STACK1
89.59
86.51
80
80
72. 64
62.26
50. 00
STACK1
62.26
72 . 64
80
80
86. 51
89.59
89. 95
STACK1
87 . 58
82.54
75
00
82.54
87.58
89. 95
STACK1
89.59
86.51
80
80
72. 64
62.26
50 . 00
XBADJ
STACK1
-47.35
-55.76
-62
48
-67.29
-70.07
-70.71
STACK1
-69.21
-65.60
-60
00
-65.60
-69.21
-70.71
STACK1
-70.07
-67.29
-62
48
-55.76
-47.35
-37.50
STACK1
-35.19
-31.82
-27
48
-22.30
-16.44
-10.09
STACK1
-3.43
3.34
10
00
3.34
-3.43
-10.09
STACK1
-16.44
-22.30
-27
48
-31.82
-35.19
-37.50
YBADJ
STACK1
34 .47
32. 89
30
31
26.81
22.50
17.50
STACK1
11. 97
6. 08
0
00
-6. 08
-11.97
-17.50
STACK1
-22.50
26.81
-30
31
-32.89
-34 .47
-35.00
STACK1
-34.47
-32.89
-30
31
-26.81
-22.50
-17.50
STACK1
-11.97
-6.08
0
00
6.08
11. 97
17 .50
STACK1
22.50
26.81
30
31
32.89
34 . 47
35.00
SRCGROUP
ALL
SO FINISHED
This example of the SO pathway inputs illustrates the use of the comment card to label the stack
parameters on the SRCPARAM card, i.e., QS for emission rate (g/s), HS for stack height (m), TS for stack
exit temperature (K), VS for exit velocity (m/s), and DS for stack diameter (m). A complete description
of the source parameter card, with a list of parameters for each source type, is provided in Section 3.3 and
in APPENDIX A.
Other optional inputs that may be entered on the SO pathway include specifying variable
emission rate factors for sources whose emissions vary as a function of month, season, hour-of-day, or
season and hour-of-day (see Section 3.3.11 for more details). The number of factors entered depends on
the option selected, and factors may be input for single sources or for a range of sources.
2-21
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2.4.4 Specifying a receptor network - RE pathway
As mentioned above, this example will illustrate the use of a single polar receptor network
centered on the stack location. Other options available on the REceptor pathway include specifying a
Cartesian grid receptor network and specifying discrete receptor locations in either a polar or a Cartesian
system. These other options are described in more detail in Section 3.4.
The RE pathway for this example will look like this:
RE
STARTING
GRIDPOLR
POLl
STA
GRIDPOLR
POLl
ORIG
STACK1
GRIDPOLR
POLl
DIST
175. 350. 500. 1000.
GRIDPOLR
POLl
GDIR
36 10 10
GRIDPOLR
POLl
END
RE
FINISHED
Looking at the example for the RE pathway, the first thing to note about these inputs is that there
is a new set of keywords, including something that looks like a STArting and ENDing. In fact, the
GRIDPOLR keyword can be thought of as a "sub-pathway," in that all of the information for a particular
polar network must be in contiguous records, and that the start and end of the sub-pathway are identified.
Like the main pathways, the order of secondary keywords within the sub-pathway is not critical. Each
card must be identified with a network ID (up to eight alphanumeric characters), in this case it is "POLl."
Multiple networks may be specified in a single model run. The model waits until the END secondary
keyword is encountered to set the variables, which may include terrain heights for receptors on elevated
terrain or flagpole receptor heights if those options are being exercised by the user. The use of these
optional secondary keywords is described in detail in Section 3.4.
For this example, the ORIG secondary keyword specifies the location of the origin for the polar
network being defined as being the location of the source STACK1. The origin can also be specified as X
and Y-coordinates. The ORIG keyword is optional, and the model will default to an origin of (0.0, 0.0) if
it is omitted. The DIST keyword identifies the distances along each direction radial at which the
receptors will be located. In this case there are four distances. More distances could be added by adding
values to that input card or by including a continuation card with the DIST keyword, if needed. The
GDIR keyword specifies that the model will Generate DIRection radials for the network, in this case there
will be 36 directions, beginning with the 10-degree flow vector and incrementing every 10 degrees
2-22
-------
clockwise. The user may elect to define Discrete DIRection radials instead by using the DDIR keyword
in place of the GDIR keyword.
2.4.5 Specifying the meteorological Input - ME pathway
The MEteorology pathway has the following four mandatory keywords in addition to the
common STARTING and FINISHED keywords:
SURFFILE - Specifies the filename and format for the input surface meteorological data
file.
PROFFILE - Specifies the filename and format for the input profile meteorological data
file.
SURFDATA - Specifies information about the surface meteorological data which will be
used in the modeling.
UAIRDATA - Specifies information about the upper air meteorological data which will be
used in the modeling.
PROFBASE - Specifies the base elevation above MSL for the potential temperature profile.
For the purposes of this example, it is assumed that the meteorological data files are for Albany, NY and
that an on-site location called Hudson has also been used. It is also assumed that the surface and profile
data files were generated by the AERMET preprocessor and are in the default format for AERMOD. The
filename of the surface file is AERMET2.SFC and it consists of four days of data for Albany/Hudson
from March 1988. The filename of the profile file is AERMET2.PFL. The data files used in this example
correspond with the on-site example files used for the AERMET preprocessor program. The control file
commands for the MEteorology pathway would look like the following:
ME
STARTING
SURFFILE
AERMET2.SFC
PROFFILE
AERMET2.PFL
SURFDATA
14735 1988
ALBANY,NY
UAIRDATA
14735 1988
ALBANY,NY
SITEDATA
99999 1988
HUDSON
PROFBASE
0.0 METERS
ME
FINISHED
2-23
-------
The first parameters on the SURFFILE and PROFFILE keywords are the filenames for the
surface and profile data file, respectively, which can be entered as a full DOS pathname, including the
drive specification and subdirectories, up to a total of 200 characters (with the maximum number of
characters controlled by the ILENFLD PARAMETER located in MODULE MAIN1 - see Section 2.2.1).
Since there is no second parameter, the model will assume the default ASCII format for the data files.
The format of the surface and profile data files is described in APPENDIX C.
The next two mandatory inputs identify the location and data period of the input meteorological
data. A separate keyword is used for the surface meteorological data and for the upper air (mixing height)
data. The parameters on these cards are the station number (e.g., WBAN number for NWS stations), the
data period (year), and a station name. In order to identify potential errors in the model inputs, the model
compares the station number from the control input file with values provided in the first record of the
surface meteorology file, and issues warning messages if there are any mismatches. The user may also
optionally input the (X,Y) coordinates for the location of the station(s), although these values are not
currently used by the model. In this case, we have also included the optional SITED ATA keyword to
identify the location for the on-site meteorological data that were preprocessed by AERMET.
The final mandatory keyword is PROFBASE, which is used to specify the base elevation (above
MSL) for the potential temperature profile generated by AERMOD for use in the plume rise calculations.
This should correspond to the base elevation for the main meteorological tower, which in this example is
specified as 0.0 meters and is the same as the source base elevation.
Other optional keywords available on the ME pathway provide the user with options to specify
selected days to process from the meteorological data file, and a wind direction rotation correction term.
These optional inputs are described in more detail in Section 3.5.
2.4.6 Selecting output options - OU pathway
All the keywords on the Output pathway are optional, although the model will warn the user if no
printed outputs are requested and will halt processing if no outputs (printed results or file outputs) are
selected. The user has considerable flexibility to select only the outputs that are needed for a particular
application. The printed table keywords are:
RECTABLE - Specifies the selection of high value by receptor table output options.
2-24
-------
MAXTABLE - Specifies the selection of overall maximum value table output options.
DAYTABLE - Specifies the selection of printed results (by receptor) for each day of data
processed (this option can produce very large files and should be used with
caution).
The RECTABLE keyword provides the highest, second highest and third highest values, etc., by
receptor. The MAXTABLE keyword provides a table of the overall maximum n number of values. For
both keywords, the user has additional flexibility to specify for which short-term averaging periods the
outputs are selected. For the MAXTABLE keyword the user can also specify the number of overall
maximum values to summarize for each averaging period selected, up to a maximum number controlled
by a parameter in the computer code. In the example below, the highest and second-highest values by
receptor and the maximum 50 values for all averaging periods are specified.
OU
STARTING
RECTABLE
ALLAVE
FIRST SECOND
MAXTABLE
ALLAVE
50
OU
FINISHED
To simplify the input for users who request the same printed table output options for all averaging
periods, these keywords recognize the secondary keyword "ALLAVE" as the first parameter for that
purpose. To obtain the overall maximum 10 values for the 24-hour averages only, the OU pathway input
would look like the following example:
OU
STARTING
RECTABLE
ALLAVE FIRST SECOND
MAXTABLE
24 10
OU
FINISHED
It should also be noted that these output table options apply only to the short-term averaging
periods, such as the 3-hour and 24-hour averages used in our example. If the user has selected that
PERIOD averages be calculated (on the CO AVERTIME keyword), then the output file will automatically
include a table of period averages summarized by receptor (the RECTABLE option does not apply since
there is only one period value for each receptor). In addition, the printed output file will include tables
summarizing the highest values for each averaging period and source group.
Other options on the OU pathway include several keywords to produce output files for
specialized purposes, such as generating contour plots of high values, identifying occurrences of
2-25
-------
violations of a particular threshold value (e.g., a NAAQS), and for postprocessing of the raw
concentration data. These options are described in detail in Section 3.7.
The complete input control file for this simple example is shown in Figure 2-2. Note that a
consistent style has been used for formatting and structuring the file to improve its readability. This input
file is comparable to the version shown earlier in Figure 2-1, which used a somewhat different style.
2-26
-------
CO STARTING
TITLEONE A Simple Example Problem for the AERMOD-PRIME Model
MODELOPT CONC
AVERT IME 3 24
POLLUTID S02
RUNORNOT RUN
CO FINISHED
FLAT
PERIOD
SO STARTING
* *
Ĥk -k
LOCATION
STACK1
POINT 0
o
o
o
o
o
Point Source
QS
HS TS
VS
DS
Parameters:
SRCPARAM
STACK1
500 . 0
65.0 425.
15. 0
5 . 0
BUILDHGT
STACK1
36*50.
BUILDWID
STACK1
62.26
72. 64
80
80
86.51
89.59
89
95
STACK1
87.58
82.54
75
00
82.54
87 . 58
89
95
STACK1
89.59
86.51
80
80
72. 64
62.26
50
00
STACK1
62.26
72. 64
80
80
86.51
89.59
89
95
STACK1
87.58
82.54
75
00
82.54
87 . 58
89
95
STACK1
89.59
86.51
80
80
72. 64
62.26
50
00
BUILDLEN
STACK1
82.54
87.58
89
95
89.59
86. 51
80
80
STACK1
72. 64
62.26
50
00
62.26
72. 64
80
80
STACK1
86.51
89.59
89
95
87.58
82.54
75
00
STACK1
82.54
87.58
89
95
89.59
86. 51
80
80
STACK1
72. 64
62.26
50
00
62.26
72. 64
80
80
STACK1
86.51
89.59
89
95
87.58
82.54
75
00
XBADJ
STACK1
-47.35
-55.76
-62
48
-67.29
-70.07
-70
71
STACK1
-69.21
-65.60
-60
00
-65.60
-69.21
-70
71
STACK1
-70.07
-67.29
-62
48
-55.76
-47.35
-37
50
STACK1
-35 .19
-31.82
-27
48
-22.30
-16.44
-10
09
STACK1
-3.43
3.34
10
00
3.34
-3.43
-10
09
STACK1
-16.44
-22.30
-27
48
-31.82
-35.19
-37
50
YBADJ
STACK1
34 . 47
32. 89
30
31
26.81
22.50
17
50
STACK1
11. 97
6. 08
0
00
-6. 08
-11.97
-17
50
STACK1
-22.50
-26.81
-30
31
-32.89
-34 .47
-35
00
STACK1
-34.47
-32.89
-30
31
-26.81
-22.50
-17
50
STACK1
-11.97
-6.08
0
00
6. 08
11. 97
17
50
STACK1
22.50
26.81
30
31
32 . 89
34 .47
35
00
SRCGROUP
ALL
SO FINISHED
RE STARTING
GRIDPOLR
GRIDPOLR
GRIDPOLR
GRIDPOLR
GRIDPOLR
RE FINISHED
POL1 STA
POL1 ORIG STACK1
POL1 DIST 175. 350.
POL1 GDIR 3 6 10 10
POL1 END
500. 1000.
ME STARTING
SURFFILE AERMET2.SFC
PROFFILE AERMET2.PFL
SURFDATA 14735 198 8 ALBANY, NY
UAIRDATA 14735 198 8 ALBANY, NY
SITEDATA 99999 1988 HUDSON
PROFBASE 0 . 0 METERS
ME FINISHED
OU STARTING
RECTABLE ALLAVE FIRST-SECOND
MAXTABLE ALLAVE 50
OU FINISHED
Figure 2-2. Example Input control file for Sample Problem
2-27
-------
2.4.7 Using the error message file to debug the input control file
The previous sections in this tutorial have provided a step-by-step construction of a sample
control input file for AERMOD. This simple example problem illustrated the usage of the more
commonly used options of the AERMOD model. However, many real-time applications of the model will
be much more complex than this example, perhaps involving multiple sources and source groups,
multiple receptor networks, the addition of discrete receptor locations, and/or elevated terrain heights. To
reduce errors in modeling applications, an effort has been made to develop detailed error handling
capabilities for the AERMOD model.
The error handling capabilities of the AERMOD model are designed to accomplish two things for
the user. First, the model reads through the complete input file and report all occurrences of errors or
suspect entries before stopping, rather than stopping on the first instance (and every instance thereafter) of
an error in the input file. Second, the model provides error and warning messages that are detailed and
descriptive enough that they will help the user in his/her effort to debug the input file. The remainder of
this section provides of brief introduction to the use of the model's error handling capabilities.
APPENDIX B of this volume provides more details about the error handling provided by the AERMOD
model.
The AERMOD model generates messages during the processing of the input data and during the
execution of model calculations. These messages inform the user about a range of possible conditions
including:
Errors that will halt any further processing, except to identify additional error conditions;
Warnings that do not halt processing but indicate possible errors or suspect conditions; and
Informational messages that may be of interest to the user but have no direct bearing on the
validity of the results.
As the model encounters a condition for which a message is generated, the model writes the
message to a temporary storage file. At the completion of the setup processing for a run, and at the
completion of the model calculations, the model rereads the message file and generates a summary of the
messages which is included in the main printed output file. If the processing of the model setup
information indicates no errors or warnings, and the user has selected the option to RUN the model
calculations on the CO RUNORNOT card, then the model will simply write a statement to the print file
that the model setup was completed successfully. Otherwise, the model will report a summary of the
2-28
-------
messages encountered. The summary of model setup messages that would be generated for the example
problem if the option NOT to run was chosen is shown in Figure 2-3. This summary table reports the total
number of occurrences for each of the message types and lists the detailed message for any fatal errors or
warning messages that were generated. In this case, since there were no errors or suspicious conditions in
the setup file, there are no error or warning messages listed.
An example of the warning message that would have been generated had we left out the card on
the RE pathway that specifies the origin of the polar receptor network is shown below:
RE W220 39 REPOLR: Missing Origin (Use Default = 0,0) In GRIDPOLR
1 1 1 1 1
POL1
1
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
1
Hints
1 1 1 1 1
III | Detailed error/warning message
ill i
III 1
| | | Subroutine from which message is generated
i i i
1 1 1
| | Line number of file where message occurred
i i
1 1
| Message code - including message type (E, W, I) and message number
i
1
Pathway ID where message originated
Since this is a warning message, it would have appeared at the end of the message summary table in the
output file, but it would not have halted processing of the data. The last item on the message line,
"Hints," may include such information as the keyword or parameter name causing the error, the source ID,
group ID or (as in this case) the network ID involved, or perhaps the date variable identifying when the
message occurred during the processing of the meteorological data, such as an informational message
identifying the occurrence of a calm wind.
For new users and for particularly complex applications, it is strongly recommended that the
model first be run with the RUNORNOT keyword (on the CO pathway) set NOT to run. In this way, the
user can determine if the model is being setup properly by the control file before committing the resources
to perform a complete run. The user should make a point of examining any warning messages carefully
to be sure that the model is operating as expected for their application, since these messages will not halt
processing by the model. The detailed messages should provide enough information for the user to
determine the location and nature of any errors in the control file.
2-29
-------
In deciphering the error and warning messages, the line number provided as part of the message
may be particularly helpful in locating the error within the input file. However, if it is an error of
omission that is caught by the error checking performed at the completion of inputs for a pathway, then
the line number will correspond to the last record for that pathway. The user may need to examine all of
the messages carefully before locating the error or errors, especially since a single occurrence of certain
types of errors may lead to other error conditions being identified later in the input file which do not
really constitute errors in themselves. An example of this is provided in Figure 2-4, which shows some
inputs for the SO pathway where the building dimension keywords have been typed incorrectly, and the
associated list of error messages. Since continuation cards (cards or records that require multiple entries
and the input continues on subsequent lines) were used for the building width inputs, and the keyword
was entered incorrectly on the first line, the subsequent records were also taken by the model to be invalid
keyword inputs. While the error messages are the same for these records, the message originates from a
different part of the model (SUBROUTINE SOCARD) for the records with the blank keyword.
Since the detailed error and warning messages are listed in the output file as part of the message
summary table, there will generally not be a need for the user to examine the contents of the detailed
message file. For this reason, the default operation of the model is to write the messages that are
generated by a particular run to a temporary file that is deleted when the run is completed. If the user
wishes to examine the complete list of detailed messages (of all types), there is an optional keyword
available on the CO pathway for that purpose. The ERRORFIL keyword, which is described in detail in
Section 3.2.19, allows the user to save the complete list of detailed messages to a user-specified filename.
*** Message Summary : AERMOD Model Execution ***
Summary of Total Messages
A Total
of 0 Fatal Error Message(s)
A Total
of 1 Warning Message(s)
A Total
of 0 Informational Message(s)
A Total
of 96 Hours Were Processed
A Total
of 0 Calm Hours Identified
A Total
of 0 Missing Hours Identified
( 0.00 Percent)
****
**** FATAL ERROR MESSAGES ********
*** NONE ***
****
**** WARNING MESSAGES ********
MX W4 03
57 PFLCNV: Turbulence data is
being used w/o ADJ U* option
SigA & SigW
****
********************************
AERMOD Finishes Successfully ***
Figure 2-3. Example Message Summary Table for AERMOD Execution
2-30
-------
SO STARTING
LOCATION
STACK1
POINT 0
0 0.0 0.0
** Point Source
QS HS TS VS
DS
** Parameters:
SRCPARAM
STACK1
500.0 65
0 425.0 15
. 0
5.0
BUILDHTS
STACK1
36*50.
BUILDWTS
STACK1
62.26
72.64 80.
80
86. 51
89.59
89. 95
STACK1
87 . 58
82.54 75.
00
82.54
87.58
89. 95
STACK1
89.59
86.51 80.
80
72. 64
62.26
50. 00
STACK1
62.26
72.64 80.
80
86. 51
89.59
89. 95
STACK1
87 . 58
82.54 75.
00
82.54
87.58
89. 95
STACK1
89.59
86.51 80.
80
72. 64
62.26
50. 00
XBADJ
STACK1
-47.35
-55.76 -62.
48
-67.29
-70.07
-70.71
STACK1
-69.21
-65.60 -60.
00
-65.60
-69.21
-70.71
STACK1
-70.07
-67.29 -62.
48
-55.76
-47.35
-37.50
STACK1
-35.19
-31.82 -27.
48
-22.30
-16.44
-10.09
STACK1
-3.43
3.34 10.
00
3.34
-3.43
-10.09
STACK1
-16.44
-22.30 -27.
48
-31.82
-35.19
-37.50
YBADJ
STACK1
34 .47
32.89 30.
31
26.81
22.50
17.50
STACK1
11. 97
6.08 0.
00
-6. 08
-11.97
-17.50
STACK1
-22.50
26.81 -30.
31
-32.89
-34.47
-35.00
STACK1
-34.47
-32.89 -30.
31
-26.81
-22.50
-17.50
STACK1
-11.97
-6.08 0.
00
6.08
11. 97
17 .50
STACK1
22.50
26.81 30.
31
32.89
34 . 47
35.00
SRCGROUP
ALL
SO FINISHED
*** Message Surrmary For AERMOD Model Setup ***
Surrmary
of Total Messages
A Total of
7 Fatal Error Message(s)
A Total of
1 Warning Message(s)
A Total of
0 Informational Message(s)
~k~k~k~k~k~k~k~k
FATAL ERROR MESSAGES ********
SO E105
15
SETUP
Invalid Keyword Specified. The Troubled Keyword
is
BUILDWTS
SO E110
16
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO E110
17
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO E110
18
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO E110
19
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO E110
20
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO E237
40
SRCQA
Not Enough
BUILDWIDs Specified for
SourcelD
STACK1
~k~k~k~k~k~k~k~k
WARNING MESSAGES ********
MX W4 03
57
PFLCNV
Turbulence
data is being
used w/o
ADJ U* option
SigA & SigW
~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k
*** SETUP Finishes UN-successfully ***
~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k
Figure 2-4. Example of Keyword Error and Associated Message Summary Table
2-31
-------
2.4.8 Running the model and reviewing the results
Now that we have a complete and error-free control input file, we are ready to run the model and
then review the results. The PC-executable file available on the SCRAM website opens the control input
and printed output files and the model can be executed from the command prompt three ways as follows:
Paih-io-A ERMOl). EXE A ER MO D
l'aih-io-A ERM()1). EXE A ERMO D runstream inputJlename
Path-to-AERMOD.EXE\AERMOD runstream input Jilename output Jilename
The first example above is applicable for all versions of AERMOD and assumes that the control input and
printed output files are AERMOD.INP and AERMOD.OUT (not case sensitive in DOS and case sensitive
on Unix and Linux systems). The other two examples apply to AERMOD versions beginning with 18081
in which the user can specify the control input filename and optionally the output filename as well. The
filenames can include a directory pathname if the files reside in a different directory than the working
directory. If the output filename is not specified, AERMOD will use the control input filename (including
pathname) and replace the input filenames extension (e.g., ".INP") with a ".OUT" extension. Otherwise,
if both files are specified, they can be in different locations. The important points are that the
AERMOD.EXE file either be in the directory from which you are attempting to run the model or in a
directory that is included on the DOS PATH command when the system is "booted-up." The control input
file (AERMOD.INP) must also be located in the directory which the model is being executed when the
control input filename is not specified. When the default control file and main output filenames are used
and reside in the working directory with AERMOD.EXE, the model can also be executed by double
clicking on the executable file from Windows Explorer.
As mentioned above, the SCRAM PC-executable file for AERMOD opens the input and output
files explicitly. One reason for this is to allow for the model to write an update on the status of processing
to the PC terminal screen. For the AERMOD model, the model first indicates that setup information is
being processed and then gives the Julian day currently being processed. If no status message is
displayed, then the model did not load into memory properly. If the model stops after completing the
setup processing, then the RUNORNOT option was set NOT to run. If a fatal error is encountered during
the setup processing, then a message to that effect will be written to the screen and model execution will
be stopped. Another reason for not sending the printed output to the default output device (i.e., to the
screen or redirected to a file), is so that any DOS error messages will be visible on the screen and not be
2-32
-------
written to the printed file. One such message might be that there is insufficient memory available to run
the program. Handling of DOS error messages may require some knowledge of DOS, unless the meaning
of the message is obvious.
The order of contents and organization of the main output file for the AERMOD model is
presented in Figure 2-5.
Echo of Input Control File Commands
Summary of Control File Messages
Summary of Inputs
Summary of Modeling Options
Summary of Source Data Summary of
Receptor Data Summary of
Meteorology Data
Model Results
Daily Results for Each Averaging Period Selected for Each Day Processed (If Applicable)
- DAYTABLE Keyword
PERIOD Results for Each Source Group (If Applicable)
- PERIOD Parameter on AVERTIME Keyword
Short-Term Average Results (High, Second High, etc.) by Receptor for Each Source
Group (If Applicable)
- RECTABLE Keyword
Overall Maximum Short-Term Average Results for Each Source Group (If
Applicable)
- MAXTABLE Keyword
Summary Tables of High Values for Each Averaging Period and Source Group (Always provided if
PERIOD averages or the RECTABLE keyword are used)
Summary of Complete Model Execution Messages
Figure 2-5. Organization of the AERMOD Model Output File
2-33
-------
Each page of the output file, except for the echo of the input file entries, is labeled with the model
name and version number, user-specified title(s), page number, and, for the PC version of the model, the
date and time of the particular run. Also included as part of the header information for each page is a one-
line summary of the modeling options used for that particular run. The modeling options are listed as the
secondary keywords used to control the options, such as DFAULT, CONC, etc.
Since the complete input file is normally echoed back as part of the output file, and since
processing of the inputs stops when the OU FINISHED card is reached, the run can be duplicated by
simply specifying the output filename as the input control file. Alternatively, the input records could be
"cut and pasted" from the output file to a separate file using a text editor.
By default, the model will echo each line of the input control file to the printed output file. This
provides a convenient record of the inputs as originally read into the model, without any rounding of
numerical values that may appear in the input summary tables. As noted above, it also means that the
output file can be used as an input file to the model to reproduce a particular application. However, for
some applications, the length of the input control file may be too cumbersome to include the entire set of
inputs at the beginning of each output file. This may happen, for example, if a large number of sources
are being defined or if a large number of discrete receptor locations are used. For this reason, the user is
provided with the option to "turn off' the echoing of the input file at any point within the control file.
This is accomplished by entering the keywords "NO ECHO" in the first two fields anywhere within the
control file. In other words, place NO in the pathway field, followed by a space and then ECHO. None
of the input control file options after the NO ECHO will be echoed to the output file. Thus, a user may
choose to place NO ECHO after the Control pathway in order to keep the control options echoed but
suppress echoing the rest of the input file.
The details of the message summary tables were discussed in the previous section. A portion of
the summary of modeling option inputs is shown in Figure 2-6 for the simple example described in this
section. The summary of source parameter input data includes separate tables for each source type, rather
than combining all sources onto a single table. In this way the column headings are specific to the source
type.
Figure 2-7 presents an example of the results output for the first highest values by receptor for our
sample problem. These values are the first highest 3-hour averages at each receptor location. The
number in parentheses following each concentration value is the date corresponding to each value. The
2-34
-------
date is given as an eight-digit integer variable that includes the year (2-digits), month, day, and hour
corresponding to the end of the averaging period.
For each of the different types of model result tables, the controlling keyword is identified in
Figure 2-5 at the end of the description. All of the outputs of the same type, e.g., high values by receptor,
are printed together, and the order of tables loops through all source groups for a particular averaging
period, and then loops through all averaging periods. The summary tables of high values at the end of the
model results follow the same order of loops. An example of the summary tables for our sample problem
is shown in Figure 2-8.
2-35
-------
+ + + AERMOD - VERSION 22112 A Simple Example Problem for the AERMOD-PRIME Model
*** 06/07/22
+ + + AERMET - VERSION 22112
*** MODELOPTs: NonDFAULT CONC FLAT RURAL SigA&SigW
*** 14:18:02
PAGE 1
*** MODEL SETUP OPTIONS SUMMARY
Model Options Selected:
* Model Allows User-Specified Options
* Model Is Setup For Calculation of Average CONCentration Values.
* NO GAS DEPOSITION Data Provided.
* NO PARTICLE DEPOSITION Data Provided.
* Model Uses NO DRY DEPLETION. DDPLETE = F
* Model Uses NO WET DEPLETION. WETDPLT = F
* Stack-tip Downwash.
* Model Assumes Receptors on FLAT Terrain.
* Use Calms Processing Routine.
* Use Missing Data Processing Routine.
* No Exponential Decay.
* Model Uses RURAL Dispersion Only.
* CCVR Sub - Meteorological data includes CCVR substitutions
* Model Assumes No FLAGPOLE Receptor Heights.
* The User Specified a Pollutant Type of: S02
**NOTE: Special processing reguirements applicable for the 1-hour S02 NAAQS have been disabled!!!
User has specified non-standard averaging periods: 3-HR 24-HR
High ranked 1-hour values are NOT averaged across the number of years modeled, and
complete years of data are NOT reguired.
**Model Calculates 2 Short Term Average(s) of: 3-HR 24-HR
and Calculates PERIOD Averages
Ĥ^This Run Includes: 1 Source(s); 1 Source Group(s); and 144 Receptor(s)
with: 1 POINT(s), including
0 POINTCAP(s) and 0 POINTHOR(s)
and: 0 VOLUME source(s)
and: 0 AREA type source(s)
and: 0 LINE source(s)
and: 0 RLINE/RLINEXT source(s)
and: 0 OPENPIT source(s)
and: 0 BUOYANT LINE source(s) with a total of 0 line(s)
and: 0 SWPOINT source(s)
**Model Set To Continue RUNning After the Setup Testing.
**The AERMET Input Meteorological Data Version Date: 22112
Ĥ^Output Options Selected:
Model Outputs Tables of PERIOD Averages by Receptor
Model Outputs Tables of Highest Short Term Values by Receptor (RECTABLE Keyword)
Model Outputs Tables of Overall Maximum Short Term Values (MAXTABLE Keyword)
**NOTE: The Following Flags May Appear Following CONC Values: c for Calm Hours
m for Missing Hours
b for Both Calm and Missing Hours
**Misc. Inputs: Base Elev. for Pot. Temp. Profile (m MSL) = 0.00 ; Decay Coef. = 0.000 ; Rot
Emission Units = GRAMS/SEC ; Emission Rate Unit Factor =
Output Units = MICROGRAMS/M* * 3
Angle = 0.0
0.10000E+07
Approximate Storage Reguirements of Model = 3.5 MB of RAM.
Figure 2-6. Sample of Model Option Summary Table from an AERMOD Model Output File
2-36
-------
*** AERMOD - VERSION 22112 *** *** A Simple Example Problem for the AERMOD-PRIME Model *** 06/07/22
*** AERMET - VERSION 22112 *** *** *** 14:18:02
PAGE 9
*** MODELOPTs: NonDFAULT CONG FLAT RURAL SigA&SigW
*** THE 1ST HIGHEST 3-HR AVERAGE CONCENTRATION VALUES FOR SOURCE GROUP: ALL ***
INCLUDING SOURCE(S): STACK1 ,
*** NETWORK ID: POL1 ; NETWORK TYPE: GRIDPOLR ***
CONC OF S02 IN MICROGRAMS/M* * 3
DIRECTION | DISTANCE (METERS)
(DEGREES) | 175.00 350.00 500.00 1000.00
10
0
1.60637
(88030212)
4.32183
(88030215)
9
87871
(88030215)
20.31341
(88030215
20
0
1.27691
(88030212)
7.75747
(88030215)
19
35471
(88030215)
43.24437
(88030215
30
0
1.31753
(88030321)
6.80000
(88030215)
16
96932
(88030215)
37 . 21008
(88030215
40
0
1.37996
(88030321)
2.78658
(88030215)
6
56111
(88030215)
13.02309
(88030215
50
0
1.41988
(88030321)
2.62563
(88030115)
4
10823
(88030115)
4 . 68748
(88030212
60
0
1.43198
(88030321)
2.82901
(88030115)
4
55254
(88030115)
4.68748
( 88030212
70
0
1.41464
(88030321)
8.49965
(88030115)
11
29511
(88030115)
11. 52741
( 88030115
80
0
2.58429
(88030115)
43.19500
(88030115)
48
25320
(88030115)
34 . 37546
( 88030115
90
0
7.93441
(88030115)
113.82878
(88030115)
143
17280
(88030115)
83.53515
( 88030115
100
0
49.08751
(88030112)
182.84906
(88030115)
220
83958
(88030115)
145.67442
( 88030115
110
0
112.74908
(88030112)
242.27766
(88030112)
278
47896
(88030115)
163.85177
( 88030115
120
0
133.57972
(88030112)
303.36789
(88030112)
329
96015
(88030112)
201.18211
( 88030112
130
0
84.37463
(88030112)
177.43472
(88030112)
193
23411
(88030112)
123.90900
(88030112
140
0
34.33105
(88030112)
78.48757
(88030115)
90
16431
(88030115)
66.26935
(88030112
150
0
3.26313
(88030112)
28 . 20306
(88030115)
35
81299
(88030112)
33.54932
(88030112
160
0
1.45757
(88030209)
8 . 53192
(88030112)
13
46873
(88030112)
12.93284
(88030112
170
0
1.33663
(88030209)
2 . 92150
(88030112)
4
70642
(88030112)
9. 87872
(88030415
180
0
1.23781
(88030212)
2 .59400
(88030115)
4
58665
(88030415)
11. 25826
(88030415
190
0
1.23781
(88030212 )
2.62640
(88030115)
4
10607
(88030115)
6.95118
( 88030415
200
0
1.23781
(88030212)
2.63486
(88030115)
4
10609
(88030115)
4.68748
( 88030212
210
0
1.23781
(88030212)
2.63700
(88030115)
4
10609
(88030115)
4.68748
( 88030212
220
0
1.23783
(88030212)
2.63762
(88030115)
4
10609
(88030115)
4 . 68748
( 88030212
230
0
1.26732
(88030212)
2.63762
(88030115)
4
10609
(88030115)
4.68767
(88030212
240
0
1.59395
(88030212)
2.63762
(88030115)
4
10609
(88030115)
4 .72694
(88030212
250
0
2.39221
(88030212 )
2.63762
(88030115)
4
10609
(88030115)
5.24318
( 88030212
260
0
3.44586
(88030212)
3.11001
(88030212)
4
10609
(88030115)
7 .70339
(88030212
270
0
4.67900
(88030212)
4.53914
(88030212)
4
60912
(88030212)
13.41550
(88030212
280
0
6.10725
(88030212)
6.15657
(88030212)
6
42897
(88030212)
21.16129
(88030212
290
0
7.47165
(88030212)
7 .75530
(88030212)
8
18188
(88030212)
27 .76976
(88030212
300
0
8.45754
(88030212)
8 . 93592
(88030212)
9
35713
(88030212)
30.22723
(88030212
310
0
8.83767
(88030212)
9.29972
(88030212)
9
54143
(88030212)
27 .40028
(88030212
320
0
8.53526
(88030212 )
8.67663
(88030212)
8
65382
(88030212)
20.68075
(88030212
330
0
7.53807
(88030212)
7.17470
(88030212)
6
91694
(88030212)
13.22924
(88030212
340
0
5.96054
(88030212)
5.15139
(88030212)
4
78244
(88030212)
8.04861
(88030212
350
0
4.10326
(88030212)
3.16494
(88030212)
4
10609
(88030115)
5.75319
(88030212
360
0
2.52862
(88030212)
2 . 63762
(88030115)
4
10609
(88030115)
4 . 96113
(88030212
Figure 2-7. Example Output Table of High Values by Receptor
2-37
-------
***
AERMOD -
VERSION
22112 *** *** A Simple
Example Problem
for the AERMOD-PRIME Model
***
06/07
722
***
AERMET -
VERSION
22112 *** ***
***
14 :18
02
PAGE
15
***
MODELOPTs
: NonDFAULT CONC FLAT RURAL
SigA&SigW
*** THE
SUMMARY OF MAXIMUM PERIOD ( 9 6 HRS) RESULTS
***
** CONC OF
302 IN MICROGRAMS/M**3
**
NETWORK
GROUP ID
AVERAGE CONC
RECEPTOR (XR, YR, ZELEV, ZHILL,
Z FLAG)
OF
TYPE
GRID-
ID
ALL
1ST
HIGHEST
VALUE IS 24 .85173 AT
( 433.01,
-250.00, 0.00, 0.
00,
0
. 00
GP
POL1
2ND
HIGHEST
VALUE IS 23.13772 AT
( 469.85,
-171.01, 0.00, 0.
00,
0
. 00
GP
POL1
3RD
HIGHEST
VALUE IS 21.03529 AT
( 303.11,
-175.00, 0.00, 0.
00,
0
. 00
GP
POL1
4 TH
HIGHEST
VALUE IS 19.33506 AT
( 328.89,
-119.71, 0.00, 0.
00,
0
. 00
GP
POL1
5TH
HIGHEST
VALUE IS 17.19044 AT
( 383.02,
-321.39, 0.00, 0.
00,
0
. 00
GP
POL1
6TH
HIGHEST
VALUE IS 16.86865 AT
( 866.03,
-500.00, 0.00, 0.
00,
0
. 00
GP
POL1
7 TH
HIGHEST
VALUE IS 15.01122 AT
( 939.69,
-342.02, 0.00, 0.
00,
0
. 00
GP
POL1
8 TH
HIGHEST
VALUE IS 14 .27336 AT
( 268.12,
-224.98, 0.00, 0.
00,
0
. 00
GP
POL1
9TH
HIGHEST
VALUE IS 12.80321 AT
( 492.40,
-86.82, 0.00, 0.
00,
0
. 00
GP
POL1
10TH
HIGHEST
VALUE IS 12 .38150 AT
( 766.04,
-642.79, 0.00, 0.
00,
0
. 00
GP
POL1
***
RECEPTOR
TYPES:
GC = GRIDCART
GP = GRIDPOLR
DC = DISCCART
DP = DISCPOLR
***
AERMOD -
VERSION
22112 *** *** A Simple
Example Problem
for the AERMOD-PRIME Model
***
06/07/
22
***
AERMET -
VERSION
22112 *** ***
***
14 :18
02
PAGE
16
***
MODELOPTs
: NonDFAULT CONC FLAT RURAL
SigA&SigW
*** THE SUMMARY
OF HIGHEST 3-HR RESULTS **
*
** CONC OF
302 IN MICROGRAMS/M**3
**
DATE
NETWORK
GROUE
ID
AVERAGE CONC
(YYMMDDHH)
RECEPTOR (XR, YR
, ZELEV,
ZHILL, Z
FLAG)
OF
TYPE
GRID-ID
ALL
HIGH
1ST HIGH VALUE IS 329.96015
ON 88030112: AT
( 433.01, -250.00,
0 .
0
0,
0 .
00,
0 .00
) GP
POL1
HIGH
2ND HIGH VALUE IS 261.07805
ON 88030112: AT
( 469.85, -171.01,
0 .
0
o,
0 .
00,
0 .00
) GP
POL1
***
RECEPTOR
TYPES:
GC = GRIDCART
GP = GRIDPOLR
DC = DISCCART
DP = DISCPOLR
***
AERMOD -
VERSION
22112 *** *** A Simple
Example Problem
for the AERMOD-PRIME Model
***
06/07
722
***
AERMET -
VERSION
22112 *** ***
***
14 :18
02
PAGE
17
MODELOPTs
: NonDFAULT CONC FLAT RURAL
SigA&SigW
2-38
-------
*** THE SUMMARY OF HIGHEST 24-HR RESULTS ***
** CONC OF
S02 IN MICROGRAMS/M**3
**
DATE
NETWORK
GROUP ID
AVERAGE CONC
(YYMMDDHH)
RECEPTOR (XR, YR,
ZELEV, ZHILL, ZFLAG)
OF
TYPE
GRID-ID
ALL HIGH
1ST
HIGH
VALUE IS 88.89517
ON 88030124 :
AT ( 433.01, -250.00,
o
o
o
o
o
o
0 .00
GP
P0L1
HIGH
2ND
HIGH
VALUE IS 10.09519
ON 88030324 :
AT ( 866.03, -500.00,
o
o
o
o
o
o
0 .00
GP
P0L1
*** RECEPTOR
TYPES
GO
= GRIDCART
GP
= GRIDPOLR
DC
= DISCCART
DP
= DISCPOLR
Figure 2-8. Example of Result Summary Tables for the AERMOD Model
2-39
-------
2.5 Modifying an existing control file
As noted earlier, one of the advantages of the keyword/parameter approach and the flexible format
adopted for the input control file is that it will be easier for the user to make modifications to the control file
and obtain the desired result. This section briefly illustrates some examples of how a control file can be
modified. It is assumed that the reader is familiar with the operation of and basic editing commands for a
text editor (i.e., a program that edits ASCII files), and is familiar with the previous sections of this tutorial.
2.5.1 Modifying modeling options
Depending on the type of analysis being performed, the user may need to modify the modeling
options and run the model again. Because of the descriptive nature of the keywords and the secondary
keywords used to control the modeling options, this can easily be done with the new control file, and usually
without having to refer back to the user's guide each time a modification is attempted.
2.5.2 Adding or modifying a source or source group
Modifying the input file to add a source or a source group, or to add a source to a source group, is as
simple as just adding it. There is no need to specify the total number of sources in the run, which would then
have to be changed if more sources were added. The same applies to the number of groups, or the number of
sources per group. If the user attempts to input more than the total number of sources or groups allowed for
a particular run, an error message will be generated to that effect. Also, modifying a source group to delete a
source is as easy as just deleting it from the input card, without having to change any other inputs.
Another way of "deleting" a source or a group from an input file is to place a "**" in the pathway
field of the card or cards which define the source or group to "comment out" those inputs. This approach,
which was discussed above in Section 2.2.2, has the advantage of leaving the input data for the source or
group in the input file for possible later use. It doesn't matter whether the "**" is entered with the text editor
in "insert" mode, in which case the other inputs of that line are moved over, or if it is in "overtype" mode,
which would replace the pathway ID that was already there.
2.5.3 Adding or modifying a receptor network
As with source data, adding to or modifying the receptor information in the AERMOD model is
relatively straight forward. The problem of having to make several changes to accomplish one small
modification, such as adding a distance to a polar receptor network, has been avoided in the new model. All
2-40
-------
that the user needs to do is to add the new distance on the appropriate input card, which is easily identifiable
because of the use of descriptive keywords. The model checks to ensure that the user does not attempt to
specify more than the maximum number of receptors for a particular run and generates an appropriate
message if too many are input.
2.5.4 Modifying output options
Modifying the output options involves many of the same principles that are described above. In
addition, all the output options are structured in a way that allows the user to select options for specific
averaging periods, so that the user may find it useful to copy a record or group of records set up for one
averaging period and simply change the averaging period parameter. The other important short cut that is
available for the printed table output options is to use the secondary keyword ALLAVE to indicate that the
option applies to all averaging periods that are calculated. In this way, there will be no need to change the
output options if a new averaging period is added to a run or if one is deleted.
2-41
-------
3.0 Detailed keyword reference
This section of the AERMOD user's guide provides a detailed reference for all the input keyword
options for the AERMOD model. The information provided in this section is more detailed than the
information provided in the Brief Tutorial in Section 2.0. Since this section is intended to meet the needs of
experienced modelers who may need to understand completely how particular options are implemented in
the model, the information for each keyword should stand on its own. This section assumes that the reader
has a basic understanding of the keyword/parameter approach used by the model for specification of input
options and data. Novice users should first review the contents of Section 2.0 to obtain that understanding.
3.1 Overview
The information in this section is organized by function, i.e., the keywords are grouped by pathway,
and are in a logical order based on their function within the model. The order of keywords presented here is
the same as the order used in the functional keyword reference in APPENDIX A. The syntax for each
keyword is provided, and the keyword type is specified - either mandatory or optional and either repeatable
or non-repeatable. Unless noted otherwise, there are no special requirements for the order of keywords
within each pathway, although the order in which the keywords are presented here and in APPENDIX A is
recommended. Any keyword which has special requirements for its order within the pathway is so noted
following the syntax and type description.
The syntax descriptions in the following sections use certain conventions. Parameters that are in all
capital letters and underlined in the syntax description are secondary keywords that are to be entered as
indicated for that keyword. Other parameters are given descriptive names to convey the meaning of the
parameter and are listed with an initial capital letter. Many of the parameter names used correspond to
variable names used in the computer code of the model. Parentheses around a parameter indicate that the
parameter is optional for that keyword. The default that is taken when an optional parameter is left blank is
explained in the discussion for that keyword.
3-1
-------
3.2 Control pathway inputs and options
The COntrol pathway contains the keywords that provide the overall control of the model run.
These include the dispersion options, averaging time options, terrain height options, and others that are
described below. The CO pathway must be the first pathway in the control input file.
3.2.1 Title information
There are two keywords that allow the user to specify up to two lines of title information that will
appear on each page of the main output file from the model. The first keyword, TITLEONE, is mandatory,
while the second keyword, TITLETWO, is optional. The syntax and type for the keywords are summarized
below:
CO TITLEONE Title 1
Syntax:
CO TITLETWO Title2
TITLEONE - Mandatory, Non-repeatable
Type
TITLETWO - Optional, Non-repeatable
The parameters Title 1 and Title2 are character parameters of length 200, which are read as a single field
starting at column 13. The title information is taken as it appears in the control file without any conversion
of lower case to upper case letters. If the TITLETWO keyword is not included in the control file, then the
second line of the title in the output file will appear blank. Note that in the output files, only the first 68
characters of TITLEONE and TITLETWO are printed.
3.2.2 Dispersion options
The dispersion options are controlled by the MODELOPT keyword on the CO pathway and are
specified using secondary keywords that represent each of the different options. The secondary keywords
and syntax are shown and described below. Some related options are mutually exclusive, others can be
specified in combination with each other, and some are dependent on others and must be specified together.
3-2
-------
Syntax:
CO MODELOPT
DFAULT ALPHA BETA CONG AREADPLT FLAT NOSTD NOCHKD NOWARN SCREEN SCIM N0MIN03 RLINEFDH
ELEV WARNCHKD NOURBTRAN VECTORWS PSDCREDIT FASTALL FASTAREA GSRM TTRM TTRM2 PVMRM OLM
ARM2 DEPOS DDEP WDEP DRYDPLT WETDPLT NODRYDPLT NOWETDPLT AREAMNDR HBP
Type:
Mandatory, Non-repeatable
Order:
Must precede POLLUTID, HALFLIFE and DCAYCOEF
where the secondary keyword parameters are described below (the order and spacing of these parameters is
not critical):
DFAULT -
ALPHA -
BETA-
CONC-
DEPOS-
DDEP -
WDEP -
AREADPLT
FLAT-
ELEV-
Specifies that the regulatory default options will be used; note that specification
of the DFAULT option will override some non-DFAULT options that may be
specified in the input file, while other non-DFAULT options will cause fatal
errors when DFAULT is specified (see below for details).
Non-regulatory option flag that allows the input control file to include
research/experimental options for review and evaluation by the user community;
(e.g., LOW WIND, PSDCREDIT, ORD DWNW. AWMADWNW,
PLATFORM, METHOD 2 particle deposition, gas deposition, RLINEFDH, and
RLINEXT with options for modeling barriers and depressed roadways) and
cannot be used with DFAULT keyword.
Non-regulatory option flag that allows the input control file to include options
that have been vetted through the scientific community and are waiting to be
promulgated as regulatory options. Prior to promulgation, BETA options require
alternative model approval for use in regulatory applications and cannot be used
with DFAULT keyword.
Specifies that concentration values will be calculated.
Specifies that total deposition flux values (both dry and wet) will be calculated.
Specifies that dry deposition flux values will be calculated.
Specifies that wet deposition flux values will be calculated.
Specifies that a non-regulatory method for optimized plume depletion due to dry
removal mechanisms will be included in calculations for area sources (cannot be
used simultaneously with the DFAULT keyword).
Specifies that the non-regulatory option of assuming flat terrain will be used;
Note that FLAT and ELEV may be specified in the same model run to allow
specifying the non-regulatory FLAT terrain option on a source-by-source basis;
FLAT sources are identified by specifying the keyword FLAT in the
MODELOPT line on the CO pathway and in place of the source elevation field
on the SO LOCATION keyword (cannot be used simultaneously with the
DFAULT keyword).
Specifies that the default option of assuming elevated terrain will be used; Note
that FLAT and ELEV may be specified in the same model run to allow
3-3
-------
specifying the non-regulatory FLAT terrain option on a source-by-source basis
(the ELEV option is set as a regulatory option with the DFAULT keyword)
NOSTD - Specifies that the non-regulatory option of no stack-tip downwash will be used
(cannot be used with the DFAULT keyword).
NOCHKD - Specifies that the non-regulatory option of suspending date checking will be
used for non-sequential meteorological data files (cannot be used with the
DFAULT keyword).
WARNCHKD - Specifies that the option of issuing warning messages rather than fatal errors
will be used for non-sequential meteorological data files.
NO WARN - Specifies that the option of suppressing the detailed listing of warning messages
in the main output file will be used (the number of warning messages is still
reported, and warning messages are still included in the error file controlled by
the CO ERRORFIL keyword).
SCREEN - Non-regulatory option for running AERMOD in a screening mode for
AERSCREEN (cannot be used when the DFAULT keyword is specified).
SCIM - Sampled Chronological Input Model - non-regulatory option used only with the
ANNUAL average option to reduce runtime by sampling meteorology at a user-
specified regular interval; SCIM sampling parameters must be specified on the
ME pathway (cannot be used with the DFAULT keyword).
PVMRM - Specifies that the Plume Volume Molar Ratio Method (PVMRM) for NO2
conversion will be used (regulatory option, can be used simultaneously with
DFAULT); cannot be used with OLM, ARM2, or GRSM; cannot be used with
TTRM without TTRM2.
Specifies that the Ozone Limiting Method (OLM) for NO2 conversion will be
used (regulatory option, can be used simultaneously with DFAULT keyword);
cannot be used with PVMRM, ARM2, or GRSM; cannot be used with TTRM
without TTRM2.
Specifies that the Ambient Ratio Method - 2 (ARM2) for NO2 conversion will
be used (regulatory option, can be used with DFAULT keyword); cannot be used
with PVMRM, OLM, or GRSM; cannot be used with TTRM without TTRM2.
Specifies that the non-regulatory Travel Time Reaction Method (TTRM) will be
used for NO2 conversion (non-regulatory ALPHA option, requires the ALPHA
keyword and cannot be used with the DFAULT keyword); cannot be used with
PVMRM, OLM, ARM2 without TTRM2; cannot be used with GRSM; cannot
be used with TTRM2 without PVMRM, OLM, or ARM2.
Specifies that the non-regulatory Travel Time Reaction Method (TTRM) will be
paired with one of OLM, PVMRM, or ARM2 for NO2 conversion (non-
regulatory ALPHA option, requires the ALPHA keyword and cannot be used
with the DFAULT keyword); cannot be used with TTRM alone or GRSM; must
be paired with one of PVMRM, OLM, or ARM2 and does not require TTRM
keyword when pairing.
Specifies that the Generic Reaction Set Method (GRSM) will be used for NO2
conversion; cannot be used with PVMRM, OLM, TTRM, TTRM2, or ARM2.
OLM-
ARM2 -
TTRM -
TTRM2 -
GRSM -
3-4
-------
PSDCREDIT -
FASTALL-
FASTAREA -
DRYDPLT -
NODRYDPLT
WETDPLT -
NOWETDPLT -
NOURBTRAN -
VECTORWS -
NOMINQ3 -
Specifies that the non-regulatory ALPHA option will be used to calculate the
increment consumption with PSD credits using the PVMRM option (cannot be
used with the DFAULT keyword).
Non-regulatory option to optimize model runtime through use of an alternative
implementation of horizontal meander for POINT and VOLUME sources; also
optimizes model runtime for AREA/AREAPOLY/AREACIRC/LINE,
OPENPIT, RLINE, and RLINEXT sources (formerly associated with TOXICS
option, now controlled by the FASTAREA and FASTALL option, cannot be
used with the DFAULT keyword).
Non-regulatory option to optimize model runtime through hybrid approach for
AREA/AREAPOLY/AREACIRC and OPENPIT sources (formerly associated
with TOXICS option, cannot be used with the DFAULT keyword).
Option to incorporate dry depletion (removal) processes associated with dry
deposition algorithms; this requires specification of dry deposition source
parameters and additional meteorological variables; dry depletion will be used
by default if dry deposition algorithms are invoked; cannot be used with
NODRYDPLT.
Option to disable dry depletion (removal) processes associated with dry
deposition algorithms; cannot be used with DRYDPLT.
Option to incorporate wet depletion (removal) processes associated with wet
deposition algorithms; this requires specification of wet deposition source
parameters and additional meteorological variables; wet depletion will be used
by default if wet deposition algorithms are invoked; cannot be used with
NOWETDPLT.
Option to disable wet depletion (removal) processes associated with wet
deposition algorithms; cannot be used with WETDPLT.
Non-regulatory option to ignore the transition from nighttime urban boundary
layer to daytime convective boundary layer (i.e., to revert to the urban option as
implemented prior to version 11059) (cannot be used with the DFAULT
keyword).
Option to specify that input wind speeds are vector mean (or resultant) wind
speeds, rather than scalar means. Under the VECTORWS option, the
adjustments to wind speeds based on Equation 112 of the AERMOD Model
Formulation document (EPA, 2024a) will be applied (can be used with the
DFAULT keyword).
Option to remove the minimum ozone used for Tier 2 & 3 NO2 options. Without
this option, AERMOD will use a minimum value of 40 ppb of ozone for
nighttime stable conditions, regardless of the value in an hourly input file (can
be used with the DFAULT keyword).
RLINEFDH - Option to have wind profile calculations without a displacement height for
RLINE and RLINEXT source types. This makes the wind profile closer to other
AERMOD source types, which do not use a displacement height in wind profile
(requires the ALPHA keyword and cannot be used with the DFAULT keyword).
3-5
-------
AREAMNDR - Option to apply plume meander to AREA. AREAPOLY, AREACIRC, and LINE
source types. Note that AREAMNDR and FASTAREA or FASTALL can be
specified in the same model run, but in that case, meander will not be applied to
those source types listed,
HBP - Option for highly buoyant plumes (HBP) when plume penetrates the top of the
mixed layer. Limited to point source types (POINT, POINTHOR, POINTCAP).
Compares convective mixing height for the current hour and next hour to
determine how much of the penetrated plume has been captured by the CBL by
the end of the current hour (requires the ALPHA keyword and cannot be used
with the DFAULT keyword).
3.2.2.1 DFAULT option
As previously discussed, the regulatory DFAULT option in AERMOD informs the model that certain
regulatory options will be invoked including stack-tip downwash, effects of elevated terrain, and calms and
missing data processing. The DFAULT option in AERMOD also forces the use of a 4-hour half-life when
modeling SO2 in an urban source and does not allow for exponential decay for other applications. If
exponential decay is requested via the DCAYCOEFF or HALFLIFE keyword, AERMOD will issue a
warning that the DFAULT overrides the requested exponential and will run the model without exponential
decay. If exponential decay is desired, then the DFAULT keyword cannot be included. The DFAULT option
also imposes a restriction on the optional urban roughness length parameter to be 1 meter for regulatory
applications. If the urban roughness length parameter is not 1 m with the DFAULT keyword, AERMOD
issues a warning and resets it to 1 m.
The missing data processing routines that are included in the AERMOD model allow the model to
handle missing meteorological data in the processing of short-term averages. The model treats missing
meteorological data in the same way as the calms processing routine, i.e., it sets the concentration values to
zero for that hour and calculates the short-term averages according to EPA's calms policy, as set forth in the
Guideline. Calms and missing values are tracked separately for the purpose of flagging the short-term
averages. An average that includes a calm hour is flagged with a 'c', an average that includes a missing hour
is flagged with an'm', and an average that includes both calm and missing hours is flagged with a 'b'. If the
number of hours of missing meteorological data exceeds 10 percent of the total number of hours for a given
model run, a cautionary message is written to the main output file, and the user is referred to Section 5.3.2 of
"Meteorological Monitoring Guidance for Regulatory Modeling Applications" (EPA, 2004). An hour is
considered missing if one or more of the following surface variables have missing value indicators for the
hour: wind speed, wind direction, ambient temperature, Monin-Obukhov length, mechanical mixing height,
3-6
-------
surface friction velocity (u*), convective mixing height (convective hours only), or convective velocity scale
(w*; for convective hours only).
The DFAULT keyword cannot be used simultaneously with either the ALPHA or BETA secondary
keywords or other secondary keywords that enable a specific ALPHA or BETA option.
3.2.2.2 ALPHA options
Beginning with version 18081, a new secondary keyword, ALPHA, was added to the MODELOPT
keyword. When included, ALPHA indicates one or more options are being used that are in a special category
of options. These can include but are not limited to:
Scientific/formulation updates that are in the research phase and have not been fully evaluated
and peer reviewed by the scientific community; and
Non-scientific model options in development that still need rigorous testing and for which EPA
is seeking feedback from the user community.
Different ALPHA options are enabled in the control file in different ways. Some ALPHA options, as
indicated above, are enabled by specifying the appropriate secondary keyword with the MODELOPT
keyword, while others are specified as either a primary keyword on the CO pathway (e.g., LOW_WIND,
AWMADWNW) or as source type with the LOCATION keyword (e.g., RLINEXT, SWPOINT) on the SO
pathway or as a primary keyword on the SO pathway to enter source-specific inputs (e.g., PLATFORM,
RBARRIER). AERMOD version 24142 includes the following ALPHA options:
Prevention of Significant Deterioration Credit (PSDCREDIT)
Low Wind Parameters (LOW WIND)
A&WMA Downwash Options (AWMADWNW)
EPA Office of Research and Development Downwash Options (ORDDWNW)
Offshore Platform Downwash (PLATFORM, applies to point sources only)
Extended RLINE Source Type (RLINEXT)
Depressed Roadway (RDEPRESS, used only with RLINEXT)
Roadway Barrier (RBARRIER, used only with RLINEXT)
Removal of Displacement Height from RLINE Wind Profile (RLINEFDH)
Particle Deposition - Method 2 (METHOD 2)
3-7
-------
Gas deposition (GDSEASON, GDLANUSE, GASDEPDF, GASDEPOS, GASDEPVD
keywords)
Travel Time Reaction Method (TTRM, for NO2 conversion, stand-alone method)
Travel Time Reaction Method 2 (TTRM2, for NO2 conversion, applies TTRM to ARM2, OLM,
or PVMRM conversion methods)
Sidewash Point Source (SWPOINT, experimental source type)
AREA Source Meander (AREAMNDR)
Highly Buoyant Plume (HBP)
Aircraft Plume Rise (ARCFTOPT, can be applied to AREA and VOLUME source types only via
SO ARCFTSRC grouping and an hourly emission file)
As noted above, METHOD 2 particle deposition and gas deposition are ALPHA options beginning
with version 19191 of AERMOD. In previous versions of AERMOD, these two deposition options were
non-default and could be used without the ALPHA or BETA keywords. The reason that these two options
are now ALPHA options is that they have not been rigorously tested and evaluated since their inclusion in
AERMOD's initial promulgation. Thus, it was decided to make the options ALPHA while deposition is
further evaluated in AERMOD. Note that METHOD 1 particle deposition is unaffected and can still be used
with AERMOD in default mode (i.e., with the DFAULT keyword).
3.2.2.3 BETA options
BETA options refer to scientific updates to the formulation of AERMOD that have been fully vetted
through the scientific community with appropriate evaluation and peer review. BETA options are planned
for future promulgation as regulatory options. However, until they are promulgated, they require alternative
model approval by the EPA Regional Office and concurrence by the Model Clearing House. AERMOD
version 24142 does not include any BETA options.
3.2.2.4 Options for capped and horizontal stack releases
Options are included in AERMOD, beginning with version 06341, for modeling releases from
capped and horizontal stacks. For sources that are not subject to building downwash influences, the plume
rise for these capped and horizontal stacks is simulated based on an EPA Model Clearinghouse
Memorandum, dated July 9, 1993. The Model Clearinghouse procedure for these sources entails setting the
exit velocity very low (0.001 m/s) to account for suppression of vertical momentum of the plume and using
an effective stack diameter that maintains the actual flow rate of the plume. Maintaining the flow rate will
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also serve to maintain the buoyancy of the plume to provide a more realistic estimate of plume rise. The
Model Clearinghouse procedure also addresses the issue of stack-tip downwash for these cases.
The Model Clearinghouse procedure is not considered to be appropriate for sources subject to
building downwash influences with the PRIME downwash algorithm for the following reason. The PRIME
algorithm uses the specified stack diameter to define the initial radius of the plume for the numerical plume
rise calculation, and the initial radius of the plume can significantly influence plume rise based on the
PRIME algorithm. As a result, use of an effective diameter adjusted to maintain the flow rate is not
appropriate and could produce unrealistic results. For PRIME downwash sources modeled using the options
for capped and horizontal releases, the basic premise of the Model Clearinghouse procedure, i.e., that the
vertical momentum is suppressed while the buoyancy of the plume is conserved has been adapted for the
PRIME numerical plume rise formulation. For capped stacks the initial radius of the plume is assumed to be
2 times the actual stack diameter to account for the interaction of the exiting plume with the cap. The initial
vertical velocity of the plume is set at 0.001 m/s, and the initial lateral velocity of the plume is set at 25% of
the initial exit velocity of the plume. For horizontal stacks, the initial vertical velocity of the plume is set at
0.001 m/s, the total exit velocity of the plume is assigned to the initial lateral velocity, and the plume is
assumed to be emitted in the downwind direction. Although this adaptation of the Model Clearinghouse
procedure to PRIME downwash sources has not been validated by field tracer or wind tunnel data, analyses
have shown that simply setting the exit velocity to 0.001 m/s without any further adjustment when
downwash is applied, as suggested in Section 6.1 of the AERMOD Implementation Guide (EPA, 2024b),
may lead to overly conservative results (EPA, 2007).
The user selects the options for capped and/or horizontal releases by specifying one of the new
source types on the SO LOCATION card: POINTCAP for capped stacks, and POINTHOR for horizontal
releases. For each of these options, the user specifies the actual stack parameters [release height (m), exit
temperature (K), exit velocity (m/s), and stack diameter (m)] using the SO SRCPARAM card as if the release
were a non-capped vertical point source. The syntax of the SO LOCATION and SRCPARAM keywords is
described in Sections 3.3.1 and 3.3.2 and is also summarized in APPENDIX A. The AERMOD model
performs the necessary adjustments internally to account for plume rise and stack-tip downwash. For
horizontal releases, the model currently assumes that the release is oriented with the wind direction, and the
model does not account for directional effects that may occur with horizontal releases. The model also does
not account for stacks oriented at a non-horizontal angle relative to vertical. For PRIME downwash sources,
the user-specified exit velocity for horizontal releases is treated initially as horizontal momentum in the
downwind direction.
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3.2.2.5 Output types (CONC. DEPPS. DDEP and/or WDEP)
The user may select any or all of the output types (CONC, DEPOS, DDEP and/or WDEP) to be
generated in a single model run. The order of these secondary keywords on the MODELOPT card has no
effect on the order of results in the output files - the outputs will always be listed in the order of CONC,
DEPOS, DDEP, and WDEP. Appropriate deposition parameters must be specified in order to output
deposition fluxes using the DEPOS, DDEP, and/or WDEP keywords (see Sections 3.3.3 and 3.3.4 for more
details). Deposition has not been implemented for RLINE/RLINEXT, BUOYLINE, or SWPOINT source
types, thus the user can only run CONC with these source types.
3.2.2.6 Deposition depletion options
Beginning with version 04300, the dry and wet removal (depletion) mechanisms (the DRYDPLT and
WETDPLT options in earlier versions of AERMOD) will automatically be included in the calculated
concentrations or deposition flux values if the dry and/or wet deposition processes are considered, unless the
user specifies the NODRYDPLT and/or NOWETDPLT options. Note that dry and wet removal effects on
calculated concentration values can be included even if deposition flux values are not being calculated.
However, the additional data requirements for dry and wet deposition, described in Sections 3.3.3 and 3.3.4,
must be met in order for dry and wet removal to be included in the concentration calculations. The use of the
NODRYDPLT and/or NOWETDPLT options will result in a more conservative estimate of concentrations
and/or deposition fluxes for applications involving deposition processes, but the degree of additional
conservatism will vary depending on the source characteristics, meteorological conditions, receptor locations
and terrain influences. However, the inclusion of particle deposition effects may increase ground-level
concentrations for some sources compared to the same source modeled as a gaseous emission due to
gravitational settling on the particulate plume. The magnitude of this effect will depend on the source
characteristics (elevated or low-level) and particle size distribution. As of version 19191, deposition has not
been implemented for RLINE/RLINEXT, BUOYLINE, or SWPOINT sources, thus the user can only run
CONC with these source types.
3.2.2.7 NO?conversion options
Beginning with version 16216r, the PVMRM and OLM Tier 3 NO2 conversion methods, as well as
the Tier 2 ARM2 method are regulatory options that can be specified with the DFAULT keyword. PVMRM,
OLM, and ARM2 assume the reaction involving NO and available O3 to form NO2 occurs instantaneously.
Although this chemical reaction is relatively rapid, it is not actually instantaneous and depends on the
transport time to the downwind receptor of interest. Beginning with version 21112, TTRM was added as an
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ALPHA option for NO2 conversion that considers the distance and the travel time from the emission source
to each receptor. In general, much of the conversion of NO to NO2 occurs within the first minute of travel
which limits the effectiveness of this method to the near field receptors.
In version 21112, TTRM, the Travel Time Reaction Method, was implemented as a stand-alone
ALPHA option which can determine the initial fraction of NO to NO2 conversion in the travel time of each
source emissions to each receptor. The conversion is capped at an upper limit, which is typically reached
after a few tens of seconds of plume travel. Beyond the distance the fraction reaches the upper limit of the
equilibrium fraction (generally 0.9), TTRM is no longer effective, and another method is needed for
receptors beyond that distance. Beginning with version 22112, TTRM was integrated to be used
simultaneously with PVMRM, OLM, or ARM2. This integration was added as the ALPHA option, TTRM2,
separate from TTRM which was retained as a stand-alone option. When TTRM2 is specified along with
PVMRM, OLM, or ARM2, TTRM will be implemented for near field receptors where the fraction of
conversion has not reached the upper limit, and the other specified method will be used for all other
receptors.
In addition to TTRM and TTRM2, beginning with version 21112, GRSM, the Generic Reaction Set
Method, was added as an ALPHA option, updated as a BETA option beginning with version 22112, and
promulgated as a regulatory option in version 24142. GRSM was adapted from the Atmospheric Dispersion
Model Method (ADMSM), documented by Carruthers et al., 2017, which accounts for the equilibrium
between NO, NO2, and ozone in the atmosphere. GRSM treats plume entrainment of ozone similar to
PVMRM but provides for treatment of reaction rates based on ozone and solar radiation intensity, N02
photolysis, and travel time from source to receptor. The reaction rate is based on the generic reaction set
(GRS) chemistry scheme, which is a semi-empirical photochemical model developed originally by CSIRO in
Australia (Azzi and Johnson, 1992; Venkatram et al., 1994) for multiple step conversions between NO, NO2,
and O3. The integration of GRSM into AERMOD is documented in EPA's related Technical Support
Document (TSD) (2024d).
Only one of ARM2, TTRM, OLM, PVMRM, or GRSM options for NO2 conversion can be specified
for a given model run. Alternatively, the TTRM2 ALPHA option (which invokes TTRM), can be paired with
ARM2, OLM, or PVMRM by specifying the TTRM2 keyword along with the ARM2, PVMRM, or OLM
with the MODELOPT keyword. Because GRSM accounts for travel time between the emission source and
receptor, it cannot be paired with TTRM2. All NO2 conversion options require that the pollutant ID be
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specified as 'N02' on the CO POLLUTID card (see Section 3.2.9.) These options have additional input
requirements as described in Section 3.3.6.
3.2.2.8 FASTAREA and FASTALL
The FASTAREA secondary keyword on the MODELOPT keyword is used to select the non-
regulatory option to optimize model runtime for AREA sources (including AREA, AREAPOLY, AREACIRC
and OPENPIT source types, as well as LINE sources introduced with version 12345 (see Section 3.3.1)).
When FASTAREA is specified, the area source integration routine is optimized to reduce model runtime by
incorporation of a three-tiered approach using the Romberg numerical integration, a 2-point Gaussian
Quadrature routine for numerical integration, or a point source approximation, depending on the location of
the receptor relative to the source. In the regulatory default mode, the Romberg numerical integration is
utilized for all receptors. The FASTAREA approach does not include meander in the AREA, AREAPOLY,
AREACIRC, or LINE source types even if the AREAMNDR keyword has been included. Also beginning
with version 09292, a non-regulatory option to optimize model runtime for POINT and VOLUME sources
was included, which is selected with the FASTALL secondary keyword on the MODELOPT keyword.
Specification of the FASTALL option also activates the FASTAREA option if AREA sources are including in
the model inputs. Both FASTALL and FASTAREA skip receptors that are more than 80 kilometers from the
source. Beginning with version 22112, the RLINE and RLINEXT sources also include a FAST option
activated with the FASTALL keyword.
The FASTALL option for POINT/POINTHOR/POINTCAP and VOLUME sources uses an
alternative implementation of the horizontal meander algorithm based on an effective horizontal dispersion
coefficient (
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speed. These estimates are made by interpolating between values of these variables computed at three
distances from the source (1 m, 10 m, and 500 m). Note that, as of version 19191, the FASTALL option
has not been implemented for the BUOYLINE and SWPOINT source types and is not applicable with
the PLATFORM keyword.
3.2.2.9 Urban transition and NOURBTRAN option
The urban option within AERMOD was modified, beginning with version 11059, to address
potential issues associated with the transition from the nighttime urban boundary layer to the daytime
convective boundary layer. Prior to version 11059, the enhanced dispersion due to the urban heat island
during nighttime stable conditions was ignored once the rural boundary layer became convective. This could
result in an unrealistic drop in the mixing height for urban sources during the morning transition to a
convective boundary layer, which could contribute to overly conservative concentrations for low-level
sources under such conditions. This potentially anomalous behavior was observed in a few cases during the
application of AERMOD for the Risk and Exposure Assessment (REA) conducted in support of a review for
the NO2 National Ambient Air Quality Standard (NAAQS) (EPA, 2008). The potential significance of this
issue for AERMOD applications in support of air quality permitting increased with the promulgation of the
more recent 1-hour NO2 and 1-hour SO2 NAAQS in 2010.
To address this issue, AERMOD was modified to continue applying the urban boundary layer option
for urban sources until the daytime (rural) convective boundary exceeds the population-dependent urban
boundary layer height. This modification to the urban option within AERMOD has been evaluated using the
1985 Indianapolis SF6 field study data (Murray and Bowne, 1988), and shows improved model performance
during daytime convective conditions compared to the original implementation of the urban option. Model-
to-monitor comparisons of 1-hour NO2 concentrations from the Atlanta NO2 REA also exhibit improved
model performance with this modification to the urban option in AERMOD. A summary of these model
evaluation results is provided in the AERMOD Model Formulation document (EPA, 2024a).
The NOURBTRAN non-regulatory option has been included to allow users to revert to the urban
option as implemented prior to version 11059, which ignores the transition from the nighttime urban
boundary layer to the daytime convective boundary layer.
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3.2.2.10 SCREEN mode
The screening mode of AERMOD, which is controlled by the SCREEN keyword on the
MODELOPT card, forces the model calculations to represent values for the plume centerline, regardless of
the source-receptor-wind direction orientation. This option is included in AERMOD to facilitate the use of
the model with the AERSCREEN (EPA, 2021) to estimate worst case impacts. Its use outside of that context
is not recommended. Since the screening model is designed to be used with a non-sequential meteorological
data file, representing a matrix of conditions, the SCREEN option also forces the use of the NOCHKD
option described above, even if NOCHKD is not included on the MODELOPT card. The SCREEN option
also restricts the averaging period options to 1-hour averages only on the AVERTIME card (see Section
3.2.2.10). Note that the SCREEN mode is only applicable for point type sources (POINT, POINTCAP, and
POINTHOR) and VOLUME sources. For all other source types, screening is not invoked, and results are
unchanged from non-screening mode.
3.2.2.11 SCIM
The AERMOD model includes the non-regulatory Sampled Chronological Input Model (SCIM)
option to reduce model runtime for some uses of the model. The SCIM option can only be used with the
ANNUAL average option and is primarily applicable to multi-year model simulations. The approach used
by the SCIM option is to sample the meteorological data at a user-specified regular interval to approximate
the long-term (i.e., ANNUAL) average impacts. Studies have shown that the uncertainty in modeled results
introduced by use of the SCIM option is generally lower for area sources than for point sources.
When only the regular sampling is selected, hourly concentrations are calculated in the normal
fashion for each sampled hour. The annual average concentration is then simply calculated by dividing the
cumulative concentration for the sampled hours by the number of hours sampled (arithmetic average), i.e.,
C = ZCS/NS
where:
C = Calculated concentration
^ = Cumulative impacts for the sampled hours
Ns = Number of sampled hours
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To use the SCIM option, the user must include the SCIM keyword on the CO MODELOPT card and
the SCIM sampling parameters on the ME SCIMBYHR card. The format and syntax of the ME
SCIMBYHRkeyword are described in Section 3.5.7.
3.2.2.12 Deposition Options
The AERMOD model includes algorithms for both dry and wet deposition of both particulate and
gaseous emissions. The deposition algorithms incorporated into AERMOD are based on the draft Argonne
National Laboratory (ANL) report (Wesely et al., 2002), with modifications based on peer review. Treatment
of wet deposition was revised from Wesely et al. (2002) based on recommendations by peer review panel
members (Walcek et al., 2001). A full technical description of the deposition algorithms implemented in
AERMOD is provided in an EPA report specific to these algorithms (EPA, 2003).
Based on the guidance provided for application of the AERMOD model in the Guideline (EPA,
2017b), and the history of the deposition algorithms in the AERMOD and ISC models, the particle
deposition algorithms with a user-specified particle size distribution (referred to below as "Method 1") can
be applied simultaneously with the regulatory DFAULT keyword. Method 1 is comparable to the particle
deposition algorithm in the ISCST3 model (EPA, 1995a). The gas deposition algorithms and the "Method 2"
option for particle deposition based on the ANL draft report (Wesely, et al, 2002) are non-regulatory ALPHA
options in AERMOD, and beginning with version 19191, the model will issue a fatal error message and abort
processing if the ALPHA keyword is not specified with the gas deposition or Method 2 particle deposition
options.
For gaseous dry deposition, the user must define seasonal categories for each of the calendar months,
direction-specific land use categories, and several pollutant-specific parameters. An optional keyword is also
provided to override default values for three parameters used in the gas deposition algorithm. The input
requirements for "Method 1" particle deposition in AERMOD are the same as for the particle deposition
algorithm in the ISCST3 model. For "Method 2" particle deposition, the user must define the fraction of the
particle mass in the fine particle category (less than 2.5 microns) and a representative mass mean diameter
for the particles. Table 3-1 summarizes the required keywords for the various deposition options within
AERMOD and whether they are allowed under the DFAULT option. For all keywords associated with
METHOD 2 or gas deposition, the ALPHA keyword must be used along with the MODELOPT keyword.
The keywords used to define inputs for deposition specified on the CO pathway are described in the sections
that follow. The keywords associated with deposition specified on the SO pathway are described in sections
3.3.3 through 3.3.5.
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Table 3-1 Summary of Deposition Options
Pollutant Type
Model Output Type
Required Keywords
Allowed under DFAULT?
Gaseous
CONC w/dry depletion
DDEP
CO GASDEPVD
or
CO GDSEASON,
CO GDLANUSE, and
SO GASDEPOS
No1
Gaseous
CONC w/wet depletion
WDEP
SO GASDEPOS
No1
Gaseous
CONC w/dry & wet
depletion
DEPOS
CO GDSEASON,
CO GDLANUSE, and
SO GASDEPOS
No1
Particulate
("Method 1")
CONC w/dry and/or wet
depletion
DEPOS
DDEP
WDEP
SO PARTDIAM,
SO PARTDENS, and
SO MASSFRAX
Yes2
Particulate
("Method 2")
CONC w/dry and/or wet
depletion
DEPOS
DDEP
WDEP
SO METHOD 2
No1
The user should be aware that one or more of the following meteorological parameters are needed
for deposition: precipitation code, precipitation rate, relative humidity, surface pressure, and cloud cover.
3.2.2.13 Definition of seasons for gaseous dry deposition
The gas deposition algorithms in AERMOD include land use characteristics and gas deposition
resistance terms based on five seasonal categories defined in Table 2 of the ANL report as:
Seasonal Category 1: Midsummer with lush vegetation
Seasonal Category 2: Autumn with unharvested cropland
Seasonal Category 3: Late autumn after frost and harvest, or winter with no snow
Seasonal Category 4: Winter with snow on ground (with generally continuous snow cover)
1 The ALPHA option must be included.
2 While "Method 1" is allowed under the regulatory "DFAULT" option within AERMOD, the use of "Method 1" for
particulate emissions in regulatory modeling applications should follow the guidance provided in Section 7.2.1.3 of the
Guideline (EPA, 2017b).
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Seasonal Category 5: Transitional spring with partial green coverage or short annuals
The user correlates these seasonal definitions to calendar months through the GDSEASON keyword on the
CO pathway. The syntax and type of the GDSEASON keyword are:
Syntax:
CO GDSEASON Jan Feb Mar .
. Dec
Type:
Optional, Non-repeatable
where a numeric value from 1 to 5 is entered for each of the twelve calendar months to associate it with the
seasonal definitions given above. This keyword is optional for the model, but mandatory when applying the
gas deposition algorithms, unless the GASDEPVD option for user-specified dry deposition velocity on the
CO pathway is used, described below in Section 3.3.3.2. Note that some of the seasonal categories defined
above may not apply for certain regions, such as Category 4, winter with continuous snow cover, for
moderate climates.
3.2.2.14 Definition of land use categories for gas dry deposition
The gas deposition algorithms also require direction-specific land use categories based on the
following land use codes and definitions (from Table 1 of the ANL report):
Land Use Category Description
1 Urban land, no vegetation
2 Agricultural land
3 Rangeland
4 Forest
5 Suburban areas, grassy
6 Suburban areas, forested
7 Bodies of water
8 Barren land, mostly desert
9 Non-forested wetlands
The user defines the land use categories by direction sector through the GDLANUSE keyword on the CO
pathway. The syntax and type of the GDLANUSE keyword are:
Syntax:
CO GDLANUSE Seel Sec2 Sec3 .
. Sec36
Type:
Optional, Non-repeatable
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where a numeric value from 1 to 9 is entered for each of the 36 direction sectors (every 10 degrees)
to associate it with the land use definitions given above. This keyword is optional for the model, but
mandatory when applying the gas deposition algorithms, unless the GASDEPVD option for user-specified
deposition velocity is used. The first value, Seel, corresponds with the land use category, downwind of the
application site, for winds blowing toward 10 degrees, plus or minus 5 degrees. The downwind sectors are
defined in clockwise order, with Sec36 corresponding to winds blowing toward 360 degrees (North) and
should generally reflect conditions downwind relative to the source location. The user can specify "repeat
values" by entering a field such as "36*3" as a parameter for the GDLANUSE keyword. The model will
interpret this as "36 separate entries, each with a value of 3." Since the model must identify this as a single
parameter field, there must not be any spaces between the repeat-value and the value to be repeated. Option
for overriding default parameters for gas dry deposition
An optional keyword is available on the Control (CO) pathway to allow the user to override the
default values of the reactivity factor and the fraction (F) of maximum green leaf area index (LAI) for
seasonal categories 2 (autumn/unharvested cropland) and 5 (transitional spring), for use with the gas dry
deposition algorithms.
The syntax and type of the GASDEPDF keyword are summarized below:
Syntax: CO GASDEPDF React F_Seas2 F_Seas5 (Refpoll)
Type: Optional, Non-repeatable
where the parameter React is the value for pollutant reactivity factor and F_Seas2 and F_Seas5 are the
fractions (F) of maximum green LAI for seasonal categories 2 and 5, respectively. The parameter Refpoll is
the optional name of the pollutant. If the optional GASDEPDF keyword is omitted, then the default value of
0 is used for React, and default values of 0.5 and 0.25 are used for F_Seas2 and F_Seas5, respectively. A
value of F= 1.0 is used for seasonal categories l,3,and4. A reactivity factor value of 1 should be input for
ozone (O3), titanium tetrachloride (TiCl4). and divalent mercury (Hg2+), and a value of 0.1 should be input for
nitrogen dioxide (NO2).
3.2.2.15 Deposition velocity and resistance outputs
In order to facilitate review and testing of the deposition algorithms in the AERMOD model, the
model includes an option to output the main resistance terms and deposition velocities for gaseous and
particle sources. These optional outputs are generated if the user specifies the 'CO DEBUGOPT MODEL'
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option described in Section 3.2.18. The gas deposition data are written to a file called GDEP.DAT, which
includes the values of Ra, Rb, Rc, and Vj:< (see Wesely, et al, 2002, for definitions) for each source and for
each hour modeled. A header record is included to identify the columns. The particle deposition data are
written to a file called PDEP.DAT, which includes the values of Ra, RP, Vg, and Vj for each source and for
each hour modeled. The particle outputs are labeled as being based on either Method 1 or Method 2. For
Method 1, results are output for each particle size category. The filename and file units for these data files
are hardcoded in the model, and the files are overwritten each time the model is executed. Since these files
include data for each source for each hour, file sizes may become large.
3.2.2.16 Remove displacement height from RLINE wind profile
Beginning with version 22112, the ALPHA option RLINEFDH was added to calculate the wind
profile for RLINE sources without a displacement height. The displacement height is used in the wind profile
to modify the wind profile below five times the surface roughness. When the surface roughness is large, such
as in urban environments this displacement height could significantly impact the calculated windspeeds
when the mean plume height is below five times the surface roughness length. RLINEFDH removes the
displacement height and the wind speed profile is similar to the wind speed profile used in other AERMOD
source types. RLINEFDH must be used along with the ALPHA keyword and cannot be used with the
DFAULT keyword.
3.2.3 Low wind parameters
An ALPHA option, LOWWIND (see Section3.2.3), is included in AERMOD (beginning with the
version dated 18081 and updated in versions 21112 and 22112) related to concerns regarding model
performance under low wind speed conditions. Inclusion of the LOWWIND keyword is intended to
facilitate further testing and evaluation of AERMOD in low wind conditions in order to better understand the
relationships of certain variables and potentially develop additional regulatory low wind options that will
improve AERMOD's performance in low wind conditions. The LOW WIND keyword has been added to
the CO pathway to allow users to override the default values for seven different parameters that can
potentially affect performance under low wind speed conditions with user-defined values. Model default
values can be overridden with user-defined values for the following parameters:
Minimum sigma-v value (SVmin) within a range of 0.01 to 1.0 m/s),
Minimum wind speed value (WSmin) within a range from 0.01 to 1.0 m/s,
Maximum value for the meander factor (FRANmax), within a range of 0.0 to 1.0,
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Minimum sigma-w value (SWMin), within a range of 0.0 to 3.0 m/s, and
Time period (BigT) used to calculate the time scale TRAN, within a range of 0.5 to 48.0 hours.
Minimum value for the meander factor (FRANmin), within a range of 0.0 to 1.0 but must be
less than or equal to FRANmax
Alternate momentum balance (PBAL) approach to determine plume meander which overrides
the default energy balance approach.
Absent user-specified values on the LOW_WIND keyword, a default value of 0.2828 m/s is used for WSmin,
consistent with the default applied in previous versions of AERMOD based on SQRT(2*SVmin*SVmin).
The default value of SVmin = 0.2 m/s, FRANMax = 1.0, SWMin = 0.02 m/s, BigT = 24.0 hours, and
FRANMin = 0.0.
The syntax and type of the LOWWIND keyword is:
Syntax: CO
LOW WIND
SVmin
[WSmin]
or
CO
LOW WIND
SVmin
WSmin
[FRANmax]
or
CO
LOW WIND
SVmin
WSmin
FRANmax
[SWmin]
or
CO
LOW WIND
SVmin
WSmin
FRANmax
SWmin
[BigT]
or
CO
LOW WIND
SVmin
WSmin
FRANmax
SWmin
BigT
[FRANmin]
or
CO
LOW WIND
SVmin
WSmin
FRANmax
SWmin
BigT
FRANmin
[PBAL]
Type: Optional, Non-repeatable
where SVmin is the minimum value of sigma-v, within a range of 0.01 to 1.0 m/s. WSmin is the minimum
wind speed and can range from 0.01 to 1.0 m/s. FRANmax is the maximum meander factor, within a range
of 0.0 to 1.0. BigT is the time scale used to calculate TRAN and can range from 0.5 to 48 hours, FRANmin is
the minimum meander factor within a range of 0.0 to 1.0 and is required to be less than or equal to
FRANmax. PBAL is a secondary keyword to replace the default energy balance approach for determining
meander with a momentum balance approach. The syntax allows one of six ways to specify one or more of
the LOW_WIND parameter values. For each syntax option, the parameter listed in square brackets, [], is
optional, but the preceding parameters are required. For example, to override the default value for SWMin,
you must also provide values for SVMin, WSMin, and FRANmax preceding the value for SWMin, in the
order listed above.
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Note: The LOWWIND keyword was previously implemented as a BETA option to
supplement the former LOWWIND1, LOWWIND2, and LOWWIND3 BETA options. These options
have since been removed from AERMOD, and the LOW WIND keyword was retained and changed to
an ALPHA option.
In addition to the LOW WIND ALPHA option, an option has been incorporated in the AERMET
meteorological processor (first as a BETA option beginning with version 12345 and a regulatory option in
version 16216) to address concerns regarding model performance under low wind conditions. The ADJU*
option in AERMET adjusts the surface friction velocity (U*) under low wind/stable conditions based on
Qian and Venkatram (2011). The ADJ U* option may be used as a regulatory option in AERMET with NWS
data or with site-specific data that does not include turbulence (i.e., sigma-w and/or sigma-theta). When the
ADJU* option is used in the absence of turbulence data, AERMOD can accept the data with the regulatory
DFAULT option enabled. Beginning with version 16216 of AERMET, an adjustment to U* under the
ADJ U* option is also available as a regulatory option for applications utilizing the Bulk Richardson
Number (BULKRN) method, based on Luhar and Raynor (2009) (see also AECOM (2010)) when used with
site-specific data that does not include turbulence parameters. The ADJ_U* option, when used with site-
specific data that does include turbulence parameters, is currently considered a non-regulatory option and is
therefore, subject to the alternative model provisions in Section 3.2 of Appendix W (40 CFR Part 51).
During processing, AERMET includes a flag in the header of the surface meteorological data file (.SFC) to
inform AERMOD that the data were processed using the ADJU* option. If AERMOD then encounters
turbulence data in the profile file (PFL) generated by AERMET and the DFAULT flag is set, AERMOD will
record the error and abort processing. Refer to the AERMET user's guide for additional details regarding the
ADJ U* option in AERMET.
3.2.4 Building downwash options
Beginning with version 19191, two distinct sets of ALPHA building downwash options are included
in AERMOD and are enabled using the ORD_DWNW and AWMADWNW keywords. These are research
grade options that have been identified as having potential to refine and improve the performance of the
PRIME downwash algorithm in AERMOD in certain situations. They have been made available to users for
testing and evaluation and require that the secondary keyword, ALPHA, be included with the MODELOPT
keyword. The options associated with ORD DWNW were developed by the EPA's Office of Research and
Development (ORD) and the AWMADWNW options were developed by a research subcommittee of the Air
and Waste Management Association (AWMA) formed for the purpose of conducting research that will lead
to the improvement of the treatment of building downwash in AERMOD.
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In addition to the ALPHA building downwash options implemented in AERMOD by ORD and
AWMA, the research and development performed by both groups of researchers used an alternative method
for determining the equivalent building dimensions for a rectangular building that is oblique to the wind
from the method used by the building preprocessor, BPIPPRM. The alternative method uses the along wind
building length and actual building width, for a given wind direction, as the equivalent building length and
width, whereas BPIPPRM, for the same wind direction, uses the maximum projected length and maximum
projected width. The alternate method reduces the footprint of the building which is reflected in the building
parameters that are input into AERMOD.
The alternate method for determining equivalent building dimensions for a rectangular building used
by ORD and AWMA has been implemented by ORD in a draft version of BPIPPRM (19191DRFT) which
can be downloaded from the EPA SCRAM website at: https://www.epa.gov/scram/air-qualitv-dispersion-
modeling-related-model-support-programs#bpipprm. It is important to note that this draft version of
BPIPPRM (19191DRFT) is a research grade version that has been provided to the modeling community for
testing, evaluation, and feedback and may not be used in a regulatory context. The changes implemented in
this draft version affect only the building parameters generated for rectangular buildings or tiers. It is also
important to note that this draft version of BPIPPRM (19191DRFT) is completely independent of the
ALPHA downwash options implemented by ORD and AWMA. Any of the ALPHA downwash options can
be tested and evaluated with and without the use of this draft version of BPIPPM.
The remainder of this section describes the usage of these keywords (ORD_DWNW and
AWMADWNW), the ALPHA building downwash options associated with each, and the corresponding
secondary keywords used to enable them for testing and evaluation. While, for the most part, the different
downwash options are independent of one another and can be used in various combinations with one another,
any conflicts and dependencies between options are noted in the sections below.
3.2.4.1 ORD building downwash options
The first is an initiative led by the EPA's Office of Research and Development (ORD). ORD has
performed wind tunnel experiments and embedded large eddy simulations (LES) to better understand how to
parameterize buildings that are elongated and angled relative to the wind flow and the parameterization of
the plume in the cavity and far wake regions. The ORD studies are concentrated on single rectangular
buildings, specifically investigating changes in plume parameters at discrete downwind distances from the
building and source, longitudinal and lateral plume profiles, the lateral plume shift on the lee side of rotated
buildings, and building characterization in BPIPPRM (Heist et al., 2016). To date, this research has led to
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recommended changes to the building preprocessor, BPIPPRM, as well as changes to the building downwash
algorithm in the AERMOD program.
ORD has performed wind tunnel experiments and embedded large eddy simulations (LES) to better
understand how to parameterize buildings that are elongated and angled relative to the wind flow and the
parameterization of the plume in the cavity and far wake regions. The ORD studies focused on single
rectangular buildings and investigated changes in plume parameters at discrete downwind distances from the
building and source and building characterization.
As previously stated, the ORD building options associated with the ORD DWNW keyword are
research grade ALPHA options and require the ALPHA secondary keyword included with the MODELOPT
keyword. There are three distinct ORD options that can be enabled individually or in combination with one
another. For detailed information on ORD's research and the options implemented in AERMOD, refer to
Heist et al., 2016; Monbureau et al., 2018; and Perry et al., 2018. The usage of the ORD_DWNW keyword
and associated secondary keywords is as follows:
CO ORD DWNW ORDUEFF
and/or
Syntax:
ORDTURB
and/or
ORDCAV
Type:
Optional, Non-repeatable
where:
ORDUEFF - Redefines the height at which the wind speed is taken from the profile wind speed
used in the calculation of concentrations from the primary plume. The PRIME
algorithm currently uses the wind speed at the stack height. ORDUEFF uses the
average of the profiled wind speed between the height of the receptor and the plume
centerline, allowing the wind speed of the plume to change with a changing
environment.
NOTE: ORDUEFF cannot be used in combination with the AWMADWNW
option AWMAUEFF.
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ORDTURB - Redefines the maximum value of the non-dimensional vertical turbulence intensity
in the wake, reduced from 0.07, the current value in PRIME, to 0.06 based on Wiel
(1996).
ORDCAV- Redefines point downwind at which the vertical and lateral dispersion coefficients
begin to grow with downwind distance from the lee edge of the building to the end
of the cavity. PRIME considers a cavity plume and a re-emitted plume to simulate
two distinct regions with a weighted distribution of mass between the two plumes.
The cavity and re-emitted plumes initially have the same lateral and vertical
dispersion on the leeward side of the building. The re-emitted plume grows with
downwind distance while the dispersion of the cavity plume remains unchanged
throughout the cavity which creates a discontinuity of the two plumes at the near-
wake boundary and results in a reduction in ground level concentrations. This option
sets the dispersion coefficients for the two plumes equal to each other at the cavity
edge eliminating the discontinuity between the two plumes.
NOTE: Each of the three ORD DWNW options listed are optional, but at least one must be
included if the ORD_ DWNW keyword is specified in the control file.
3.2.4.2 AWMAbuilding downwash options
AWMA's research focused on the reanalysis of existing wind tunnel data, as well as the completion
of new wind tunnel experiments to investigate the decay of the building wake above the top of the building,
appropriate height at which approach turbulence and wind speed are calculated, the reduction of wake effects
for streamlined structures, and the effect of approach roughness on the wake.
Five ALPHA building downwash options developed by the AWMA have been implemented in
AERMOD and require the ALPHA secondary keyword included with the MODELOPT keyword. For
detailed information on AWMA's research and the development of these ALPHA building downwash
options, refer to Petersen et al., 2017 and Petersen et al., 2018. The usage of the AWMADWNW keyword
and the associated secondary keywords to enable the AWMA building downwash ALPHA options is as
follows:
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CO AWMADWNW AWMAUEFF and/or
AWMAENTRAIN and/or
y" X: ((AWMAUTURB or AWMAUTURBHX) w/wo STREAMLINE(D))
Type: Optional, Non-repeatable
where:
AWMAUEFF - Redefines the height at which the wind speed is taken from the profile wind
speed used in the calculation of concentrations from the primary plume. The
PRIME algorithm currently uses the wind speed at the stack height.
AWMAUEFF uses the wind speed at the height of the plume centerline.
NOTE: AWMAUEFF cannot be used in combination with the
ORD DWNW option ORDUEFF.
AWMAENTRAIN - AWMAENTRAIN changes beta (B) entrainment coefficient for PRIME
downwash from default value of 0.60 to 0.35.
AWMAUTURB - Enables enhanced calculations of turbulence and wind speed using the
minimum of the final momentum plume rise or a representative PRIME
plume rise height for all calculations. Also, uses the final momentum plume
rise height used to compute effective wind speed (UEFF), effective cr
(SWEFF), effective av (SVEFF), effective potential temperature gradient
(TGEFF), and initial turbulence intensities (ambiy and ambiz) and computes
mean wind speed, Ğr, and a at 30 meters (U30, SW30 and SV30,
respectively).
AWMAUTURBHX - Enables enhanced calculations of turbulence and wind speed using the
PRIME plume rise at the downwind distance X, for all calculations. Uses
the final momentum plume rise height to initially compute effective wind
speed (UEFF), effective aw (SWEFF), effective a (SVEFF), effective
potential temperature gradient (TGEFF), and initial turbulence intensities
(ambiy and ambiz) and then then uses the PRIME computed plume rise at
each downwind distance. Also, computes mean wind speed, Ğr, and a at
30 meters (U30, SW30 and SV30, respectively).
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NOTE: If AWMAUTURB and AWMAUTURBHX are both specified,
AERMOD will issue a warning and continue processing using the
AWMAUTURBHX option.
STREAMLINE(D) - Reduces dispersion in the wake of streamlined structures such as storage
tanks and cooling towers. Uses alternate formulations for turbulence
enhancement and velocity deficit associated with the AWMUTURB and
AWMATURBHX options with modifications for streamlined structures.
When specified, all structures will be treated as streamlined structures.
NOTE: The STREAMLINE option can only be specified in conjunction
with the AWMAUTURB and AWMAUTURBHX options. When
specified, AERMOD assumes all buildings defined in the input control
file are streamlined structures.
NOTE: Each of the AWMADWNW options listed are optional, but at least one must be
included if the AWMADWNW is used.
Refer to Section 3.2.18 for debug output options associated with the ALPHA building downwash
options.
3.2.5 Input parameters for NO? conversion options
This section provides a description of the AERMOD inputs related to the PVMRM, OLM, GRSM,
and ARM2 regulatory options for modeling the conversion of NO to NO2, as well as the ALPHA options,
TTRM and TTRM2. TTRM and GRSM were both added as ALPHA options beginning with version 21112.
Beginning with version 22112, GRSM was updated to a BETA option, and TTRM2 was added as an ALPHA
option to invoke TTRM simultaneously with ARM2, PVMRM, or OLM. GRSM was updated to a regulatory
option beginning in version 24142. As a stand-alone option, TTRM is only effective for near field receptors.
TTRM2 paired with ARM2, PVMRM, or OLM, will invoke TTRM for near field receptors and use the other
method specified for all other receptors. While TTRM as a method has now been integrated to be paired
with these other options using the TTRM2 keyword, the TTRM keyword has been retained as a stand-alone
option for testing and diagnostic purposes. Note that the TTRM2 option cannot be paired with GRSM. Also
note that beginning with version 16216r, ARM2 replaced the original Ambient Ratio Method (ARM) Tier 2
option for NO conversion to NO2. ARM is no longer an option in AERMOD.
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A technical description of the PVMRM algorithm as incorporated within AERMOD is provided in
the AERMOD Model Formulation document (EPA, 2024a). Additional information regarding the regulatory
options for NO2 modeling are provided in Technical Support Document (TSD) for NC^-related AERMOD
Modifications (EPA, 2015). Background on the original development of the PVMRM option is provided by
Hanrahan (1999a and 1999b).
The ARM2 option is based on work sponsored by API (API, 2013) to develop a method to adjust the
modeled NOx concentrations based on an empirical relationship between ambient NOx and ambient NO2
concentrations. A key difference between the PVMRM and OLM methods, as compared to the ARM2
method, is that ARM2 does not require the user to input background ozone (O3) concentrations or in-stack
NO2/NOX ratios, as required by PVMRM and OLM; however, the default minimum ratio utilized in the
ARM2 method may not be appropriate in cases where the sources being modeled are known to have
relatively high in-stack NO2/NOX ratios. ARM2 sums all NOX impacts from all sources modeled in a single
model run to determine the N02/N0X ratio that's applied for each source group (SRCGROUP) specified.
While the SRCGROUP keyword is required with at least one source group defined, if source group 'ALL' is
omitted, AERMOD will automatically assume a source group 'ALL' internally and apply ARM2 to that
assumed source group. In this case, AERMOD will generate a warning message to indicate that source
group 'ALL' is missing but not required. Thus, ARM2 will not be calculated based on separate source
groups NOX impacts. For example, if NOX emissions from five stacks are modeled with the ARM2 option,
and only one source group is specified for one stack, ARM2 will first determine the total NOX impact from
all five stacks, calculate the empirically derived N02/N0X ratio from the total NOX impact (using a 5th
order polynomial equation discussed in API, 2013), and the final N02 impact concentration for the single
stack source group would be calculated as the product of the N02/N0X ratio and the discreet NOX impact
for the single stack source group.
The ARM2 has been implemented as a regulatory Tier 2 option while the PVMRM, OLM, and
GRSM algorithms have been implemented as regulatory Tier 3 screening options. Therefore, any one of the
four options can be used with the DFAULT keyword. TTRM/TTRM2 have been added as non-regulatory
ALPHA options and cannot be used with the DFAULT keyword. As with all other ALPHA options, they
require the use of the ALPHA keyword. With exception to daytime GRSM NO2 calculations, it is important
to note that the OLM, PVMRM, ARM2, and TTRM/TTRM2 options are NOT applied to the background
NO2 concentrations input through the SO BACKGRND option (described in Section 3.3.8.2). The
background NO2 concentrations, if provided, will be added to the modeled NO2 concentrations after the NO-
NO2 conversion has been calculated. GRSM daytime NO2 model concentrations are calculated based on the
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net production of NO2 from the following: NO2 in-stack ratio, ozone entrainment and conversion of NOx to
NO2, photolysis of NO2 to NO, and time-of-travel of the NOx plume from source to receptor. GRSM
nighttime NO2 model concentrations are calculated similar to OLM and PVMRM, i.e., limited by ozone
conversion of NO to NO2 with background NO2 concentrations (as specified through SO BACKGRND
pathway) simply added to the post-chemistry total NO2 concentration.
It should be noted that not all NO2 conversion options have been implemented for all source types in
AERMOD. Table 3-2 summarizes which NO2 conversion options have been implemented for each of the
AERMOD source types and which options have not.
Table 3-2. Implemented N02 Conversion Options by AERMOD Source Type
AERMOD
Source Type
Implemented
N02 Options
Not Implemented
Warning Issued
POINT (inc. POINTCAP and
POINTHOR)
ALL
NONE
AREA (inc. AREAPOLY,
AREACIRC, and LINE)
ALL
NONE
VOLUME
ALL
NONE
OPENPIT
ARM2, PVMRM, OLM,
TTRM, GRSM
TTRM2 (unpaired or paired with
ARM2, OLM, or PVMRM), TTRM2
by itself produces zero-values!
RLINE/RLINEXT
ARM2
PVMRM, OLM, TTRM, TTRM2,
GRSM
BUOYLINE
ARM2
PVMRM, OLM, TTRM, TTRM2,
GRSM
SWPOINT
NONE
ARM2, PVMRM, OLM, TTRM,
TTRM2, GRSM
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As described in Section 3.3.7, the ALPHA model option, PSDCREDIT, has been included for testing
and evaluation for increment consumption with PSD credits using PVMRM. The special source grouping
required for the PSDCREDIT option is also described below in Section 3.3.7.
3.2.5.1 Specifying ozone concentrations for PVMRM. OLM. TTRM/TTRM2. and GRSM options
The background ozone concentrations for the PVMRM, OLM, TTRM/TTRM2, and GRSM options
can be input as a single value through the OZONEVAL keyword on the CO pathway, as temporally varying
values through the 03VALUES keyword on the CO pathway, or as hourly values from a separate data file
specified through the OZONEFIL keyword on the CO pathway. The user must specify background ozone
concentrations through the OZONEVAL, 03VALUES, or OZONEFIL keyword to use the PVMRM, OLM,
TTRM/TTRM2, or GRSM option. The OZONEVAL or 03VALUES keyword may also be specified with
the OZONEFIL keyword, in which case the value(s) entered on the OZONEVAL or 03VALUES keyword
will be used to substitute for hours with missing ozone data in the hourly ozone data file. Users are strongly
encouraged to utilize the OZONEVAL or 03VALUES keyword with the OZONEFIL keyword to substitute
for missing ozone concentrations in the hourly data file. Beginning with version 13350 users can vary
background ozone concentrations by wind sector. For applications that include sector-varying background
ozone concentrations, the sectors are defined based on the CO 03SECTOR keyword, as follows:
Syntax:
CO 03 SECTOR StartSectl StartSect2 .
. StartSect/V, where N< 6
Type:
Optional, Non-Repeatable
For applications that include sector-varying background concentration the minimum sector width allowed is
30 degrees and warning messages will be issued for sector widths less than 60 degrees. Sector-varying
background concentrations will be selected based on the flow vector, i.e., the downwind direction based
on the wind direction specified in the surface meteorological data file.
The syntax of the OZONEVAL keyword is as follows:
CO OZONEVAL 03Value (03Units) (w/o sectors)
Syntax: or
CO OZONEVAL SECTx 03Value (03Units), where x < 6 (w/ sectors)
Type: Optional, Non-repeatable
where the 03Value parameter is the background ozone concentration in the units specified by the optional
03Units parameter (PPM, PPB, or UG/M3), and SECTx refers to the user-specified sector defined on the
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optional 03SECT0R keyword for which the 03Value inputs are applied. Implement as SECT1 or SECT2
... or SECTx where x < 6, and x is an integer and corresponds to the Nth sector defined by 03 SECTOR. If
the optional 03Units parameter is missing, then the model will assume units of micrograms/cubic-meter
(UG/M3) for the background ozone values. If units of PPM or PPB are used, then the model will convert the
concentrations to micrograms/cubic-meter based on reference temperature (25 C) and pressure (1013.25 mb).
If 03 SECTOR has been implemented, then OZONEVAL can only be applied for a single sector. However, if
using multiple sectors user should use 03VALUES.
The syntax of the 03 VALUES keyword is as follows, and is similar to the EMISFACT keyword on
the SO pathway (Section 3.3.11) for specifying temporally varying emission rates:
CO 03VALUES 03Flag 03values(i), i=l, n
(w/o sectors)
Syntax:
or
CO 03VALUES SECTx 03Flag 03values(i), i=l, n
where x < 6 (w/ sectors)
Type:
Optional, Repeatable
where the SECTx parameter specifies the applicable sector as defined on the optional 03SECTOR keyword.
Implement as SECT1 or SECT2 ... or SECTx where x < 6, and x is an integer and corresponds to the Nth
sector defined by 03SECTOR. The parameter 03Flag is the variable ozone concentration flag, and must be
specified as one of the following secondary keywords (the number in parentheses indicates the number of
values required for each option):
ANNUAL - annual ozone value (n = 1); equivalent to OZONEVAL keyword in PPB,
SEASON - ozone values vary seasonally (n = 4),
MONTH - ozone values vary monthly (n = 12),
HROFDY - ozone values vary by hour-of-day (n = 24),
WSPEED - ozone values vary by wind speed (n = 6),
SEASHR - ozone values vary by season and hour-of-day (n = 96),
HRDOW - ozone values vary by hour-of-day, and day-of-week [M-F, Sat, Sun] (n = 72),
HRD0W7 - ozone values vary by hour-of-day, and the seven days of the week [M, Tu, W, Th, F,
Sat, Sun] (n = 168),
SHRDOW - ozone values vary by season, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n = 288),
SHRD0W7 - ozone values vary by season, hour-of-day, and the seven days of the week [M, Tu,
W, Th, F, Sat, Sun] (n = 672),
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MHRDOW - ozone values vary by month, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n = 864), and
MHRDOW7 - ozone values vary by month, hour-of-day, and the seven days of the week [M, Tu,
W, Th, F, Sat, Sun] (n = 2,016).
The 03Values array is the array of ozone values, where the number of values is shown above for
each 03Flag option. The seasons are defined in the following order: Winter (Dec., Jan., Feb.), Spring (Mar.,
Apr., May), Summer (Jun., Jul., Aug.), and Fall (Sep., Oct., Nov.). The wind speed categories used with the
WSPEED option may be defined using the ME WINDCATS keyword. If the WINDCATS keyword is not
used, the default wind speed categories are defined by the upper bound of the first five categories as follows
(the sixth category is assumed to have no upper bound): 1.54, 3.09, 5.14, 8.23, and 10.8 m/s. The
03VALUES keyword may be repeated as many times as necessary to input all of the ozone values and repeat
values may be used for the numerical inputs.
The order of inputs specified for the hour-of-day/day-of-week options (HRDOW, SHRDOW,
SHRDOW7, etc.) are by hour-of-day, then season or month, if applicable, and then by day-of-week. For the
HRDOW/SHRDOW/MHRDOW options, the days of the week are specified in the order of Weekdays (M-F),
Saturdays, and Sundays. For the HRDOW7/SHRDOW7/ MHRDOW7 options, the days of the week are
specified in the order of Mondays, Tuesdays, etc., through Sundays. Section 3.3.11 below includes an
example illustrating the order of inputs for these options for the EMISFACT keyword.
Ozone concentrations specified on the 03VALUES keyword are assumed to be in units of PPB
unless the OZONUNIT keyword is specified.
The syntax of the OZONUNIT keyword is as follows:
Syntax:
CO OZONUNIT OzoneUnits
Type:
Optional, Non-repeatable
where the OzoneUnits parameter specifies the units as parts-per-billion (PPB), parts-per-million (PPM), or
micrograms/cubic-meter (UG/M3). Units specified on the CONCUNIT keyword are only applied to ozone
concentrations input thought 03VALUES keyword, which assumes default units of PPB if the OZONUNIT
keyword is not specified. Ozone concentrations specified in units of PPB or PPM are converted to UG/M3
based on reference temperature (25 C) and pressure (1013.25 mb).
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Hourly ozone concentrations can be input through the optional OZONEFIL keyword. The syntax of
the OZONEFIL keyword is as follows:
CO OZONEFIL 03FileName (03Units) (03Format) (w/o sectors)
Syntax: or
CO OZONEFIL SECTx 03FileName (03Units) (03Format), where x < 6 (w/ sectors)
Type: Optional, Non-repeatable
where the 03FileName parameter is the filename for the hourly ozone concentration file, the optional
03Units parameter specifies the units of the ozone data (PPM, PPB, or UG/M3, with UG/M3 as the default),
and the optional 03Format parameter specifies the Fortran format to read the ozone data. If sector-varying
ozone concentrations are being used, based on the CO 03 SECTOR keyword, then the applicable sector ID
needs to be specified, e.g., ' SECT 1' indicates that values are specified for the first downwind sector. The
03FileName can be up to 200 characters in length based on the default parameters in AERMOD. Double
quotes (") at the beginning and end of the filename can also be used as field delimiters to allow filenames
with embedded spaces.
The hourly ozone file must include the year, month, day, and hour, followed by the ozone
concentration, in that order (unless specified differently through the 03Format parameter). The year can be
specified as either a 2-digit or 4-digit year. If an optional Fortran format is specified using the 03Format
parameter, the year, month, day, and hour variables must be read as integers using the Fortran 'I' format
specifier, and the ozone concentration must be read as a real variable, using the Fortran 'F,' 'E,' or 'D' format
specifiers, e.g., (412, F8.3). Note that ozone values that do not include decimal places can be read as Fx.O,
where x is the length of the data field. However, ozone values that to not include decimal places may be read
incorrectly if the 03Format specified for reading the data includes decimal places. For example, a value of
' 1234' would be interpreted as ' 123.4' if a format of F4.1 was used. The 03Format parameter must include
the open and close parentheses as shown in the example and may also include embedded spaces if double
quotes (") are used to delimit the field. A warning message will be generated if the specified format does not
meet these requirements, and AERMOD may also issue a fatal error message when reading the file in cases
where real variables are read with an integer format, or vice versa.
If the optional 03Format parameter is missing, then the model will read the ozone data using a
Fortran 'free' format, i.e., assuming commas or spaces separate the data fields, and that the fields are in the
order given above. The date sequence in the ozone data file must match the date sequence in the hourly
meteorological data files. As with the OZONEVAL keyword, if units of PPM or PPB are used, then the
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model will convert the concentrations to micrograms/cubic-meter based on reference temperature (25 C) and
pressure (1013.25 mb).
Values of ozone concentrations in the ozone data file that are less than zero or greater than or equal
to 900.0 will be regarded as missing. If background ozone values have been specified using the
OZONEVAL and/or 03VALUES keyword, then the appropriate value will be used to substitute for missing
ozone data from the ozone file. If no OZONEVAL or 03 VALUES keywords are used, then the model will
assume full conversion of NO to NO2 for hours with missing ozone data.
AERMOD will apply a minimum ozone value for NO conversion during stable hours, based on the
maximum minimum of 40 ppb and the maximum hourly ozone from the previous 24-hours of ozone data.
This minimum ozone restriction can be turned off with the NOMIN03 keyword. As with all NO2 options,
this option shall be used in agreement with the appropriate reviewing authority.
NOTE: The OLM method for estimating NO2 concentrations, outlined by Cole and Summerhays
(1979), assumes NO conversion to NO2 by first dividing total NOx into a thermal NO2 component directly
emitted from a stack, with the remaining NOx assumed as NO and available for reaction with O3. If ambient
O3 is greater than the portion of NOx assumed as NO, all NO is converted to NO2, otherwise, the amount of
NO converted to NO2 is limited to available O3. AERMOD, for OLM processing, only incorporates user-
defined, background ozone values in concentration calculations for hours that are "ozone-limited", when
sufficient atmospheric ozone is not present for NOx chemistry reactions. Determination of ozone-limited
hours is dependent on the relative values of background ozone concentrations to NO2 emissions multiplied
by the in-stack NO2/NOX ratio, described in Section 3.2.5.4, defined by the user. It is possible, therefore, to
define scenarios that will result in an absence of ozone-limited hours. Users interested in evaluating
concentrations sensitivities to background ozone should consider the potential that modification of the
background ozone concentration may not appear to impact output concentrations if relatively low in-stack
N02/NOx and/or emissions rates are defined. This behavior does not apply to the AERMOD PVMRM
method.
3.2.5.2 Specifying NOx background concentrations for the GRSM option
The background NOx concentrations for the GRSM option is input similarly to the ozone
background concentrations. The background NOx concentrations can be input as a single value through the
NOXVALUE keyword on the CO pathway, as temporally varying values through the NOX_VALS keyword
on the CO pathway, or as hourly values from a separate data file specified through the NOX FILE keyword
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on the CO pathway. The user may specify background NOx concentrations through the NOXVALUE,
NOX_VALS, or NOX_FILE keyword in order to use the GRSM option. The NOXVALUE or NOXVALS
keyword may also be specified with the NOX_FILE keyword, in which case the value(s) entered on the
NOXVALUE or NOX_VALS keyword will be used to substitute for hours with missing NOx background
data in the hourly NOx data file. Users are strongly encouraged to utilize the NOXVALUE or NOX_VALS
keyword with the NOX_FILE keyword to substitute for missing NOx concentrations in the hourly data file.
If no NOx input is supplied, GRSM will assume equilibrium with NOx. As with background ozone, users can
vary background NOx concentrations by wind sector. For applications that include sector-varying
background NOx concentrations, the sectors are defined based on the CO NOXSECTR keyword, as follows:
Syntax:
CO NOXSECTR StartSectl StartSect2 .
. StartSect/V, where N< 6
Type:
Optional, Non-Repeatable
For applications that include sector-varying background concentration the minimum sector width allowed is
30 degrees and warning messages will be issued for sector widths less than 60 degrees. Sector-varying
background concentrations will be selected based on the flow vector, i.e., the downwind direction,
based on the wind direction specified in the surface meteorological data file.
The syntax of the NOXVALUE keyword is as follows:
CO NOXVALUE NOXValue (NOXUnits) (w/o sectors)
Syntax: or
CO NOXVALUE SECTx NOXValue (NOXUnits), where x < 6 (w/sectors)
Type: Optional, Non-repeatable
where the NOXValue parameter is the background NOx concentration in the units specified by the optional
NOXUnits parameter (PPM, PPB, or UG/M3), and SECTx refers to the user-specified sector defined on the
optional NOXSECTR keyword for which the NOXValue inputs are applied. Implement as SECT1 or
SECT2 ... or SECTx where x < 6, and x is an integer and corresponds to the Nth sector defined by
NOXSECTR. If the optional NOXUnits parameter is missing, then the model will assume units of
micrograms/cubic-meter (UG/M3) for the background NOx values. If units of PPM or PPB are used, then
the model will convert the concentrations to micrograms/cubic-meter based on reference temperature (25 C)
and pressure (1013.25 mb).
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The syntax of the NOX_VALS keyword is as follows and is similar to the 03VALUES keyword
described above in Section 3.2.5.1 for specifying temporally varying ozone background concentrations:
CONOX_VALS NOXFlag NOXvalues(i), i=l, n (w/o sectors)
Syntax: or
CONOX_VALS SECTx NOXFlag NOXvalues(i), i=l, n andx<6 (w/sectors)
Type: Optional, Repeatable
where the SECTx parameter specifies the applicable downwind sector as defined on the optional
NOXSECTR keyword and the parameter NOXFlag is the variable NOx concentration flag and must be
specified as one of the following secondary keywords (the number in parentheses indicates the number of
values required for each option):
ANNUAL - annual NOx value (n = 1); equivalent to NOXVALUE keyword in PPB,
SEASON - NOx values vary seasonally (n = 4),
MONTH - NOx values vary monthly (n = 12),
HROFDY - NOx values vary by hour-of-day (n = 24),
WSPEED - NOx values vary by wind speed (n = 6),
SEASHR - NOx values vary by season and hour-of-day (n = 96),
HRDOW - NOx values vary by hour-of-day, and day-of-week [M-F, Sat, Sun] (n = 72).
HRDOW7 - NOx values vary by hour-of-day, and the seven days of the week [M, Tu, W, Th, F,
Sat, Sun] (n = 168),
SHRDOW - NOx values vary by season, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n = 288),
SHRDOW7 - NOx values vary by season, hour-of-day, and the seven days of the week [M, Tu, W,
Th, F, Sat, Sun] (n = 672),
MHRDOW - NOx values vary by month, hour-of-day, and day-of-week [M-F, Sat, Sun] (n = 864),
and
MHRDOW7 - NOx values vary by month, hour-of-day, and the seven days of the week [M, Tu, W,
Th, F, Sat, Sun] (n = 2,016).
The NOX values array is the array of NOx values, where the number of values is shown above for
each NOXFlag option. The seasons are defined in the following order: Winter (Dec., Jan., Feb.), Spring
(Mar., Apr., May), Summer (Jun., Jul., Aug.), and Fall (Sep., Oct., Nov.). The wind speed categories used
with the WSPEED option may be defined using the ME WINDCATS keyword. If the WINDCATS keyword
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is not used, the default wind speed categories are defined by the upper bound of the first five categories as
follows (the sixth category is assumed to have no upper bound): 1.54, 3.09, 5.14, 8.23, and 10.8 m/s. The
NOX_VALS keyword may be repeated as many times as necessary to input all the NOx values and repeat
values may be used for the numerical inputs.
The order of inputs specified for the hour-of-day/day-of-week options (HRDOW, SHRDOW,
SHRDOW7, etc.) are by hour-of-day, then season or month, if applicable, and then by day-of-week. For the
HRDOW/SHRDOW/MHRDOW options, the days of the week are specified in the order of Weekdays (M-F),
Saturdays, and Sundays. For the HRDOW7/SHRDOW7/ MHRDOW7 options, the days of the week are
specified in the order of Mondays, Tuesdays, etc., through Sundays. Section 3.3.11 below includes an
example illustrating the order of inputs for these options for the EMISFACT keyword.
NOx concentrations specified on the NOX_VALS keyword are assumed to be in units of PPB unless
the NOX_UNIT keyword is specified.
The syntax of the NOXUNIT keyword is as follows:
Syntax:
CO NOX UNIT NOXUnits
Type:
Optional, Non-repeatable
where the NOXUnits parameter specifies the units as parts-per-billion (PPB), parts-per-million (PPM), or
micrograms/cubic-meter (UG/M3). Units specified on the CONCUNIT keyword are only applied to ozone
concentrations input thought NOX_VALS keyword, which assumes default units of PPB if the NOXUNIT
keyword is not specified. NOx concentrations specified in units of PPB or PPM are converted to UG/M3
based on reference temperature (25 C) and pressure (1013.25 mb).
Hourly NOx concentrations can be input through the optional NOXFILE keyword. The syntax of
the NOX FILE keyword is as follows:
CO NOX FILE NOXFileName (NOXUnits) (NOXFormat) (w/o sectors)
Syntax: or
CO NOX_FILE SECTx NOXFileName (NOXUnits) (NOXFormat), where x < 6 (w/ sectors)
Type: Optional, Non-repeatable
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where the NOXFileName parameter is the filename for the hourly ozone concentration file, the optional
NOXUnits parameter specifies the units of the ozone data (PPM, PPB, or UG/M3, with UG/M3 as the
default), and the optional NOXFormat parameter specifies the Fortran format to read the NOx data. If
sector-varying NOx concentrations are being used, based on the CO NOXSECTR keyword, then the
applicable sector ID needs to be specified, e.g., 'SECT 1' indicates that values are specified for the first
downwind sector. The NOXFileName can be up to 200 characters in length based on the default parameters
in AERMOD. Double quotes (") at the beginning and end of the filename can also be used as field delimiters
to allow filenames with embedded spaces.
The hourly NOx file must include the year, month, day, and hour, followed by the NOx
concentration, in that order (unless specified differently through the NOXFormat parameter). The year can
be specified as either a 2-digit or 4-digit year. If an optional Fortran format is specified using the
NOXFormat parameter, the year, month, day, and hour variables must be read as integers using the Fortran 'I'
format specifier, and the ozone concentration must be read as a real variable, using the Fortran 'F,' 'E,' or 'D'
format specifiers, e.g., (412, F8.3). Note that NOx values that do not include decimal places can be read as
Fx.O, where x is the length of the data field. However, NOx values that to not include decimal places may be
read incorrectly if the NOXFormat specified for reading the data includes decimal places. For example, a
value of'1234' would be interpreted as '123.4' if a format of F4.1 was used. The NOXFormat parameter
must include the open and close parentheses as shown in the example and may also include embedded spaces
if double quotes (") are used to delimit the field. A warning message will be generated if the specified format
does not meet these requirements, and AERMOD may also issue a fatal error message when reading the file
in cases where real variables are read with an integer format, or vice versa.
If the optional NOXFormat parameter is missing, then the model will read the NOx data using a
Fortran 'free' format, i.e., assuming commas or spaces separate the data fields, and that the fields are in the
order given above. The date sequence in the NOx data file must match the date sequence in the hourly
meteorological data files. As with the NOXVALUE keyword, if units of PPM or PPB are used, then the
model will convert the concentrations to micrograms/cubic-meter based on reference temperature (25 C) and
pressure (1013.25 mb).
Values of NOx concentrations in the NOx data file that are less than zero will be regarded as missing.
If background NOx values have been specified using the NOXVALUE and/or NOX_VALS keyword, then
the appropriate value will be used to substitute for missing NOx data from the NOx file. If no NOXVALUE
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or NOX_VALS keywords are used, then the model will assume equilibrium of NOx with NO2 predicted from
GRSM based on NOx emissions and hourly ozone for hours with missing NOx data.
3.2.5.3 Specifying the ambient equilibrium NO?/NOx ratio (PVMRM. OLM. TTRM/TTRM2)
The PVMRM option for modeling conversion of NO to NO2 incorporate a default NO2/NOX ambient
equilibrium ratio of 0.90. Beginning with version 11059 of AERMOD, a default equilibrium ratio of 0.90
has also been incorporated in the OLM option, as well as the TTRM option beginning with version 21112. A
NO2/NOX equilibrium ratio other than 0.90 can be specified for the PVMRM, OLM, or TTRM/TTRM2
option through the optional N02EQUIL keyword on the CO pathway. The syntax of the N02EQUIL
keyword is as follows:
Syntax:
CO N02EQUIL N02Equil
Type:
Optional, Non-repeatable
where the N02Equil parameter is the NO2/NOX equilibrium ratio and must be between 0.10 and 1.0,
inclusive. Note the N02EQUIL option is invalid for GRSM simulations given that GRSM calculates the
NO2/NOX conversion equilibrium ratio explicitly.
3.2.5.4 Specifying the default in-stack NO?/NOx ratio (PVMRM. OLM. TTRM/TTRM2. GRSM)
The PVMRM, OLM, TTRM/TTRM2, and GRSM options for modeling conversion of NO to NO2
require that an in-stack NO2/NOX ratio be specified. Based on guidance issued June 28, 2010 (EPA, 2010b),
regarding the 1-hour NO2 NAAQS, AERMOD has been modified to require the user to specify in-stack
NO2/NOX ratios for each source under the OLM and PVMRM options, i.e., AERMOD no longer assumes a
default in-stack ratio of 0.10 for the OLM or PVMRM option. This requirement has been carried forward
with the addition of the TTRM/TTRM2 and GRSM options.
The in-stack NO2/NOX ratio can be specified for the PVMRM, OLM, TTRM/TTRM2, or GRSM
option by using either the CO N02STACK keyword to specify a default value to be used for all sources, or
by using the SO N02RATIO keyword to specify a value on a source-by-source basis. The SO N02RATIO
keyword can also be used to override the default value for specific sources if the CO N02STACK keyword
has been specified. The syntax of the N02STACK keyword is as follows:
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Syntax:
CO N02STACK N02Ratio
Type:
Optional, Non-repeatable
where the N02Ratio parameter is the default in-stack NCh/NOx ratio that will be used, unless overridden on
a source-by-source basis by the SO N02RATI0 keyword (described below). The value of N02Ratio must
be between 0.0 and 1.0, inclusive. Users should note that while CO N02STACK is an optional keyword, the
OLM, PVMRM, TTRM/TTRM2, and GRSM options require the user to specify an in-stack N02/N0X ratio
for each source, using either the CO N02STACK or SO N02RATI0 keyword (described in Section 3.3.6.1),
or both.
3.2.6 Averaging time options
The averaging periods for AERMOD are selected using the AVERTIME keyword on the CO
(Control) pathway. The syntax and type of the AVERTIME keyword are summarized below:
CO AVERTIME Timel Time2 .
. Time A' MONTH PERIOD
Syntax:
or
ANNUAL
Type:
Mandatory, Non-repeatable
where the parameters Time 1 . . . Timc/v' refer to the user-specified short-term averaging periods of 1, 2, 3, 4,
6. 8,12, and/or 24 hours, the secondary keyword MONTH refers to monthly averages (for calendar months),
the secondary keyword PERIOD refers to the average for the entire data period, and the secondary keyword
ANNUAL refers to an annual average. Any of the short-term averaging periods listed above may be selected
for a given run. Since the monthly averages are treated as short-term averages, the user can select
appropriate output options, such as the second highest values by receptor, on the OU pathway. The location
of the PERIOD or ANNUAL keyword in the parameter list is not critical. The order of the short-term
averaging periods (including MONTH) is also not critical, although it does control the order of the averaging
period result tables in the main output file. Generally, it is recommended that the short-term averaging
periods be input in increasing order, unless there is a clear advantage in doing otherwise.
The user may specify either the PERIOD keyword or the ANNUAL keyword, but not both. For
concentration calculations for a single year data file, the PERIOD and ANNUAL keywords produce the same
results. However, the ANNUAL average option applies only to complete years of data, and for multi-
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year data files, the ANNUAL average output is based on the average of the ANNUAL values across the
years of data processed.
For deposition calculations, the PERIOD keyword will provide a total deposition flux for the full
period of meteorological data that is modeled, including multi-year data files, with default units of g/m2,
whereas the ANNUAL keyword will provide an annualized rate of the deposition flux with default units of
g/m2/yr.
Use of the ANNUAL average option for meteorological data periods of less than a year will result in
a fatal error. For meteorological data periods of longer than a year, if the meteorological data file does not
contain complete years of data, any data remaining after the last complete year will be ignored for the
ANNUAL average, and a warning message will be generated. The treatment of short-term averages with
multiple-year data files is comparable to their treatment when the CO MULTYEAR option is used.
3.2.7 Performing multiple year analyses with MULTYEAR option
The MULTYEAR keyword on the CO pathway provides an option for the user to perform a multiple
year analysis such as would be needed to determine the "high-sixth-high in five years" design value for
determining PM-10 impacts without the need for postprocessing of multiple concentration files, and for
multiple year analyses associated with the 24-hour PM2.5 NAAQS and 1-hour NO2 and SO2 NAAQS which
are based on concentrations averaged across the number of years processed. More information regarding the
24-hour PM2.5 and l-hourN02 and SO2 NAAQS is provided in Sections 3.2.16 and 3.2.17. Since the
multiple year option makes use of the model re-start capabilities described in the Section 3.2.15, the
MULTYEAR keyword is not compatible with the SAVEFILE or INITFILE keywords. The model will
generate a fatal error message if the user attempts to exercise both options in a single run. The syntax and
type of the MULTYEAR keyword is summarized below:
Syntax:
CO MULTYEAR (H6H) Savfil (Inifil)
Type:
Optional, Non-repeatable
where the optional H6H field, formerly used to highlight the use of the MULTYEAR option for determining
the High-6th-High (H6H) 24-hour average for the "pre-1997" PM-10 NAAQS, is no longer required since the
"post-1997" PM-10 NAAQS was vacated. A warning message will be generated if the H6H field is included
on the MULTYEAR keyword indicating that it is not required. The Savfil parameter specifies the filename
for saving the results arrays at the end of each year of processing, and the Inifil parameter specifies the
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filename to use for initializing the results arrays at the beginning of the current year. The Inifil parameter is
optional and should be left blank for the first year in the multi-year series of runs. The MULTYEAR option
works by accumulating the high short-term average results from year to year through the mechanism of the
re-start save file. The model may be setup to run in a batch file with several years of meteorological data, and
at the end of each year of processing, the short-term average results reflect the cumulative high values for the
years that have been processed. The PERIOD average results are given for only the current year, but the
model carries the highest PERIOD values from year to year and includes the cumulative highest PERIOD
averages in the summary table at the end of the run.
When setting up a batch file to perform a multiple year analysis, the user would first create an input
control file for the first year with all the applicable modeling options, the source inventory data, the receptor
locations, the meteorology options for the first year and the output file options. To obtain the PM-10 design
value, be sure to include the SIXTH highest value on the OU RECTABLE card (see Section 3.7.1). For the
CO MULTYEAR card for the first year, the user would only specify the Savfil parameter, and may use a card
such as:
CO MULTYEAR YEAR1.SAY
For the subsequent years, the user could copy the input file created for Year-1 and edit the files to change the
year parameters and meteorology filename on the ME pathway (and possibly in the title information) and
edit the MULTYEAR cards. For the subsequent years, both the Savfil and Inifil parameters must be
specified, with the Savfil for Year-1 becoming the Inifil for Year-2, and so on. The MULTYEAR cards (one
for each AERMOD run) might look like this:
CO MULTYEAR YEAR1.SAV (First year)
CO MULTYEAR YEAR2.SAVYEAR1.SAV (Second year)
CO MULTYEAR YEAR3 .SAV YEAR2.SAV (Third year)
CO MULTYEAR YEAR4.SAV YEAR3 .SAV (Fourth year)
CO MULTYEAR YEAR5 .SAV YEAR4.SAV (Fifth year)
The MULTYEAR keyword option is separate from the ability of the AERMOD model to process a multiple-
year meteorological data file in a single model run. The latter capability can be used for applications of the
model to long term risk assessments where the average impacts over a long time period are of concern rather
than the maximum annual average determined from five individual years. The MULTYEAR option can only
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be used when PM10. PM-10. PM25. PM2.5. PM-2.5. PM-25. LEAD. N02. S02. or OTHER is specified as
the pollutant ID.
3.2.8 Urban modeling option
The AERMOD model allows the user to incorporate the effects of increased surface heating from an
urban area on pollutant dispersion under stable atmospheric conditions. Beginning with version 06341,
multiple urban areas can be specified within the same model run. Multiple areas may be applicable for large
domains that encompass more than one identifiable urban area where the separation is large enough to
warrant separate treatment of the urban boundary layer effects. Use of the option for multiple urban areas
eliminates the need for post-processing for such applications. The urban area(s) are defined using one or
more instances of the URBANOPT keyword on the CO pathway. The sources that are to be modeled with
urban effects and the urban area that will be applied to each source are identified using the URBANSRC
keyword on the SO pathway (see Section 3.3.10). The syntax and type of the URBANOPT keyword are
summarized below:
For Multiple Urban Areas:
CO URBANOPT UrbanID UrbPop (UrbName) (UrbRoughness)
Syntax:
For Single Urban Areas:
CO URBANOPT UrbPop (UrbName) (UrbRoughness)
Type:
Optional, Repeatable for multiple urban areas
where the UrbanID parameter is the alphanumeric urban ID defined by the user (up to eight characters)
when multiple urban areas are defined, the UrbPop parameter specifies the population of the urban area, the
optional UrbName parameter may be used to identify the name of the urban area, and the optional
UrbRoughness parameter may be used to specify the urban surface roughness length. Note the UrbName
must be specified if the user wants to specify the urban roughness length. A default value of 1.0 meter will be
used for the urban roughness length if the UrbRoughness parameter is omitted. Beginning with version
09292, any value for the urban roughness length other than 1.0 meter will be treated as a non-regulatory
option. Caution should be used when specifying a non-default urban roughness length and use of a non-
default value should be clearly documented and justified. Note that the syntax of the URBANOPT keyword
for single urban areas has not changed from previous versions of AERMOD, so that existing input files will
not require modification.
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3.2.9 Specifying the pollutant type
The POLLUTID keyword is used to identify the type of pollutant being modeled for a particular run.
The syntax, type, and order of the POLLUTID keyword are summarized below:
Syntax:
CO POLLUTID Pollut (H1H or H2H or INC)
Type:
Mandatory, Non-repeatable
where the Pollut parameter may be a pollutant name of up to eight characters. Examples include SQ2. NOX.
CO. PM10. TSP. and OTHER. Some pollutant names, by themselves or in combination with other model
options, have special meaning and will affect how AERMOD computes the final results based on the current
NAAQS. The parameters H1H, H2H, and INC disable the special processing requirements associated the 1-
hr NO2 and SO2 NAAQS and the 24-hr PM2.5 NAAQS. Specifying one of these keywords will allow for
modeling PM2.5 24-hr increments which are based on the H2H value, and also allow evaluating NO2 options
in AERMOD based on incomplete years of field measurements. The pollutants names with special meaning
that will affect how AERMOD computes the results include:
PM10 (or PM-10) with the multi-year option for generating the high-sixth-high in five years
(see Section 3.2.16.2),
PM25 (or PM-2.5. PM2.5. or PM-25) (see Section 3.2.16.1).
NQ2 when computing 1-hour averages (See Sections 3.2.7 and 3.2.17),
NQ2 is required when using the OLM, PVMRM, TTRM/TTRM2, or GRSM option for
simulating the conversion of NO to NO2 (see Section 3.2.2.7),
SQ2 when computing 1-hour averages (see Sections 3.2.7 and 3.2.17),
SQ2 triggers the use of a 4-hour half-life for S02 decay for urban applications under both the
regulatory default options and non-default options(see Sections 3.2.2.1 and 3.2.10), and
The MULTYEAR option can only be used when PM10. PM-10. PM25. PM2.5. PM-2.5. PM-
25. LEAD. NQ2. SQ2. or OTHER is specified as the pollutant ID.
3.2.10 Modeling with exponential decay
The model provides the option to use exponential decay of the pollutant being modeled. Two
keywords are available for this purpose, the HALFLIFE and DCAYCOEF keywords. The syntax, type, and
order of these keywords are summarized below:
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CO HALFLIFE Haflif
syntax: CQ DCAYC0EF Decay
Type: Optional, Non-repeatable
where the Haflif parameter is used to specify the half life for exponential decay in seconds, and the
parameter Decay is used to specify the decay coefficient in units of s"1. The relationship between these
parameters is DECAY = 0.693/HAFLIF.
Only one of these keywords may be specified in a given run. If more than one is encountered, a non-
fatal warning message is generated, and the first specification is used in the modeling.
3.2.11 Flagpole receptor height option
The FLAGPOLE keyword specifies that receptor heights above local ground level (i.e., flagpole
receptors) are allowed on the REceptor pathway. The FLAGPOLE keyword may also be used to specify a
default flagpole receptor height other than 0.0 meters. The syntax and type of the FLAGPOLE keyword are
summarized below:
Syntax: CO FLAGPOLE (Flagdf)
Type: Optional, Non-repeatable
where Flagdf is an optional parameter to specify a default flagpole receptor height. If no parameter is
provided, then a default flagpole receptor height of 0.0 meters is used. Any flagpole receptor heights that are
entered on the Receptor pathway will override the default value but are ignored if the FLAGPOLE keyword
is not present on the Control pathway, and a non-fatal warning message is generated.
3.2.12 Plume Rise from Aircraft Emissions
An ALPHA option to simulate aircraft emissions was added to AERMOD beginning with version
23132. Aircraft emissions from jet engines experience plume rise from both momentum and buoyancy but
are commonly modeled as AREA and VOLUME source types in AERMOD which do not account for either
momentum or buoyancy. The aircraft plume rise ALPHA option extends the formulation of AREA
(including AREAPOLY, AREACIRC, and LINE) and VOLUME source types with additional input
parameters based on the work of Pandey, et. al. (2023). The option can be applied to AREA (including
AREAPOLY, AREACIRC, and LINE) and VOLUME source types identified as aircraft sources by
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specifying the primary keyword ARCFTOPT in the CO pathway. Aircraft sources are identified on the SO
pathway with the primary keyword ARCFTSRC followed by a list of source IDs and/or a range of source
IDs (see Section 3.3.18). The syntax for ARCFTOPT is summarized below:
Syntax: CO ARCFTOPT (AirportID)
Type:
Optional, Non-Repeatable
Where AirportID is an optional alphanumeric character string that can be included to identify the airport at
which the sources are located. The current implementation of aircraft plume rise requires that an additional
seven aircraft parameters be supplied to AERMOD using an hourly varying emissions input file. The
additional aircraft parameter variables are read from the hourly emissions file by AERMOD in the following
order:
MFUEL: Fuel burn rate (g/s)
THRUST: Aircraft thrust (newtons)
VAA: Aircraft speed (m/s)
AFR: Air-fuel ratio
BYPR: Bypass ratio (> 0 for turbofan and -999 for shaft-based engines)
RPWR: Rated power (kW) (-99999 for turbofan and > 0 for shaft-based)
SRCANGLE: Landing/takeoff angle with the ground (degrees) (airborne sources)
Note that AERMOD will issue a fatal error if ARCFTOPT and ARCFTSRC are specified and the aircraft
parameters are missing from the hourly emissions file, or if the hourly emissions file is missing altogether.
3.2.13 To run or not to run
Because of the improved error handling and the "defensive programming" that has been employed in
the design of the AERMOD model, the model will read through all of the inputs in the control file regardless
of any errors or warnings that may be encountered. If a fatal error occurs in processing of the control file
information, then further model calculations will be aborted. Otherwise, the model will attempt to run.
Because of the great many options available in the AERMOD model, and the potential for wasted resources
if a large run is performed with some incorrect input data, the RUNORNOT keyword has been included on
the Control pathway to allow the user to specify whether to RUN the model and perform all of the
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calculations, or NOT to run and only process the input control file commands and summarize the setup
information. The NOT option allows the user to check the syntax of the model keywords without performing
possible time-consuming model calculations. The syntax and type of the RUNORNOT keyword are
summarized below:
Syntax:
CO RUNORNOT RUN or NOT
Type:
Mandatory, Non-repeatable
3.2.14 Generating an input file for EVENT processing
The EVENTFIL keyword can be included on the CO pathway to generate an input file for EVENT
processing. The syntax and type of the EVENTFIL keyword are summarized below:
Syntax:
CO EVENTFIL (Evfile) (Evopt)
Type:
Optional, Non-repeatable
where the optional Evfile parameter specifies the name of the EVENT input file to be generated (the
maximum length of the file name is set by the ILENFLD parameter in MODULE MAIN1), and the optional
parameter, Evopt, specifies the level of detail to be used in the EVENT output file. Valid inputs for the
Evopt parameter are the secondary keywords of SOCONT and DETAIL (see the EVENTOUT keyword on
the OUtput pathway, Section 3.7.2). The default filename used if no parameters are specified is
EVENTS.INP, and the default for the level of detail is DETAIL. If only one parameter is present, then it is
taken to be the Evfile, and the default will be used for Evopt.
The primary difference between routine AERMOD and EVENT processing is in the treatment of
source group contributions. The AERMOD model treats the source groups independently. EVENT
processing is designed to provide source contributions to specific events such as the design concentrations
determined from AERMOD or user specified events. The user may specify the "events" to process using the
EVent pathway, which lists specific combinations of receptor location, source group, and averaging period.
By specifying the EVENTFIL keyword, an input control file will be generated that can be used directly for
EVENT processing. The events included in the generated EVENT processing input file are the design
concentrations defined by the RECTABLE keyword and the threshold violations identified by the
MAXIFILE keyword on the OU pathway.
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3.2.15 The model re-start capability
The AERMOD model has an optional capability to store intermediate results into an unformatted
file, so that the model run can be continued later in case of a power failure or a user interrupt. This re-start
option is controlled by the SAVEFILE and INITFILE keywords on the CO pathway. The syntax and type of
these keywords are summarized below:
CO SAVEFILE (Savfil) (Dayinc) (Savfl2)
Syntax: CQ ,N1TF1LE (lmfil)
Type: Optional, Non-repeatable
The SAVEFILE keyword instructs the model to save the intermediate results to a file and controls
the save options. All three parameters for this keyword are optional. If the user specifies only the Savfil
parameter, then the intermediate results are saved to the same file (and overwritten) each time. If the user
specifies both the Savfil and the Savfl2 parameters, then the model alternates between the two files for
storing intermediate results. The latter approach requires additional disk space to handle two storage files.
However, selecting two files avoids the potential problem like a power failure or interrupt that might occur
while the temporary file is open, and the intermediate results are being copied to it. In such a case, the
temporary results file would be lost.
The optional Dayinc parameter allows the user to specify the number of days between successive
dumps. The default is to dump values at the end of each day, i.e., Dayinc = 1. For larger modeling runs,
where the SAVEFILE option is most useful, the additional execution time required to implement this option
is very small compared to the total runtime. To be most effective, it is recommended that results be saved at
least every 5 days.
If no parameters are specified for the SAVEFILE keyword, then the model will store intermediate
results at the end of each day using a default filename of TMP.FIL.
The INITFILE keyword works in conjunction with the SAVEFILE keyword and instructs the model
to initialize the results arrays from a previously saved file. The optional parameter, Inifil, identifies the
unformatted file of intermediate results to use for initializing the model. If no Inifil parameter is specified,
then the model assumes the default filename of TMP.FIL. If the file doesn't exist or if there are any errors
encountered in opening the file, then a fatal error message is generated, and processing is halted.
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Note: It is important to note that if both the SAVEFILE and INITFILE keywords are used in the
same model run, then different filenames must be specified for the Savfil and Inifil parameters. Otherwise,
the model will encounter an error in opening the files, and further processing will be halted.
3.2.16 Processing for particulate matter (PM) NAAQS
3.2.16.1 Processing for fine particulate matter (PM-2.5)
A NAAQS for fine particulate matter, with aerodynamic particle diameters of 2.5 microns or less
(PM-2.5), was promulgated in 1997, and the 24-hour standard was revised in December 2006. For
attainment demonstrations, the PM-2.5 standard is based on a 3-year average of the 98th percentile 24-hour
average and a 3-year average of the annual mean concentration at each ambient monitor. EPA issued new
recommendations in May 2014 (EPA, 2014b) regarding appropriate modeling procedures for use in modeling
demonstrations of compliance with the PM2.5 NAAQS that is intended to supersede the earlier guidance
issued in March 2010 (EPA, 2010a). The May 2014 guidance, which addresses the issue of secondary
formation of PM2.5 due to precursor emissions, has modified the earlier guidance regarding use of the
average of the first-highest 24-hour average concentrations across the number of years modeled to represent
the modeled contribution for a cumulative impact assessment and recommends using the average of the
eighth-highest (98th percentile) of 24-hour concentrations to represent the modeled contribution for a
cumulative impact assessment. Use of the first-highest 24-hour average is still appropriate for significant
contribution determinations. Note that the use of a 3-year average for monitored design values to determine
attainment of the NAAQS does not preempt the requirement in Section 8.3.1.2 of the Guideline (EPA,
2017b) for use of 5 years of National Weather Service (NWS) data, and the 5-year average of modeled
impacts serves as an unbiased estimate of the 3-year average for purposes of modeling demonstrations of
compliance with the NAAQS.
Based on EPA's May 2014 draft recommendations, the 24-hour modeled contribution to the design
value for purposes of modeling demonstrations of compliance with the PM-2.5 NAAQS is based on the
highest of the eighth-highest (H8H) concentrations at each receptor, if one year of site-specific
meteorological data is input to the model, or the highest of the multi-year average of the eighth-highest
(H8H) concentrations at each receptor, if more than one year of meteorological data is input to the model. In
other words, the model calculates the eighth-highest 24-hour concentration at each receptor for each year
modeled, averages those eighth-highest concentrations at each receptor across the number of years of
meteorological data, and then selects the highest, across all receptors, of the N-year averaged eighth-highest
values.
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Similar to the 24-hour averages, an unbiased estimate of the 3-year average annual mean is simply
the annual mean, if only one year of site-specific meteorological data is input to the model, or the multi-year
average of the annual means if multiple years of meteorological data are used. The annual design value for
PM-2.5 is then based on the highest annual average across the receptor domain for single-year
meteorological data input, or the highest of the multi-year averaged annual means across the receptor domain
for multi-year meteorological data input.
The special processing of the 24-hour and annual averages for the PM-2.5 NAAQS is triggered by
specifying a pollutant ID of 'PM25', 'PM-2.5', 'PM2.5' or 'PM-25' on the CO POLLUTID card. In this case,
the model will compute the 24-hour and annual average design values as described in the previous
paragraphs. In order for the PM-2.5 processing to work correctly for multiple year periods, the yearly
meteorological data files can be concatenated into a single multi-year file for input into the model, or the
MULTYEAR option (Section 3.2.7) can be used with separate model runs for each year. There is no
requirement to remove the header records between concatenated surface meteorological data files prior to
running the model, and multi-year meteorological data files can also be generated by processing multi-year
inputs in AERMET. (NOTE: While the MULTYEAR option with separate yearly meteorological data files
can be used to determine the modeled design values for PM2.5. the OU MAXDCONT option (see Section
3.7.2.8) to determine contributions from other source groups to the cumulative modeled design value will not
work with the MULTYEAR option or with separate meteorological data files for each year.) Processing the
average of the individual annual mean values across multiple years for PM-2.5 also requires use of the
ANNUAL average option on the AVERTIME keyword, rather than PERIOD average. The PERIOD option
computes a single multi-year average concentration for each receptor, which may give slightly different
results than the multi-year average of individual ANNUAL mean concentrations due to differences in the
number of calms and/or missing data from year to year.
To comply with these processing requirements, the following restrictions are applied to the PM-2.5
NAAQS processing whenever a pollutant ID of 'PM25', 'PM2.5', 'PM-2.5' or 'PM-25' is specified on the
CO POLLUTID keyword:
1. The averaging periods on the AVERTIME keyword are limited to the 24-hour and ANNUAL
averages. Use of the PERIOD average or use of a short-term average other than 24-hour will
result in a fatal error message being generated.
2. The FIRST (or 1ST) highest value should be requested on the RECTABLE keyword for 24-
hour averages for estimating modeled PM2.5 contributions for compliance with the
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NAAQS. However, the model places no restriction on the ranks requested on the
RECTABLE keyword since selection of ranks lower than the FIRST highest may be needed
to determine whether a source or group of sources is contributing significantly to modeled
violations of the NAAQS.
3. The model will only process meteorological data for periods of record that span complete
years, although the meteorological data period does not need to follow calendar years (i.e.,
the data period does not need to start on January 1, hour 1). If the period of record spans less
than one complete year of data, a fatal error message will be generated, and the model run
will be unsuccessful. If additional meteorological data remains after the end of the last
complete year of data, the remaining data will be ignored, and a non-fatal warning message
will be generated specifying the number of hours ignored.
4. The MULTYEAR keyword on the CO pathway can be used to calculate multi-year averages
for the PM-2.5 NAAQS; however, the MAXDCONT option will not work with the
MULTYEAR. Multiple year analyses are best accomplished by including the multiple years
of meteorology in a single data file.
5. Since the 24-hour average design values for PM-2.5 analyses, based on the H1H averaged
over N years, may consist of averages over a multi-year period, they are not compatible with
the EVENT processor, and the high ranked values generated based on the RECTABLE
keyword will not be included in the EVENTFIL. However, if the MAXIFILE option is used
to output 24-hour averages exceeding a user-defined threshold, these individual exceedances
may be used with the EVENT processor. Therefore, if the EVENTFIL option is used without
the MAXIFILE option for PM-2.5 analyses, a non-fatal warning message will be generated,
and the EVENTFIL option will be ignored.
3.2.16.2 Processing for particulate matter of 10 microns or less (PM-10)
The 24-hour NAAQS for particulate matter with aerodynamic particle diameters of 10 microns or
less (PM-10) is in the form of an expected exceedance value, which cannot be exceeded more than once per
year on average over a three year period for purposes of monitored attainment demonstrations. Modeling
demonstrations of compliance with the PM-10 NAAQS are based on the High-/V /-High value over TV years,
or in the case of five years of NWS meteorological data, the High-6th-High (H6H) value over five years. In
the AERMOD model, the H6H 24-hour average over five years can be modeled in one of two ways: 1)
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running five individual years and combining the results using the CO MULTYEAR option, as described
above in Section 3.2.7) using a single five-year meteorological data file and specifying the SIXTH (or 6TH)
highest value on the OU RECTABLE card. If applied properly, the 24-hour average results of these two
approaches will be equivalent. The special processing consisting of the 99th percentile 24-hour value
averaged over Nyears for PM-10 in versions of AERMOD prior to 09292, referred to as the "Post-1997"
PM-10 option, has been removed since that standard was vacated.
3.2.17 Processing for 1-hour NO? and SO? NAAQS
New 1-hour NAAQS for NO2 and SO2 were promulgated in February 2010 and June 2010,
respectively. EPA has issued guidance related to dispersion modeling in support of these 1-hour standards
(EPA, 2010b; EPA, 2010c; EPA, 2011; EPA, 2014a; and EPA, 2017a). The form of these 1-hour standards is
similar, based on a percentile rank from the annual distribution of daily maximum 1-hour values, averaged
across the number of years processed. For the 1-hour NO2 standard, the modeled design value is based on
the 98th-percentile of the daily maximum 1-hour values, which is represented by the eighth highest of the
daily maximum 1-hour values across the year. The 1-hour SO2 modeled design value is based on the 99th-
percentile, or fourth highest, of the daily maximum 1-hour values across the year. For typical multi-year
modeling analysis based on 5 years of NWS meteorological data, the modeled design value is the 5-year
average of the eighth-highest values daily maximum 1-hour values for NO2, or fourth-highest values for SO2.
The form of these 1-hour standards complicates the process of determining the modeled design value
as well as the analyses that may be required to determine whether a particular source or group of sources
contributes significantly to any modeled violations of the standards, paired in time and space. Several
enhancements have been incorporated into AERMOD, beginning with version 11059, to facilitate the
modeling analyses required to demonstrate compliance with these new standards. These enhancements are
described in Section 3.7.2. The ability of the model to exercise these options is facilitated by specifying
'N02' or 'S02' as the pollutant ID on the CO POLLUTID keyword, with the following restrictions.
Whenever a pollutant ID of 'N02' or 'S02' is specified and 1-hour averages are selected, the options to
calculate 1-hour NO2 or SO2 design values based on the distribution of daily maximum 1-hour values will be
allowed, unless short-term averaging periods other than 1-hour are also specified on the AVERTIME
keyword. If other short-term averages are specified, non-fatal warning messages will be generated and the
options for processing 1-hour NO2 or SO2 design values will be disabled. In that case, the 1-hour modeled
design values will be processed the same as other short-term averages, based on the overall distribution of
hourly values. Also, if ANNUAL or PERIOD averages are specified on the AVERTIME keyword along with
1-hour averages, a non-fatal warning message will be generated unless the CO MULTYEAR keyword is
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specified, since the annual NAAQS for NO2 and SO2 is based on the highest PERIOD or ANNUAL average
from an individual year, rather than an average across the years modeled. However, the special processing
based on daily maximum 1-hour values will be still applied for the 1-hour averages in these cases since the
ANNUAL or PERIOD averages may be appropriate if only 1 year of site-specific meteorological data is
modeled.
Modeling 1-hour 'S02' or 'N02' for less than a full year without specifying additional short-term
averaging periods will result in an error during processing since AERMOD attempts to generate a 1-hour
value based on the form of the SO2 or NO2 1-hour standard. When modeling with a dataset that contains less
than a full year of data or by restricting the days or hours that are modeled using the STARTEND or
DAYRANGE keywords on the ME pathway, the NOCHKD option should be specified on the CO pathway
along with the MODELOPT keyword to avoid an error during the processing phase (Refer to sections 3.2.2
and 3.5.4 for information on the use of the NOCHKD option and the STARTEND and DAYRANGE
keywords).
3.2.18 Debugging output options
The DEBUGOPT keyword on the CO pathway allows the user to request detailed files of
intermediate calculation results for debugging purposes. There are several types of debug information that
AERMOD can generate. For each type specified, the user can also specify a filename of the file to which the
debug output should be written. Filenames are optional with the exception of the DEPOS debug. If omitted,
AERMOD will use a default filename. The syntax and type of the DEBUGOPT keyword are summarized
below. Listed are the debug types and filename pairs. While multiple types of debugging information can be
specified, note that there are some related types in which case only one type within the group can be
specified:
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CO DEBUGOPT MODEL (Dbefil)
and/or
METEOR (Dbmfil)
and/or
PRIME (Prmfil)
and/or
AWMADW (AwmaDwfil)
and/or
PLATFORM (PlatfmDbgfil)
and/or
DEPOS
and/or
[AREA (AreaDbFil) or LINE (LineDbFil)]
and/or
RLINE (RlineDbgFil)
and/or
Syntax:
BLPDBUG (BLPDbFil)
URBANDB (UrbanDbFil)
[PVMRM (Dbpvfil) (and TTRM2) or
OLM (OLMfil) (and TTRM2) or
ARM2 (ARM2fil) (and TTRM2) or
TTRM (TTRMfil) or
and/or
and/or
GRSM (GRSMfil)]
and/or
SWPOINT (SWfil)
and/or
HBPDBG (HBPfil)
and/or
AIRCRAFT (DbARCFTfil)
Type:
Optional, Non-repeatable
where the types of debug information and optional filename references include:
MODEL (Dbgfil): Model type debug data. Default filename: MODEL.DBG.
METEOR (Dbmfile): Meteorological profile data. Default filename: METEOR.DBG.
PRIME (Prmfil): PRIME downwash debug data. Default filename: PRIME.DBG.
AWMADW (Awmafil): AWMA downwash debug data. Default filename: AWMADW.DBG
PLATFORM (PlatfmDbgfil): Platform downwash debug file. Default filename:
PLATFORM. DBG
DEPOS: Deposition debug information. Only default filenames will be used: GDEPDAT for
gas deposition and PDEP.DAT for particle deposition. If the MODEL debug option is not
chosen, a debug file containing wet deposition debug information is also created called
DEPOS.DBG. If the MODEL debug option is chosen with the DEPOS debug option, the wet
deposition debug information is included in the model debug file.
AREA (AreaDbFil) or LINE (LineDbFil): Area or Line source debugging data (includes
OPENPIT). May only specify one. Default filename: AREA.DBG (same default filename
used for AREA, LINE, and OPENPIT sources)
RLINE (RlineDbgFil): RLINE and RLINEXT source type debug file. Default filename:
RLINE.DBG
BLPDBUG (BLPDbFil): Debug information for the BUOYLINE source. Default filename:
BLPDBUG.DBG
URBANDB (UrbanDbFil): Debug information for the urban option (URBANOPT, see Section
3.2.8). This will produce three output files, one for the surface meteorology, two for the profile
meteorology. If the filename is specified by the user, then the filename will be used for the
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surface meteorology debug file. The same name will be assigned for the two profile debug
files with a "1" and "2" appended to the filename, respectively. Default filenames:
URBDBUG.DBG, URBDBUG1 DBG, and URBDBUG2.DBG.
PVMRM (Dbpvfil) (and TTRM2) or OLM (OLMfil) (and TTRM2) or ARM2 (ARM2fil) (and
TTRM2) or TTRM (TTRMfil) or GRSM (GRSMfil): NO to N02 conversion debug data.
Default filenames: PVMRM.DBG, OLM.DBG, ARM2.DBG, TTRM.DBG, GRSM.DBG,
respectively. May only specify one of PVMRM, OLM, ARM2, TTRM, or GRSM debug
options, consistent with the NO2 conversion option specified with the MODELOPT keyword.
The TTRM2 debug option can be paired with PVMRM, OLM, or ARM2 debug options when
both options are specified with the MODELOPT keyword. A user-defined filename cannot be
specified for the TTRM2 debug option. The TTRM2 debug option will generate three separate
debug files named AFTER TTRM.DBG, AFTER_opftoĞ.DBG, and TTRM2 MERGE DBG,
where option is the NO2 conversion option with which TTRM2 is paired, (e.g.,
AFTER PVMRM.DBG).
SWPOINT (SWfil): Sidewash point source type debug information and optional debug
filename. Default filename: SWPOINT.DBG
HBPDBG (HBPfil): Debug information for HBP option and optional debug filename. Default
filename: HBP DEBUG.DBG.
AIRCRAFT (DbARCFTfil): Debug information for the aircraft plume rise option
(ARCFTOPT) and optional debug filename. Default filename: AIRCRAFT.DBG.
CAUTION!! Use the DEBUGOPT keyword with extreme CAUTION: it can produce very large files!
Note that the model will overwrite the debug files, without warning, if they already exist.
3.2.19 Detailed error listing file
The ERRORFIL keyword on the CO pathway allows the user to request a detailed listing file of all
the messages generated by the model. This includes the error and warning messages that are listed as part of
the message summaries provided in the main output file and any informational messages (such as
occurrences of calm winds) and quality assurance messages that are generated. The syntax and type of the
ERRORFIL keyword are summarized below:
Syntax: CO ERRORFIL (Errfil)
Type: Optional, Non-repeatable
where the Errfil parameter is the name of the detailed message file. If the optional Errfil parameter is left
blank, then the model will use a default filename of ERRORS.LST. A complete description of the error and
other types of messages generated by the model is provided in APPENDIX B.
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3.3 Source pathway inputs and options
The SOurce pathway contains the keywords that define the source information for a particular model
run. The model currently handles six source types identified as point, volume, area sources (including non-
buoyant line and open pit sources), non-buoyant line (e.g., roadway sources), buoyant line sources, and a
newly added source type to research the sidewash effect from building downwash when the winds are
oblique to the face of a building. The input parameters vary depending on the source type. For point
sources, the user can also identify building dimensions for nearby structure that cause aerodynamic
downwash influences on the source. The user can also identify groups of sources for which the model will
combine the results.
The LOCATION keyword, which identifies the source type and location, must be the first keyword
entered for each source. In general, the order of the keywords is not important. However, there are some
exceptions such as, the SRCGROUP keyword must be the last keyword before the SO FINISHED keyword
unless the PSDCREDIT keyword is specified on the MODELOPT card, in which case SRCGROUP is
replaced with the PSDGROUP keyword. Additional exceptions are discussed in the sections specific to
applicable keywords. The user may group all the LOCATION cards together, then group the source
parameter cards together, or they may want to group all input cards for a particular source together. All
sources are given a source ID by the user, which is used to link the source parameter inputs to the correct
source or sources. The source ID can be any alphanumeric string of up to 12 characters.
The number of sources is allocated dynamically at the time AERMOD is run. This value, in concert
with the other dynamically allocated arrays and input requirements, is limited only by the amount of
available memory.
3.3.1 Identifying source types and locations
The LOCATION keyword is used to identify the source type and the location of each source to be
modeled. The LOCATION card must be the first card entered for each source since it identifies the source
type and dictates which parameters are needed and/or accepted. The syntax, type and order of the
LOCATION keyword are summarized below:
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Syntax:
When Srctyp = POINT, POINTHOR, POINTCAP, VOLUME, AREA, AREAPOLY,
AREACIRC, OPENPIT, or SWPOINT
SO LOCATION Srcid Srctyp Xs Ys (Zs)
When Srctyp = LINE, RLINE, or BUOYLINE
SO LOCATION Srcid Srctyp Xsl Ysl Xs2 Ys2 (Zs)
When Srctyp = RLINEXT
SO LOCATION Srcid Srctyp Xsl Ysl Zsl Xs2 Ys2 Zs2 (Zs)
Type:
Mandatory, Repeatable
Order:
Must be first card for each source input
where the Srcid parameter is the alphanumeric source ID defined by the user (up to 12 characters), Srctyp is
the source type, which is identified by one of the secondary keywords - POINT. POINTHOR. POINTCAP.
VOLUME. AREA. AREAPOLY. AREACIRC. OPENPIT. LINE. RLINE. RLINEXT. BUOYLINE. or
SWPOINT. Xs and Ys, are the x and y coordinates of the source location in meters for POINT, POINTHOR,
POINTCAP, VOLUME, AREA, AREAPOLY, AREACIRC, OPENPIT, and SWPOINT source types. For the
LINE and RLINE source type, Xsl and Ysl are the x and y coordinates for the midpoint of one end of the
LINE or RLINE source while Xs2 and Ys2 are the x and y coordinates for the midpoint of the other end of
the LINE or RLINE source. For the RLINEXT source type, Zsl and Zs2 are the release heights for the
endpoints of the source. For the OPENPIT source type, Zs is the elevation at the top of the pit, and the
effective depth is calculated based on the lateral dimensions and volume of the pit.
Beginning with version 19191, the RLINE and RLINEXT source types were added to the SO
pathway for roadway sources. Beginning with AERMOD version 24142, the RLINE source type was
updated to a regulatory option while the RLINEXT source type is an ALPHA option and requires the
ALPHA keyword with the MODELOPT keyword. The original implementation of RLINE and RLINEXT
was based on the numerical integration and algorithms in the Research LINE-source model, version 1.2, for
near-surface releases (Snyder et al., 2013). The implementation has since been updated to better harmonize
the RLINE and RLINEXT source types with AERMOD similar to the POINT, AREA, and VOLUME source
types as described in EPA's related TSD (EPA, 2023). The R-LINE model was formulated for flat terrain,
and the original implementation in AERMOD required terrain to be specified as FLAT. Beginning in
AERMOD version 23132, RLINE/RLINEXT can account for elevated terrain; however, when modeling for
project level transportation conformity and hot-spot analyses, refer to the EPA's Office of Transportation and
Air Quality (OTAQ) for the most up-to-date guidance on how to model roadway sources
(https://www.epa.gov/state-and-local-transportation/proiect-level-conformitv-and-hot-spot-analvses).
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RLINEXT sources require the user to input the offset distance from road centerline, number of lanes,
width per lane and initial vertical dispersion for each specified road link. These parameters are discussed in
more detail in Section 3.3.2.10. Also, refer to the user's guide for R-LINE Model Version 1.2 (Snyder and
Heist, 2013) and EPA's 2023 TSD (EPA, 2023) for detailed information about the original formulation of the
RLINE source algorithms as well as the reformulation beginning in AERMOD version 23132.
Beginning with version 15181, the BUOYLINE source type was added to the SO pathway for
buoyant line sources. The current implementation is based on the buoyant line source algorithm in the
Buoyant Line and Point Source (BLP) dispersion model (Schulman and Scire, 1980) with very little
modification and similar limitations. A buoyant line source is, comprised of one or multiple lines. Multiple
lines are assumed to be parallel, though each line can have a different length, height, and base elevation.
AERMOD will check to see if the lines in a single source are parallel, within a 5° tolerance, to the first line
in the source. If an individual buoyant line exceeds the tolerance, AERMOD will issue a warning message,
but will continue the model run. The BUOYLINE source type also requires the user to input average values
of length, width, height, and separation distance for the set of lines that comprise the buoyant line source.
These parameters are discussed in more detail in Section 3.3.2.11. Refer to the BLP user's guide (Schulman
and Scire, 1980) for detailed information about the formulation of the buoyant line source algorithm.
Beginning with version 22112, the SWPOINT source type was added to the SO pathway as a
research tool to study the sidewash effects of the recirculation cavity that forms on the lee side a building and
shifts laterally when the wind is oblique to the face of the building. The SWPOINT source has been added
for continued research and development and requires the ALPHA secondary keyword as a model option
using the MODELOPT keyword on the CO pathway.
For the BUOYLINE source, the definitions of Xs 1, Ys 1, Xs2, and Ys2 are similar to the definitions
for the LINE source, but there is a subtle difference due to the current implementation of the buoyant line
source algorithm in AERMOD. When specifying a buoyant line source, the LOCATION keyword and
parameters should be repeated for each individual line that comprises the buoyant line source. BUOYLINE
should be specified as the source type (Srctyp), and each line should be given a unique source ID (Srcid).
Note that the order that the individual lines are entered using the LOCATION keyword in the control
file is important. Again, as in BLP, AERMOD assumes all of the buoyant lines are parallel. As noted
above, AERMOD performs a check to see if the lines are within an allowable tolerance, currently 5°, and
issues a warning message if a line exceeds this tolerance. For lines that are not oriented exactly north-south
but are angled either southeast-to-northwest or southwest-to-northeast, the individual lines should be entered
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in the order of there location from south to north. In other words, the southern most line should be defined
first in the control file, followed by the adjacent line to the north and so on, ending with the northernmost
line. For an individual line, the most westerly endpoint should be entered first followed by the easterly
endpoint where Xsl and Ysl are the x and y coordinates of the most westerly endpoint of the line, and Xs2
and Ys2 are the x and y coordinates of the most easterly endpoint of the line. Zs is the optional elevation of
the source above sea-level and is applicable for all source types.
In the case where the buoyant lines are parallel to the Y axis, the order that the lines should be
entered is dependent on which endpoint is entered first, the southern or northern endpoint of the lines. If the
southern endpoint is entered first, the lines should be entered in the order of the eastern most line to
the western most line. If the northern endpoint is entered first, lines should be ordered west to east.
The convention used for the first line should be used for all subsequent lines.
The three area source types (AREA, AREACIRC, and AREAPOLY), as well as the LINE source
type use the same numerical integration algorithm for estimating impacts from area sources and are merely
different options for specifying the shape of the area source. The AREA source keyword may be used to
specify a rectangular-shaped area source with arbitrary orientation; the AREAPOLY source keyword may be
used to specify an area source as an irregularly shaped polygon of up to 20 sides; and the AREACIRC source
keyword may be used to specify a circular-shaped area source (modeled as an equal-area polygon of 20
sides). The LINE source type option allows users to specify line-type sources based on a start point and end
point of the line and the width of the line, as an alternative to the current AREA source type for rectangular
sources. The LINE source type utilizes the same routines as the AREA source type and will give identical
results for equivalent source inputs. The LINE source type also includes an optional initial sigma-z
parameter on the SRCPARAM keyword to account for initial dilution of the emissions. AREA, AREAPOLY,
AREACIRC, LINE, and OPENPIT source types do not, by default, include the horizontal meander
component in AERMOD. AREAMNDR was added in 23132 as an ALPHA option on the CO pathway
which incorporates meander into the AREA, AREAPOLY, AREACIRC, and LINE sources if specified. Since
the LINE source type utilizes the AREA source algorithms, the runtime optimizations associated with the
FASTAREA option will also apply to LINE sources if included. The AREAMNDR option will not add
meander to the AREA, AREAPOLY, AREACIRC, or LINE sources if the FASTAREA option has been
included.
The RLINE and RLINEXT source types use the numerical integration algorithms described in
Snyder et. al. 2013, intended mainly for roadway sources. Beginning with version 19191, the RLINE and
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RLINEXT source types were added as an option to the SO pathway. Initial sigma-z (vertical
dispersion/dilution) and width are specified using the SRCPARAM keyword on the SO pathway for an
RLINE and RLINEXT source. The RLINEXT source requires an additional distance from the centerline
parameter on the SRCPARAM keyword, used in the barrier and depressed roadway algorithms. The RLINE
and RLINEXT source types contain a horizontal meander component for roadway sources.
The OPENPIT source algorithm can be used to model particulate or gaseous emissions from open
pits, such as surface coal mines and rock quarries. The OPENPIT algorithm uses an effective area for
modeling pit emissions, based on meteorological conditions, and then utilizes the numerical integration area
source algorithm to model the impact of emissions from the effective area sources. A complete technical
description of the OPENPIT source algorithm is provided in the ISC3 Model User's Guide - Volume II (EPA,
1995b).
Note that the source elevation, Zs, is an optional parameter. If the default option to include elevated
terrain effects is used and the source elevation is omitted, a warning message will be generated, and the
source elevation will be given a value of 0.0. The source elevation is not used by the model if the non-
default FLAT terrain option is used. While the default units of Zs are meters, the user may also specify
source elevations to be in feet by adding the SO ELEVUNIT FEET card immediately following the SO
STARTING card. The x (east-west) and y (north-south) coordinates are for the center of the source for
POINT. POINTHOR. POINTCAP. VOLUME. AREACIRC. SWPOINT sources, for one of the vertices of
the source for AREA. AREAPOLY. and OPENPIT sources, and the endpoints for RLINE. RLINEXT. and
BUOYLINE sources. The source coordinates may be input as Universal Transverse Mercator (UTM)
coordinates or may be referenced to a user-defined origin.
Certain types of non-buoyant line sources can be handled in AERMOD using a string of volume
sources, an elongated area source, or a roadway source. The volume source algorithms are most applicable
to line sources with some initial plume depth, such as conveyor belts and rail lines. Section 1.2.2 of the ISC
Model User's Guide - Volume II (EPA, 1995b) provides technical information on how to model a line source
with multiple volume sources. The use of the AERMOD area source algorithm for elongated rectangles
would be most applicable to near ground level line sources, such as a viaduct. The area source algorithm is
applied identically to both AREA and LINE source types and AERMOD should produce the same results for
an elongated area source defined as either an AREA or LINE source type.
The source ID entered on the LOCATION card identifies that source for the remainder of the SO
pathway inputs. Since the model accepts alphanumeric strings of up to 12 characters for the source ID, the
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sources can be identified with descriptive names, such as STACK1, STACK2, BOILER3, SLAGPILE, etc.
This may also be useful if line sources are being modeled as multiple volume or areas, as discussed above.
Since they are part of the same physical source, they can be given names that will identify them as being
related, such as LINE 1 A, LINE IB, LINE1C, etc.
It should be noted that not all NO2 conversion options have been implemented for all source types in
AERMOD. Table 3-2 summarizes which NO2 conversion options have been implemented for each of the
AERMOD source types and which options have not.
3.3.2 Specifying source release parameters
The main source parameters are input on the SRCPARAM card, which is a mandatory keyword for
each source being modeled. Since the input parameters vary depending on the source type, the different
source types handled by the AERMOD model are discussed separately.
3.3.2.1 POINT. POINTHOR, and POINTCAP source inputs
The AERMOD POINT source algorithms are used to model releases from stacks and isolated vents,
as well as other kinds of sources. The syntax, type and order for the SRCPARAM card for POINT.
POINTHOR, and POINTCAP sources are summarized below:
Syntax:
SO SRCPARAM Srcid Ptemis Stkhgt Stktmp Stkvel Stkdia
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
Ptemis - point emission rate in g/s,
Stkhgt - release height above ground in meters,
Stktmp - stack gas exit temperature in degrees K,
Stkvel - stack gas exit velocity in m/s, and
Stkdia - stack inside diameter in meters.
An example of a valid SRCPARAM input card for a point source is given below:
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SO SRCPARAM STACK1 16.71 35.0 444.0 22.7 2.74
where the source ID is STACK1, the emission rate is 16.71 g/s, the release height is 35.0 m, the exit
temperature is 444.0 K, the exit velocity is 22.7 m/s, and the inside stack diameter is 2.74 m. All the
parameters must be present on the input card.
If a value of 0.0 is input for the exit temperature, AERMOD will adjust the exit temperature for each
hour to match the ambient temperature. This option allows the user to model a plume that is released at
ambient temperature. The user may also model a plume with an exit temperature that exceeds the ambient
temperature by a fixed amount by entering a negative value for exit temperature equal in magnitude to the
temperature difference. The model will add the absolute value of a negative exit temperature to the ambient
temperature for each hour to obtain the exit temperature used in computing the buoyancy flux of the plume.
The AERMOD model does not include algorithms to model plumes that are released at temperatures below
ambient temperature. Such releases should be modeled with a dense gas model.
AERMOD model uses direction-specific building dimensions for POINT, POINTHOR, and
POINTCAP sources subject to building downwash. Building dimensions for these source types are entered
on the BUILDHGT, BUILDWID, BUILDLEN, XBADJ, and YBADJ cards described below in Section 3.3.9.
Offshore platform dimensions for these source types are entered for each source ID using the PLATFORM
keyword as described below in Section 3.3.16.
3.3.2.2 VOLUME source inputs
The AERMOD VOLUME source algorithms are used to model releases from a variety of industrial
sources, such as building roof monitors, multiple vents, and conveyor belts. Beginning with AERMOD
version 23132, the input parameters for VOLUME (and AREA) source types were expanded to characterize
aircraft emissions to account for the effects of buoyancy and momentum (see Section 3.2.12). The additional
parameters are required to be input as hourly data in the hourly emissions file (see Section 3.3.12). Thus,
aircraft sources can only be modeled as a VOLUME source using an hourly emissions file that includes the
non-aircraft VOLUME source parameters described in Section 3.3.12, as well as the extended set of
parameters required to characterize the aircraft source as a VOLUME source as described in Section 3.3.12.
The syntax, type, and order for the SRCPARAM card for VOLUME sources are summarized below:
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Syntax:
SO SRCPARAM Srcid Vlemis Relhgt Syinit Szinit
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
Vlemis - volume emission rate in g/s,
Relhgt - release height (center of volume) above ground, in meters,
Syinit - initial lateral dimension of the volume in meters, and
Szinit - initial vertical dimension of the volume in meters.
Table 3-3, which is explained in more detail in Section 1.2.2 of the ISC Model User's Guide - Volume II,
summarizes the suggested procedures to be used for estimating the initial lateral and vertical dimensions for
various types of volume and line sources.
Table 3-3. Summary of Suggested Procedures for Estimating Initial Lateral Dimensions oyo
and Initial Vertical Dimensions ozo for Volume and Line Sources
Procedure for Obtaining
Type of Source Initial Dimension
(a) Initial Lateral Dimension (oy0)
Single Volume Source oy0 = length of side divided by 4.3
Line Source Represented by Adjacent Volume oy0 = length of side divided by 2.15
Sources (see Figure 1-8 (a) in EPA, 1995a)
Line Source Represented by Separated Volume oy0 = center to center distance divided by 2.15
Sources (see Figure l-8(b) in EPA, 1995a)
(b) Initial Vertical Dimension (oZ0)
Surface-Based Source (he ~ 0) oZ0 = vertical dimension of source divided by 2.15
Elevated Source (he > 0) on or Adjacent to a oZ0 = building height divided by 2.15
Building
Elevated Source (he > 0) not on or Adjacent to oZ0 = vertical dimension of source divided by 4.3
a Building
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3.3.2.3 AREA source type
The AERMOD area source algorithm is used to model low level or ground level releases with no
plume rise (e.g., storage piles, slag dumps, and lagoons). The AERMOD model uses a numerical integration
approach for modeling impacts from area sources. When the FASTAREA or FASTALL option is specified,
the area source integration routine is optimized to reduce model runtime. This is accomplished by
incorporation of a three-tiered approach using the Romberg numerical integration, a 2-point Gaussian
Quadrature routine for numerical integration, or a point source approximation based on the location of the
receptor relative to the source. In the regulatory default mode, the Romberg numerical integration is utilized
for all receptors.
The AERMOD model includes various options for specifying the shape of an area source: the AREA
source type may be used to specify rectangular areas that may also have a rotation angle specified relative to
a north-south orientation; the LINE source type is a simplified representation of an elongated area source and
does not utilize a rotation angle; the AREAPOLY source type may be used to specify an area source as an
irregularly-shaped polygon of up to 20 sides; the AREACIRC source keyword may be used to specify a
circular-shaped area source (modeled as an equal-area polygon of 20 sides); and the OPENPIT source type
can be used to model open rectangular pits such as surface coal mines and rock quarries. The OPENPIT
source type also includes an optional rotation angle. The source parameter inputs for each of the area source
types is described below.
3.3.2.4 AREA source inputs
The rotation angle for rectangular AREA sources is specified relative to the vertex used to define the
source location on the SO LOCATION card (e.g., the southwest corner). The syntax, type and order for the
SRCPARAM card for AREA sources are summarized below:
Syntax:
SO SRCPARAM Srcid Aremis Relhgt Xinit (Yinit) (Angle) (Szinit)
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
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Aremis - area emission rate in g/(s-m2),
Relhgt - release height above ground in meters,
Xinit - length of X side of the area (in the east-west direction if Angle is 0 degrees)
in meters,
Yinit - length of Y side of the area (in the north-south direction if Angle is 0
degrees) in meters (optional),
Angle - orientation angle for the rectangular area in degrees from North, measured
positive in the clockwise direction (optional), and
Szinit - initial vertical dimension of the area source plume in meters (optional).
It should be noted that the emission rate for the area source is an emission rate per unit area, which is
different from the point and volume source emission rates, which are total emissions for the source.
If the optional Yinit parameter is omitted, then the model assumes that the area is a square, i.e., Yinit
= Xinit. If the optional Angle parameter is omitted, then the model assumes that the area is oriented in the
north-south and east-west directions, i.e., Angle = 0.0. If the Angle parameter is input, and the value does
not equal 0.0, then the model will rotate the area clockwise around the vertex defined on the SO LOCATION
card for this source. Figure 3-1 illustrates the relationship between the Xinit, Yinit, and Angle parameters
and the source location, (Xs,Ys), for a rotated rectangle. The Xinit dimension is measured from the side of
the area that is counterclockwise along the perimeter from the vertex defined by (Xs,Ys), while the Yinit
dimension is measured from the side of the area that is clockwise from (Xs,Ys). The Angle parameter is
measured as the orientation relative to North of the side that is clockwise from (Xs,Ys), i.e., the side with
length Yinit. The Angle parameter may be positive (for clockwise rotation) or negative (for
counterclockwise rotation), and a warning message is generated if the absolute value of Angle is greater than
180 degrees. The selection of the vertex to use for the source location is not critical, as long as the
relationship described above for the Xinit, Yinit, and Angle parameters is maintained.
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Figure 3-1. Relationship of Area Source Parameters for Rotated Rectangle
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By making the Yinit and Angle parameters optional, the area source input data for the previous
versions of the ISC model can be used with the AERMOD model. The aspect ratio (i.e., length/width) for
area sources should generally be less than about 100 to 1. If this is exceeded, then the model will generate a
non-fatal warning message, and the user should consider subdividing the area to achieve a 100 to 1 aspect
ratio (or less) for all subareas.
The optional Szinit parameter may be used to specify an initial vertical dimension to the area source
plume, similar to the use of the Szinit parameter for volume sources. This parameter may be important when
the area source algorithm is used to model mechanically generated emission sources, such as mobile sources.
In these cases, the emissions may be turbulently mixed near the source by the process that is generating the
emissions, and therefore occupy some initial depth. For more passive area source emissions, such as
evaporation or wind erosion, the Szinit parameter may be omitted, which is equivalent to using an initial
sigma-z of zero.
An example of a valid SRCPARAM input card for a rectangular area source is given as
SO SRCPARAM SLAGPILE 0.00155.0 50.0 100.0 30.0
where the source ID is SLAGPILE, the emission rate is 0.0015 g/(s-m2), the release height is 5.0 m, the X-
dimension is 50.0 m, the Y-dimension is 100.0 m, and the orientation angle is 30.0 degrees clockwise from
North.
Since the numerical integration algorithm can handle elongated areas with aspect ratios of up to 100
to 1, the AERMOD area source algorithm may be useful for modeling certain types of line sources. User's
now have the option of specifying a line-type source as either AREA or LINE. There are no restrictions on
the placement of receptors relative to area sources for the AERMOD model. Receptors may be placed within
the area and at the edge of an area. The AERMOD model will integrate over the portion of the area that is
upwind of the receptor. However, since the numerical integration is not performed for portions of the area
that are closer than 1.0 meter upwind of the receptor, caution should be used when placing receptors within
or adjacent to areas that are less than a few meters wide. More technical information about the application of
the AERMOD area source algorithm is provided in Sections 1.2.3 and 2.2.3 of the ISC Model User's Guide -
Volume II (EPA, 1995b).
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Beginning with AERMOD version 23132, the input parameters for AREA (and VOLUME) source
types were expanded to characterize aircraft emissions to account for the effects of buoyancy and momentum
(see Section 3.2.12). The additional parameters are required to be input as hourly values in the hourly
emission rate file (see Section 3.3.12). Thus, aircraft sources can only be modeled using an hourly emissions
file that that includes the standard non-aircraft AREA source parameters described in Section 3.3.12, as well
as the extended set of parameters required to characterize the aircraft source as an AREA source as described
in Section 3.3.12.
3.3.2.5 AREAPOLY source inputs
The AREAPOLY source type may be used to specify an area source as an arbitrarily- shaped
polygon of between 3 and 20 sides (the number of sides allowed may be increased by modifying the
NVMAX parameter in MODULE MAIN1). This source type option provides the user with considerable
flexibility for specifying the shape of an area source. The syntax, type and order for the SRCPARAM card
for AREAPOLY sources are summarized below:
Syntax:
SO SRCPARAM Srcid Aremis Relhgt Nverts (Szinit)
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
Aremis - area emission rate in g/(s-m2),
Relhgt - release height above ground in meters,
Nverts - number of vertices (or sides) of the area source polygon,
Szinit - initial vertical dimension of the area source plume in meters (optional).
As with AREA sources, the emission rate for the source is an emission rate per unit area, which is different
from the point and volume source emission rates, which are total emissions for the source. The locations of
the vertices are specified by use of the AREAVERT keyword, which applies only to AREAPOLY sources.
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The syntax, type and order for the AREAVERT keyword used for AREAPOLY sources are summarized
below:
Syntax:
SO AREAVERT Srcid Xv(l) Yv(l) Xv(2) Yv(2) ... Xv(i) Yv(i)
Type:
Mandatory for AREAPOLY sources. Repeatable
Order:
Must follow the LOCATION card for each source input
where the Xv(i) and Yv(i) are the x-coordinate and y-coordinate values of the vertices of the area source
polygon. There must by Nverts pairs of coordinates for the area source, where Nverts in the number of
vertices specified for that source on the SRCPARAM card. The first vertex, Xv(l) and Yv(l), must also
match the coordinates given for the source location on the LOCATION card, Xs and Ys. The remaining
vertices may be defined in either a clockwise or counter- clockwise order from the point used for defining the
source location.
Receptors may be placed within the area and at the edge of an area. The AERMOD model will
integrate over the portion of the area that is upwind of the receptor. However, since the numerical integration
is not performed for portions of the area that are closer than 1.0 meter upwind of the receptor, caution should
be used when placing receptors within or adjacent to areas that are less than a few meters wide.
3.3.2.6 AREACIRC source inputs
The AREACIRC source type may be used to specify an area source as a circular shape. The model
will automatically generate a regular polygon of up to 20 sides to approximate the circular area source. The
polygon will have the same area as that specified for the circle. The syntax, type and order for the
SRCPARAM card for AREACIRC sources are summarized below:
Syntax:
SO SRCPARAM Srcid Aremis Relhgt Radius (Nverts) (Szinit)
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
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Aremis -
Relhgt -
Radius -
Nverts -
Szinit -
area emission rate in g/(s-m2),
release height above ground in meters,
radius of the circular area in meters,
number of vertices (or sides) of the area source polygon (optional, 20 sides will be
used if omitted),
initial vertical dimension of the area source plume in meters (optional).
As with AREA sources, the emission rate for the source is an emission rate per unit area, which is different
from the point and volume source emission rates, which are total emissions for the source.
3.3.2.7 OPENPIT source inputs
The AERMOD model accepts rectangular pits with an optional rotation angle specified relative to a
north-south orientation and the vertex used to define the source location on the SO LOCATION card (e.g.,
the southwest corner). The syntax, type and order for the SRCPARAM card for OPENPIT sources are
summarized below:
Syntax:
SO SRCPARAM Srcid Opemis Relhgt Xinit Yinit Pitvol (Angle)
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
Opemis - open pit emission rate in g/(s-m2),
Relhgt - average release height above the base of the pit in meters,
Xinit - length of X side of the open pit (in the east-west direction if Angle is 0 degrees) in
meters,
Yinit - length of Y side of the open pit (in the north-south direction if Angle is 0 degrees) in
meters,
Pitvol - volume of open pit in cubic meters, and
Angle - orientation angle for the rectangular open pit in degrees from North, measured positive
in the clockwise direction (optional).
The same emission rate is used for both concentration and deposition calculations in the AERMOD
model. It should also be noted that the emission rate for the open pit source is an emission rate per unit area
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as with the other area source types. This is different from the point and volume source emission rates, which
are total emissions for the source. The Relhgt parameter cannot exceed the effective depth of the pit, which
is calculated by the model based on the length, width, and volume of the pit. A Relhgt of 0.0 indicates
emissions that are released from the base of the pit.
If the optional Angle parameter is input, and the value does not equal 0.0, then the model will rotate
the open pit clockwise around the vertex defined on the SO LOCATION card for this source. The
relationship between the Xinit, Yinit, and Angle parameters and the source location, (Xs,Ys), for a rotated pit
is the same as for rectangular area sources. The Xinit dimension is measured from the side of the area that is
counterclockwise along the perimeter from the vertex defined by (Xs,Ys), while the Yinit dimension is
measured from the side of the open pit that is clockwise along the perimeter from (Xs,Ys). Unlike the area
source inputs, the Yinit parameter is not optional for open pit sources. The Angle parameter is measured as
the orientation relative to North of the side that is clockwise from (Xs,Ys), i.e., the side with length Yinit.
The Angle parameter may be positive (for clockwise rotation) or negative (for counterclockwise rotation),
and a warning message is generated if the absolute value of Angle is greater than 180 degrees. The selection
of the vertex to use for the source location is not critical, as long as the relationship described above for the
Xinit, Yinit, and Angle parameters is maintained.
The aspect ratio (i.e., length/width) of open pit sources should be less than 10 to 1. However, since
the pit algorithm generates an effective area for modeling emissions from the pit, and the size, shape and
location of the effective area is a function of wind direction, an open pit cannot be subdivided into a series of
smaller sources. Aspect ratios of greater than 10 to 1 will be flagged by a warning message in the output file,
and processing will continue. Since open pit sources cannot be subdivided, the user should characterize
irregularly-shaped pit areas by a rectangular shape of equal area. Receptors should not be located within
the boundaries of the pit; concentration and/or deposition at such receptors will be set to zero. Such
receptors will be identified during model setup and will be flagged in the summary of inputs.
An example of a valid SRCPARAM input card for an open pit source is given below:
SO SRCPARAM NORTHPIT 1.15E-4 0.0 150.0 500.0 3.75E+6 30.0
where the source ID is NORTHPIT, the emission rate is 1.15E-4 g/(s-m2), the release height is 0.0 m, the
X-dimension is 150.0 m, the Y-dimension is 500.0 m, the pit volume is 3.75E+6 cubic meters (corresponding
to an effective pit depth of about 50 meters) and the orientation angle is 30.0 degrees clockwise from North.
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Note, that unlike the ISC model formulation for OPENPIT sources, particle information (diameter, mass
fraction, and density) are not needed by AERMOD except when modeling with particle deposition or
depletion.
3.3.2.8 LINE source inputs
The syntax, type and order for the SRCPARAM card for LINE sources are summarized below:
Syntax:
SO SRCPARAM Srcid Lnemis Relhgt Width (Szinit)
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
Lnemis - line source emission rate in g/(s-m2),
Relhgt - average release height above ground in meters,
Width - width of the source in meters (with a minimum width of lm),
Szinit - initial vertical dimension of the line source in meters (optional).
As noted above, the LINE source type option in AERMOD uses the same algorithms as used for the AREA
source type for rectangular sources and will give identical results for equivalent source definitions. The
LINE source emission rate is in g/(s-m2) and the model assumes that emissions are uniformly distributed
across the dimensions of the LINE source. As with the AREA source type, the LINE source type does not
include the horizontal meander component that is incorporated for POINT and VOLUME sources unless the
AREAMNDR and ALPHA keywords have been specified. Also, as with the AREA source type, the LINE
source type will estimate concentrations (and/or deposition) at receptors located within the dimensions of the
source.
3.3.2.9 RLINE source inputs
The AERMOD RLINE source algorithm is used to model near-surface releases from mobile sources
and can be used to represent a travelled roadway with either single or multiple lanes of traffic. The
AERMOD model simulates mobile source emissions using Romberg numerical integration of point sources,
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with the number of points included in the integration determined by error analysis. Beginning with version
24142, the RLINE source type has been updated to a regulatory option and can be used with the DFAULT
option.
RLINE was originally formulated as a flat terrain model, and in the original implementation,
AERMOD required that the FLAT MODELOPT flag was specified. If FLAT and ELEV were both used, Zs
for all RLINE sources needed to be = 0.0 or = 'FLAT'. Beginning with version 23132, the RLINE source
type can account for terrain elevations. However, when modeling for project level transportation
conformity and hot-spot analyses, refer to the EPA's Office of Transportation and Air Quality (OTAQ)
for current guidance on how to model and configure roadway sources (https://www.epa.gov/state-and-
local-transportation/proiect-level-conformitv-and-hot-spot-analvses).
The syntax, type, and order for the SRCPARAM card for RLINE sources are summarized below:
Syntax:
SO SRCPARAM Srcid Lnemis Relhgt Width (Szinit)
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
Lnemis3 - line source emission rate in g/s/m2,
Relhgt - average release height above ground in meters,
Width - width of the source in meters (with a minimum width of lm),
Szinit - initial vertical dimension of the line source in meters (optional).
Notice these are identical to the LINE source type above, thus allowing the user to use the RLINE
dispersion calculations by simply changing the source type from LINE to RLINE. The RLINE source
emission rate is in grams/second/meter2, and the model assumes that emissions are uniformly distributed. If
the keyword RLEMCONV is used on the SO pathway, then the emission units for all RLINE sources should
be in g/hr/link (see Section 3.3.13).
3 Alternatively, the user may specify emissions units of grams per link per hour for the RLINE and RLINEXT source
types using the RLEMCONV keyword on the SO pathway (See Section 3.3.13.)
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3.3.2.10 RLINEXT source inputs
Like the RLINE source type, the RLINEXT source type is used to model near-surface releases from
mobile sources and can be used to represent a travelled roadway with either single or multiple lanes of
traffic. Unlike RLINE, RLINEXT source type is a non-regulatory ALPHA option. The RLINEXT source
type cannot be used with the DFAULT option and requires use of the non-regulatory ALPHA flag with the
Control pathway MODELOPT keyword. RLINE and RLINEXT sources use the same dispersion
calculations, but the parameter requirements to characterize each of the source types are different. Prior to
version 23132, AERMOD also required that the FLAT MODELOPT flag was specified when using the
RLINEXT source. If FLAT and ELEV were both used, Zs for all RLINEXT sources needed to be = 0.0 or =
'FLAT'. Beginning with version 23132, the RLINEXT source type can process terrain elevations as does the
RLINE source type. However, when modeling for project level transportation conformity and hot-spot
analyses, refer to the EPA's Office of Transportation and Air Quality (OTAQ) for current guidance on
how to model and configure roadway sources (https://www.epa.gov/state-and-local-
transportation/proiect-level-conformitv-and-hot-spot-analvses).
The syntax, type, and order for the SRCPARAM card for RLINEXT sources are summarized below:
Syntax:
SO SRCPARAM Srcid Rlemis DCL Width Szinit
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
Rlemis3 -
DCL -
Width -
Szinit -
roadway source emission rate in g/s/m,
distance from the roadway centerline to the center of the source (e.g., the center of the
lane of traffic for a one-lane source) in meters,
width for each source in meters (e.g., for a one lane source, Width would be the width of
the lane),
initial vertical dimension of the line source in meters.
All parameters are required for an RLINEXT source type, however, the user may enter "0" for any
unused parameters. The RLINEXT source emission rate is in grams/second/meter and the model assumes
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that emissions are uniformly distributed across the dimensions of the RLINEXT source. If the keyword
RLEMCONV is used on the SO pathway, then the emission units for all RLINEXT sources should be in
g/hr/link (see Section 3.3.13).
The distance from the centerline (DCL) parameter determines the offset from the roadway centerline
for a source representing a single lane of traffic, as shown in Figure 3-2. For example, in the case of a multi-
lane, divided highway with traffic travelling in the northbound and southbound directions, the centerline
would be defined as the midpoint of the highway median. The DCL would be the perpendicular distance
from the midpoint of the median to the midpoint of each source, i.e., middle distance between source end
points. If a source is one lane, the DCL would be the distance from the midpoint of the median to the center
of the lane. A positive DCL value indicates the source is to the east of the median for a north-south oriented
source, or to the north of the median for an east-west oriented source. A negative DCL value means the
source is to the west of the median for a north-south oriented source, or to the south of the median for an
east-west oriented source.
Most
(+DCL) Source East of median (-DCL) Source West of median
Orientations
Exception:
East-West (+DCL) Source North of median (-DCL) Source South of median
Orientation
DCL can be 0 for lanes of traffic with defined source coordinates, unless the user includes the RDEPRESS
keyword, explained below, in which case DCL must represent the distance from the roadway centerline for
each individual source. In the multi-lane, divided highway example where each lane is a unique source, each
source would have a DCL reflecting the distance from the midpoint of the median to the middle of the
individual lane of traffic, with the easternmost-lane having the largest-magnitude positive DCL value and the
westernmost-lane having the largest-magnitude negative DCL value.
It should be noted that use of the RDEPRESS keyword requires that all RLINEXT sources have
coordinates reflecting the roadway centerline coordinates, and not coordinates representing the individual
lane of traffic. DCL with the RDEPRESS keyword must, therefore, define the distance of each source to a
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common location. The user may apply similar source characterization to RLINEXT sources without the use
of RDEPRESS, so that DCL defines the location of each lane from a common set of coordinates.
Figure 3-2. Definition of DCL for RLINEXT sources. Dashed lines represent lanes of a
roadway with an offset (DCL) from the median (solid line).
The Width parameter specifies the width of the RLINEXT source (e.g., the width of a lane or
multiple lanes, depending on how the source is defined). A warning message is issued if Width is less than
zero.
Optionally, RLINEXT sources can also contain source configurations to represent solid barriers or a
depressed location. A roadside barrier is specified with the RBARRIER keyword. The syntax, type, and order
for the RBARRIER card for RLINEXT sources are summarized below:
Syntax:
SO RBARRIER Srcid Htwall DCLwall (Htwall2 DCLwall2)
Type:
Optional, Repeatable
Order:
Must follow the SRCPARAM card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source, and the other parameters are as follows:
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Htwall - height of the solid barrier (wall) in meters,
DCLwall - the distance from the centerline of the source to the barrier (wall) in meters,
Htwall2 - height of a second solid barrier (wall) in meters, if present,
DCLwall2 - the distance from the centerline of the source to the second barrier (wall) in meters.
RBARRIER inputs should be on opposite sides of the RLINEXT source (DCLwall and DCLwall2). If two
RBARRIERs are input that are on the same side of the source, a warning will be issued, the closest of the
two barriers will be kept and the other will be ignored.
Barrier - Source Orientation
X
X
Barrier - Source Orientation with Median
X -DCL
+DCL X
X -DCLWALL
Figure 3-3. Definition of DCLWALL for RLINEXT sources. Dashed black lines represent
roadway sources and dashed orange lines represent barriers with an offset (DCLWALL). The
solid line in the right-hand panel represents the median
From Figure 3-2, the DCL is defined and the DCLWALL is defined when there is a median. This median
DCL is subtracted from the DCLWALL within the RLINE barrier processing, so only the relative distance
between each source and wall (barrier) is used when estimating concentrations.
A roadside located in a depression is specified with the RDEPRESS keyword. The syntax, type and order for
the RDEPRESS card for RLINEXT sources are summarized below
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Syntax:
SO RDEPRESS Srcid Depth Wtop Wbottom
Type:
Optional, Repeatable
Order:
Must follow the SRCPARAM card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a
particular source, and the other parameters are as follows:
Depth: depth of the depression in meters (should be negative),
Wtop: width of the top of the depression containing the RLINE source in meters,
Wbottom: width of the bottom of the depression containing the RLINE source in meters (must be
less than, or equal to, Wtop).
The barrier and depressed roadway source configurations can only be used if the ALPHA flag is
present with the MODELOPT keyword in the CO pathway.
Roadside barrier configurations are specified by the height of the barrier (Htwall) and the distance
from the centerline to the wall (DCLwall). Currently, there is no limit to the Htwall parameter, but a fatal
error message is issued if the height of the barrier is less than zero. If a second barrier is specified with
Htwall2 and DCLwall2, this barrier should be on the opposite side of the roadway from barrier 1. Positive
values of DCLwall (and DCLwall2) indicate barriers east of the roadway centerline (or north if the roadway
runs directly east-west). Negative values indicate barriers west of the roadway centerline (or south if the
roadway runs directly east-west).
Depressed roadway dimensions are specified by the Depth parameter, defining the depth of the
roadway relative to surrounding terrain, in meters, and the Wtop and Wbottom parameters, defining the
widths of the depression top and depression bottom, respectively. The Depth parameter must be a negative
value, reflecting a lower elevation than the surrounding terrain. A fatal error is issued if the Depth parameter
is greater than zero. A fatal error is issued if either the Wtop or Wbottom parameters are less than zero, or if
the specified Wbottom parameter is greater than the Wtop parameter for the source. Wbottom can, however,
have a greater value than the width of the roadway, if the inclusion of shoulders or other areas are considered
within the depression.
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3.3.2.11 BUOYLINE source inputs
The syntax, type and order for the SRCPARAM, BLPINPUT, and BLPGROUP cards for a
BUOYLINE source are summarized below:
Syntax:
SO SRCPARAM Srcid Blemis Relhgt
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each line input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
line within the buoyant line source, and the other parameters are as follows:
Blemis - buoyant line emission rate in g/(s) for the individual line,
Relhgt - average release height of the individual line above ground in meters. Since the original
BLP model was developed for elevated sources, a minimum release height of 2.0 m is
enforced for the individual buoyant lines when AERMOD processes the buoyant line
sources. If a release height less than 2.0 m is detected, AERMOD changes the height to
2.0 meters, issues a warning message, and continues processing.
The buoyant line source also requires the user to enter average values representative of a buoyant
line source as a whole and not for the individual lines that comprise the buoyant line source.
As of version 21112, the user can specify multiple buoyant line groups (i.e., multiple buoyant line
sources) each comprised of individual buoyant lines. Each buoyant line source group (previously referred to
as a buoyant line source) requires the user to enter average values representative of the group using the
BLPINPUT keyword. The average parameters are applied to the buoyant line group by associating each
individual buoyant line with a buoyant line group using the BLPGROUP keyword (described below) through
the BLPGrpID. The BLPGrpID is optional on the BLPINPUT keyword if only one buoyant line group is
modeled. Allowing BLPGrpID to be optional when a single buoyant line group is being modeled lets legacy
control files run with AERMOD. These are entered as parameters on the BLPINPUT keyword:
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Syntax:
SO BLPINPUT BLPGrpID Blavgblen Blavgbhgt Blavgbwid Blavglwid Blavgbsep
Blavgfprm
Type:
Mandatory, Repeatable
BLPINPUT keywords must appear before the BLPGROUP keywords
Order:
The order of the BLPINPUT records and their associated buoyant lines (as defined on the
BLPGROUP keywords and linked through the BLPGrpIDs) must be in the same order as
the lines on the SO LOCATION records
where the parameters are defined as follows (the order shown is the same as the input in BLP with the
variable names used in BLP shown in parentheses):
BLPGrpID:
Blavgblen (L):
Blavgbhgt (HB):
Blavgbwid (WB):
Blavglwid (WM):
Blavgbsep (DX):
Blavgfprm (FPRIME):
buoyant line group ID,
average building length (m),
average building height (m),
average building width (m),
average line source width (m) (of the individual lines),
average building separation (m) (between the individual lines),
average buoyancy parameter (m4/s3).
When multiple buoyant line groups are in a model run, the order of the individual buoyant lines
associated with the BLPINPUT keywords (as defined on the BLPGROUP keywords and linked via the
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BLPGrpIDs) in the control file must be in the order of the individual buoyant lines defined by the SO
LOCATION keywords. For example, assume a model run consists of SO LOCATION records for a 3-line
buoyant line group followed by the SO LOCATION records for a 2-line buoyant line group (i.e., five total
individual buoyant lines in two BL groups). The BLPINPUT records for the 3-line group must be specified
before the BLPINPUT record for the 2-line group in the control file. If they are in the opposite order,
AERMOD will issue an error message and fail to run.
The user should use caution in defining the average buoyancy parameter (FPRIME) above. This
parameter should be calculated as in Equation 2-47 of the BLP user guide (Schulman and Scire, 1980), also
shown below. The FPRIME parameter is dependent on BUOYLINE parameters listed above and additional
source parameters that are not input to AERMOD such as the line source exit velocity and difference in exit
and ambient temperatures.
g L Wmw (Ts - Ta)
FPRIME = -
T
Where:
FPRIME = average line source buoyancy parameter (m4/s3)
g = acceleration of gravity (9.81 m/s2)
L = line source length (m)
Wm = line source width (m)
w = exit velocity (m/s)
Ts = exit temperature (°K)
Ta = ambient air temperature (°K)
Selection and computation of FPRIME should be done with caution and sufficiently justified before
being used in an AERMOD BUOYLINE application. Also note, FPRIME should be computed for each line
in a BUOYLINE and averaged for all lines in a BUOYLINE source and source group, as suggested in the
BLP user guide (Schulman and Scire, 1980).
The BLPGROUP keyword associates one or more individual buoyant lines with a buoyant line group
and a corresponding BLPINPUT keyword. To process two or more buoyant line sources this keyword is
mandatory; for modeling a single buoyant line source the keyword is optional, i.e., when omitted all
individual lines are treated as a single buoyant line source.
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Syntax:
SO BLPGROUP BLPGrpID SrcID (or SrcRng)
or
SO BLPGROUP ALL
Type:
Mandatory, Repeatable
Order:
BLPGROUP keywords must appear after the BLPINPUT keywords
where BLPGrpID identifies a group individual buoyant lines to be treated as a single buoyant line source and
the Srcid or Srcrng identifies the group of buoyant lines to be included in the BLP group. As with the SO
SRCGROUP card, individual source IDs and source ranges may be used on the same record, and if more
than one input record is needed to define the sources for a particular BLP group, then additional records may
be input by repeating the pathway, keyword and BLPGrpID. A user can also specify a BLPGrpID of ALL,
which means that all the individual line sources are to be treated as a single buoyant line source. There must
be one, and only one, associated BLPINPUT record for BLPGrpID ALL. Another constraint for the
BLPGROUP keyword is that a buoyant line source cannot be associated with more than one BLPGrpID.
When using buoyant line sources in event processing the BLPGRPID must be equivalent to the SRCGROUP
ID, and the source IDs in each must be the same.
Note: The secondary keyword, ALL, is used in different source grouping contexts (e.g.,
BLPGROUP, SRCGROUP, OLMGROUP). Refer to the appropriate section of this user's guide to see
the usage of the secondary keyword, ALL, for the group of sources to be identified. For SRCGROUP
see Section 3.3.15. For OLMGROUP, see Section 3.3.6.2.
3.3.2.12 SWPOINT source inputs
The SWPOINT source type has been added beginning with version 22112 as a research tool to
further study the phenomena researchers have coined as "sidewash" which is a lateral shift of the building
wake cavity that forms on the lee side a building that occurs when the wind is oblique to one of the longer
sides of an elongated building. Yang et al. (2020) investigated the flow structures and concentration fields
under oblique wind conditions. A key finding was that the flow is not only entrained downward (downwash)
but also directed by the oblique wind along the building leeward surface (sidewash), which creates a
sidewash-downwash (S-D) vortex. This S-D vortex causes the plume to shift in the lateral direction. The
use of the SWPOINT source type requires the non-regulatory ALPHA flag to be entered as a model option
with the MODELOPT keyword on the CO pathway. The syntax, type and order for the SRCPARAM cards
for a SWPOINT source are summarized below:
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Syntax:
SO SRCPARAM Srcid Swemis Stkhgt Bw B1 Bh Ba
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each line input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
SWPOINT source, and the other parameters are as follows:
Swemis Sidewash point source emission rate in g/s,
Stkhgt Release height above ground in meters,
Bw Building width in meters,
B1 Building length in meters,
Bh Building height in meters, and
Ba Building angle in decimal degrees measured clockwise where north is 0 degrees.
As a research tool, the SWPOINT source has a number of limitations in the implementation in
version 23132 that need to be highlighted for the user who uses the SWPOINT source type to investigate and
study the sidewash effect. These limitations include the following:
Produces downwind concentrations from short stacks assumed to be centered along the
leeward side of elongated buildings. Refer to Figure X below for an illustration of the assumed
stack location with respect to the building and wind flow orientation.
Model concentrations are limited to the building wake cavity. Impacts at receptors outside or
in the transition zone from the building wake cavity are not calculated.
Terrain impacts are not considered.
Plume rise due to mechanical and thermal buoyancy is not considered.
Building representation is assumed to be rectangular.
PRIME downwash is not applied.
SWPOINT sources have not been configured for use with EVENT processing, NOx-to-N02
conversion methods, or the MAXDCONT source culpability processing.
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Stack top wind speeds below approximately 2 m/s have been shown to cause anomalously
high concentrations. This parameter is quite sensitive and currently can shift from reasonable
predicted concentrations to values several orders of magnitude with the adjustment of a few
tenths of a meter per second.
Building'^
Figure 3-4.Fixed Stack location with respect to Building and Wind Flow Orientation
3.3.3 Specifying gas deposition parameters
3.3.3.1 Source parameters for gas deposition (dry and/or wet)
The input of source parameters for dry and wet deposition of gaseous pollutants is controlled by the
GASDEPOS keyword on the SO pathway. The gas deposition variables may be input for a single source or
may be applied to a range of sources.
The syntax, type, and order for the GASDEPOS keyword are summarized below:
Syntax:
SO GASDEPOS Srcid (or Srcrng) Da Dw rcl Henry
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid or Srcrng identify the source or sources for which the inputs apply, the parameter Da is the
diffusivity in air for the pollutant being modeled (cm2/s), Dw is the diffusivity in water for the pollutant
being modeled (cm2/s), rcl is the cuticular resistance to uptake by lipids for individual leaves (s/cm), and
Henry is the Henry's Law constant (Pa m3/mol). Values of the physical parameters for several common
pollutants may be found in the appendices to the ANL report (Wesely, et. al, 2002).
As of version 21112, optional default gas deposition parameters (Da, Dw, rcl, Henry) are included
for elemental mercury, divalent mercury, dioxins, polycyclic aromatic hydrocarbons (PAH), SO2, and NO2.
There are two requirements to use the default gas deposition parameters. First, the POLLUTID keyword
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must be set to a specific value, depending on the pollutant (see below). Second, the deposition parameter
must be set to a value of 0 in the GASDEPOS keyword. If each parameter is to be a default value, a 0 must
be entered for each parameter. The user can also specify a mix of default versus user-entered parameters. For
example, the user can specify a value for diffusivity in air with the user entered value and a default value of
diffusivity in water by entering a 0. If any default values are used for a particular source, the user will
receive a message in the ERRORFIL.
The pollutants, POLLUTID, and default gas deposition parameters used are:
Pollutant POLLUTID Diffusivity in air Diffusivity in water Cuticular resistance Henry's Law
(Da) (Dw) (rcl) (Henry)
Elemental
Mercury
HG0
0.055
6.4E-6
100000
719
Divalent
Mercury
HGII
0.045
5.2E-6
100000
0.000072
Dioxin
(as TCDD)
TCDD
0.05196
4.39E-6
9.67
1.46
PAH
(as BaP)
BAP
0.0513
4.44E-6
0.441
0.046
S02
S02
0.1122
1.83E-5
732
72
N02 N02 0.1361 1.4E-5 12000 8444
Note, that for elemental mercury, the third character of the POLLUTID is a zero, not a capital O.
The POLLUTID for S02 and N02 contains a capital O and not a zero.
3.3.3.2 Option for specifying the deposition velocity for gas dry deposition
An optional keyword is available on the Control (CO) pathway to allow the user to specify the dry
deposition velocity for gaseous emissions. A single dry deposition velocity can be input for a given model
run and is used for all sources of gaseous pollutants. Selection of this option will by-pass the algorithm for
computing deposition velocities for gaseous pollutants and should only be used when sufficient data to run
the algorithm are not available. Results of the AERMOD model based on a user-specified deposition
velocity should be used with extra caution.
The syntax and type of the GASDEPVD keyword are summarized below:
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Syntax:
CO GASDEPVD Uservd
Type:
Optional, Non-repeatable
where the parameter Uservd is the gaseous dry deposition velocity (m/s). A non-fatal warning message is
generated by the model if a value of Uservd greater than 0.05 m/s (5 cm/s) is input by the user. When the
GASDEPVD keyword is used, the GDSEASON, GDLANUSE, and GASDEPRF keywords for the CO
pathway, and the GASDEPOS keyword for the SO pathway, are no longer applicable and cannot be used in
the same model run. As a result, gas wet deposition processes (DEPOS, WDEP, and WETDPLT) cannot be
simulated with the GASDEPVD option is used.
3.3.4 Specifying source parameters for particle deposition
The AERMOD model includes two methods for handling dry and/or wet deposition of particulate
emissions. Method 1 is used when a significant fraction (greater than about 10 percent) of the total
particulate mass has a diameter of 10 ^m or larger, or when the particle size distribution is known. The
particle size distribution must be known reasonably well in order to use Method 1. Method 2 may be used
when the particle size distribution is not well known and when a small fraction (less than 10 percent of the
mass) is in particles with a diameter of 10 ^m or larger. The deposition velocity for Method 2 is calculated
as the weighted average of the deposition velocity for particles in the fine mode (i.e., less than 2.5 |im in
diameter) and the deposition velocity for the coarse mode (i.e., greater than 2.5 |im but less than 10 |im in
diameter). As described in Section 3.2.2.2, use of the Method 2 option is considered a non-DFAULT option
and cannot be used when the DFAULT keyword is specified.
3.3.4.1 Specifying particle inputs for Method 1
The input of source variables for particle deposition using Method 1 is controlled by three keywords
on the SO pathway, PARTDIAM, MASSFRAX, and PARTDENS. These inputs are comparable to the
particulate inputs used in the ISCST3 model (EPA, 1995a). The particle variables may be input for a single
source or may be applied to a range of sources.
The syntax, type and order for these three keywords are summarized below:
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Syntax:
SO PARTDIAM Srcid (or Srcrng) Pdiam(i), i=l,Npd
SO MASSFRAX Srcid (or Srcrng) Phi(i), i=l,Npd
SO PARTDENS Srcid (or Srcrng) Pdens(i), i=l,Npd
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid or Srcrng identify the source or sources for which the inputs apply, and where the Pdiam
array consists of the mass-mean aerodynamic particle diameter (microns) for each of the particle size
categories, the Phi array is the corresponding mass fractions (between 0 and 1) for each of the categories, and
the Pdens array is the corresponding particle density (g/cm3) for each of the categories.
The number of particle size categories for a particular source is Npd. The user does not explicitly tell
the model the number of categories being input, but if continuation cards are used to specify particle size
variables, all inputs of a keyword for a particular source or source range must be contiguous, and the number
of categories must agree for each of the three keywords input for a particular source. As many continuation
cards as needed may be used to define the inputs for a particular keyword. The model checks the inputs to
ensure that the mass fractions sum to 1.0 (within 2 percent) for each source input and issues a warning
message if that range is exceeded. The model also ensures that mass fractions for each particle size category
are within the proper range (between 0 and 1), and issues fatal error messages for any value exceeded that
range.
3.3.4.2 Specifying particle inputs for Method 2
The Method 2 particle information is input through the METHOD2 keyword on the SO pathway.
The syntax, type, and order for the METHOD2 keyword are summarized below:
Syntax:
SO METHOD 2 Srcid (or Srcrng) FineMassFraction Dmm
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid or Srcrng identify the source or sources for which the inputs apply, the parameter
FineMassFraction is the fraction (between 0 and 1) of particle mass emitted in the fine mode, less than 2.5
microns, and Dmm is the representative mass-mean aerodynamic particle diameter in microns. Estimated
values of fine particle fractions and mass mean diameters for various pollutants are provided in Appendix B
of the ANL report (Wesely, et al, 2002).
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As of version 21112, optional default Method 2 particle deposition parameters (FineMassFraction
and Dmm) are included for arsenic, cadmium, lead, mercury, and poly cyclic aromatic hydrocarbons (PAH).
There are two requirements to use the default Method 2 particle deposition parameters. First, the POLLUTID
keyword must be set to a specific value, depending on the pollutant (see below). Second, the deposition
parameter must be set to a value of 0 in the METHOD2 keyword. If each parameter is to be a default value,
a 0 must be entered for each parameter. The user can also specify a mix of default versus user-entered
parameters. For example, the user can specify a value for fine mass fraction with the user entered value and
a default value of mean particle diametr by entering a 0. If any default values are used for a particular
source, the user will receive a message in the ERRORFIL.
The pollutants, POLLUTID, and default Method 2 particle deposition parameters used are:
Pollutant
POLLUTID
Fine mass
fraction
Mean particle diameter
(Dmm)
Arsenic
AS
0.75
0.5
Cadmium
CD
0.70
0.6
Lead
PB
0.75
0.5
Mercury
HG
0.80
0.4
PAH (as
POC)
POC
0.90
0.1
3.3.5 Specifying Emission and Output Units
Since the AERMOD model allows for both concentration and deposition to be output in the same
model run, the EMISUNIT keyword (see Section 3.3.13) cannot be used to specify emission unit factors if
more than one output type is being generated. The AERMOD model therefore allows for concentration and
deposition units to be specified separately through the CONCUNIT and DEPOUNIT keywords, respectively.
The syntax and type of the CONCUNIT keyword are summarized below:
Syntax:
SO CONCUNIT Emifac Emilbl Conlbl
Type:
Optional, Non-repeatable
where the parameter Emifac is the factor to convert emission rate input units to the desired output units,
Emilbl is the label for the emission input units (up to 40 characters), and Conlbl is the output unit label (up to
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40 characters) for concentration calculations. The default conversion is from g/s to |a,g/m3 and the value is
lxlO6. The conversion from g/s to mg/m3 would simply be lxlO3 and the conversion from g/s to ppb is
simply the grams/m3 to ppb conversion factor for the pollutant. The syntax and type of the DEPOUNIT
keyword are summarized below:
Syntax:
SO DEPOUNIT Emifac Emilbl Deplbl
Type:
Optional, Non-repeatable
where the parameter Emifac is the factor to convert emission rate input units to the desired output units,
Emilbl is the label for the emission input units (up to 40 characters), and Deplbl is the output unit label (up to
40 characters) for deposition calculations. The default conversion is g/s to g/m2 and the value is 3600. To
convert to units such as ng/m2, the conversion would be 3.6xl012 (3600 * lxlO9) where lxlO9 is the
conversion from g to nanograms.
3.3.6 Source input parameters for NO? conversion options
It should be noted that not all NO2 conversion options have been implemented for all source types in
AERMOD. Table 3-2 summarizes which NO2 conversion options have been implemented for each of the
AERMOD source types and which options have not.
3.3.6.1 Specifying in-stack NO?/N(X ratios by source for PVMRM. OLM. TTRM/TTRM2. and GRSM
As noted above, the PVMRM, OLM, TTRM/TTRM2, and GRSM options for modeling NO2
conversion require in-stack N02/NOx ratios to be specified for each source, i.e., AERMOD no longer
assumes a default in-stack ratio of 0.10 for the OLM option. The user can specify in-stack N02/NOx ratios
through the optional N02RATIO keyword on the SO pathway. The syntax of the N02RATIO keyword is as
follows:
Syntax:
SO N02RATIO SrcID or SrcRange N02Ratio
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the SrcID or SrcRange identify the source or sources for which the inputs apply, and where the
N02Ratio parameter specifies the in-stack ratio. In this way, the user can specify a single in-stack NO2/NOX
ratio for a group of stacks. For example, the following input:
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SO N02RATI0 STACK 1-STACK 10 0.15
will apply the in-stack ratio of 0.15 to sources with IDs falling within the range STACK 1 to STACK10. Any
value specified on the SO N02RATI0 card will override the default ratio, if any, specified on the CO
N02STACK card. Users should note that while SO N02RATI0 is an optional keyword, the PVMRM and
OLM options require the user to specify an in-stack N02/N0X ratio for each source, using either the CO
N02STACK (Section 3.2.5.4) or SO N02RATI0 cards, or both.
3.3.6.2 Specifying combined plumes for OLM
The OLM option for modeling NO2 conversion includes an option for specifying which sources are
to be modeled as combined plumes, i.e., where the NOx within the plumes competes for the available
ambient ozone. Sources which are not specified for modeling as combined plumes will be modeled as
individual plumes, i.e., where all of the ambient ozone is available for conversion of NO to NO2. The
selection of individual or combined plume option for OLM is specified through the OLMGROUP keyword
on the SO pathway. The syntax of the OLMGROUP card is as follows:
Syntax:
SO OLMGROUP OLMGrpID SrcID's and/or SrcRange's
or
SO OLMGROUP ALL
Type:
Optional, Repeatable (except for OLMGROUP ALL)
Order:
Must follow the LOCATION card for each source input;
OLMGROUP ALL must follow the LOCATION card for all sources
where OLMGrpID identifies a group to be treated as a combined plume with OLM, and the SrcID's and/or
SrcRange's identify the sources to be included in the OLM group. As with the SO SRCGROUP card,
individual source IDs and source ranges may be used on the same record, and if more than one input card is
needed to define the sources for a particular OLM group, then additional records may be input by repeating
the pathway, keyword and OLM group ID. A user can also specify an OLMGrpID of ALL, which means that
OLM will be applied on a combined plume basis to all sources. However, unlike the SO SRCGROUP card,
the results will not be output for a specific OLM group unless the same group of sources is also identified on
a SRCGROUP card. Another constraint for the OLMGROUP keyword is that a source cannot be included in
more than one OLM group.
Note: The secondary keyword, ALL, is used in different source grouping contexts (e.g.,
BLPGROUP, SRCGROUP, OLMGROUP). Refer to the appropriate section of this user's guide to see
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the usage of the secondary keyword, ALL, for the group of sources to be identified. For SRCGROUP
see Section 3.3.15. For BLPGROUP, see Section 3.3.2.11.
If a source is not selected for an OLMGROUP card, then OLM will be applied to that source as an
individual plume. Other than the similarity in syntax, there is no connection in the model between the
groups defined on the OLMGROUP card and groups defined on the SRCGROUP card. The OLMGROUP
card relates to how the results are processed within the model for the OLM option, and the SRCGROUP card
simply controls how source impacts are grouped in the model outputs.
If the user identifies one or more groups of sources to apply OLM on a combined plume basis using
the OLMGROUP card, the model will still need to calculate the concentration for individual plumes within
the OLM group in order for the model to sum the results for the sources listed on the SRCGROUP card(s).
The individual source concentrations are calculated by applying the ratio of the combined concentration for
the OLM group with and without OLM to each source within the OLM group.
3.3.6.3 Specifying ambient NO--/NO., ratios for the ARM2 option
The ARM2 option in AERMOD is based on applying an ambient ratio of N02/N0X to a modeled
NOx concentration to estimate ambient NO2 concentrations. The ARM2 option applies an ambient ratio to
the 1-hr modeled NOx concentrations based on a formula derived empirically from ambient monitored ratios
ofN02/NOx. The default upper and lower limits on the ambient ratio applied to the modeled NOx
concentration are 0.9 and 0.5, respectively. These limits can be modified using the optional ARMRATIO on
the CO pathway as follows:
Syntax: CO ARMRATIO ARM2 Min ARM2 Max
Type: Optional, Non-Repeatable
When the regulatory DFAULT keyword is included on the MODELOPT line, the allowed range for the
ARM2 ratio represented by ARM2_Min and ARM2_Max is 0.5 to 0.9, respectively. When the DFAULT
keyword is not included, the allowed range is extended to a lower limit greater than 0 to an upper limit of
1.0.
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3.3.7 Modeling NO? increment credits with PVMRM
Due to the ozone limiting effects of the PVMRM option, the predicted concentrations of NO2 are not
linearly proportional to the emission rate. Therefore, the approach of modeling NO2 increment consumption
with PSD credits through the use of a negative emission rate for credit sources cannot be used with the
PVMRM option. However, the ALPHA PSDCREDIT option allows modeling PSD increment credits for
NO2 when the PVMRM option is specified. The PSDCREDIT option is currently implemented as an
ALPHA option and requires that the PVMRM and ALPHA options be specified on the CO MODELOPT
card (see Section 3.2.2). As an ALPHA option, PSDCREDIT requires additional testing and evaluation
before it should be considered for use in a regulatory application. The PSDCREDIT option utilizes a the
PSDGROUP keyword, described below, to identify which sources consume or expand increment. This
option is not valid if the OLM, TTRM/TTRM2, or GRSM option is specified, and no comparable option is
available for modeling increment credits with the any of those options. The user should check with the
appropriate reviewing authority for further guidance on modeling increment credits for NO2.
A general discussion of concepts related to modeling increment consumption is provided below,
followed by a description of inputs required to use the ALPHA PSDCREDIT option for PVMRM.
3.3.7.1 Increment consuming and baseline sources
Increment is the maximum allowable increase in concentration of a pollutant above a baseline
concentration for an area defined under the Prevention of Significant Deterioration (PSD) regulations. The
PSD baseline area can be an entire State or a subregion of a State such as a county or group of counties.
Increment consumption is the additional air quality impact above a baseline concentration.
The baseline concentration is the ambient concentration of the pollutant that existed in the area at the
time of the submittal of the first complete permit application by any source in that area subject to PSD
regulations. A baseline source is any source that existed prior to that first application and the baseline date is
the date of the PSD application. This baseline date is referred to as the minor source baseline date in PSD
regulations. By definition, baseline sources do not consume increment. However, any baseline source that
retires from service after the baseline date expands the increment available to new sources. Therefore, a PSD
modeling analysis performed for a new source may need to account for this increment expansion. Such an
analysis may therefore involve identification of three groups of sources: 1) increment-consuming sources; 2)
retired (increment-expanding) baseline sources; and 3) existing, non-retired, baseline sources.
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3.3.7.2 Calculating increment consumption under the PSDCREDIT option
Calculating increment consumption under the PSDCREDIT option in AERMOD is not a simple
arithmetic exercise involving the three groups of sources defined above. Since the amount of ozone
available in the atmosphere limits the conversion of NO to NO2, interactions of plumes from the existing and
retired baseline sources with those from the increment consuming sources must be considered as part of the
calculation of net increment consumption. Without the PSDCREDIT option, properly accounting for the
potential interaction of plumes among the different source categories would require post-processing of
results from multiple model runs. Internal "posf'-processing algorithms have been incorporated in
AERMOD under the PSDCREDIT option to account for the apportioning of the three groups of sources to
properly calculate increment consumption from a single model run.
Define the following three source groupings for the discussion that follows:
A = increment-consuming sources;
B = non-retired baseline sources; and
C = retired baseline, increment-expanding sources.
The calculation of the amount of increment consumption by the A sources cannot simply be
estimated by modeling the A sources alone because of the possible interaction of those plumes with the
plumes from B sources. The PVMRM algorithm is designed to account for such plume interactions and
calculate the total NO to NO2 conversion in the combined plumes based on the amount of ozone available.
Therefore, the total increment consumption by the A sources is given by the difference between (1) the total
future impact of increment consuming sources and non-retired baseline sources (A+B) and (2) the total
current impact (B), which can be expressed as (A+B) - (B). Here (A+B) represents the value that would be
compared against the National Ambient Air Quality Standard (NAAQS) for NO2 during PSD review of the A
sources.
In a case where some of the baseline sources have been retired from service (C sources), the PSD
regulations allow the consideration of increment expansion when assessing compliance with the PSD
increment. However, the amount of increment expansion cannot be estimated by simply modeling the C
sources alone because of the possible interaction of those plumes with the plumes from B sources.
Therefore, the total increment expansion, i.e., PSD credit, is calculated as the difference between (1) the total
impact prior to the retirement of C sources, i.e., (B+C), and (2) the total impact from existing (non-retired)
baseline sources (B), which can be expressed as (B+C) - (B).
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Finally, the net increment consumption is given by the difference between total increment
consumption and the total increment expansion, or
[(A+B) - (B)] - [(B+C) - (B)] (Equation 1)
Note that in the absence of any increment expansion, the net increment consumption is equal to the total
increment consumption [(A+B) - (B)], as described above.
These expressions of net increment consumption and expansion cannot be interpreted as algebraic
equations. Instead, the terms within parentheses represent the results of separate model runs that account for
the combined effects of NOx conversion chemistry on specific groups of sources. The expression shown in
Equation 1 above represents four model simulations: (A+B), (B), (B+C), and (B) again. In this case, the two
(B) terms do cancel each other, and we are left with:
[(A+B)] - [(B+C)] (Equation 2)
The expression presented in Equation 2 summarizes how the net increment consumption calculation is
performed under the PSDCREDIT option. Under this option, AERMOD first models the A and B groups
together, then models the B and C groups together, and finally computes the difference to obtain the desired
result, i.e., the value to compare to the PSD increment standard. For AERMOD to perform the special
processing associated with this option, the user must define which sources belong to each of the groupings
defined above. The next section describes how this is accomplished.
3.3.7.3 Specifying source groups under the PSDCREDIT option
The PSDCREDIT option introduces limitations on grouping sources to calculate increment
consumption as described in the previous section. A new keyword, PSDGROUP, is used to group the
sources to correctly calculate the increment consumption. The syntax, type, and order are similar to the
regular SRCGROUP keyword and are summarized below:
Syntax:
SO PSDGROUP Grpid Srcid's and/or Srcrng's
Type:
Mandatory for PSDCREDIT option, Repeatable
Order:
Must follow the last keyword in the SO pathway before FINISHED
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If the PSDCREDIT model option is specified, the PSDGROUP keyword must be used. The SRCGROUP
keyword cannot be used with the PSDCREDIT option since results from other groupings beyond these three
do not have any meaning when the PSDCREDIT option is invoked, and sources are allocated to the
calculation of increment consumption. Special source groups for outputting model results are defined within
AERMOD for the PSDCREDIT option, as described in the next section.
Only the following special PSD group ID's can be used. Failure to use these group ID's will result
in a fatal error message during setup processing by AERMOD. The group ID's are:
INCRCONS - increment-consuming sources (group A above); these can be new sources or
modifications to existing sources;
NONRBASE - existing, non-retired baseline sources (group B above); and
RETRBASE - retired (increment-expanding or PSD credit) baseline sources (group C above).
It is important to note that the source emission inputs for sources included in the RETRBASE PSD
group must be entered as positive numbers, unlike other types of PSD credit modeling where negative
emissions are input to simulate the impact of the credit sources on the increment calculation. The increment-
expanding contribution from RETRBASE sources is accounted for within the AERMOD model under the
PSDCREDIT option.
The group ID's can appear in any order, but these are the only three that can be specified. If there are
no retired baseline sources (i.e., no baseline sources are retired), the keyword RETRBASE can be omitted.
Likewise, if there are no non-retired baseline sources (i.e., all baseline sources have been retired), the
NONRBASE keyword can be omitted. The special group ID 'ALL' that can be used with the SRCGROUP
keyword cannot be used with the PSDGROUP keyword. As with the SRCGROUP keyword for non-
PSDCREDIT applications, the group IDs are repeatable, and they must be the last keyword before
FINISHED on the SO pathway when the PSDCREDIT option is specified.
Source ranges, which are described in more detail in Section 3.3.9, are input as two source IDs
separated by a dash, e.g., STACK1-STACK10. Individual source IDs and source ranges may be used on the
same card. If more than one input card is needed to define the sources for a particular group, then additional
cards may be input, repeating the pathway, keyword and group ID. A source can appear in only one of these
source groups and must be assigned to one of the groups.
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The requirements for specifying sources and source groups under the PSDCREDIT option are
summarized below:
The SRCGROUP keyword cannot be used with the PSDCREDIT option;
Special PSD group ID's must be used with the PSDGROUP keyword;
The group ID ALL is not allowed when the PSDCREDIT option is specified;
A source must appear in one, and only one, of the PSDGROUPs; and
Emission rates for increment-expanding (RETRBASE) sources must be entered as positive
values.
3.3.7.4 Model outputs under the PSDCREDIT option
Unlike the regular SRCGROUP keyword, the PSDGROUP keyword does not define how the source
impacts are grouped for model output. As described in the previous sections, the PSDGROUP keyword
defines the different categories of sources needed, in order to properly account for NOx conversion chemistry
under the PVMRM option.
The model outputs under the PSDCREDIT option in AERMOD are based on demonstrating
compliance with the air quality standards, i.e., the NAAQS and PSD increment for NO2. As a result,
AERMOD uses hardcoded "SRCGROUP" names of 'NAAQS' and 'PSDINC' to label these two types of
outputs. The results output under the 'NAAQS' source group label are based on the calculation of (A+B) as
described above in Section 3.3.7.2. The results reported under the 'PSDINC' source group label are based on
the expression presented above in Equation 2.
3.3.8 Background concentrations
Beginning with version 11059, users can specify uniform or temporally varying background
concentrations using the BACKGRND keyword on the SO pathway and beginning with version 13350 users
can vary background concentrations by wind sector. Background concentrations can be included with any
source group to estimate cumulative ambient impacts. Background concentrations can be specified using a
range of options, similar to those available with the EMISFACT keyword for source emissions, or on an
hourly basis from a separate data file.
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3.3.8.1 Defining background concentration sectors
For applications where multiple ambient monitors outside of the modeling domain are available and
representative of background concentrations within the modeling domain depending on the wind direction,
the user may define sector-varying background concentrations. The sectors are defined based on the SO
BGSECTOR keyword, as follows:
Syntax:
SO BGSECTOR StartSectl StartSect2 .
. StartSectN, where N < 6
Type:
Optional, Non-Repeatable
3.3.8.2 For applications that include sector-varying background concentration the minimum sector width
allowed is 30 degrees and warning messages will be issued for sector widths less than 60 degrees. Sector-
varying background concentrations will be selected based on the flow vector, i.e., the downwind
direction, based on the wind direction specified in the surface meteorological data file. During periods
of specific wind directions, the associated user input sector-varying background concentrations will be
applied to the entire modeling domain (i.e., all receptorsVSpecifving the background concentration
For applications that do not include sector-varying background concentrations, the syntax of the
BACKGRND keyword is as follows:
SO BACKGRND BGflag BGvalue(i), i=l,n
Syntax:
and/or
SO BACKGRND HOURLY BGfilnam (BGformat)
Type:
Optional, Repeatable
where the BGflag parameter is the variable background concentration flag, BGvalue is the array of
background concentration values associated with BGflag, HOURLY indicates use of an hourly background
file, BGfilnam is the filename for the hourly background data, and BGformat is the optional Fortran format
of the hourly background file ('free' format is used by default). The BGfilnam can be up to 200 characters in
length based on the default parameters in AERMOD. Double quotes (") at the beginning and end of the
filename can also be used as field delimiters to allow filenames with embedded spaces.
For applications that include sector-varying background concentrations, the syntax of the
BACKGRND keyword is as follows:
SO BACKGRND SECTx BGflag BGvalue(i), i=l, and x < 6
and/or
SO BACKGRND SECTx HOURLY BGfilnam (BGformat), where
x < 6
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Type: Optional, Repeatable
where the SECTx parameter identifies the applicable sector as defined on the SO BGSECTOR keyword.
Implement as SECT1 or SECT2 ... or SECTx where x < 6, and x is an integer and corresponds to the Nth
sector defined by BGSECTOR. The other parameters are as defined above.
The HOURLY background file must include the year, month, day, and hour, followed by the
background concentration, in that order (unless specified differently through the BGformat parameter). The
year can be specified as either a 2-digit or 4-digit year. If an optional Fortran format is specified using the
BGformat parameter, the year, month, day, and hour variables must be read as integers using the Fortran I
format, and the background concentration must be read as a real variable, using the Fortran F, E, or D format,
e.g., (412,F8.3). Note that background values that do not include decimal places can be read as Fx.O, where x
is the length of the data field. The BGformat parameter must include the open and close parentheses as
shown in the example and may also include embedded spaces if double quotes (") are used to delimit the
field. A warning message will be generated if the specified format does not meet these requirements, and
AERMOD may also issue a fatal error message when reading the file in cases where real variables are read
with an integer format, or vice versa.
If the optional BGformat parameter is missing, then the model will read the background data using a
Fortran 'free' format, i.e., assuming commas or spaces separate the data fields, and that the fields are in the
order given above. The date sequence in the background data file must also match the date sequence in the
hourly meteorological data files.
Note that the HOURLY option and an option to specify values based on the BGflag parameter can
both be specified in the same model run. This allows the user to specify background concentrations on a
temporally varying basis, such as SEASHR. that can be used to substitute for missing values in an hourly
background file. NOTE: AERMOD will issue a fatal error message and abort processing if missing
data are encountered in an HOURLY background file unless the user provides other temporally
varying background concentrations (e.g., SEASHR, etc.) to substitute for missing data. Background
concentration units can be specified using the BACKUNIT keyword, described below. If the BACKUNIT
keyword is omitted, default units of PPB are assumed for background NO2 and SO2, PPM for CO, and
UG/M3 for all other pollutants. Background concentrations specified in units of PPB or PPM are converted
to UG/M3 based on reference temperature (25 C) and pressure (1013.25 mb).
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To include background concentrations with a particular source group, the reserved "source ID" of
BACKGROUND (or BACKGRND) can be included on the SRCGROUP keyword, including source group
ALL. NOTE: AERMOD will NOT automatically include background concentrations in source group ALL,
but the user can specify that background be included in results for group ALL by including the
BACKGROUND (or BACKGRND) keyword after 'ALL' on the SRCGROUP keyword. Users can also
include the NOBACKGROUND (or NOBACKGRND) keyword after 'ALL' on the SRCGROUP keyword to
explicitly indicate that BACKGROUND is NOT included with group 'ALL.' The contribution of
background concentrations can also be tracked separately by including a source group with BACKGROUND
as the only "source ID." NOTE: The source of background concentrations and the method used to
incorporate background concentrations in a cumulative impact assessment involves several
considerations and should be documented and justified on a case-by-case basis.
Background concentrations specified with the BACKGRND keyword are combined with source
impacts on a temporally paired basis to estimate cumulative ambient impacts. However, since modeled
concentrations are not calculated for hours with calm or missing meteorological data, background
concentrations are also omitted for those hours. This may result in the background contribution being lower
than expected for short-term averages of 3-hours up to 24-hours for periods when the denominator used to
calculate the multi-hour average is adjusted in accordance with EPA's calms policy (see Section 8.4.6.2 of the
Guideline, EPA, 2017b), which is implemented within the AERMOD model. Section 8.4.6.2 of the Guideline
states:
"Model predicted concentrations for 3-, 8-, and 24-hour averages should be calculated by dividing the
sum of the hourly concentrations for the period by the number of valid or non-missing hours. If the
total number of valid hours is less than 18 for 24-hour averages, less than 6 for 8-hour averages, or
less than 3 for 3- hour averages, the total concentration should be divided by 18 for the 24-hour
average, 6 for the 8-hour average, and 3 for the 3-hour average. For annual averages, the sum of all
valid hourly concentrations is divided by the number of non-calm hours during the year."
For example, if 12 hours out of a 24-hour period are calm or missing, the calms policy dictates that the 24-
hour average concentration would be based on the sum of the 12 non-calm/non-missing hours divided by 18.
The contribution from background concentrations would also be based on the sum of background values for
the 12 non-calm/non-missing hours, divided by 18. If background was specified as uniform during that 24-
hour period, then the contribution from background would appear to be 33.3% lower than expected (i.e.,
12/18).
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The BGflag parameter must be specified as one of the following secondary keywords (the number in
parentheses indicates the number of values required for each option):
ANNUAL - annual background value (n=l),
SEASON - background values vary seasonally (n=4),
MONTH - background values vary monthly (n=12),
HROFDY - background values vary by hour-of-day (n=24),
WSPEED - background values vary by wind speed (n=6),
SEASHR - background values vary by season and hour-of-day (n=96),
HRDOW - background values vary by hour-of-day, and day-of-week [M-F, Sat, Sun] (n=72),
HRDOW7 - background values vary by hour-of-day, and the seven days of the week [M, Tu, W,
Th, F, Sat, Sun] (n=168),
SHRDOW - background values vary by season, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n=288),
SHRDOW7 - background values vary by season, hour-of-day, and the seven days of the week [M,
Tu, W, Th, F, Sat, Sun] (n=672),
MHRDOW - background values vary by month, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n=864), and
MHRDOW7 - background values vary by month, hour-of-day, and the seven days of the week [M,
Tu, W, Th, F, Sat, Sun] (n=2,016).
The seasons are defined in the following order: Winter (Dec., Jan., Feb.), Spring (Mar., Apr., May),
Summer (Jun., Jul., Aug.), and Fall (Sep., Oct., Nov.).4 The wind speed categories used with the WSPEED
option may be defined using the ME WINDCATS keyword. If the WINDCATS keyword is not used, the
default wind speed categories are defined by the upper bound of the first five categories as follows (the sixth
category is assumed to have no upper bound): 1.54, 3.09, 5.14, 8.23, and 10.8 m/s. The BACKGRND
keyword may be repeated as many times as necessary to input all of the background values and repeat values
may be used for the numerical inputs, e.g., 12*25.6 can be used to specify a value of 25.6 for 12 adjacent
"cells" within the array of values.
4 Note that the seasons are based on northern hemisphere seasons. For applications in the southern hemisphere using
the seasonal factors (SEASHR, SHRDOW, and SHRDOW7), background concentrations that would be associated with
the southern hemisphere winter, for example, should be assigned to the summer seasonal background concentrations
input to AERMOD. Similarly, spring southern hemisphere concentrations should be assigned to the fall season
background concentrations input to AERMOD.
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3.3.8.3 Specifying background concentration units
Background concentration units can be specified on the optional BACKUNIT keyword on the SO
pathway. The syntax of the BACKUNIT keyword is as follows:
Syntax:
SO BACKUNIT BGUnits
Type:
Optional, Non-repeatable
where the BGUnits parameter specifies the units as parts-per-billion (PPB), parts-per-million (PPM), or
micrograms/cubic-meter (UG/M3). Units specified on the BACKUNIT keyword are applied to HOURLY
and temporally varying background values if both are included in the same model run. If the BACKUNIT
keyword is omitted, default units of PPB are assumed for background NO2 and SO2, PPM for CO, and
UG/M3 for all other pollutants. Background
concentrations specified in units of PPB or PPM are converted to UG/M3 based on reference temperature
(25 C) and pressure (1013.25 mb). NOTE: When using the BACKUNIT keyword, PPB and PPM may only
be used with the N02, S02, and CO POLLUTID. AERMOD will issue a fatal error if PPB and PPM are
used with any other pollutant types. Use micrograms/cubic-meter (UG/M3) when specifying any other
pollutant type.
3.3.9 Specifying building downwash information
As noted above, the AERMOD model include algorithms to model the effects of buildings
downwash on emissions from nearby or adjacent point sources. The building downwash algorithms do not
apply to volume or area sources. For a technical description of the building downwash algorithms in
AERMOD, the user is referred to Schulman, et. al. (2000). The AERMOD model uses direction-specific
information for all building downwash cases.
There are five keywords that are used to specify building downwash information: BUILDHGT,
BUILDWID, BUILDLEN, XBADJ, YBADJ. The syntax, type and order for the BUILDHGT keyword, used
to input direction specific building heights, are summarized below:
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Syntax:
SO BUILDHGTSrcid (or Srcrng) Dsbh(i),i=l,36 (16 for LT)
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source. The user also has the option of specifying a range of sources (the Srcrng parameter) for which the
building heights apply, instead of identifying a single source. This is accomplished by two source ID
character strings separated by a dash, e.g., STACK1-STACK10. Since the model reads the source range as a
single input field there must not be any spaces between the source IDs. The model then places the building
heights that follow (the Dsbh(i) parameter) into the appropriate arrays for all Srcid's that fall within that
range, including STACK 1 and STACK10.
When comparing a source ID to the range limits for a Srcrng parameter, the model separates the
source IDs into three parts: an initial alphabetical part, a numerical part, and then the remainder of the string.
Each part is then compared to the corresponding parts of the source range, and all three parts must satisfy the
respective ranges for the source ID to be included. If there is no numeric part, then the ID consists of only
one alphabetical part. If the ID begins with a numeric character, then the initial alphabetical part defaults to a
single blank. If there is no trailing alphabetical part, then the third part also defaults to a single blank part. If
the trailing part consists of more than one alphabetical or numeric field, it is all lumped into one-character
field. For example, the source ID 'STACK2' consists of the parts 'STACK' plus '2' plus a single trailing
blank,''. By comparing the separate parts of the source IDs, it can be seen that STACK2 falls between the
range 'STACK1-STACK10.' For a three-part example, it can also be seen that VENT1B falls within the
range of VENT1A-VENT1C. However, VENT2 does not fall within the range of VENTlAto VENT3B,
since the third part ofVENT2 is a single blank, which does not fall within the range of A to C. This is
because a blank character will precede a normal alphabetical character. Normally, the source ranges will
work as one would intuitively expect for simple source names. Most importantly, for names that are made up
entirely of numeric characters, the source ranges will be based simply on the relative numerical values. The
user is strongly encouraged to check the summary of model inputs to ensure that the source ranges were
interpreted as expected and to avoid using complex source names in ranges, such as AA1B2C-AB3A3C.
Since the order of keywords within the SO pathway is quite flexible, it is also important to note that the
building heights will only be applied to those sources that have been defined previously in the input file.
Following the Srcid or the Srcrng parameter, the user inputs 36 direction-specific building heights
(Dsbh parameter) in meters, beginning with the 10-degree flow vector (wind blowing toward 10 degrees
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from north), and incrementing by 10 degrees in a clockwise direction. Some examples of building height
inputs are presented below:
so
BUILDHGT
STACK1
34. 34.
34
. 34
. 34 .
34. 34.
34 . 34
34
. 34
. 34 .
so
BUILDHGT
STACK1
34. 34.
34
. 34
. 34 .
34. 34.
34 . 34
34
. 34
. 34 .
so
BUILDHGT
STACK1
34. 34.
34
. 34
. 34 .
34. 34.
34 . 34
34
. 34
. 34 .
so
BUILDHGT
STACK1
36*34.0
so
BUILDHGT
STACK1
-STACK10
33
*34 .
0 3*0
0
so
BUILDHGT
STACK1
35.43
36.
45
36.37
35 .18
32. 92
29.
66
25.50
20.56
so
BUILDHGT
STACK1
15.00
20.
56
25.50
29. 66
32. 92
35.
18
36.37
36.45
so
BUILDHGT
STACK1
35.43
33.
33
35 .43
36.45
0. 00
35.
18
32. 92
29. 66
so
BUILDHGT
STACK1
25.50
20.
56
15 . 00
20.56
25.50
29.
66
32. 92
35.18
so
BUILDHGT
STACK1
36.37
36.
45
35 .43
33.33
The first example illustrates the use of repeat cards if more than one card is needed to input all of the values.
The values are processed in the order in which they appear in the input file and are identified as being repeat
cards by repeating the Srcid parameter. The first and second examples produce identical results within the
model. The second one illustrates the use of a repeat value that can simplify numerical input in some cases.
The field "36*34.0" is interpreted by the model as "repeat the value 34.0 a total of 36 times." This is also
used in the third example where the building height is constant for directions of 10 degrees through 330
degrees, and then is set to 0.0 (e.g., the stack may be outside the region of downwash influence) for
directions 340 through 360. The third example also uses a source range rather than a single source ID. The
last example illustrates building heights which vary by direction and shows that the number of values on
each card need not be the same. For improved readability of the input file, the user may want to put the
numerical inputs into "columns," but there are no special rules regarding the spacing of the parameters on
this keyword.
The BUILDWID keyword is used to input direction-specific building widths for downwash analyses.
The syntax for this keyword, which is very similar to the BUILDHGT keyword, is summarized below, along
with the type and order information:
3-102
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Syntax:
SO BUILDWID Srcid (or Srcrng) Dsbw(i),i=l,36 (16 for LT)
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
For a description of the Srcid and Srcrng parameters, and for a discussion and examples of the numeric input
options, refer to the BUILDHGT keyword above. The Dsbw(i) parameter contains the 36 direction-specific
building widths. The directions proceed in a clockwise direction, beginning with the 10-degree flow vector.
The BUILDLEN keyword is used to input direction-specific along-flow building lengths for
downwash analyses. Figure 3-3 shows the relationship of the projected building to this dimension. The
syntax for this keyword, which is very similar to the BUILDHGT keyword, is summarized below, along with
the type and order information:
Syntax:
SO BUILDLEN Srcid (or Srcrng) Dsbl(i),i=l,36
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
For a description of the Srcid and Srcrng parameters, and for a discussion and examples of the numeric input
options, refer to the BUILDHGT keyword above. The Dsbl(i) parameter contains the 36 direction-specific
building lengths. The directions proceed in a clockwise direction, beginning with the 10-degree flow vector.
Figure 3-3 shows the relationship of the projected building to these distances.
3-103
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Flow
J
Stack w
Xbadj
k
I Ybadj (along flow)
*
P
^Bmldlen_^
Projected
Building
Figure 3-5. Schematic Diagram Identifying New Building
Data for Prime Downwash
The XBADJ and YBADJ keywords are used to input direction-specific along-flow and across-flow
distances from the stack to the center of the upwind face of the projected building, respectively. Figure 3-2
shows the relationship of the projected building to these distances. The syntax for these keywords, which is
very similar to the BUILDHGT keyword, are summarized below, along with the type and order information:
Syntax:
SO XBADJ Srcid (or Srcrng) Xbadj(i),i=l,36
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
Syntax:
SO YBADJ Srcid (or Srcrng) Ybadj(i),i=l,36
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
For a description of the Srcid and Srcrng parameters, refer to the BUILDHGT keyword above. The Xbadj(i)
parameter contains the 36 direction-specific along-flow distances from the stack to the center of the upwind
face and the Ybadj(i) parameter contains the 36 direction-specific across-flow distances from the stack to the
center of the upwind face. The directions proceed in a clockwise direction, beginning with the 10-degree
flow vector.
3-104
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3.3.10 Specifying urban sources
As discussed in Section 3.2.8, the AERMOD model allows the user to incorporate the effects of
increased surface heating from an urban area on pollutant dispersion under stable atmospheric conditions.
The user specifies the parameters for one or more urban areas on the CO URBANOPT card (see Section
3.2.8), and identifies which sources are to be modeled with urban effects and the urban area that will apply to
each source affected using the SO URBANSRC card. If a source is not included on the URBANSRC card, it
will be modeled without the urban effects. The syntax, type and order for the URBANSRC keyword are
summarized below:
For Multiple Urban Areas:
SO URBANSRC UrbanID SrcID's and/or SrcRng's
Syntax:
For Single Urban Areas:
SO URBANSRC SrcID's and/or SrcRng's
or
SO URBANSRC ALL (to specify all sources as URBAN)
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the UrbanID parameter is the alphanumeric urban ID (up to eight characters) defined by the user on
the CO URBANOPT keyword when multiple urban areas are defined, and the SrcID's and SrcRng's are the
individual source IDs and/or source ID ranges that are to be modeled with urban effects. Source ranges are
described in more detail in Section 3.3.9. As with the URBANOPT keyword, the syntax of the URBANSRC
keyword for applications with single urban areas has not changed from the previous version of AERMOD, so
that existing input files will not require modification. However, beginning with version 12060, users can
specify that all sources are to be treated as urban sources by specifying 'ALL' on the SO URBANSRC
keyword for applications with a single urban area. Since the URBANSRC ALL option is identified during
the pre-SETUP phase, there are no restrictions on the order of the URBANSRC ALL keyword within the SO
pathway.
3.3.11 Specifying variable emission factors (EMISFACT)
The AERMOD model provides the option of specifying variable emission rate factors for individual
sources or for groups of sources. The syntax, type and order of the EMISFACT keyword are summarized
below:
3-105
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Syntax:
SO EMISFACT SrcID or SrcRange Qflag Qfact(i), i=l,n
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the SrcID parameter is the same source ID that was entered on the LOCATION card for a particular
source. The user also has the option of using the SrcRange parameter for specifying a range of sources for
which the emission rate factors apply, instead of identifying a single source. This is accomplished by two
source ID character strings separated by a dash, e.g., STACK1-STACK10. The use of the SrcRange
parameter is explained in more detail in the description of the BUILDHGT keyword (see Section 3.3.9).
The parameter Qflag is the variable emission rate flag, and must be specified as one of the following
secondary keywords (the number in parentheses indicates the number of values required for each option):
SEASON - emission rates vary seasonally (n=4),
MONTH - emission rates vary monthly (n=12),
HROFDY - emission rates vary by hour-of-day (n=24),
WSPEED - emission rates vary by wind speed (n=6),
SEASHR - emission rates vary by season and hour-of-day (n=96),
HRDOW - emission rates vary by hour-of-day, and day-of-week [M-F, Sat, Sun] (n=72),
HRDOW7 - emission rates vary by hour-of-day, and the seven days of the week [M, Tu, W, Th,
F, Sat, Sun] (n=168),
SHRDOW - emission rates vary by season, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n=288),
SHRDOW7 - emission rates vary by season, hour-of-day, and the seven days of the week [M, Tu,
W, Th, F, Sat, Sun] (n=672),
MHRDOW - emission rates vary by month, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n=864), and
MHRDOW7 - emission rates vary by month, hour-of-day, and the seven days of the week [M, Tu,
W, Th, F, Sat, Sun] (n=2,016).
The Qfact array is the array of factors, where the number of factors is shown above for each Qflag
option. The seasons are defined in the following order: Winter (Dec., Jan., Feb.), Spring (Mar., Apr., May),
Summer (Jun., Jul., Aug.), and Fall (Sep., Oct., Nov.).5 The wind speed categories used with the WSPEED
5 Note that the seasons are based on northern hemisphere seasons. For applications in the southern hemisphere using
the seasonal factors (SEASHR, SHRDOW, and SHRDOW7), emission factors that would be associated with the
3-106
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option may be defined using the ME WINDCATS keyword. If the WINDCATS keyword is not used, the
default wind speed categories are defined by the upper bound of the first five categories as follows (the sixth
category is assumed to have no upper bound): 1.54, 3.09, 5.14, 8.23, and 10.8 m/s. The EMISFACT card
may be repeated as many times as necessary to input all of the factors and repeat values may be used for the
numerical inputs. Examples for the more recent HRDOW and MHRDOW options are presented below, with
column headers to indicate the order in which values are to be to input:
southern hemisphere winter, for example, should be assigned to the summer seasonal emission factors input to
AERMOD. Similarly, spring southern hemisphere emission factors should be assigned to the fall season emission
factors input to AERMOD.
3-107
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SO
EMISFACT
STK1
HRDOW
enter 24
hourly scalars for
each of the
"days", first for Weekdays
(Monday-Friday), then for
Saturdays, anc
finally for Sundays, e.g.,
**
Weekdays:
Hrs :
1-5
6
7-17 18
19-24
so
EMISFACT
STK1
HRDOW
5
*0.3
0.
en
i1
i1
i1
o
o
CJ1
6*0.3
**
Saturdays
Hrs :
1-5
6
7-17 18
19-24
so
EMISFACT
STK1
HRDOW
5
*0.3
0.
en
i1
i1
i1
o
o
CJ1
6*0.3
**
Sundays:
Hrs :
1-5
6
7-17 18
19-24
so
EMISFACT
STK1
HRDOW
5
*0.3
0.
en
i1
i1
i1
o
o
CJ1
6*0.3
so
EMISFACT
STK1
HRDOW7
enter 24
hourly scalars for
each of the
"days",
first for
Mondays, then for
Tuesdays, . .
., then for Saturdays,
and
finally
for Sundays, e
g. ,
**
Mondays:
Hrs :
1-5
6 7-17 18
19-24
so
EMISFACT
STK1
HRDOW7
5*0. 3
0
en
i1
i1
i1
o
o
5
6*0.3
**
Tuesdays:
Hrs :
1-5
6 7-17 18
19-24
so
EMISFACT
STK1
HRDOW7
5*0. 3
0
en
i1
i1
i1
o
o
5
6*0.3
Saturdays
Hrs :
1-5
6 7-17 18
19-24
so
EMISFACT
STK1
HRDOW7
5*0. 3
0
en
i1
i1
i1
o
o
5
6*0.3
**
Sundays:
Hrs :
1-5
6 7-17 18
19-24
so
EMISFACT
STK1
HRDOW7
5*0. 3
0
en
i1
i1
i1
o
o
5
6*0.3
so
EMISFACT
STK1
MHRDOW
enter 24
hourly scalars for
each of the
twelve months, first for Weekdays
(Monday-Friday), then for
Saturdays, anc
finally for Sundays, e.g.,
**
Weekdays
JAN
FEB
MAR APR
MAY JUN
. . . NOV DEC
so
EMISFACT
STK1
MHRDOW
2 4*1.
0 24*
0.8
24*0.6 24*0.8
24*1.0 24*0.8
24*0.6 24*0.8
**
Saturdays
so
EMISFACT
STK1
MHRDOW
2 4*1.
0 24*
0.8
24*0.6 24*0.8
24*1.0 24*0.8
24*0.6 24*0.8
**
Sundays:
so
EMISFACT
STK1
MHRDOW
2 4*1.
0 24*
0.8
24*0.6 24*0.8
24*1.0 24*0.8
24*0.6 24*0.8
so
EMISFACT
STK1
MHRDOW7
enter 24
hourly scalars for
each of the
twelve months,
first for
Mondays, then for
Tuesdays, ..
., then for Saturdays,
and
finally
for Sundays, e
g. ,
**
Mondays
JAN
FEB
MAR APR
MAY JUN
. . . NOV DEC
so
EMISFACT
STK1
MHRDOW7
24*1
. 0 24
*0.
8 24*0.6 24*0.
8
24*1.0 24*0.
CO
K>
O
K>
O
CO
**
Tuesdays
JAN
FEB
MAR APR
MAY JUN
. . . NOV DEC
so
EMISFACT
STK1
MHRDOW7
24*1
. 0 24
*0.
8 24*0.6 24*0.
8
24*1.0 24*0.
CO
K>
o
K>
o
CO
Saturdays
so
EMISFACT
STK1
MHRDOW7
24*1
. 0 24
*0.
8 24*0.6 24*0.
8
24*1.0 24*0.
CO
K>
o
K>
o
CO
**
Sundays:
so
EMISFACT
STK1
MHRDOW7
24*1
. 0 24
*0.
8 24*0.6 24*0.
8
24*1.0 24*0.
CO
K>
o
K>
o
CO
3.3.12 Specifying an hourly emission rate file (HQUREMIS)
The source (SO) pathway includes an option for inputting hourly emission rates for the AERMOD
model, controlled by the HOUREMIS keyword. AERMOD currently allows for a single hourly emission file
to be used with each model run. The syntax, type and order for this keyword are summarized below:
3-108
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Syntax:
SO HOUREMIS Emifil Srcid's (and/or Srcrng's)
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Emifil parameter specifies the filename for the hourly emission file, and Srcid or Srcrng identify
the source or sources for which hourly emission rates are included. The Emifil filename can be up to 200
characters in length based on the default parameters in AERMOD. Double quotes (") at the beginning and
end of the filename can also be used as field delimiters to allow filenames with embedded spaces. Source
ranges, which are described in more detail in Section 3.3.9, are input as two source IDs separated by a dash,
e.g., STACK1-STACK10. The user may include more than one HOUREMIS card in a control file, if needed
to specify additional sources, but there can be only one hourly emissions file, and therefore the filename
must be the same on all HOUREMIS cards.
The format of each record of the hourly emissions file includes a pathway and keyword (SO
HOUREMIS), followed by the Year, Month, Day, Hour, Source ID, and emission rate (in the appropriate
units). For POINT/POINTHOR/POINTCAP sources, an hourly stack gas exit temperature (K) and stack gas
exit velocity (m/s) are also required. Beginning with version 09292, the release heights and initial dispersion
coefficients can also be varied on an hourly basis for AREA, AREAPOLY, AREACIRC, LINE, and
VOLUME sources using the HOUREMIS option.
As discussed in Sections 3.2.12, 3.3.2.2, 3.3.2.4, and 3.3.18, the ALPHA option ARCFTOPT was
added to AERMOD beginning in version 23132 to account for plume rise associated with aircraft emissions
due to momentum and buoyancy when modeling aircraft as AREA (including AREAPOLY, AREACIRC, and
LINE) and/or VOLUME source types. To characterize an aircraft source requires additional source
parameters beyond those required for non-aircraft AREA and VOLUME source types. The additional
aircraft source parameters must be specified in an hourly emission rate file. In addition to the required
hourly emission rate for AREA and VOLUME source types, the following aircraft parameters must be
included for each hour and aircraft source in the hourly emission rate file, appended to each record, in the
following order:
MFUEL: Fuel burn rate (g/s)
THRUST: Aircraft thrust (newtons)
3-109
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VAA: Aircraft speed (m/s)
AFR: Air-fuel ratio
BYPR: Bypass ratio (> 0 for turbofan and -999 for shaft-based engines)
RPWR: Rated power (kW) (-99999 for turbofan and > 0 for shaft-based)
SRCANGLE: Landing/takeoff angle with the ground (degrees) (airborne sources)
The parameters listed above must be included each hour in the hourly emission rate file for all AREA
and VOLUME sources identified as an aircraft source with the ARCFTSRC keyword. These parameters
must not be included for any AREA or VOLUME source that is not identified as an aircraft source. If
AERMOD determines there are too many or too few parameters a fatal error message will be issued, and
processing will not complete.
Beginning with version 19191, release heights and initial dispersion can be varied for RLINE and
RLINEXT sources. The user selects this enhanced option by including the additional source parameters in
the hourly emissions file. AERMOD determines whether hourly release heights and initial dispersion
coefficients are being used based on the first HOUREMIS record for each source, and these additional
parameters must be included on all HOUREMIS records unless the emissions are missing, which is indicated
by leaving the emission rate and all fields beyond the source ID blank.
When hourly emissions are specified for a buoyant line source, each of the individual lines
(BUOYLINE sources) that comprise the buoyant line source must be represented in the hourly
emissions file for every hour, and the buoyancy (m4/s3) of each line must be specified after the hourly
emission rate. The buoyancy of each line can vary within an hour and from hour to hour. AERMOD
computes an average buoyancy of the buoyant line source for each hour using the buoyancy values specified
for each individual line that comprises the buoyant line source.
The hourly emissions file is processed using the same routines used to process the control file,
therefore each of the parameters must be separated by at least one space, but otherwise the format is flexible.
It is also not necessary to include the SO HOUREMIS on each line, as long as the parameters (Year, Month,
etc.) do not begin before column 13. The data in the hourly emission file must also include the exact same
dates as are included in the meteorological input files, and the source IDs must correspond to the source IDs
defined on the SO LOCATION cards and be in the same order as defined in the 'aermod.inp' file.
3-110
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The model will check for a date mismatch between the hourly emissions file and the meteorological
data files. However, it is not necessary to process the entire hourly emissions file on each model run, i.e., the
correct emissions data will be read if the ME DAYRANGE or the ME STARTEND cards (see Section 3.5.4)
are used, as long as all the dates (including those that are processed and those that are skipped) match the
meteorological data files.
An example of several lines from an hourly emissions file for two point sources is provided below:
so
HOUREMIS
88
8
16
1
STACK1
52.5
382.60
12.27
so
HOUREMIS
88
8
16
1
STACK2
44 .3
432.33
22. 17
so
HOUREMIS
88
8
16
2
STACK1
22.3
377.88
9. 27
so
HOUREMIS
88
8
16
2
STACK2
42.2
437.68
19. 67
so
HOUREMIS
88
8
16
3
STACK1
51 .5
373.72
11. 87
so
HOUREMIS
88
8
16
3
STACK2
41.3
437.28
18 . 77
so
HOUREMIS
88
8
16
4
STACK1
36.0
374.83
9. 63
so
HOUREMIS
88
8
16
4
STACK2
43.7
437.68
18 . 23
The use of hourly varying release heights and initial dispersion coefficients for VOLUME and AREA sources
is illustrated in the following example:
SO
HOUREMIS 8i
3
1
1
VOL1
500.0
2.0
2.0
2.0
SO
HOUREMIS 8i
3
1
1
AREA1
5.000
2.0
2.0
so
HOUREMIS 8i
3
1
2
VOL1
500.0
2.0
2.0
3.0
so
HOUREMIS 8i
3
1
2
AREA1
5.000
2.0
3.0
so
HOUREMIS 8i
3
1
3
VOL1
500.0
2.0
2.0
4.0
so
HOUREMIS 8i
3
1
3
AREA1
5.000
2.0
4.0
For POINT/POINTHOR/POINTCAP sources, the model will use the stack release height and stack inside
diameter defined on the SO SRCPARAM card, but will use the emission rate, exit temperature and exit
velocity from the hourly emission file. As noted above regarding VOLUME and AREA sources, if the
emission rate, exit temperature and exit velocity are not included for a particular hour, i.e., any or all of those
fields are blank, the model will interpret emissions data for that hour as missing and will set the parameters
to zero. Since the emission rate will be zero, there will be no calculations made for that hour and that source.
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3.3.13 Adjusting the emission rate units for output
The default emission rate units for the AERMOD model are grams per second (g/s) for
POINT/POINTHOR/POINTCAP, VOLUME, and BUOYLINE sources, grams per second per meter (g/s/m)
for RLINEXT sources, and grams per second per square meter (g/s/m2) for AREA, LINE, OPENPIT, and
RLINE sources. By default, the model converts these input units to output units of micrograms per cubic
meter (ng/m3) for concentration calculations. This is accomplished by applying a default emission rate unit
factor of 1.0E06 for concentration.
The EMISUNIT keyword on the SO pathway allows the user to specify a different unit conversion
factor, and to specify the appropriate label for the output units for either concentration calculations. The
syntax and type of the EMISUNIT keyword are summarized below:
Syntax:
SO EMISUNIT Emifac Emilbl Conlbl
Type:
Optional, Non-repeatable
Order:
Must follow the LOCATION card for each source input
where the parameter Emifac is the emission rate unit factor, Emilbl is the label for the emission units (up to
40 characters), and Conlbl is the output unit label (up to 40 characters) for concentration calculations. For
example, to produce output concentrations in milligrams per cubic meter, assuming input units of grams per
sec, the following card could be input:
SO EMISUNIT 1.0E3 GRAMS/SEC MILLIGRAMS/M* * 3
since there are 1.0E3 milligrams per gram. The emission rate unit factor applies to all sources for a given
run. Since the model uses one or more spaces to separate different fields on the input control file commands,
it is important that there not be any spaces within the label fields on this card. Thus, instead of entering
'GRAMS PER SECOND' for the emission label, a label of'GRAMS/SECOND', or 'GRAMS-PER-SECOND'
or an equivalent variation should be used.
For the RLINE or RLINEXT source types, an additional keyword was introduced in version 19191to
allow alternate units of grams per link per hour. These alternate units can be used if the keyword
RLEMCONV (RLine EMission CONVersion) is used on the SO card. This keyword has no additional
inputs, but when present, emissions for all RLINE and RLINEXT sources are assumed to be in grams per
3-112
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link per hour. The model converts such units internally to its native units for each source and the
computation proceeds as normal. The syntax and type of the RLEMCONV keyword are summarized below:
Syntax:
SO RLEMCONV
Type:
Optional, Non-repeatable
Order:
Can be present anywhere on the SO card
3.3.14 Including source data from an external file
The user has the option of including source data from an external file by using the INCLUDED
keyword on the source (SO) pathway. A SO INCLUDED card may be placed anywhere within the source
pathway, after the STARTING card and before the FINISHED card (i.e., the SO STARTING and SO
FINISHED cards cannot be included in the external file). The data in the included file will be processed as
though it were part of the control file. The syntax and type of the INCLUDED keyword are summarized
below:
Syntax:
SO INCLUDED Incfil
Type:
Optional, Repeatable
where the Incfil parameter is a character field of up to 200 characters that identifies the filename for the
included file. The contents of the included file must be valid control file commands for the source pathway.
If an error is generated during processing of the included file, the error message will report the line number
of the included file (see APPENDIX B). If more than one INCLUDED file is specified for the source
pathway, the user will first need to determine which file the error occurred in. If the starting column of the
main control input file is shifted from column 1 (see Section 2.4.8), then the control file commands in the
included file must be offset by the same amount.
3.3.15 Using source groups
The AERMOD model allows the user to group contributions from particular sources together.
Several source groups may be setup in a single run, and they may, for example, be used to model impacts
from the source being permitted, the group of increment consuming PSD sources, and the group of all
sources for comparison to a NAAQS in a single run. There is always at least one source group in a run,
which may consist of all sources, so the SRCGROUP keyword has been made mandatory in the AERMOD
3-113
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model unless the PSDGROUP is specified, which is mandatory when using the PSDCREDIT keyword with
the PVMRM NO to NO2 conversion option (See Section 3.3.7). The SRCGROUP keyword cannot be used
when the PSDGROUP keyword is used. The syntax, type and order of the SRCGROUP keyword are
summarized below:
Syntax:
SO SRCGROUP Grpid Srcid's and/or Srcrng's
Type:
Mandatory (conditional), Repeatable
Order:
Must be the last keyword in the SO pathway before FINISHED
where the Grpid parameter is an alphanumeric string of up to eight characters that identifies the group name.
The Srcid's and Srcrng's are the individual source IDs and/or source ranges that make up the group of
sources. Source ranges, which are described in more detail in the description of the BUILDHGT keyword
(Section 3.3.9), are input as two source IDs separated by a dash, e.g., STACK1-STACK10. Individual source
IDs and source ranges may be used on the same card. If more than one input card is needed to define the
sources for a particular group, then additional cards may be input, repeating the pathway, keyword and group
ID.
A special group ID has been reserved for use in specifying the group of all sources. When Grpid =
ALL, the model will automatically setup a source group called ALL that includes all sources modeled for
that particular run. If desired, the user can setup a group of all sources with a different group ID by explicitly
specifying all sources on the input card(s).
Note: The secondary keyword, ALL, is used in different source grouping contexts (e.g.,
BLPGROUP, SRCGROUP, OLMGROUP). Refer to the appropriate section of this user's guide to see
the usage of the secondary keyword, ALL, for the group of sources to be identified. For BLPGROUP
see Section 3.3.2.11. For OLMGROUP, see Section 3.3.6.2.
The number of source groups is allocated dynamically at the time AERMOD is run. This value, in
concert with the other dynamically allocated arrays and input requirements, is limited only by the amount of
available memory.
As discussed in Sections 1.2.9 and 3.2.14, it is sometimes important for a user to know the
contribution of a particular source to the total result for a group. These source contribution analyses are
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facilitated for short-term averages by the use the EVENT processing capabilities in the AERMOD model.
EVENT processing uses the same source groups that are identified by AERMOD (when the input file is
generated using the CO EVENTFIL option), but the model is structured in a way that it retains individual
source results for particular events. Refer to the sections noted above for a more complete description of
EVENT processing and its uses.
With respect to buoyant line sources, note that the SRCGROUP keyword treats the individual lines
(BUOYLINE) that comprise a buoyant line source as if they are individual sources. A SRCGROUP can
consist of all or a subset of the individual lines by specifying the source IDs from the LOCATION keyword
for those lines that should make up the SRCGROUP.
Note that when modeling with Tier 2 or Tier 3 NO2 conversion and using source groups, the
conversion mechanism will be based on the total NOx at each receptor for all sources rather than the
NOx concentration just for each source group.
3.3.16 Specifying platform downwash information (POINT. POINTHOR, POINTCAP sources ONLY)
The Offshore and Coastal Dispersion (OCD) Model is the EPA's preferred model for estimating near
field air pollutant impacts from overwater emission sources, for both deep water and shoreline applications.
The original platform downwash algorithms were developed by Petersen (1984) and adapted when
implemented into OCD by Hanna and Dicristofaro (1988). The platform downwash algorithms from OCD
were integrated into AERMOD for POINT/POINTHOR/POINTCAP source types ONLY.
The SRCPARAM input for stack height is used with inputs via a new PLATFORM keyword to
simulate a platform's influence on the dispersion from a POINT or POINTHOR or POINTCAP source.
When the PLATFORM keyword is included in the AERMOD control file, platform downwash will be
applied to the source identified by the source ID. The syntax, type, and order for the PLATFORM keyword
are summarized below:
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Syntax:
SO PLATFORM Srcid Zelp Hb Wb
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
POINT/POINTHOR/POINTCAP source, and the other parameters are as follows:
Zelp - Base height (in meters) defined as the height of the bottom of the platform above the sea surface.
NOTE: This input is consistent with the input for OCD, but this input is not currently used in the
AERMOD implementation of platform downwash specific algorithms, because the full height of the
source as defined for the POINT/POINTHOR/POINTCAP source is used, no adjustment is made for
the height of the platform.
Hb - Total height (in meters), above the sea surface, of the tallest solid or ""influential" building (i.e.,
the sum of the height of the base of the platform above the sea surface and the height of the building
above the base of the platform)
Wb - The lesser of the two distances (in meters) from outer edges of the leftmost and rightmost
buildings on top of the platform that can influence downwash when comparing the side and end views
of the platform as shown in Figure 3-7. The platform downwash influence is not adjusted for platform
dimension normal to the wind, the influence will be identical for all wind directions.
Figure 3-6. New platform parameter figure with correct parameter definitions. Adapted from
Petersen (1984)
All parameters are required for a POINT or POINTHOR or POINTCAP source located on a
platform. POINT or POINTHOR or POINTCAP sources located on a platform are NOT subject to the
PRIME building downwash options. An ERROR message will occur if the same source ID is used with the
building downwash keywords.
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3.3.17 Specifying highly buoyant point sources for HBP option (POINT. POINTHOR. POINTCAP sources
ONLY)
Beginning with version 23132, HBP, specified with the MODELOPT keyword in the CO pathway
(see Section 3.2.2), was added as an ALPHA option for highly buoyant plumes that penetrate the top of the
convective mixed layer (Weil, 2020; Warren et. al., 2022). The HBP option is only applicable to POINT,
POINTHOR, and POINTCAP source types. When the HBP option is specified with the MODELOPT
keyword, the sources to which the HBP option should be applied must be identified using the HBPSRCID
keyword on the SO pathway.
Syntax: SO HBPSRCID Srcid's and/or Srcrng's
or
SO HBPSRCID ALL
Type: Mandatory (conditional), Repeatable
where the Srcid's and Srcrng's are the individual source IDs and/or source ranges that make up the group of
sources. Source ranges, which are described in more detail in the description of the BUILDHGT keyword
(Section 3.3.9), are input as two source IDs separated by a dash, e.g., STACK1-STACK10. Individual source
IDs and source ranges may be used on the same card. If more than one input card is needed to define the
sources for a particular group, then additional cards may be input, repeating the pathway (SO), keyword
(HBPSRCID), and source IDs and/or ranges. The secondary keyword ALL can be entered in the place of
specific source IDs or ranges to apply the HBP option to all POINT, POINTHOR, and POINTCAP source
types. Any source types other than POINT, POINTHOR, and POINTCAP that are included in the model
simulation and specified with the HBPSRCID keyword, either by source ID or by specifying ALL, will be
ignored. In that case, AERMOD will generate an informational message to indicate the non-POINT source
type that was ignored.
3.3.18 Specifying aircraft sources (AREA and VOLUME sources ONLY)
As discussed in Section 3.2.12, the ALPHA option ARCFTOPT was added to AERMOD version
23132 to account for plume rise from aircraft emissions when aircraft are modeled as either VOLUME or
AREA source types. Because additional parameters are required to characterize an aircraft source, all
aircraft sources must be identified in the AERMOD control file using the ARCFTSRC primary keyword in
the SO pathway, followed by a list of source IDs or ranges of source IDs. The syntax for the ARCFTSRC
keyword is shown here
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SO ARCFTSRC Srcid's and/or Srcrng's
Syntax:
or
SO ARCFTSRC ALL
Type:
Mandatory (conditional), Repeatable
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a particular
source. The user also has the option of specifying a range of sources (the Srcrng parameter) instead of
identifying a single source or a list of single sources.
Source ranges, which are described in more detail in the description of the BUILDHGT keyword
(Section 3.3.9), are input as two source IDs separated by a dash, e.g., STACK1-STACK10. Individual source
IDs and source ranges may be used on the same card. If more than one input card is needed to identify all
aircraft sources, then additional cards may be input, repeating the pathway, keyword, and group ID. The
secondary keyword ALL can be entered in the place of specific source IDs or ranges to apply the
AIRCFTOPT option to all AREA and VOLUME source types. Source types other than AREA and
VOLUME sources that are included in the model simulation and specified with the ARCFTSRC keyword,
either by source ID or by specifying ALL, will be ignored. The ARCFTSRC keyword is mandatory when the
ARCFTOPT keyword is included in the CO pathway as described in Section 3.2.12. Failure to identify
aircraft sources in the SO pathway with the ARCFTSRC keyword will generate a fatal error and processing
will stop.
3.4 Receptor pathway inputs and options
The REceptor pathway contains keywords that define the receptor information for a particular model
run. The RE pathway contains keywords that allow the user to define Cartesian grid receptor networks
and/or polar grid receptor networks, with either uniform or non-uniform grid spacing, as well as discrete
receptor locations referenced to a Cartesian or a polar system. The number of receptors and receptor
networks are allocated dynamically at the time AERMOD is run. This value, in combination with the other
dynamically allocated arrays and input requirements, is limited only by the amount of available memory.
All of the receptor options in AERMOD allow the user to input terrain elevations and hill height
scales for each receptor, both of which are needed when applying AERMOD in an elevated terrain situation.
To facilitate the generation of hill height scales for AERMOD, a terrain preprocessor, called AERMAP, has
been developed (EPA, 2004c). The AERMAP terrain preprocessor, which can process U.S. Geological
Survey (USGS) Digital Elevation Model (DEM) data and data from the National Elevation Dataset (NED),
may also be used to generate the terrain elevations for the receptor locations. The AERMAP program
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generates an output file that contains the receptor pathway data for AERMOD in the format described below.
This file may be cut and pasted into the AERMOD control file or included as an external file using the RE
INCLUDED card (see Section 3.4.4).
The default units for receptor elevations for the AERMOD model are in meters; however, the user
may specify receptor elevations to be in units of feet by adding the RE ELEVUNIT FEET card immediately
after the RE STARTING card. Since the AERMAP terrain preprocessor outputs elevations in meters and
includes the RE ELEVUNIT METERS card as the first record, the AERMAP data must be placed at the
beginning of the receptor pathway.
3.4.1 Defining networks of gridded receptors
Two types of receptor networks are allowed by the AERMOD model. A Cartesian grid network,
defined through the GRIDCART keyword, includes an array of points identified by their x (east-west) and y
(north-south) coordinates. A polar network, defined by the GRIDPOLR keyword, is an array of points
identified by direction and distance from a user-defined origin. Each of these keywords has a series of
secondary keywords associated with it that are used to define the network, including any receptor elevations
for elevated terrain and flagpole receptor heights. The GRIDCART and GRIDPOLR keywords can be
thought of as "sub-pathways," since their secondary keywords include a STArt and an END card to define
the start and end of inputs for a particular network.
3.4.1.1 Cartesian grid receptor networks
Cartesian grid receptor networks are defined by use of the GRIDCART keyword. The GRIDCART
keyword may be thought of as a "sub-pathway," in that there are a series of secondary keywords that are used
to define the start and the end of the inputs for a particular network, and to select the options for defining the
receptor locations that make up the network. The syntax and type of the GRIDCART keyword are
summarized below:
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RE GRIDCART Netid STA
XYINC Xinit Xnum Xdelta Yinit Ynum Ydelta
XPNTS Gridxl Gridx2 Gridx3 .... Gridxn. and
Syntax:
or YPNTS Gridvl Gridv2 Gridv3 .... Gridvn
ELEV Row Zelevl Zelev2 Zelev3 ... Zelevn
HILL Row Zhilll Zhill2 Zhill3 ... Zhilln
FLAG Row Zflael Zflae2 Zflae3 ... Zflaen
END
Type:
Optional, Repeatable
where the parameters are defined as follows:
Netid
Receptor network identification code (up to eight alphanumeric characters)
STA
Indicates the STArt of GRIDCART inputs for a particular network, repeated for each
new Netid
XYINC
Xinit
Xnum
Xdelta
Yinit
Ynum
Ydelta
Keyword identifying uniform grid network generated from x and y increments
Starting x-axis grid location in meters
Number of x-axis receptors
Spacing in meters between x-axis receptors
Starting y-axis grid location in meters
Number of y-axis receptors
Spacing in meters between y-axis receptors
XPNTS
Gridxl
Gridxn
Keyword identifying grid network defined by a series of discrete x and y coordinates
(used with YPNTS)
Value of first x-coordinate for Cartesian grid (m) Value
of 'nth' x-coordinate for Cartesian grid (m)
YPNTS
Gridyl
Gridyn
Keyword identifying grid network defined by a series of discrete x and y coordinates
(used with XPNTS)
Value of first y-coordinate for Cartesian grid (m) Value
of 'nth' y-coordinate for Cartesian grid (m)
ELEV
Row
Zelev
Keyword to specify that receptor elevations follow (optional)
Indicates which row (y-coordinate fixed) is being
input (Row=l means first, i.e., southmost row) An
Array of receptor terrain elevations (m) for a
particular Row (default units of meters may be changed to feet by use of
RE ELEVUNIT keyword), number of entries per
row equals the number of x-coordinates for that network
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HILL
Row
Zelev
Keyword to specify that hill height scales follow (optional)
Indicates which row (y-coordinate fixed) is being
input (Row=l means first, i.e., southmost row) An
Array of hill height scales (m) for a
particular Row (default units of meters may be changed to feet by use of
RE ELEVUNIT keyword), number of entries per
row equals the number of x-coordinates for that network
FLAG
Row
Zflag
Keyword to specify that flagpole receptor heights follow (optional)
Indicates which row (y-coordinate fixed) is being
input (Row=l means first, i.e., southmost row)
An array of receptor heights (m) above local terrain
elevation for a particular Row (flagpole receptors), number of
entries per row equals the number of x-coordinates for that
network
END
Indicates the END of GRIDCART inputs for a particular network, repeated for each
new Netid
The ELEV. HILL, and FLAG keywords are optional inputs, and are only needed if elevated terrain
or flagpole receptor heights are to be used. If elevated terrain is being used, then both the ELEV and HILL
inputs are needed for each receptor. If the ELEV and HILL keywords are used and the model is being run
with the flat terrain option (see Section 3.2.2), then the elevated terrain height inputs will be ignored by the
model, and a non-fatal warning message will be generated. If the elevated terrain option is selected, and no
elevated terrain heights are entered, the elevations will default to 0.0 meters, and warning messages will also
be generated. The model handles flagpole receptor height inputs in a similar manner.
The order of cards within the GRIDCART subpathway is not important, as long as all inputs for a
particular network are contiguous and start with the STA secondary keyword and end with the END
secondary keyword. It is not even required that all ELEV cards be contiguous, although the input file will be
more readable if a logical order is followed. The network ID is also not required to appear on each control
file command (except for the STA card). The model will assume the previous ID if none is entered, similar
to the use of continuation cards for pathway and keywords. Thus, the following two examples produce the
same 8X4 Cartesian grid network:
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RE
GRIDCART
CAR1
STA
RE
GRIDCART
CAR1
XPNTS
-500.
-400.
-200.
-100
100.
200
. 400. 500.
RE
GRIDCART
CAR1
YPNTS
-500.
-250.
250 .
500.
RE
GRIDCART
CAR1
ELEV
1
10.
10.
10 .
10.
10.
10 .
10.
10.
RE
GRIDCART
CAR1
ELEV
2
20.
20.
20 .
20.
20.
20 .
20.
20.
RE
GRIDCART
CAR1
ELEV
3
30.
30.
30 .
30.
30.
30 .
30.
30.
RE
GRIDCART
CAR1
ELEV
4
40.
40.
40 .
40.
40.
40 .
40.
40.
RE
GRIDCART
CAR1
HILL
1
50.
50.
50 .
50.
50.
50 .
50.
50.
RE
GRIDCART
CAR1
HILL
2
60.
60.
60 .
60.
60.
60 .
60.
60.
RE
GRIDCART
CAR1
HILL
3
70.
70.
70 .
70.
70.
70 .
70.
70.
RE
GRIDCART
CAR1
HILL
4
80.
80 .
80.
80.
80 .
80.
80.
80 .
RE
GRIDCART
CAR1
FLAG
1
10.
10 .
10.
10.
10 .
10.
10.
10 .
RE
GRIDCART
CAR1
FLAG
2
20.
20 .
20.
20.
20 .
20.
20.
20 .
RE
GRIDCART
CAR1
FLAG
3
30.
30 .
30.
30.
30 .
30.
30.
30 .
RE
GRIDCART
CAR1
FLAG
4
40.
40 .
40.
40.
40 .
40.
40.
40 .
RE
GRIDCART
CAR1
END
RE
GRIDCART
CAR1
STA
XPNTS
-500.
-400 .
-200. -100. 10C
. 20C
. 400
. 500.
YPNTS
-500.
-250 .
250
. 500
ELEV
1
8*10.
HILL
1
8*50.
FLAG
1
8*10.
ELEV
2
8*20.
HILL
2
8*60.
FLAG
2
8*20.
ELEV
3
8*30.
HILL
3
8*70 .
FLAG
3
8*30.
ELEV
4
8*40.
HILL
4
8*80.
FLAG
4
8*40.
RE
GRIDCART
CAR1
END
The Row parameter on the ELEV. HILL, and FLAG inputs may be entered as either the row number,
i.e., 1, 2, etc., or as the actual y-coordinate value, e.g., -500., -250., etc. in the example above. The model
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sorts the inputs using Row as the index, so the result is the same. The above example could therefore be
entered as follows, with the same result:
RE
GRIDCART
CAR1
STA
XPNTS
-500 .
-400.
-200. -100.
100.
200.
400 .
500.
YPNTS
-500 .
-250.
250. 500.
ELEV
-500 .
8*10.
FLAG
-500 .
8*10.
ELEV
-250 .
8*20.
FLAG
-250 .
8*20.
ELEV
250 .
8*30.
FLAG
250 .
8*30.
ELEV
500 .
8*40.
FLAG
500 .
8*40.
RE
GRIDCART
CAR1
END
Of course, one must use either the row number or y-coordinate value consistently within each network to
have the desired result.
The following simple example illustrates the use of the XYINC secondary keyword to generate a
uniformly spaced Cartesian grid network. The resulting grid is 11 x 11, with a uniform spacing of 1
kilometer (1000. meters), and is centered on the origin (0., 0.). No elevated terrain heights or flagpole
receptor heights are included in this example.
RE
GRIDCART
CGI
STA
XYINC
-5000.
11 1000.
-5000.
11 1000.
RE
GRIDCART
CGI
END
3.4.1.2 Polar grid receptor networks
Polar receptor networks are defined by use of the GRIDPOLR keyword. The GRIDPOLR keyword
may also be thought of as a "sub-pathway," in that there are a series of secondary keywords that are used to
define the start and the end of the inputs for a particular network, and to select the options for defining the
receptor locations that make up the network. The syntax and type of the GRIDPOLR keyword are
summarized below:
3-123
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RE GRIDPOLR Netid STA
ORIG Xinit Yinit,
or ORIG Srcid
DIST Ringl Ring2 Ring3 ... Ringn
DDIR Dirl Dir2 Dir3 ... Dim,
Syntax. or GDIR Dirnum Dirini Dirinc
ELEV Dir Zelevl Zelev2 Zelev3 ...Zelevn
HILL Dir Zhilll Zhill2 Zhill3 ... Zhilln
FLAG Dir Zflagl Zflag2 Zflag3 ... Zflagn
END
Type: Optional, Repeatable
where the parameters are defined as follows:
Netid
Receptor network identification code (up to eight alphanumeric characters)
STA
Indicates STArt of GRIDPOLR inputs for a particular network, repeat for each
new Netid
ORIG
Xinit
Yinit
Srcid
Keyword to specify the origin of the polar network (optional)
x-coordinate for origin of polar network
y-coordinate for origin of polar network
Source ID of source used as origin of polar network
DIST
Ringl
Ringn
Keyword to specify distances for the polar network
Distance to the first ring of polar coordinates
Distance to the 'nth' ring of polar coordinates
DDIR
Dirl
Dim
Keyword to specify discrete direction radials for the polar network
First direction radial in degrees (1 to 360)
The 'nth' direction radial in degrees (1 to 360)
GDIR
Dimum
Dirini
Dirinc
Keyword to specify generated direction radials for the polar network
Number of directions used to define the polar system
Starting direction of the polar system
Increment (in degrees) for defining directions
ELEV
Dir
Zelev
Keyword to specify that receptor elevations follow (optional)
Indicates which direction is being input
An array of receptor terrain elevations for a
particular direction radial (default units of meters may be
changed to feet by use of RE ELEVUNIT keyword),
number of entries per radial equals the number of distances for
that network
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HILL
Dir
Zelev
Keyword to specify that hill height scales follow (optional)
Indicates which direction is being input
An array of receptor hill height scales for a
particular direction radial (default units of meters may be
changed to feet by use of RE ELEVUNIT keyword),
number of entries per radial equals the number of distances for
that network
FLAG
Dir
Zflag
Keyword to specify that flagpole receptor heights follow (optional)
Indicates which direction is being input
An array of receptor heights above local terrain
elevation for a particular direction (flagpole
receptors)
END
Indicates END of GRIDPOLR subpathwav. repeat for each new Netid
The ORIG secondary keyword is optional for the GRIDPOLR inputs. If omitted, the model assumes a
default origin of (0.,0.) in x,y coordinates. The ELEV. HILL, and FLAG keywords are also optional inputs,
and are only needed if elevated terrain or flagpole receptor heights are to be used. If elevated terrain is being
used, then both the ELEV and HILL inputs are needed for each receptor. If the ELEV and HILL keywords
are used and the model is being run with the flat terrain option (see Section 3.2.2), then the elevated terrain
height inputs will be ignored by the model, and a non-fatal warning message will be generated. If the
elevated terrain option is selected, and no elevated terrain heights are entered, the elevations will default to
0.0 meters, and warning messages will also be generated. The model handles flagpole receptor height inputs
in a similar manner.
As with the GRIDCART keyword described above, the order of cards within the GRIDPOLR
subpathway is not important, as long as all inputs for a particular network are contiguous and start with the
STA secondary keyword and end with the END secondary keyword. It is not even required that all ELEV
cards be contiguous, although the input file will be more readable if a logical order is followed. The network
ID is also not required to appear on each control file command (except for the STA card). The model will
assume the previous ID if none is entered, similar to the use of continuation cards for pathway and keywords.
The following example of the GRIDPOLR keyword generates a receptor network consisting of 180
receptor points on five concentric distance rings centered on an assumed default origin of (0.,0.). The
receptor locations are placed along 36 direction radials, beginning with 10. degrees and incrementing by 10.
degrees in a clockwise fashion.
3-125
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RE
GRIDPOLR
POL1
STA
DIST
100. 300. 500.
1000.
2000 .
GDIR
36 10. 10.
RE
GRIDPOLR
POL1
END
Another example is provided illustrating the use of a non-zero origin, discrete direction radials and
the specification of elevated terrain and flagpole receptor heights:
RE
GRIDPOLR
POL1
STA
ORIG
500 .
500
DIST
100 .
300
500.
1000. 2000.
DDIR
90 .
180
270.
360.
ELEV
90 .
5 .
10
15.
20.
25.
ELEV
180 .
5 .
10
15.
20.
25.
ELEV
270 .
5 .
10
15.
20.
25.
ELEV
360 .
5 .
10
15.
20.
25.
HILL
90 .
50 .
60
75.
80.
95.
HILL
180 .
50 .
60
75.
80.
95.
HILL
270 .
50 .
60
75.
80.
95.
HILL
360 .
50 .
60
75.
80.
95.
FLAG
90 .
5 .
10
15.
20.
25.
FLAG
180 .
5 .
10
15.
20.
25.
FLAG
270 .
5 .
10
15.
20.
25.
FLAG
360 .
5 .
10
15 .
20.
25.
RE
GRIDPOLR
POL1
END
The user has the option of specifying the radial number (e.g., 1, 2, 3, etc.) on the ELEV. HILL, and
FLAG inputs, or the actual direction associated with each radial.
For purposes of model calculations, all receptor locations, including those specified as polar, are
stored in the model arrays as x, y and z coordinates and flagpole heights. For the purposes of reporting the
results by receptor in the main print file, the tables are labeled with the polar inputs, i.e., directions and
distances.
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3.4.2 Using multiple receptor networks
For some modeling applications, the user may need a fairly coarsely spaced network covering a large
area to identify the area of significant impacts for a plant, and a denser network covering a smaller area to
identify the maximum impacts. To accommodate this modeling need, the AERMOD model allows the user
to specify multiple receptor networks in a single model run. The user can define either Cartesian grid
networks or polar networks, or both. With the use of the ORIG option in the GRIDPOLR keyword, the user
can easily place a receptor network centered on the facility being permitted, and also place a network
centered on another background source known to be a significant contributor to high concentrations.
Alternatively, the polar network may be centered on a receptor location of special concern, such as a nearby
Class I area.
As noted in the introduction to this section (3.4), the model dynamically allocates array storage
based on the number of receptors and receptor networks when the AERMOD model is run, up to the
maximum amount of memory available on the computer.
3.4.3 Specifying discrete receptor locations
In addition to the receptor networks defined by the GRIDCART and GRIDPOLR keywords
described above, the user may also specify discrete receptor points for modeling impacts at specific locations
of interest. This may be used to model critical receptors, such as the locations of schools or houses, nearby
Class I areas, or locations identified as having high concentrations by previous modeling analyses. The
discrete receptors may be input as either Cartesian x,y points (DISCCART keyword) or as polar distance and
direction coordinates (DISCPOLR keyword). Both types of receptors may be identified in a single run. In
addition, for discrete polar receptor points the user specifies the source whose location is used as the origin
for the receptor.
3.4.3.1 Discrete Cartesian receptors.
Discrete Cartesian receptors are defined by use of the DISCCART keyword. The syntax and type of
this keyword are summarized below:
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Syntax:
RE DISCCART Xcoord
Ycoord (Zelev Zhill) (Zflag)
Type:
Optional, Repeatable
where the Xcoord and Ycoord parameters are the x-coordinate and y-coordinate (m), respectively, for the
receptor location. The Zelev parameter is an optional terrain elevation (m) and Zhill is a corresponding hill
height scale for the receptor for use in elevated terrain modeling. Both the Zelev and Zhill parameters must
be specified for use with the elevated terrain algorithms and are referenced to the same reference elevation
(e.g., mean sea level) used for source elevations. The Zflag parameter is the optional receptor height above
ground (m) for modeling flagpole receptors. All of the parameters are in units of meters, except for Zelev and
Zhill, which default to meters but may be specified in feet by use of the RE ELEVUNIT keyword.
If neither the elevated terrain option (Section 3.2.2) nor the flagpole receptor height option (Section
3.2.11) are used, then the optional parameters are ignored if present. In other words, the FLAGPOLE
keyword is required on the CO pathway if Zflag values are to be used and, the ELEV option must be
specified with the MODELOPT keyword on the CO pathway if Zelev and Zhill values are to be used. If
only the elevated terrain height option is used (no flagpoles), then the third parameter (the field after the
Ycoord) is read as the Zelev parameter. If only the flagpole receptor height option is used (no elevated
terrain), then the third parameter is read as the Zflag parameter. If both options are used, then the parameters
are read in the order indicated for the syntax above. If the optional parameters are left blank, then default
values will be used. The default value for Zelev is 0.0, and the default value for Zflag is defined by the CO
FLAGPOLE card (see Section 3.2.11). Note: If both the elevated terrain and flagpole receptor height
options are used, then the third parameter will always be used as Zelev, and it is not possible to use a default
value for Zelev while entering a specific value for the Zflag parameter.
3.4.3.2 Discrete polar receptors
Discrete polar receptors are defined by use of the DISCPOLR keyword. The syntax and type of this
keyword are summarized below:
Syntax:
RE DISCPOLR Srcid Dist Direct (Zelev Zhill) (Zflag)
Type:
Optional, Repeatable
where the Srcid is the alphanumeric source identification for one of the sources defined on the SO pathway
which will be used to define the origin for the polar receptor location. The Dist and Direct parameters are the
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distance in meters and direction in degrees for the discrete receptor location. Degrees are measured
clockwise from north. The Zelev parameter is an optional terrain elevation for the receptor and Zhill is the
corresponding hilltop elevation (m) for use in elevated terrain modeling. Both the Zelev and Zhill
parameters must be specified for use with the elevated terrain algorithms and are referenced to the same
reference elevation (e.g., mean sea level) used for source elevations. The units of Zelev and Zhill are in
meters, unless specified as feet by the RE ELEVUNIT keyword. The Zflag parameter is the optional
receptor height above ground (meters) for modeling flagpole receptors.
If neither the elevated terrain option (Section 3.2.2) nor the flagpole receptor height option (Section
3.2.11) are used, then the optional parameters are ignored if present. If only the elevated terrain height
option is used (no flagpoles), then the third parameter (the field after the Ycoord) is read as the Zelev
parameter. If only the flagpole receptor height option is used (no elevated terrain), then the third parameter is
read as the Zflag parameter. If both options are used, then the parameters are read in the order indicated for
the syntax above. If the optional parameters are left blank, then default values will be used. The default
value for Zelev is 0.0, and the default value for Zflag is defined by the CO FLAGPOLE card (see Section
3.2.11). Note: If both the elevated terrain and flagpole receptor height options are used, then fourth
parameter will always be used as Zelev, and it is not possible to use a default value for Zelev while entering a
specific value for the Zflag parameter.
3.4.3.3 Discrete Cartesian receptors for evalfile output
The EVALCART keyword is used to define discrete Cartesian receptor locations, similar to the
DISCCART keyword, but it also allows for grouping of receptors, e.g., along arcs. It is designed to be used
with the EVALFILE option, described later for the output pathway, which outputs arc maxima values to a
separate file for evaluation purposes. The EVALCART keyword can be used without the use of the
EVALFILE option, in which case the receptor groupings are ignored. The syntax and type for the modified
EVALCART keyword are summarized below:
Syntax:
RE EVALCART Xcoord Ycoord Zelev Zhill Zflag Arcid (Name)
Type:
Optional, Repeatable
where the Xcoord and Ycoord parameters are the x-coordinate and y-coordinate (m), respectively, for the
receptor location. The Zelev parameter is the terrain elevation (m) for the receptor and Zhill is the
corresponding hilltop elevation (m) for use in elevated terrain modeling. Both the Zelev and Zhill
parameters must be specified for use with the elevated terrain algorithms and are referenced to the same
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reference elevation (e.g., mean sea level) used for source elevations. The elevation (Zelev) and hill heights
(Zhill) inputs are set to zero, by default, if ELEV is NOT specified as a MODELOPT on the CO card. The
Zflag parameter is the receptor height above ground (m) for modeling flagpole receptors and must be
specified for use with the receptor flagpole option. The flagpole height (Zflag) inputs are set to zero, by
default, if CO FLAGPOLE is NOT specified on the CO card. All of the parameters are in units of meters,
except for Zelev and Zhill, which default to meters but may be specified in feet by use of the RE ELEVUNIT
keyword. The Arcid parameter is the receptor grouping identification, which may be up to eight characters
long, and may be used to group receptors by arc. The Name parameter is an optional name field that may be
included to further identify a particular receptor location. The Name parameter is ignored by the model.
Unlike the DISCCART keyword, all of the parameters (except for the Name) must be present on each card
with the EVALCART keyword. The elevation, hill height, and flagpole height are set to zero, by default, if
the appropriate options are not specified the CO card.
3.4.4 Including receptor data from an external file
The user has the option of including receptor data from an external file by using the INCLUDED
keyword on the receptor pathway. A RE INCLUDED card may be placed anywhere within the source
pathway, after the STARTING card and before the FINISHED card (i.e., the RE STARTING and RE
FINISHED cards cannot be included in the external file). The data in the included file will be processed as
though it were part of the control file. The syntax and type of the INCLUDED keyword are summarized
below:
Syntax:
RE INCLUDED Incfil
Type:
Optional, Repeatable
where the Incfil parameter is a character field of up to 200 characters that identifies the filename for the
included file. The contents of the included file must be valid control file commands for the receptor
pathway. If an error is generated during processing of the included file, the error message will report the line
number of the included file (see APPENDIX B). If more than one INCLUDED file is specified for the
receptor pathway, the user will first need to determine which file the error occurred in. If the starting column
of the main control input file is shifted from column 1 (see Section 2.4.8), then the control file commands in
the included file must be offset by the same amount. The INCLUDED option allows the user to include
receptor data that have been generated by the AERMOD Terrain Preprocessor, AERMAP, in the control file
without having to cut and paste the AERMAP output file. Since AERMAP generates terrain elevations in
meters and includes the RE ELEVUNIT METERS card as the first record, an AERMAP file must be
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INCLUDED at the beginning of the receptor pathway, immediately following the RE STARTING card. If
more than one AERMAP output file is INCLUDED on the receptor pathway, the RE ELEVUNIT METERS
card must be deleted from all but the first one.
3.5 Meteorology pathway inputs and options
The Meteorology pathway contains keywords that define the input meteorological data for a
particular model run.
3.5.1 Specifying the input data files and formats
The AERMOD model uses hourly meteorological data from separate surface and profile data files as
one of the basic model inputs. These input meteorological data filenames for AERMOD are identified by the
SURFFILE and PROFFILE keywords on the ME pathway. The syntax and type of these keywords are
summarized below:
Syntax:
ME SURFFILE Sfcfil (Format)
ME PROFFILE Profil (Format)
Type:
Optional, Repeatable
where the Srcfil and Profil parameters are character fields of up to 200 characters that identify the filenames
for the input meteorological data files. For running the model on an IBM-compatible PC, the filename
parameters may include the complete DOS pathname for the file or will assume the current directory if only
the filename is given. The optional Format parameter specifies the format of the meteorological data files.
The default formats for the surface and profile data files corresponds with the format of the files generated by
the AERMET meteorological preprocessor program. The user also has the option of specifying the Fortran
read format for each of these files. The contents of the meteorological data files are described below, and
the file formats are documented in APPENDIX C.
The surface meteorological data file consists of a header record containing information on the
meteorological station locations, and one record for each hour of data. These data are delimited by at least
one space between each element, i.e., the data may be read as free format. The contents of the surface file are
as follows:
Year
Month (1 - 12)
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Day of Month (1-31)
Julian Day (Day ofYear) (1 - 366)
Hour of Day (1 - 24)
Heat Flux (W/m2)
Surface Friction Velocity, u* (m/s)
Convective Velocity Scale, w* (m/s)
Lapse Rate above Mixing Height (K/m)
Convective Mixing Height (m)
Mechanical Mixing Height (m)
Monin-Obukhov Length, L (m)
Surface Roughness Length, zo (m)
Bowen Ratio
Albedo
Reference Wind Speed (m/s)
Reference Wind Direction (degrees)
Reference Height for Wind (m)
Ambient Temperature (K)
Reference Height for Temperature (m)
Precipitation Code (0-45)
Precipitation Amount (mm)
Relative Humidity (%)
Surface Pressure (mb)
Cloud Cover (tenths)
Wind Speed Adjustment and Data Source Flag
The sensible heat flux, Bowen ratio and albedo are not used by the AERMOD model but are passed through
by AERMET for information purposes only.
The profile meteorological data file consists of one or more records for each hour of data. As with
the surface data file, the data are delimited by at least one space between each element and may be read as
Fortran free format. The contents of the profile meteorological data file are as follows:
Year
Month (1 - 12)
Day (1-31)
Hour (1 - 24)
Measurement height (m)
Top flag = 1, if this is the last (highest) level for this hour,
0, otherwise
Wind direction for the current level (degrees)
Wind speed for the current level (m/s)
Temperature at the current level (°C)
Standard deviation of the wind direction, o2 (degrees)
Standard deviation of the vertical wind speed, o w (m/s)
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The data in this file include the on-site meteorological data that are processed by AERMET. Since
AERMET was designed to be able to perform dispersion parameter calculations with NWS data only, i.e., no
on-site data, the profile data may consist of a one-level "profile" based on the NWS winds and temperature.
3.5.2 Specifying station information
Three keywords are used to specify information about the meteorological stations, SURFDATA for
the surface meteorological station, UAIRDATA for the upper air station, and the optional SITED ATA for any
on-site meteorological data that may be used. The syntax and type of these keywords are summarized below:
Syntax:
ME SURFDATA Stanum Year (Name) (Xcoord) (Ycoord)
Syntax:
ME UAIRDATA Stanum Year (Name) (Xcoord) (Ycoord)
Syntax:
ME SITED ATA Stanum Year (Name) (Xcoord) (Y coord)
Type:
Mandatory, Non-repeatable for SURFDATA and UAIRDATA
Optional, Non-repeatable for SITED ATA
where Stanum is the station number, e.g., the 5-digit WBAN number for NWS stations; Year is the year of
data being processed (either 2 or 4 digits); Name is an optional character field (up to 40 characters with no
blanks) specifying the name of the station; and Xcoord and Ycoord are optional parameters for specifying the
x and y coordinates for the location of the stations. Note: The Year should indicate the first year of data
that are present in the meteorological data, regardless if only a subset of complete temporal period will
be modeled by AERMOD using the STARTEND keyword (Section 3.5.4). The station locations are not
utilized in the model. Therefore, no units are specified for Xcoord and Ycoord, although meters are
suggested for consistency with the source and receptor coordinates. The AERMOD model compares the
station numbers that are input using these keywords with the numbers in the header record of the surface
meteorological data file, and issues non-fatal warning messages if there are any mismatches.
3.5.3 Specifying the base elevation for potential temperature profile
The AERMOD model generates a gridded vertical profile of potential temperatures for use in the
plume rise calculations. Since potential temperature is dependent on the elevation above mean sea level
(MSL), the user must define the base elevation for the profile with the PROFBASE keyword. The syntax
and type for the PROFBASE keyword are summarized below:
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Syntax: ME PROFBASE BaseElev (Units)
Type: Mandatory, Non-repeatable
where the BaseElev parameter specifies the base elevation above MSL for the potential temperature profile,
and the optional Units parameter specifies the units of BaseElev. Valid inputs of Units are the secondary
keywords METERS or FEET. The default units for BaseElev are in meters if Units is left blank. The base
elevation should correspond with the base elevation of the primary meteorological tower.
3.5.4 Specifying a data period to process
There are two keywords that allow the user to specify particular days or ranges of days to process
from the sequential meteorological file input for the AERMOD model. The STARTEND keyword controls
which period within the meteorological data file is read by the model, while the DAYRANGE keyword
controls which days or ranges of days (of those that are read) for the model to process. When the
STARTEND keyword is omitted from the control file, the default for the model is to read the entire
meteorological data file and to process all days within that period.
The syntax and type for the STARTEND keyword are summarized below:
Syntax: ME STARTEND Strtyr Strtmn Strtdy (Strthr) Endyr Endmn Enddy (Endhr)
Type: Optional, Non-repeatable
where the Strtyr Strtmn Strtdy parameters specify the year, month and day of the first record to be read (e.g.,
87 01 31 for January 31, 1987), and the parameters Endyr Endmn Enddy specify the year, month and day of
the last record to be read. The Strthr and Endhr are optional parameters that may be used to specify the start
and end hours for the data period to be read. If either Strthr or Endhr is to be specified, then both must be
specified. Any records in the data file that occur before the start date are ignored, as are any records in the
data file that occur after the end date. In fact, once the end date has been reached, the model does not read
any more data from the meteorological file. If Strthr and Endhr are not specified, then processing begins
with hour 1 of the start date, and ends with hour 24 of the end date, unless specific days are selected by the
DAYRANGE card described below.
Any PERIOD averages calculated by the model will apply only to the period of data actually
processed. Therefore, if someone wanted to calculate a six-month average, they could select PERIOD
averages on the CO AVERTIME card, and then specify the period as follows:
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ME STARTEND 87 01 01 87 06 30
for the period January 1, 1987 through June 30, 1987.
The syntax and type for the DAYRANGE keyword are summarized below:
Syntax: ME DAYRANGE Range 1 Range2 RangeS ... Range/V
Type: Optional, Repeatable
where the Range parameters specify particular days or ranges of days to process. The days may be specified
as individual days (e.g., 1 2 3 4 5) or as a range of days (e.g., 1-5). The user also has the option of specifying
Julian day numbers, from 1 to 365 (366 for leap years), or specifying month and day (e.g., 1/31 for January
31). Any combination of these may also be used. For example, the following card will tell the model to
process the days from January 1 (Julian day 1) through January 31 (1/31):
ME DAYRANGE 1-1/31
The DAYRANGE keyword is also repeatable, so that as many cards as needed may be included in the ME
pathway.
As with the STARTEND keyword, any PERIOD averages calculated by the model will apply only to
the period of data actually processed. If the STARTEND keyword is also used, then only those days selected
on the DAYRANGE cards that fall within the period from the start date to the end date will be processed.
Thus, if the ME pathway included the following two cards:
ME
STARTEND
87 02 01
87 12 31
ME
DAYRANGE
1-31
then no data would be processed, since the days 1 through 31 are outside the period 2/1 to 12/31.
3.5.5 Correcting wind direction alignment problems
The WDROTATE keyword allows the user to correct the input meteorological data for wind
direction alignment problems. All input wind directions or flow vectors are rotated by a user-specified
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amount. Since the model results at particular receptor locations are often quite sensitive to the transport wind
direction, this optional keyword should be used only with extreme caution and with clear justification.
The syntax and type of this keyword are summarized below:
Syntax: MEWDROTATE Rotang
Type: Optional, Non-repeatable
where the Rotang parameter specifies the angle in degrees to rotate the input wind direction measurements.
The value of Rotang is subtracted from the wind direction measurements. It may be used to correct for
known (and documented) calibration errors, or to adjust for the alignment of a valley if the meteorological
station is located in a valley with a different alignment than the source location.
3.5.6 Specifying wind speed categories
Variable emission rate factors may be input to the model that vary by wind speed category. The
model uses six wind speed categories, and these are defined by the upper bound wind speed for the first five
categories (the sixth category is assumed to have no upper bound). The default values for the wind speed
categories are as follows: 1.54, 3.09, 5.14, 8.23, and 10.8 m/s. The syntax and type of the WINDCATS
keyword, which may be used to specify different category boundaries, are summarized below:
Syntax:
ME WINDCATS Wsl Ws2 Ws3 Ws4 Ws5
Type:
Optional, Non-repeatable
where the Wsl through Ws5 parameters are the upper bound wind speeds of the first through fifth categories
in meters per second. The upper bound values are inclusive, i.e., a wind speed equal to the value of Wsl will
be placed in the first wind speed category.
3.5.7 Specifying SCIM parameters
The SCIM parameters on the SCIMBYHR card specify the starting hour and sampling interval for
the regular sample and an optional file name. The syntax and type of the SCIMBYHR keyword are
summarized below:
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Syntax:
ME SCIMBYHR NRegStart NReglnt NwetStart Nwetlnt (SfcFilnam PflFilnam)
Type:
Optional, Non-repeatable
where the NRegStart and NReglnt parameters specify the first hour to be sampled and the sampling interval,
respectively, when performing the regular sampling. The NWetStart and NWetlnt parameters are used to
specify the first wet hour (i.e., with non-zero precipitation) and the wet sampling interval for wet sampling.
However, since the AERMOD model currently does not include wet deposition algorithms, the wet sampling
option is not operational, and the user should enter a value of zero (0) for bot NWetStart and NWetlnt.
Optionally, the user can create output files containing the surface and profile meteorological data for the
sampled hours by specifying the SfcFilnam and PflFilnam parameters. These output files are in the same
format used in the summary of the first 24 hours of data included in the main output file.
In order to use the SCIM option, the user must specify the non-DFAULT SCIM option on the CO
MODELOPT card. Although the ME SCIMBYHR is an optional card, it is required when using the SCIM
option. NRegStart is required to have a value from 1 through 24, i.e., the first sampled hour must be on the
first day in the meteorological data file. There are no restrictions for NReglnt; however, NReglnt would
generally be greater than one. For example, NReglnt could be based on the formula (24n+l), where "n" is
the number of days to skip between samples, in order to ensure a regular diurnal cycle to the sampled hours
(e.g., 25 or 49).
3.5.8 SpecifV the number of years to process
The NUMYEARS keyword on the ME pathway allows the user to specify the number of years of
data being processed for purposes of allocating array storage for the MAXDCONT option (see Section
3.7.2.8), with a default value of five (5) years being assumed if the optional NUMYEARS keyword is
omitted. The syntax of the optional NUMYEARS keyword is summarized below:
Syntax: ME NUMYEARS NumYrs
Type: Optional, Non-repeatable
where NumYrs specifies the number of (full) years of meteorological data being processed.
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3.5.9 SpecifV turbulence treatment options
Beginning with version 21112, the user can prompt AERMOD to set non-missing values for
turbulence (oe or o) from the profile file to missing for certain conditions. These options were
included to facilitate the use of meteorological data with turbulence under certain conditions. For
example, these options allow for the user to use an urban meteorological site with turbulence data
with the URBAN option in AERMOD without rerunning AERMET to ignore the site-specific
turbulence as discussed Section 3.3 of the AERMOD Implementation Guide (EPA, 2024b). The
syntax of the turbulence options is summarized below:
Syntax:
ME TurbOpt
Type:
Optional, Non-repeatable
Where TurbOpt is defined as:
NOTURB: set oe and oto missing for all hours
NOTURBST: set oe and o for stable hours only
NOTURBCO: set oe and o for convective hours only
NOSA: set oe to missing for all hours
NOSW: set o to missing for all hours
NOSAST: set oe to missing for stable hours only
NOSWST: set o to missing for stable hours only
NOSACO: set oe to missing for convective hours only
NOSWCO set o to missing for convective hours only
Where stable (convective) hours are defined as hours where the Monin-Obukhov length is positive
(negative). The options NOTURB and NOTURBST can be used with the DFAULT keyword on the
MODELOPT pathway. The remaining options cannot be used with the DFAULT keyword and if they are
used with the DFAULT keyword, AERMOD will warn the user that the option can not be used with the
DFAULT keyword and the option will not set the appropriate turbulence parameters to missing, i.e.,
AERMOD will ignore the turbulence option. For the options that only reset turbulence under stable
conditions only or convective conditions only, AERMOD will report the day and hour and turbulence
parameter that is being reset to the file specified with the ERRORFIL keyword.
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3.6 Event pathway inputs and options
EVENT processing is specifically designed to facilitate analysis of source contributions to specific
events for short-term averages (less than or equal to 24 hours). These events may be design concentrations
generated by the AERMOD model, occurrences of violations of an air quality standard, or user-specified
events. These events are input to the AERMOD model through the EVent pathway. Each event is defined
by an averaging period and specific data period, a source group, and a receptor location. Since the locations
are only of interest in combination with particular averaging and data periods, the REceptor pathway is not
used with EVENT processing.
There are two keywords that are used to define the events on the EV pathway. The EVENTPER
keyword defines the averaging period, data period and source group, while the EVENTLOC keyword
defines the receptor location for the event. Each event is also given an alphanumeric name that links the two
input cards for that event.
The syntax and type of the EVENTPER and EVENTLOC keywords are summarized below:
Syntax:
EV EVENTPER Evname Aveper Grpid Date
Syntax:
EV EVENTLOC Evname XR=Xr YR= Yr (Zelev) (Zflas)
Or Evname RNG= Rns DIR= Dir (Zelev) (Zflag)
Type:
Mandatory, Repeatable
where the parameters are as follows:
Evname - event name (an alphanumeric string of up to 8 characters),
Aveper - averaging period for the event (e.g., J_, 3, 8, 24 hr)
Grpid - source group ID for the event (must be defined on SO pathway),
Date - date for the event, input as an eight-digit integer for the ending hour of the data
period (YYMMDDHH), e.g., 84030324 defines a data period ending at hour 24 on
March 3, 1984. The length of the period corresponds to Aveper.
XR= - X-coordinate (m) for the event location, referenced to a Cartesian coordinate system
YR= - Y-coordinate (m) for the event location, referenced to a Cartesian coordinate system
RNG=
distance range (m) for the event location, referenced to a polar coordinate
system with an origin of (0., 0.)
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DIR= - radial direction (deg.) for the event location, referenced to a polar coordinate system
with an origin of (0., 0.)
Zelev - optional terrain elevation for the event location (m)
Zflag - optional receptor height above ground (flagpole receptor) for the event
location (m)
Each event is defined by the two input cards EVENTPER and EVENTLOC, and these inputs are linked by
the event name, which must be unique among the events being processed in a given run. There is no
particular requirement for the order of cards on the EV pathway. Note that the location for the event may be
specified by either Cartesian coordinates or by polar coordinates, however, the polar coordinates must be
relative to an origin of (0,0).
3.6.1 Using events generated by the AERMOD model
The AERMOD model has an option (CO EVENTFIL described in Section 3.2.14) to generate an
input file for the AERMOD EVENT processing. When this option is used, the AERMOD model copies
relevant inputs from the AERMOD control input file to the Event processing input file and generates the
inputs for the EVent pathway from the results of the modeling run. These events are the design
concentrations identified by the OU RECTABLE keyword (see Section 2.1.1.1), such as the highest and
high-second-high 24-hour averages, etc., and any threshold violations identified by the OU MAXIFILE
keyword (see Section 2.1.1.2). The inputs generated by the AERMOD model correspond to the syntax
described above for the EVENTPER and EVENTLOC keywords. The locations for events generated by the
AERMOD model are always provided as Cartesian coordinates.
To easily identify the events generated by the AERMOD model, and to provide a mechanism for the
AERMOD model to manage the events generated from the model run, a naming convention is used for the
EVNAME parameter. The following examples illustrate the event names used by the AERMOD model:
H1H01001 - High-first-high 1-hour average for source group number 1
H2H24003 - High-second-high 24-hour average for source group number 3
TH030010 - Threshold violation number 10 for 3-hour averages
TH240019 - Threshold violation number 19 for 24-hour averages
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The high value design concentrations are listed first in the EVENT processing input file, followed by the
threshold violations (grouped by averaging period). To make it easier for the user to review the EVENT
processing input file generated by the AERMOD model, and determine which events are of most concern,
the actual concentration value associated with the event is included as the last field on the EVENTPER card.
This field is ignored by the AERMOD model and is included only for informational purposes. The user
should be aware that the same event may appear in the AERMOD model input file as both a design value and
as a threshold violation, depending on the options selected and the actual results. Since the model processes
the events by date sequence and outputs the results for each event as it is processed, the order of events in the
output file will generally not follow the order of events in the input file, unless all of the events were
generated by the MAXIFILE option.
3.6.2 Specifying discrete events
The user can specify discrete events by entering the EVENTPER and EVENTLOC cards as
described above. The averaging period and source group selected for the event must be among those
specified on the CO AVERTIME and SO SRCGROUP cards. If the EVENT processing input file was
generated by the AERMOD model, the user may include additional events for those averaging periods and
source groups used in the original AERMOD model run. They may also add averaging periods or define new
source groups in the Event processing input file in order to define additional events.
3.6.3 Including event data from an external file
The user has the option of including event data from an external file by using the INCLUDED
keyword on the source (EV) pathway. An EV INCLUDED card may be placed anywhere within the event
pathway, after the STARTING card and before the FINISHED card (i.e., the EV STARTING and EV
FINISHED cards cannot be included in the external file). The data in the included file will be processed as
though it were part of the control file. The syntax and type of the INCLUDED keyword are summarized
below:
Syntax:
EV INCLUDED Incfil
Type:
Optional, Repeatable
where the Incfil parameter is a character field of up to 40 characters that identifies the filename for the
included file. The contents of the included file must be valid control file commands for the event pathway.
If an error is generated during processing of the included file, the error message will report the line number
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of the included file (see APPENDIX B). If more than one INCLUDED file is specified for the event
pathway, the user will first need to determine which file the error occurred in. If the starting column of the
main control input file is shifted from column 1 (see Section 2.4.8), then the control file commands in the
included file must be offset by the same amount.
3.7 Output pathway inputs and options
The OUtput pathway contains keywords that define the output options for the model runs.
Beginning with version 11059, a number of enhancements have been incorporated in AERMOD to more
fully support the form of more recent l-hourN02 and SO2 standards, as well as the 24-hour PM2 5 standard.
The form of these NAAQS is similar in that they are based on a ranked percentile value averaged over the
number of years processed.
The options on the OUtput pathway have been divided into five categories: 1) options that control
different types of tabular output in the main output files of the model; 2) output files for specialized purposes
that that can be generated for any pollutant and averaging period; 3) options that are specific to more recent
24-hour PM2 5, 1-hour NO2, and/or 1-hour SO2 standards; 4) options related to EVENT processing; and 5)
miscellaneous options. The user may select any combination of output option for a particular application.
3.7.1 Selecting options for tabular printed outputs
The three tabular printed output options are controlled by the following keywords:
RECTABLE: Controls output option for high value summary tables by receptor;
MAXTABLE: Controls output option for overall maximum value summary tables; and
DAYTABLE: Controls output option for tables of concurrent values summarized by
receptor for each day processed.
The keywords are described in more detail in the order listed above.
The syntax and type for the RECTABLE keyword are summarized below:
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OU RECTABLE Aveper FIRST SECOND ... SIXTH ... TENTH and/or
Syntax: 1ST 2ND ... 6TH .... 'OTH and/or
1 2 ... 6 ... 10 .... N .... 999
Type: Optional, Repeatable
where the Aveper parameter is the short-term averaging period (e.g., 1, 3, 8 or 24 hr or MONTH) for which
the receptor table is selected, and the secondary keywords, FIRST. SECOND, etc., indicate which high
values are to be summarized by receptor for that averaging period. The RECTABLE card may be repeated
for each averaging period. For cases where the user wants the same RECTABLE options for all short-term
averaging periods being modeled, the input may be simplified by entering the secondary keyword ALLAVE
for the Aveper parameter.
In order to support the implementation of recent guidance regarding modeling to demonstrate
compliance with these NAAQS, the RECTABLE keyword had been modified to allow user-specified ranks
of short-term averages (for all pollutants) up to the 999th highest value. The previous version of AERMOD
was limited to the lOth-highest value and also restricted the rank for the 24-hour PM2 5 NAAQS to the 8th
highest value (corresponding to the 98th percentile of daily values during a year).
The following example will select summaries of the highest, second highest and third highest values
by receptor for all averaging periods:
OU RECTABLE ALLAVE FIRST SECOND THIRD
The model will also recognize a range of high values on the RECTABLE input card, and therefore the
following card will have the effect:
OU RECTABLE ALLAVE FIRST-THIRD
The output file will include tables for only the high values selected. Tables for all source groups for
a particular averaging period are grouped together, and the averaging periods are output in the order that they
appear the CO AVERTIME card. For each averaging period and source group combination, the tables of
high values for the receptor networks (if any) are printed first, followed by any discrete Cartesian receptors,
and any discrete polar receptors.
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If the CO EVENTFIL keyword has been used to generate an input file for EVENT processing, then
the design values identified by the RECTABLE options, e.g., the high-second-high 24-hour average, are
included in the events that are defined in the EVENT processing input file.
If the PLOTFILE (3.7.2.3) and/or MAXDCONT (0) keywords are used, the RECTABLE keyword is
required and must be specified prior to these keywords in the OU pathway. The rank or high value (e.g.,
FIRST, SECOND, etc.) specified for each PLOTFILE must also be included on the RECTABLE keyword.
There will need to be a RECTABLE entry that includes each of the high values and averaging periods for
which a PLOTFILE is generated, or a single RECTABLE entry with the ALLAVE keyword and each high
value specified can be used. However, because the RECTABLE only relates to short-term averaging periods,
a RECTABLE entry is not required for a PLOTFILE that is generated for either an ANNUAL or a PERIOD
average. When the MAXDCONT keyword is used, the UpperRank and LowerRank values of the
MAXDCONT file must be within the range of ranks specified on the RECTABLE keyword. The
MAXDCONT THRESH value analysis is limited to the range of ranks specified on the RECTABLE
keyword (but not the individual ranks that are specified). Read more about the requirements of the of
RECTABLE as it relates to the PLOTFILE and MAXDCONT keywords in Sections 3.7.2.3 and 0,
respectively.
The syntax and type for the MAXTABLE keyword are summarized below:
Syntax:
OU MAXTABLE Aveper Maxnum
Type:
Optional, Repeatable
where the Aveper parameter is the short-term averaging period (e.g., J_, 3, 8 or 24 hr or MONTH) for which
the receptor table is selected, and the Maxnum parameter specifies the number of overall maximum values to
be summarized for each averaging period. The MAXTABLE card may be repeated for each averaging
period. As with the RECTABLE keyword, for cases where the user wants the same MAXTABLE options for
all short-term averaging periods being modeled, the input may be simplified by entering the secondary
keyword ALLAVE for the Aveper parameter. The following example will select the maximum 50 table for
all averaging periods:
OU MAXTABLE ALLAVE 50
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A separate maximum overall value table is produced for each source group. The maximum value
tables follow the RECTABLE outputs in the main print file. All source group tables for a particular
averaging period are grouped together, and the averaging periods are output in the order that they appear on
the CO AVERTIME card.
The syntax and type for the DAYTABLE keyword are summarized below:
Syntax:
OU DAYTABLE Avperl Avper2 Avper3
Type:
Optional, Non-repeatable
where the Avpern parameters are the short-term averaging periods (e.g., J_, 3, 8 or 24 hr or MONTH) for
which the daily tables are selected. The DAYTABLE card is non-repeatable, but as with the RECTABLE
and MAXTABLE keywords, for cases where the user wants daily tables for all short-term averaging periods
being modeled, the input may be simplified by entering the secondary keyword ALLAVE for the first
parameter. The following example will select the daily tables for all averaging periods:
OU DAYTABLE ALLAVE
For each averaging period for which the DAYTABLE option is selected, the model will print the
concurrent averages for all receptors for each day of data processed. The receptor networks (if any) are
printed first, followed by any discrete Cartesian receptors, and any discrete polar receptors. Results for each
source group are output. For example, if 1, 3, and 24-hour averages are calculated, and the OU DAYTABLE
ALLAVE option is used, then for the first day of data processed, there will be 24 sets of tables of hourly
averages (one for each hour in the day), eight sets of 3-hour averages (one for each 3-hour period in the day),
and one set of 24-hour averages. The averages are printed as they are calculated by the model, but for hours
where more than one averaging period is calculated (e.g., hour 24 is the end of an hourly average, a 3-hour
average, and a 24-hour average), the order in which the averages are output will follow the order used on the
CO AVERTIME card. Note: This option can produce very large output files, especially when used with a
full year of data and very short period averages, such 1-hour and 3-hour. It should therefore be used with
CAUTION.
3.7.2 Selecting options for special purpose output files
The AERMOD model provides options for seven types of output files for specialized purposes.
These options are controlled by the following keywords that create the output file described:
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MAXIFILE -
Occurrences of violations of user-specified threshold value;
POSTFILE - Concurrent (raw) results at each receptor suitable for post-processing;
PLOTFILE - Design values that can be imported into graphics software for plotting
contours;
TOXXFILE - Unformatted files of raw results above a threshold value with a special
structure for use with the TOXX model component of TOXST;
RANKFILE - Output values by rank for use in Q-Q (quantile) plots;
EVALFILE -
SEASONHR -
MAXDCONT-
MAXDAILY -
Output values, including arc-maximum normalized concentrations,
suitable for model evaluation studies;
Output values by season and hour-of-day;
Ranked values for individual source groups to determine
source contributions for 24-hour PM2.5, 1-hour NO2 and 1-
hour SO2 standards;
Daily maximum 1-hour concentrations for a specified source
group, for each day in the data period processed, useful for
analyzing the 1-hour NO2 and SO2 NAAQS; and
MAXDYBY-R - Summary of daily maximum 1-hour concentrations by year for
each rank specified on the RECTABLE keyword.
The keywords are described in more detail in the order listed above.
3.7.2.1 MAXIFILE
The syntax and type for the MAXIFILE keyword are summarized below:
Syntax:
OU MAXIFILE Aveper Grpid Thresh Filnam (Funit)
Type:
Optional, Repeatable
where the Aveper parameter is the short-term averaging period (e.g., 3, 8, 24 for 3, 8 and 24-hour averages,
or MONTH for monthly averages) and Grpid is the source group ID for which the MAXIFILE option is
selected. The Thresh parameter is the user-specified threshold value, and Filnam is the name of the file
where the MAXIFILE results are to be written. The optional Funit parameter allows the user the option of
specifying the Fortran logical file unit for the output file. Please note, when specifying the FUNIT 1 to 32
are reserved for input/output files, internally computed file units range 100 to 730, and the following are
3-146
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reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941, 8837, 8932, 9937, 9938, 9939, 9940.
Therefore, to ensure there will be no file conflicts, it is recommended that user-specified units begin at a
large integer value such as 10,000 and increment by one. By specifying the same filename and unit for more
than one MAXIFILE card, results for different source groups and/or averaging periods may be combined into
a single file. If the Funit parameter is omitted, then the model will dynamically allocate a unique file unit for
this file (see Section 2.1.2).
The MAXIFILE card may be repeated for each combination of averaging period and source group,
and a different filename should be used for each file. The resulting maximum value file will include several
header records identifying the averaging period, source group and the threshold value for that file, and a
listing of every occurrence where the result for that averaging period/source group equals or exceeds the
threshold value. Each of these records includes the averaging period, source group ID, date for the threshold
violation (ending hour of the averaging period), the x, y, z and flagpole receptor height for the receptor
location where the violation occurred, and the concentration value.
Each of the threshold violations, except for monthly averages, identify events that may be modeled
for source contribution information with EVENT processing by selecting the CO EVENTFIL option (see
Sections 3.2.14 and 2.1). Each of the threshold violations is included as an event on the EV pathway and is
given a name of the form THxxyyyy, where xx is the averaging period, and yyyy is the violation number for
that averaging period. For example, an event name of TH240019 identifies the 19th threshold violation for
24-hour averages. Monthly average threshold violations are included in the file specified on the MAXIFILE
card but are not included in the EVENT processing input file since the AERMOD model currently handles
only averaging periods of up to 24 hours.
The following examples illustrate the use of the MAXIFILE option:
ou
MAXIFILE
24
ALL
364 . 0
MAX2 4ALL . OUT
ou
MAXIFILE
24
PSD
91. 0
MAXPSD.OUT
50
ou
MAXIFILE
3
PSD
365.0
MAXPSD.OUT
50
ou
MAXIFILE
3
PLANT
25.0
C:\OUTPUT\MAXI3HR.FIL
ou
MAXIFILE
MONTH
ALL
10.0
MAXMONTH . OUT
where the 3-hour example illustrates the use of a DOS pathname for the PC, and the last example illustrates
the use of monthly averages. The FILNAM parameter may be up to 200 characters in length. It should also
be noted that only one MAXIFILE card may be used for each averaging period/source group combination.
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Note: The MAXIFILE option may produce very large files for runs involving a large number of receptors if
a significant percentage of the results exceed the threshold value.
3.7.2.2 POSTFILE
The syntax and type for the POSTFILE keyword are summarized below:
Syntax:
OU POSTFILE Aveper Grpid Format Filnam (Funit)
Type:
Optional, Repeatable
where the Aveper parameter is the averaging period (e.g., 3, 8, 24 for 3, 8 and 24-hour averages, MONTH for
monthly averages, PERIOD for period averages, or ANNUAL for annual averages) and Grpid is the source
group ID for which the POSTFILE option is selected. The Format parameter specifies the format of the
POSTFILE output and may either be the secondary keyword UNFORM for unformatted concentration files,
or the secondary keyword PLOT to obtain formatted files of receptor locations (x- and y-coordinates) and
concentrations suitable for plotting contours of concurrent values. The Filnam parameter is the name of the
file where the POSTFILE results are to be written. The optional Funit parameter allows the user the option
of specifying the Fortran logical file unit for the output file. Please note, when specifying the FUNIT, 1 to 32
are reserved for input/output files, internally computed file units range 100 to 730, and the following are
reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941, 8837, 8932, 9937, 9938, 9939, 9940.
Therefore, to ensure there will be no file conflicts, it is recommended that user-specified units begin at a
large integer value such as 10,000 and increment by one. By specifying the same filename and unit for more
than one POSTFILE card, results for different source groups and/or averaging periods may be combined into
a single file. If the Funit parameter is omitted, then the model will dynamically allocate a unique file unit for
this file (see Section 2.1.2).
The POSTFILE card may be repeated for each combination of averaging period and source group,
and a different filename should be used for each file. If UNFORM is specified for the Format parameter,
then the resulting unformatted file includes a constant-length record for each of the selected averaging
periods calculated during the model run. The first variable of each record is an integer variable (4 bytes)
containing the ending date (YYMMDDHH) for the averages on that record. The second variable for each
record is an integer variable (4 bytes) for the number of hours in the averaging period. The third variable for
each record is a character variable of length eight containing the source group ID. The remaining variables
of each record contain the calculated average concentration values for all receptors, in the order in which
they were defined in the input runstream.
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The following examples illustrate the use of the POSTFILE option:
OU
POSTFILE
24
ALL
UNFORM
PST24ALL.BIN
OU
POSTFILE
24
PSD
UNFORM
PST24PSD.BIN
OU
POSTFILE
3
PLANT
UNFORM
C:\BINOUT\PST3HR.FIL
OU
POSTFILE
MONTH ALL
PLOT
PSTMONTH.PLT
OU
POSTFILE
PERIOD ALL
PLOT
PSTANN. PLT
where the 3-hour example illustrates the use of a DOS pathname for the PC, and the last example illustrates
the use of monthly averages. The Filnam parameter may be up to 200 characters in length. The use of
separate files for each averaging period/source group combination allows the user flexibility to select only
those results that are needed for post-processing for a particular run, and also makes the resulting
unformatted files manageable. Note: The POSTFILE option can produce very large files and should be used
with some caution. For a file of hourly values for a full year (8760 records) and 400 receptors, the resulting
file will use about 14 megabytes of disk space. To estimate the size of the file (in bytes), use the following
equation:
# Hrs/Yr
File Size (bytes) = - * (# Rec + 4) * 4
# Hrs/Ave
Divide the result by 1000 to estimate the number of kilobytes (KB) and divide by 1.0E6 to estimate the
number of megabytes (MB).
3.7.2.3 PLOTFILE
The syntax and type for the PLOTFILE keyword are summarized below:
OU PLOTFILE Aveper Grpid Hivalu Filnam (Funit), or
Syntax: OU PLOTFILE PERIOD Grpid Filnam (Funit)
OU PLOTFILE ANNUAL Grpid Filnam (Funit)
Type: Optional, Repeatable
where the Aveper parameter is the averaging period (e.g., 3, 8, 24 for 3, 8 and 24-hour averages, MONTH for
monthly averages, PERIOD for period averages, or ANNUAL for annual averages), Grpid is the source
group ID for which the PLOTFILE option is selected, and Hivalu specifies which short-term high values are
to be output (FIRST for the first highest at each receptor, SECOND for the second highest at each receptor,
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etc.) Note that the Hivalu parameter is not specified for PERIOD or ANNUAL averages, since there is only
one period or annual average for each receptor. The Filnam parameter is the name of the file where the
PLOTFILE results are to be written. The optional Funit parameter allows the user the option of specifying
the Fortran logical file unit for the output file. Please note, when specifying the FUNIT 1 to 32 are reserved
for input/output files, internally computed file units range 100 to 730, and the following are reserved for
debug files: 731, 931, 932, 933, 937, 938, 939, 941, 8837, 8932, 9937, 9938, 9939, 9940. Therefore, to
ensure there will be no file conflicts, it is recommended that user-specified units begin at a large integer
value such as 10,000 and increment by one. By specifying the same filename and unit for more than one
PLOTFILE card, results for different source groups and/or averaging periods may be combined into a single
file. If the Funit parameter is omitted, then the model will dynamically allocate a unique file unit for this file
(see Section 2.1.2).
Note: The averaging period and high value for which a PLOTFILE is generated must also be
included on the RECTABLE keyword (see Section 3.7.1). The RECTABLE keyword entry must be
specified on the OU pathway prior to the PLOTFILE entry. However, a RECTABLE entry is not
required for a PLOTFILE generated for the ANNUAL or PERIOD average.
The PLOTFILE card may be repeated for each combination of averaging period, source group, and
high value, and a different filename should be used for each file. The resulting formatted file includes
several records with header information identifying the averaging period, source group and high value
number of the results, and then a record for each receptor which contains the x and y coordinates for the
receptor location, the appropriate high value at that location, and the averaging period, source group and high
value number. The data are written to the file in the order of x-coord, y-coord, concentration so that the file
can easily be imported into a graphics package designed to generate contour plots. Many such programs will
read the PLOTFILEs directly without any modification, ignoring the header records, and produce the desired
plots.
The following examples illustrate the use of the PLOTFILE option:
OU
PLOTFILE
24
ALL
FIRST
PLT24ALL.FST
OU
PLOTFILE
24
ALL
SECOND
PLT24ALL.SEC
OU
PLOTFILE
24
PSD
2ND
PLTPSD.OUT 75
OU
PLOTFILE
3
PSD
2ND
PLTPSD.OUT 75
OU
PLOTFILE
3
PLANT
1ST
C:\PLOTS\PLT3HR.FIL
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ou
PLOTFILE
MONTH
ALL THIRD
PLTMONTH.OUT
ou
PLOTFILE
PERIOD
ALL
PSTANN.PLT
where the 3-hour example illustrates the use of a DOS pathname for the PC, and the last example illustrates
the use of monthly averages. As illustrated by the second and third examples, the high value parameter may
also be input as secondary keywords using the standard abbreviations of 1ST. 2ND. 3RD . . . 10TH. The
Filnam parameter may be up to 40 characters in length. The use of separate files for each averaging period,
source group, high value combination allows the user flexibility to select only those results that are needed
for plotting from a particular run.
3.7.2.4 TOXXFILE
The syntax and type for the TOXXFILE keyword are summarized below:
Syntax:
OU TOXXFILE Aveper Cutoff Filnam (Funit)
Type:
Optional, Repeatable
where the Aveper parameter is the short-term averaging period (e.g., 1, 3, 8, 24 for 1, 3, 8 and 24-hour
averages, or MONTH for monthly averages) for which the TOXXFILE option has been selected. The Cutoff
(threshold) parameter is the user-specified threshold cutoff value in g/m3, and Filnam is the name of the file
where the TOXXFILE results are to be written. It is important to note that the units of the Cutoff parameter
are g/m3, regardless of the input and output units selected with the SO EMISUNIT card. The optional Funit
parameter allows the user the option of specifying the Fortran logical file unit for the output file. Please note,
when specifying the FUNIT 1 to 32 are reserved for input/output files, internally computed file units range
100 to 730, and the following are reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941, 8837,
8932, 9937, 9938, 9939, 9940. Therefore, to ensure there will be no file conflicts, it is recommended that
user-specified units begin at a large integer value such as 10,000 and increment by one. If the Funit
parameter is omitted, then the model will dynamically allocate a unique file unit for this file (see Section
2.1.2). While the TOXXFILE option may be specified for any of the short-term averaging periods that are
identified on the CO AVERTIME card for a particular run, a non-fatal warning message will be generated if
other than 1-hour averages are specified. This is because the TOXST model currently supports only 1-hour
averages.
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The TOXXFILE card may be repeated for each averaging period, but a different filename should be
used for each file since the structure of the output file generated by the TOXXFILE option does not allow for
a clear way to distinguish between results for different averaging periods. The resulting output file for the
AERMOD model is an unformatted file with several header records identifying the title, averaging period,
receptor information, and the threshold value for that file, followed by records listing every occurrence
where the result for any source group for that averaging period equals or exceeds the threshold value. When
one of the source groups exceeds the threshold value, the results for all source groups for that averaging
period and receptor location are output. Each concentration that is output through the TOXXFILE option is
paired with an integer ID variable that identifies the averaging period (hour number of the year), the source
group number, and the receptor number corresponding to that value. The concentration values and
corresponding ID variables are stored in buffer arrays, and the arrays are then written to the unformatted
output file when full. The size of the arrays is controlled by the NPAIR PARAMETER defined in MODULE
MAIN 1 and is initially set at 100. At the end of the modeling run, any values remaining in the buffer arrays
are written to the file, padded to the right with zeroes. The structure of the output file generated by the
TOXXFILE option is described in more detail in Section 2.1.2 and in APPENDIX C. When using the
TOXXFILE option, the user will normally place a single source in each source group. The user should refer
to the user's guide for TOXST for further instructions on the application of the TOXXFILE option of the
AERMOD model.
The following examples illustrate the use of the TOXXFILE option:
ou
TOXXFILE
1
1.OE-5
T0XX1HR.BIN
ou
TOXXFILE
24
2.5E-3
TOXX24HR.BIN 50
The Filnam parameter may be up to 200 characters in length. It should be noted that only one TOXXFILE
card may be used for each averaging period. Note: The TOXXFILE option may produce very large files for
runs involving a large number of receptors if a significant percentage of the results exceed the threshold
value.
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3.7.2.5 RANKFILE
The RANKFILE keyword outputs values by rank for use in Q-Q (quantile) plots. The MAXTABLE
option must be specified first in order to use the RANKFILE option for a particular averaging period.
However, the RANKFILE output differs from the results in the MAXTABLE output in that duplicate
date/hour occurrences are removed. The syntax and type for the RANKFILE keyword are summarized
below:
Syntax:
OU RANKFILE Aveper Hinum Filnam (Funit)
Type:
Optional, Repeatable
where the Aveper parameter is the averaging period (e.g., 3, 8, 24 for 3, 8, and 24-hour averages, or MONTH
for monthly averages), and Hinum is the number of high values to be ranked. The RANKFILE keyword
cannot be used with PERIOD averages. As noted above, the MAXTABLE option must be specified first for
the particular Aveper, and the Hinum parameter on the RANKFILE card must be less than or equal to the
Maxnum parameter on the corresponding MAXTABLE card. Since duplicate dates are removed from the
RANKFILE output, the output file may contain less than the number of requested high values. The NMAX
parameter, which controls the maximum number of values that can be stored, has been set initially to 400.
The Filnam parameter is the name of the file (up to 200 characters) where the RANKFILE results are to be
written. The optional Funit parameter allows the user the option of specifying the Fortran logical file unit for
the output file. Please note, when specifying the FUNIT, 1 to 32 are reserved for input/output files, internally
computed file units range 100 to 730, and the following are reserved for debug files: 731, 931, 932, 933, 937,
938, 939, 941, 8837, 8932, 9937, 9938, 9939, 9940. Therefore, to ensure there will be no file conflicts, it is
recommended that user-specified units begin at a large integer value such as 10,000 and increment by one.By
specifying the same filename and unit for more than one RANKFILE card, results for different averaging
periods may be combined into a single file. If the Funit parameter is omitted, the model will dynamically
allocate a unique file unit for this file according to the following formula:
IRKUNT = 100 + IAVE
where IRKUNT is the Fortran unit number and IAVE is the averaging period number (the order of the
averaging period as specified on the CO AVERTIME card).
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3.7.2.6 EVALFILE
The EVALFILE option is specifically designed for use in generating residuals for model evaluation
studies. The EVALFILE output consists of the arc-maximum normalized concentration values for each hour
of meteorology and for each source specified. The arc groupings of the receptors must be specified using the
RE EVALCART keyword described above. The syntax and type for the EVALFILE keyword are
summarized below:
Syntax:
OU EVALFILE Srcid Filnam (Funit)
Type:
Optional, Repeatable
where the Srcid parameter is the source ID for which EVALFILE results are requested, the Filnam parameter
is the name of the file (up to 200 characters) where the EVALFILE results are to be written, and the optional
Funit parameter allows the user the option of specifying the Fortran logical file unit for the output file. Please
note, when specifying the FUNIT, 1 to 32 are reserved for input/output files, internally computed file units
range 100 to 730, and the following are reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941,
8837, 8932, 9937, 9938, 9939, 9940. Therefore, to ensure there will be no file conflicts, it is recommended
that user-specified units begin at a large integer value such as 10,000 and increment by one. By specifying
the same filename and unit for more than one EVALFILE card, results for different sources may be combined
into a single file. If the Funit parameter is omitted, the model will dynamically allocate a unique file unit for
this file according to the following formula:
IELUNT = 400 + ISRC*5
where IELUNT is the Fortran unit number and ISRC is the source number (the order of the source as
specified on the SO pathway).
For each hour of meteorological data processed and for each receptor grouping (e.g., arc), the
EVALFILE option outputs five records containing the source ID, date, arc ID, arc-maximum normalized
concentration (P/Q), emission rate, and other plume dispersion and meteorological variables associated with
the arc-maximum. Since the EVALFILE option looks at receptor groupings, it must be used in conjunction
with the EVALCART keyword described above for the RE pathway, and a fatal error is generated if no
receptor groups are identified.
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3.7.2.7 SEASONHR
The SEASONHR option is used to output a file containing the average results by season and hour-
of-day. To select this option, the user must include the SEASONHR keyword on the OU pathway. The
syntax, type, and order for the SEASONHR keyword are summarized below:
Syntax:
OU SEASONHR GroupID Filenam (FUnit)
Type:
Optional, Repeatable
where the GroupID parameter specifies the source group to be output, FileName specifies the name of the
output file, and the optional FileUnit parameter specifies an optional file unit. Please note, when specifying
the FUNIT, 1 to 32 are reserved for input/output files, internally computed file units range 100 to 730, and
the following are reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941, 8837, 8932, 9937, 9938,
9939, 9940. Therefore, to ensure there will be no file conflicts, it is recommended that user-specified units
begin at a large integer value such as 10,000 and increment by one. If FileUnit is left blank, then the model
will dynamically assign a file unit based on the formula 302+IGRP* 10, where IGRP is the group index
number. A sample from a SEASONHR output file is shown below:
3-155
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*
MODELING OPTIONS
USED:
*
CONC
WDEP
RURAL FLAT
TOXICS
*
FILE OF
SEASON/HOUR
VALUES FOR SOURCE
GROUP
: ALL
*
FOR A TOTAL OF 216
RECEPTORS.
*
FORMAT:
(4(IX,F13.5)
,IX,F8.2,2X,A8,
2X,
14, 2X
,14,2X,I4
2X,A8
*
Ĥk
X
Y
AVERAGE CONC
ZELEV
GRP
NHRS
SEAS
HOUR
NET ID
8.68241
49.24039
0.00000
0
. 00
ALL
87
1
1
POL1
17.36482
98.48077
0.00000
0
. 00
ALL
87
1
1
POL1
86.82409
492.40387
0.18098
0
. 00
ALL
87
1
1
POL1
173.64818
984.80774
2.52520
0
. 00
ALL
87
1
1
POL1
868.24091
4924.03857
2.07470
0
. 00
ALL
87
1
1
POL1
1736.48181
9848.07715
0.93252
0
. 00
ALL
87
1
1
POL1
17.10101
46.98463
0.00000
0
. 00
ALL
87
1
1
POL1
34.20201
93.96926
0.00000
0
. 00
ALL
87
1
1
POL1
171.01007
469.84631
0.15772
0
. 00
ALL
87
1
1
POL1
342.02014
939.69263
2.48554
0
. 00
ALL
87
1
1
POL1
1710.10071
4698.46289
6.09119
0
. 00
ALL
87
1
1
POL1
3420.20142
9396.92578
4.49830
0
. 00
ALL
87
1
1
POL1
25.00000
43.30127
0.00000
0
. 00
ALL
87
1
1
POL1
50.00000
86.60254
0.00000
0
. 00
ALL
87
1
1
POL1
250.00000
433.01270
0.10114
0
. 00
ALL
87
1
1
POL1
500.00000
866.02539
2.12970
0
. 00
ALL
87
1
1
POL1
2500.00000
4330.12695
2.79993
0
. 00
ALL
87
1
1
POL1
5000.00000
8660.25391
1.97200
0
. 00
ALL
87
1
1
POL1
The NHRS column in the output file contains the number of non-calm and non-missing hours used to
calculate the season-by-hour-of-day averages. The SEAS column is the season index, and is 1 for winter, 2
for spring, 3 for summer and 4 for fall. The records loop through hour-of-day first, and then through the
seasons.
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3.7.2.8 MAXDCONT
Beginning with version 11059, three output options have been incorporated on the OU pathway to
support the 1 -hour NO2 and SO2 standards, especially the analyses that may be required to determine a
source's (or group of sources) contributions to modeled violations of the NAAQS for comparison to the
Significant Impact Level (SIL). The form of the standards, based on averages of ranked values across years,
complicates this analysis, especially for the 1-hour NO2 and SO2 standards which are based on ranked values
from the distribution of daily maximum 1-hour averages. One of the options (MAXDCONT) can also be
used for the 24-hour PM2 5 NAAQS.
The MAXDCONT option, applicable to 24-hour PM25, 1-hour NO2 and 1-hour SO2 standards, can
be used to determine the contribution of each user-defined source group to the high ranked values for a target
source group, paired in time and space. This is accomplished as an internal post-processing routine after the
main model run is completed. The user can specify the range of ranks to analyze, or can specify an upper
bound rank, e.g., 8th-highest for 1-hour NO2 (note that "upper bound" rank implies a higher concentration,
while "lower bound" rank implies a lower concentration), and a threshold value, such as the NAAQS, for the
target source group. The model will process each rank within the range specified but will stop after the first
rank (in descending order of concentration) that is below the threshold.
The syntax, type and order of the optional MAXDCONT keyword are summarized below:
OU MAXDCONT GrpID UpperRank LowerRank FileName (FileUnit)
Syntax: or
OU MAXDCONT GrpID UpperRank THRESH ThreshValue FileName (FileUnit)
Type: Optional, Repeatable
where GrpID is the target or reference source group toward which contributions are being determined,
UpperRank and LowerRank are the upper bound and lower bound ranks (where upper bound rank implies
higher concentrations and lower bound rank implies lower concentrations), THRESH indicates that the lower
bound rank is determined based on a lower concentration threshold, ThreshValue is the user-specified
concentration threshold for GrpID impacts which serves as a lower bound on the range of ranks analyzed,
FileName is the output file name, and (FileUnit) is the optional file unit. The filename can be up to 200
characters in length based on the default parameters in AERMOD. Double quotes (") at the beginning and
end of the filename can also be used as field delimiters to allow filenames with embedded spaces. Please
note, when specifying the FUNIT 1 to 32 are reserved for input/output files, internally computed file units
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range 100 to 730, and the following are reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941,
8837, 8932, 9937, 9938, 9939, 9940. Therefore, to ensure there will be no file conflicts, it is recommended
that user-specified units begin at a large integer value such as 10,000 and increment by one. When the
THRESH option is selected AERMOD will skip the contribution analysis for any receptor where the target
GrpID impact is less than the threshold and will stop processing completely after the first rank where the
target GrpID values are below the threshold for all receptors. NOTE: It is important note that the range
of ranks that can be analyzed under the MAXDCONT option is limited to the range of ranks (not the
individual ranks) specified on the OU RECTABLE keyword, even when the THRESH option is used in
lieu of specifying a LowerRank value. AERMOD will issue a fatal error if the THRESH option is used
and the range of ranks is less than or equal to 8 for the 1-hr SO2 NAAQS, or less than or equal to 12
for the 1-hr NO2 and 24-hr PM2.5 NAAQS. Non-fatal warning messages will be generated if the
THRESH option is used and the range of ranks is less than or equal to 24 for the 1-hr SO2 NAAQS, or
less than or equal to 28 for the 1-hr NO2 and 24-hr PM2.5 NAAQS. The RECTABLE keyword entry
must be specified on the OU pathway prior to the MAXDCONT entry.
When the MAXDCONT option is specified, AERMOD stores all meteorological variables in
memory for each hour during the initial stage of processing in order to optimize the model runtime during
the post-processing stage. Any temporally varying emissions and background concentrations, including
background ozone concentrations for the OLM and PVMRM options, are also stored in memory for each
hour. While optimizing runtime for the post-processing, this approach may also significantly increase the
memory storage requirements of the model. In addition, since the MAXDCONT option extracts
meteorological variables and other temporally-varying data stored in memory to optimize runtime, the
MAXDCONT option cannot be used with the model "re-start" option using the INITFILE and SAVEFILE
keywords (Section 3.2.15) on the CO pathway, or with the MULTYEAR option (Section 3.2.7) on the CO
pathway.
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3.7.2.9 MAXDAILY
The MAXDAILY option, introduced with version 11059, is applicable to 1-hour NO2 and 1-hour
SO2 NAAQS and generates a file of daily maximum 1-hour concentrations for a specified source group, for
each day in the data period processed. The MAXDAILY file provides an interim output that may be useful
for analyzing the 1-hour NO2 and SO2 NAAQS. The syntax, type and order of the optional MAXDAILY
keyword are summarized below:
Syntax: OU MAXDAILY GrpID FileName (FileUnit)
Type: Optional, Non-repeatable
where GrpID is the source group selected for daily maximum 1-hour values, FileName is the name of the
MAXDAILY output file, and FileUnit is the optional file unit. The filename can be up to 200 characters in
length based on the default parameters in AERMOD. Double quotes (") at the beginning and end of the
filename can also be used as field delimiters to allow filenames with embedded spaces. Please note, when
specifying the FUNIT, 1 to 32 are reserved for input/output files, internally computed file units range 100 to
730, and the following are reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941, 8837, 8932,
9937, 9938, 9939, 9940. Therefore, to ensure there will be no file conflicts, it is recommended that user-
specified units begin at a large integer value such as 10,000 and increment by one.
3.7.2.10 MAXDYBYYR
Another option applicable to 1-hour NO2 and 1-hour SO2 NAAQS introduced with version 11059,
the MXDYBYYR keyword, generates a summary of daily maximum 1-hour concentrations by year for each
rank specified on the RECTABLE keyword. The ranks included in the MXDYBYYR file are the ranks used
in the MAXDCONT postprocessing option. The syntax, type and order of the optional MXDYBYYR
keyword are summarized below:
Syntax: OU MXDYBYYR GrpID FileName (FileUnit)
Type: Optional, Non-repeatable
where GrpID is the source group selected for daily maximum 1-hour values summarized by year, FileName
is the name of the MXDYBYYR output file, and FileUnit is the optional file unit. The filename can be up to
200 characters in length based on the default parameters in AERMOD. Double quotes (") at the beginning
and end of the filename can also be used as field delimiters to allow filenames with embedded spaces. Please
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note, when specifying the FUNIT 1 to 32 are reserved for input/output files, internally computed file units
range 100 to 730, and the following are reserved for debug files: 731, 931, 932, 933, 937, 938, 939, 941,
8837, 8932, 9937, 9938, 9939, 9940. Therefore, to ensure there will be no file conflicts, it is recommended
that user-specified units begin at a large integer value such as 10,000 and increment by one.
3.7.3 EVENT processing options
EVENT processing in the AERMOD model is designed specifically to perform source contribution
analyses for short-term average (less than or equal to 24-hour) events. The events may either be generated
by the AERMOD model, or they may be user-specified events, or both. Because of this rather narrow focus
of applications, the output options are limited to a single keyword. The EVENTOUT keyword controls the
level of detail in the source contribution output from the EVENT model. The syntax and type of the
EVENTOUT keyword are summarized below:
Syntax: OU EVENTOUT SOCONT DETAIL
Type: Mandatory, Non-repeatable
where the SOCONT secondary keyword specifies the option to produce only the source contribution
information in the output file, and the DETAIL secondary keyword specifies the option to produce more
detailed summaries in the output file. The SOCONT option provides the average concentration (or total
deposition) value (i.e., the contribution) from each source for the period corresponding to the event for the
source group. The basic source contribution information is also provided with the DETAIL option. In
addition, the DETAIL option provides the hourly average concentration (or total deposition) values for each
source for every hour in the averaging period, and a summary of the hourly meteorological data for the event
period. In general, the DETAIL option produces a larger output file than the SOCONT file, especially if there
are a large number of sources. There is no default setting for the EVENTOUT options.
3.7.4 Miscellaneous output options
The optional SUMMFILE keyword can be used to generate a separate formatted output file
containing the summary of high ranked values included at the end of the standard 'aermod.out' file. The
optional FILEFORM keyword can be used to specify the use of exponential notation, rather than fixed
format as currently used, for results that are output to separate result files. The optional NOHEADER
keyword can be used to suppress file headers in formatted output file options. These new options are
described below.
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The syntax, type, and order of the optional SUMMFILE keyword are summarized below:
Syntax: OU SUMMFILE SummFileName
Type: Optional, Non-repeatable
where the SummFileName is the name of the external file containing the summary of high ranked values.
The SUMMFILE filename can be up to 200 characters in length based on the default parameters in
AERMOD. Double quotes (") at the beginning and end of the filename can also be used as field delimiters
to allow filenames with embedded spaces. In addition to the summary of high ranked values, the
SUMMFILE also includes the "MODEL SETUP OPTIONS SUMMARY" page from the main 'aermod.out'
file.
The syntax, type, and order of the optional FILEFORM keyword are summarized below:
Syntax:
OU FILEFORM EXP or FIX
Type:
Optional, Non-repeatable
where the EXP parameter specifies that output results files will use exponential-formatted values, and the
FIX parameter specifies that the output results files will use fixed-formatted values. The default option is to
use fixed-formatted results, so use of FILEFORM = 'FIX' is extraneous. Note that AERMOD only examines
the first three characters of the input field, so that the full terms of 'EXPONENTIAL' or 'FIXED' can also be
used. The format specified on this optional keyword is applicable to PLOTFILEs, plot formatted
POSTFILEs, MAXIFILEs, RANKFILEs, and SEASONHR files, but will not affect the format of results in
the standard 'aermod.out' file or the optional SUMMFILE. The FILEFORM optional may be useful to
preserve precision in applications with relatively small impacts, especially for the purpose of post-processing
hourly concentrations using the POSTFILE option. The option may also be useful for applications with
relatively large impacts that may overflow the Fortran format specifier of F13.5 used for fixed-formatted
outputs. AERMOD will issue a warning message if values that exceed the range allowed for fixed format are
detected unless the FILEFORM EXP option has been selected.
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The syntax, type, and order of the optional NOHEADER keyword are summarized below:
OU NOHEADER FileTypel FileType2 FileType3 ... FileTypeN
Syntax:
or
OU NOHEADER ALL
Type:
Optional, Non-repeatable
where FileTypeN identifies the keywords for formatted output files for which the file headers will be
suppressed, which may include the includes the following file types: POSTFILE, PLOTFILE, MAXIFILE,
RANKFILE, SEASONHR, MAXDAILY, MXDYBYYR, and MAXDCONT. The keyword ALL may be
used to specify that header records will be suppressed for ALL applicable output file types.
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4.0 References
AECOM, 2010: AERMOD Low Wind Speed Evaluation Study Results, AECOM Environment, Westford,
MA.
API, 2013: Ambient Ratio Method Version 2 (ARM2) for use with AERMOD for 1-hr N02 Modeling:
Development and Evaluation Report. American Petroleum Institute, Washington, DC.
http://www.epa.gov/ttn/scram/models/aermod/ARM2 Development and Evaluation Report-
September 20 2013.pdf.
Azzi M. and Johnson G (1992). An Introduction to the Generic Reaction Set Photochemical Smog
Mechanism. Proc. 11th Clean Air Conf. 4th Regional IUAPPA Conf., Brisbane, Australia.
Carruthers, D.J., Stacker, J.R., Ellis, A., Seaton, M.D. and Smith, S.E. (2017). Evaluation of an explicit
NOX chemistry method in AERMOD. Journal of the Air & Waste Management Association, 67(6),
pp.702-712.
EPA, 1995a: User's Guide for the Industrial Source Complex (ISC3) Dispersion Models, Volume-I - User
Instructions. EPA-454/B-95-003a. U.S. Environmental Protection Agency, Research Triangle Park,
North Carolina 27711.
EPA, 1995b: User's Guide for the Industrial Source Complex (ISC3) Dispersion Models, Volume II -
Description of Model Algorithms. EPA-454/B-95-003b. U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711.
EPA, 2000: Meteorological Monitoring Guidance for Regulatory Modeling Applications. EPA-454/R-99-
005. U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
EPA, 2003: AERMOD Deposition Algorithms - Science Document (Revised Draft). U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina 27711.
EPA, 2007: AERMOD Modeling System Update. Presented at EPA R/S/L Modelers Workshop, Virginia
Beach, VA.
EPA, 2008: Risk and Exposure Assessment to Support the Review of the NO2 Primary National Ambient
Air Quality Standard. EPA-452/R-08-008a. U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711.
EPA, 2010a: Modeling Procedures for Demonstrating Compliance with PM2.5 NAAQS. Stephen D. Page
Memorandum, dated March 23, 2010. U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina 27711.
EPA, 2010b: Applicability of Appendix W Modeling Guidance for the 1 -hour NO2 National Ambient Air
Quality Standard. Tyler Fox Memorandum, dated June 28, 2010. U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina 27711.
EPA, 2010c: Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air
Quality Standard. Tyler Fox Memorandum, dated August 23, 2010. U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina 27711.
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2011: Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1-
hour NO2 National Ambient Air Quality Standard. Tyler Fox Memorandum, dated March 1, 2011.
U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
2014a: Clarification on the Use of AERMOD Dispersion Modeling for Demonstrating Compliance
with the N02 National Ambient Air Quality Standard. Air Quality Modeling Group Memorandum,
dated September 30, 2014. U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711.
2014b: Guidance for PM2 5 Modeling. May 20, 2014, Publication No. EPA-454/B-14-001. Office of
Air Quality Planning & Standards, Research Triangle Park, NC.
https://www.epa.gov/sites/production/files/2015-07/documents/pm25guid2.pdf
2015: Technical support document (TSD) for N02-related AERMOD modifications. July 2015,
Publication No. EPA-454/B-15-004. Office of Air Quality Planning & Standards, Research Triangle
Park, NC.
2017a: Clarification on the AERMOD Modeling System Version for Use in S02 Implementation
Efforts and Other Regulatory Actions. AQAD Memorandum, dated March 8, 2017. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
EPA, 2018: User's Guide for the AERMOD Terrain Preprocessor (AERMAP). EPA- 454/B-18-004. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
EPA. 2021: AERSCREEN User's Guide. December 2016. Publication No. EPA-454/B-21-005. Office of Air
Quality Planning & Standards, Research Triangle Park, NC.
EPA, 2023: Incorporation and Evaluation of the RLINE source type in AERMOD for Mobile Source
Applications. EPA-2023/R-23-011, Office of Air Quality Planning and Standards, Research Triangle
Park, North Carolina 27711.
EPA, 2024a: AERMOD Model Formulation. EPA-454/B-24-010. U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711.
EPA, 2024b: AERMOD Implementation Guide. EPA-454/B-24-009. U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711.
EPA, 2024c. Guideline on Air Quality Models: Ehancements to the AERMOD Dispersion Modeling System;
Final Rule. 40 CFR Part 51, Appendix W.
EPA, 2024d: Technical Support Document (TSD) for Adoption of the Generic Reaction Set Method (GRSM)
as a Regulatory Non-Default Tier-3 N02 Screening Option. EPA-454/R-24-005. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina. October 2024.
EPA, 2024e: User's Guide for the AERMOD Meteorological Preprocessor (AERMET). EPA-454/B-24-004.
U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
Hanna, S.R., Dicristofaro, D.C., 1988. Development and Evaluation of the OCD/API (Offshore and Coastal
Dispersion / American Petroleum Institute) Model.
EPA,
EPA,
EPA,
EPA,
EPA.
4-2
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Hanrahan, P.L., 1999a. "The plume volume molar ratio method for determining NC^/NOx ratios in modeling.
Part I: Methodology," J. Air & Waste Manage. Assoc., 49, 1324-1331.
Hanrahan, P.L., 1999b. "The plume volume molar ratio method for determining NC^/NOx ratios in
modeling. Part II: Evaluation Studies," J. Air & Waste Manage. Assoc., 49, 1332-1338.
Heist, D., Perry, S., Monbureau, E., Brouwer, L., and L. Brixey, 2016: "An overview of recent building
downwash research at EPA/ORD. U.S. Environmental Protection Agency." 2016 Regional, State,
and Local Modelers'Workshop, RTP, NC. November 15 17, 2016.
Luhar, A.K., and K. N. Rayner, 2009: "Methods to Estimate Surface Fluxes of Momentum and Heat from
Routine Weather Observations for Dispersion Applications under Stable Stratification", Boundary-
Layer Meteorology, 132,437-454.
Monbureau, E. M., Heist, D. K., Perry, S. G., Brouwer, L. H., Foroutan, H., Tang, W., 2018: "Enhancements
of AERMOD's building downwash algorithms based on wind tunnel and Embedded-LES
modeling." Atmospheric Environment, 179, 321-330.
Murray, D. R., and N. E. Bowne, 1988: Urban power plant plume studies. EPRI Report No. EA 5468,
Research Project 2736-1, Electric Power Research Institute, Palo Alto, CA.
Pandey, G., A Venkatram, and S. Arunachalam, 2023: "Accounting for plume rise of aircraft emissions in
AERMOD." Atmospheric Environment, 314. https://doi.Org/10.1016/i.atmosenv.2023.120106.
Perry, S.G., Heist, D.K., Brouwer, L.H., Monbureau, E.M., and L.A. Brixley, 2016: "Characterization of
pollutant dispersion near elongated buildings based on wind tunnel simulations." Atmospheric
Environment, 42, 286-295.
Petersen, R. L., Sergio A. Guerra & Anthony S. Bova, 2017: "Critical Review of the Building Downwash
Algorithms in AERMOD." J. Air Waste Management Association, Vol. 67, Issue 8, 826-835.
Petersen, R. L. and Guerra, S. A., 2018: PRIME2: "Development and evaluation of improved building
downwash algorithms for rectangular and streamlined structures." Journal of Wind Engineering and
Industrial Aerodynamics, 173, 67-78.
Petersen, R.L., 1984: Dispersion of Emissions from Offshore Oil Platforms - A Wind-Tunnel Modeling
Evaluation: API Publication NO. 4402
Qian, W., and A. Venkatram, 2011: "Performance of Steady-State Dispersion Models Under Low Wind-
Speed Conditions", Boundary Layer Meteorology, 138, 475-491.
Schulman, L.L., and J.S. Scire, 1980: Boyant Line and Point Source (BLP) Dispersion Model User's Guide.
Final Report. Environmental Research & Technology, Inc. P-7304B. July 1980.
Schulman, L.L., D.G. Strimaitis, and J.S. Scire, 2000: Development and Evaluation of the PRIME Plume
Rise and Building Downwash Model. Journal of the Air & Waste Management Association, Vol. 50,
pp 378-390.
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Snyder, M.G., Venkatram, A., Heist, D.K., Perry, S.G., Petersen, W.B. and Isakov, V., 2013. RUNE: A line
source dispersion model for near-surface releases. Atmospheric environment, 77, pp.748-756.
Snyder, M.G., and D. Heist, 2013. User's Guide for R-LINE Model Version 1.2: A Research LINE source
model for near-surface releases. EPA- MD-81. U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711.
Venkatram A., Karamchandani P., Pai P. & Goldstein R. (1994). The Development and Application of a
Simplified Ozone Modelling System (SOMS). Atmos. Environ. 28 (22), pp 3365-3678.
doi: 10.1016/1352-2310(94)00190-V
Walcek, C., G. Stensland, L. Zhang, H. Huang, J. Hales, C. Sweet, W. Massman, A. Williams, J, Dicke,
2001: Scientific Peer-Review of the Report "Deposition Parameterization for the Industrial Source
Complex (ISC3) Model." The KEVRIC Company, Durham, North Carolina.
Warren, C. J., R. J. Paine, J. A. Connors, C. Szembek and E. Knipping: 2022. Evaluation of a revised
AERMOD treatment of plume dispersion in the daytime elevated stable layer, Journal of the Air &
Waste Management Association, 72:9, 1040-1052, DOI: 10.1080/10962247.2022.2094031
Weil, J. C. 2020: New Dispersion Model for Highly-Buoyant Plumes in the Convective Boundary Layer.
Modeling Report to the Western Australia Department of Environmental Conservation. January
2020.
Wesely, M.L, P.V. Doskey, and J.D. Shannon, 2002: Deposition Parameterizations for the Industrial Source
Complex (ISC3) Model. Draft ANL report ANL/ER/TRB01/003, DOE/xx-nnnn, Argonne National
Laboratory, Argonne, Illinois 60439.
Yang, B., Gu, J., & Zhang, K. M., 2020. Parameterization of the building downwash and sidewash effect
using a mixture model. Building and Environment, 172, 106694.
Note: Many of the references listed can be found on the U.S. EPA SCRAM website at the following url:
https://www. epa. aov/scram.
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APPENDIX A. Functional keyword/parameter reference
This appendix provides a functional reference for the primary keywords and related secondary
keywords and parameters used by the input control files for the AERMOD model. The keywords are
organized by functional pathway. Except where noted, there is not a required order that the primary
keywords within a pathway must be specified. Similarly, there is not a required order in which secondary
keywords that follow a primary keyword must be specified, unless noted. However, AERMET assumes
that user-entered values for parameters following a primary keyword are specified in the order listed in the
tables below. The pathways used by the model are as follows, in the order in which they appear in the
control file and in the tables that follow:
CO - for specifying overall job COntrol options;
SO - for specifying SOurce information;
RE - for specifying REceptor information;
ME - for specifying MEteorology information and options;
EV - for specifying EVent information and options;
OU - for specifying OUtput options.
The pathways and keywords are presented in the same order as in the Detailed Keyword Reference in
Section 3.0, and in the Quick Reference at the end of the manual.
Two types of tables are provided for each pathway. The first table lists all of the keywords for
that pathway, identifies each keyword as to its type (either mandatory or optional and either repeatable or
non-repeatable), and provides a brief description of the function of the keyword. The second type of
table, which takes up more than one page for most pathways, presents the parameters for each keyword, in
the order in which they should appear in the control file where order is important, and describes each
parameter in detail.
The following convention is used for identifying the different types of input parameters.
Parameters corresponding to secondary keywords which should be input "as is" are listed on the tables
with all capital letters and are underlined, although none of the inputs to AERMOD are treated as case
sensitive. Other parameter names are given with an initial capital letter and are not input "as is." In all
cases, the parameter names are intended to be descriptive of the input variable being represented, and they
often correspond to the Fortran variable names used in the AERMOD code. Parentheses around a
parameter indicate that the parameter is optional for that keyword. The default that is taken when an
optional parameter is left blank is explained in the discussion for that parameter.
A-l
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Table A-l. Description of Control Pathway Keywords
CO Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of CONTROL pathway inputs
TITLEONE
M-N
First line of title for output
TITLETWO
0 - N
Optional second line of title for output
MODELOPT
M-N
Job control and dispersion options
AVERTIME
M-N
Averaging time(s) to process
URBANOPT
0 - R
Specifies parameters for urban dispersion option
POLLUTID
M-N
Identifies type of pollutant being modeled
HALFLIFE1
0 - N
Optional half life used for exponential decay
DCAYCOEF1
0 - N
Optional decay coefficient
GASDEPDF
0 - N
Option to override default parameters for gas dry deposition
GASDEPVD
0 - N
Option to specify deposition velocity for gas dry deposition
GDLANUSE
0 - N
Specify land use categories by sector for gas dry deposition
GDSEASON
0 - N
Specify seasonal definitions for gas dry deposition
LOWWIND
0 - N
ALPHA option for low wind conditions that allows user to specify values for
minimum sigma-v, minimum wind speed, and maximum meander factor
AWMADWNW
0 - N
Specifies downwash options developed by AWMA
ORDDWNW
0 - N
Specifies downwash options developed by ORD
N02EQUIL
0 - N
Option to override default N02/N0X equilibrium ratio for PVMRM, OLM, or
TTRM/TTRM2
N02STACK
0 - N
Option to specify default in-stack N02/N0X equilibrium ratio for PVRM, OLM,
TTRM/TTRM2, and GRSM options; may be overridden by N02RATI0 option on
SO pathway
NOX FILE
0 - N
Specifies hourly NOx file for the GSRM option
NOX UNIT
0 - N
Option to specify units for temporally varying NOx concentrations for the
NOX_VALS keyword used with the GSRM option for estimating NO2
NOXVALUE
0 - N
Specifies background value of NOx for the GSRM option for estimating NO2
NOXSECTR
0 - N
Option to specify wind sectors for use in varying background NOx concentrations
by wind direction for use with the GSRM option for estimating NO2; can be used
with the NOX FILE, NOXVALUE, and NOX_VALS options
NOX VALS
0 - R
Option to specify temporally varying NOx concentrations for use with the GSRM
option for estimating NO2
ARMRATIO
0 - N
Option to override default minimum and maximum (equilibrium) ratios for the
ARM2 option
03 SECTOR
0 - N
Specifies optional wind sectors for use in varying background ozone (03)
concentrations by wind direction for use with OLM, PVMRM, TTRM/TTRM2,
A-2
-------
and GRSM options; can be used with the OZONEFIL, OZONEVAL, and
03VALUES options
OZONEFIL
0 - N
Specifies filename for hourly ozone file for use with OLM, PVMRM,
TTRM/TTRM2, and GRSM options
OZONEVAL
0 - R
Specifies background value of ozone for use with OLM, PVMRM,
TTRM/TTRM2, and GRSM options
03VALUES
0 - R
Option to specify temporally varying ozone concentrations for use with OLM,
PVMRM, TTRM/TTRM2, and GRSM options for estimating NO2
OZONUNIT
0 - N
Option to specify units for temporally varying ozone concentrations for the
03VALUES keyword
FLAGPOLE
0 - N
Specifies whether to accept receptor heights above local terrain (m) for use with
flagpole receptors, and allows for default flagpole height to be specified
ARCFTOPT
0 - N
Option to apply aircraft plume rise to AREA and VOLUME source types identified
as aircraft using the ARCFTSRC keyword in the SO pathway
RUNORNOT
M-N
Identifies whether to run model or process setup information only
EVENTFIL2
0 - N
Specifies whether to generate an input file for EVENT model
SAVEFILE3
0 - N
Option to store intermediate results for restart of model after user or system
interrupt
INITFILE3
0 - N
Option to initialize model from intermediate results generated by SAVEFILE
option
MULTYEAR3
0 - N
Option to process multiple years of meteorological data (one year per run) and
accumulate high short-term values across years
DEBUGOPT
0 - N
Option to generate detailed result and meteorology files for debugging purposes
ERRORFIL
0 - N
Option to generate detailed error listing file
FINISHED
M-N
Identifies the end of CONTROL pathway inputs
Type: M - Mandatory, O - Optional, N - Non-Repeatable, R - Repeatable
1) Either HALFLIFE or DCAYCOEF may be specified. If both cards appear a warning message will
be issued and the first value entered will be used in calculations. The DFAULT option assumes a
half-life of 4 hours for SO2 modeled in urban mode.
2) The EVENTFIL keyword controls whether to generate an input file for EVENT processing. The
primary difference between AERMOD "regular" processing and EVENT processing by AERMOD is
in the treatment of source group contributions. The AERMOD model treats the source groups
independently, whereas EVENT processing determines individual source contributions to particular
events, such as the design concentrations determined from AERMOD, or user specified events. By
specifying the EVENTFIL keyword, an input control file will be generated that can be used directly
for EVENT processing. The events included in the generated EVENT processing input file are
defined by the RECTABLE and MAXIFILE keywords on the OU pathway and are placed in the
EVENT pathway.
3) The SAVEFILE and INITFILE keywords work together to implement the model's re-start
capabilities. Since the MULTYEAR option utilizes the re-start features in a special way to
A-3
-------
accumulate high short-term values from year to year, it cannot be used together with the SAVEFILE
or INITFILE keyword in the same model run.
A-4
-------
Table A-2. Description of Control Pathway Keywords and Parameters
Keyword
Parameters
TITLEONE
Title 1
where:
Title 1
First line of title for output, character string of up to 68
characters (additional characters can be included on the
TITLEONE keyword, but only the first 68 characters are printed
in the output files).
TITLETWO
Title2
where:
Title2
Optional second line of title for output, character string of up to
68 characters (any additional characters are not printed).
MODELOPT
DFAULT ALPHA BETA CONC AREADPLT FLAT NOSTD NOCHKD NOWARN SCREEN SCIM N0MIN03
RLINEFDH ELEV WARNCHKD NOURBTRAN VECTORWS PSDCREDIT FASTALL FASTAREA GSRM TTRM
TTRM2 PVMRM OLM ARM2 DEPOS DDEP WDEP DRYDPLT WETDPLT NODRYDPLT NOWETDPLT
AREAMNDR HBP
where:
DFAULT
ALPHA
BETA
CONC
DEPOS
DDEP
WDEP
AREADPLT
FLAT
Specifies that the regulatory default options will be used; note
that specification of the DFAULT option will override some
non-DFAULT options that may be specified in the input file,
while other non-DFAULT options will cause fatal errors when
DFAULT is specified (see below for details).
Non-regulatory option flag that allows the input control file to
include research/experimental options for review and
evaluation by the user community; (e.g., LOW WIND,
PSDCREDIT, ORD DWNW. AWMADWNW, PLATFORM,
METHOD 2 particle deposition, gas deposition, RLINEFDH,
and RLINEXT with options for modeling barriers and
depressed roadways) and cannot be used with DFAULT
keyword.
Non-regulatory option flag that allows the input control file to
include options that have been vetted through the scientific
community and are waiting to be promulgated as regulatory
options. Prior to promulgation, BETA options require
alternative model approval for use in regulatory applications
and cannot be used with DFAULT keyword.
Specifies that concentration values will be calculated.
Specifies that total deposition flux values will be calculated.
Specifies that dry deposition flux values will be calculated.
Specifies that wet deposition flux values will be calculated.
Specifies use of non-regulatory method for optimized plume
depletion due to dry removal mechanisms for area sources
(cannot be used when the DFAULT keyword is specified).
Specifies that the non-regulatory option of assuming flat terrain
will be used; Note that FLAT and ELEV may be specified in
the same model run to allow specifying the non-regulatory
FLAT terrain option on a source-by-source basis; FLAT
sources are identified bv specifVins the kevword FLAT in
place of the source elevation field on the SO LOCATION
A-5
-------
Keyword
Parameters
ELEV
NOSTD
NOCHKD
WARNCHKD
NOWARN
SCREEN
SCIM
PVMRM
OLM
ARM2
TTRM
keyword (cannot be used simultaneously with the DFAULT
keyword)..
Specifies that the default option of assuming elevated terrain will
be used; Note that FLAT and ELEV may be specified in the
same model run to allow specifying the non-regulatory FLAT
terrain option on a source-by-source basis (the ELEV option is
set as a regulatory option with the DFAULT keyword).
Specifies that the non-regulatory option of no stack-tip
downwash will be used (cannot be used with the DFAULT
keyword).
Specifies that the non-regulatory option of suspending date
checking will be used for non-sequential meteorological data
files (cannot be used with the DFAULT keyword).
Specifies that the option of issuing warning messages rather than
fatal errors will be used for non-sequential meteorological data
files.
Specifies that the option of suppressing the detailed listing of
warning messages in the main output file will be used (the
number of warning messages is still reported, and warning
messages are still included in the error file controlled by the
CO ERRORFIL keyword).
Non-regulatory option for running AERMOD in a screening
mode for AERSCREEN will be used (cannot be used when the
DFAULT keyword is specified).
Sampled Chronological Input Model - non-regulatory option
used only with the ANNUAL average option to reduce
runtime by sampling meteorology at a user-specified regular
interval; SCIM sampling parameters must be specified on the
ME pathway (cannot be used with the DFAULT keyword).
Specifies that the Plume Volume Molar Ratio Method (PVMRM)
for NO2 conversion will be used (regulatory option, can be
used simultaneously with DFAULT); cannot be used with
OLM, ARM2, or GRSM; cannot be used with TTRM without
TTRM2.
Specifies that the Ozone Limiting Method (OLM) for NO2
conversion will be used (regulatory option, can be used
simultaneously with DFAULT keyword); cannot be used with
PVMRM, ARM2, or GRSM; cannot be used with TTRM
without TTRM2.
Specifies that the Ambient Ratio Method - 2 (ARM2) for NO2
conversion will be used (regulatory option, can be used with
DFAULT keyword); cannot be used with PVMRM, OLM, or
GRSM; cannot be used with TTRM without TTRM2.
Specifies that the non-regulatory Travel Time Reaction Method
(TTRM) will be used forN02 conversion (non-regulatory
alpha option, requires the ALPHA keyword and cannot be
used with the DFAULT keyword); cannot be used with
PVMRM, OLM, ARM2 without TTRM2; cannot be used with
A-6
-------
Keyword
Parameters
GRSM; cannot be used with TTRM2 without PVMRM, OLM,
or ARM2.
Specifies that the non-regulatory Travel Time Reaction Method
TTRM2
(TTRM) will be paired with OLM, PVMRM, or ARM2 for
NO2 conversion (non-regulatory alpha option, requires the
ALPHA keyword and cannot be used with the DFAULT
keyword); cannot be used with TTRM alone or GRSM; must
be paired with one of PVMRM, OLM, or ARM2
Specifies that the Generic Reaction Set Method (GRSM) will be
GRSM
used for NO2 conversion; cannot be used with PVMRM,
OLM, TTRM, TTRM2, or ARM2.
Specifies that the non-regulatory ALPHA option will be used to
calculate the increment consumption with PSD credits using
the PVMRM option (cannot be used with the DFAULT
PSDCREDIT
keyword).
Non-regulatory option to optimize model runtime through use of
an alternative implementation of horizontal meander for
POINT and VOLUME sources; also optimizes model runtime
FASTALL
for AREA/AREAPOLY/AREACIRC/LINE, OPENPIT,
RLINE, and RLINEXT sources (formerly associated with
TOXICS option, now controlled by the FASTAREA and
FASTALL option, cannot be used with the DFAULT
keyword).
Non-regulatory option to optimize model runtime through hybrid
approach for AREA/AREAPOLY/AREACIRC and OPENPIT
sources (formerly associated with TOXICS option, cannot be
FASTAREA
used with the DFAULT keyword).
Option to incorporate dry depletion (removal) processes
associated with dry deposition algorithms; this requires
specification of dry deposition source parameters and
DRYDPLT
additional meteorological variables; dry depletion will be used
by default if dry deposition algorithms are invoked; cannot be
used with NODRYDPLT.
Option to disable dry depletion (removal) processes associated
with dry deposition algorithms; cannot be used with
DRYDPLT.
NODRYDPLT
Option to incorporate wet depletion (removal) processes
associated with wet deposition algorithms; this requires
specification of wet deposition source parameters and
WETDPLT
additional meteorological variables; wet depletion will be used
by default if wet deposition algorithms are invoked; cannot be
used with NOWETDPLT.
Option to disable wet depletion (removal) processes associated
with wet deposition algorithms; cannot be used with
WETDPLT.
NOWETDPLT
Non-regulatory option to ignore the transition from nighttime
urban boundary layer to daytime convective boundary layer
A-7
-------
Keyword
Parameters
NOURBTRAN
VECTORWS
N0MIN03
RLINEFDH
AREAMNDR
HBP
(i.e., to revert to the urban option as implemented prior to
version 11059) (cannot be used with the DFAULT keyword).
Option to specify that input wind speeds are vector mean (or
resultant) wind speeds, rather than scalar means. Under the
VECTORWS option, the adjustments to wind speeds based on
Equation 112 of the AERMOD Model Formulation document
(EPA, 2024a) will be applied (can be used with the DFAULT
keyword).
Option to remove the minimum ozone used for Tier 2 & 3 NO2
options. Without this option, AERMOD will use a minimum
value of 40 ppb of ozone for nighttime stable conditions,
regardless of the value in an hourly input file (can be used
with the DFAULT keyword).
Option to have wind profile calculations without a displacement
height for RLINE and RLINEXT source types. This makes the
wind profile closer to other AERMOD source types, which do
not use a displacement height in wind profile (requires the
ALPHA keyword and cannot be used with the DFAULT
keyword).
Option to apply plume meander to AREA. AREAPOLY,
AREACIRC, and LINE source types. Note that AREAMNDR
and FASTAREA or FASTALL can be specified in the same
model run, but in that case, meander will not be applied to
those source types listed.
Option for highly buoyant plumes (HBP) when plume penetrates
the top of the convective mixed layer. Limited to point source
types (POINT, POINTHOR, POINTCAP). Compares
convective mixing height for the current hour and next hour to
determine how much of the penetrated plume has been
captured by the CBL by the end of the current hour (requires
the ALPHA keyword and cannot be used with the DFAULT
keyword).
AVERTIME
Timel Time2 . . . Time A' MONTH PERIOD
or
ANNUAL
where:
Timc/v'
MONTH
PERIOD
ANNUAL
Nth optional averaging time (J_, 2, 3, 4, 6, 8, 12, or 24-hr)
Option to calculate MONTHlv averaaes.
Option to calculate averaaes for the entire data PERIOD; for the
MULTYEAR option, the summary of highest PERIOD
averages is based on the highest PERIOD average across the
individual years processed with MULTYEAR.
Option to calculate ANNUAL averaaes (assumes complete
years); for multi-year meteorological data files, with and
without the MULTYEAR option, the multi-year average of the
ANNUAL values is reported.
URBANOPT
For multiple urban areas:
A-8
-------
Keyword
Parameters
UrbanID Urbpop (Urbname) (UrbRoughness)
For single urban area:
Urbpop (Urbname) (UrbRoughness)
where:
UrbanID
UrbPop
(UrbName)
(UrbRoughness)
Specifies the alphanumeric urban ID (up to eight characters).
Specifies the population of the urban area.
Specifies the name of the urban area (optional).
Specifies the urban surface roughness length, meters (optional,
defaults to 1 .Om; value other than 1,0m treated as non-
DFAULT).
POLLUTID
Pollut (H1H or H2H or INC)
where:
Pollut
Identifies type of pollutant being modeled. Any name of up to
eight characters mav be used. e.g.. S02. NOX. CO. PM25.
PM-2.5. PM10. PM-10. TSP or OTHER.
NOTE: Some processing options are pollutant-specific, and
require the user to specify the appropriate pollutant ID. For
example, use of PM10. PM-10. PM25. PM2.5. PM-2.5. PM-
25. LEAD. N02. S02. or OTHER allows for the use of the
MULTYEAR option.
Use of PM25. PM2.5. PM-2.5. or PM-25. triggers special
processing for the PM-2.5 NAAQS, based on values averaged
across the number of years processed (see Section 3.2.16.1).
Use ofN02 or S02 triggers special processing for their
respective 1-hr NAAQS based on daily maximum 1-hr
concentrations, averaged across the number of years modeled
if the CO AVERTIME keyword includes 1-hr averages (see
Section 3.2.17).
Use ofN02 is required in order to use the OLM and PVMRM
options for simulating conversion of NO to NO2.
Use of S02 also triggers the use of a 4-hour half-life for SO2
decay for urban applications under the regulatory default
option.
H1H or
H2H or
INC
Use of the H1H or H2H or INC kevword (not case-specific)
disables the special processing requirements associated the 1-
hr NO2 and SO2 NAAQS and the 24-hr PM2 5 NAAQS.
Specifying one of these keywords would allow for modeling
PM2 5 24-hr increments which are based on the H2H value and
allow evaluating NO2 options in AERMOD based on
incomplete years of field measurements.
HALFLIFE
Haflif
A-9
-------
Keyword
Parameters
where:
Haflif
Half-life used for exponential decay (s).
DCAYCOEF
Decay
where:
Decay
Decay coefficient for exponential decay (s1) = 0.693/HAFLIF
GASDEPDF
React F_Seas2 F_Seas5 (Refpoll)
The ALPHA option must be specified as a MODELOPT on the CO pathway to use
the GASDEPDF keyword.
where:
React
F_Seas2
F_Seas5
(Refpoll)
Value for pollutant reactivity factor
Fraction (F) of maximum green LAI for seasonal category 2.
Fraction (F) of maximum green LAI for seasonal category 5.
Optional name of reference pollutant.
GASDEPVD
Uservd
The ALPHA option must be specified as a MODELOPT on the CO pathway to use
the GASDEPVD keyword.
where:
Uservd
User-specified dry deposition velocity (m/s) for gaseous
pollutants.
GDLANUSE
Seel Sec2 ... Sec36
The ALPHA option must be specified as a MODELOPT on the CO pathway to use
the GDLANUSE keyword.
where:
Seel
Sec2
Land use category for winds blowing toward sector 1 (10
degrees).
Land use category for winds blowing toward sector 2 (20
degrees).
Sec36
Land use category for winds blowing toward sector 36 (360
degrees).
GDSEASON
Jan Feb ... Dec
The ALPHA option must be specified as a MODELOPT on the CO pathway to use
the GDSEASON keyword.
where:
Jan
Seasonal category for January:
1 = Midsummer/Lush vegetation;
2 = Autumn/Unharvested cropland;
3 = Late autumn after harvest or Winter with no snow;
4 = Winter with continuous snow cover; or
5 = Transitional spring/partial green coverage/short annuals)
Dec
Seasonal category for December.
LOWWINd
SVmin (WSmin) or
A-10
-------
Keyword
Parameters
SVmin WSmin (FRANmax) or
SVmin WSmin FRANmax (SWmin) or
SVmin WSmin FRANmax SWmin (BigT) or
SVmin WSmin FRANmax SWmin BigT (FRANmin) or
SVmin WSmin FRANmax SWmin BigT FRANmin (PBAL)
The ALPHA option must be specified as a MODELOPT on the CO pathway to use the
LOW WIND keyword
where:
SVmin
WSmin
FRANmax
SWmin
BigT
FRANmin
PBAL
Minimum value of sigma-v, within a range of 0.01 to 1.0 m/s.
Minimum value of wind speed, within a range of 0.01 to 1.0 m/s.
Maximum value for meander factor, within a range of 0.0 to 1.0.
Minimum value of sigma-w, within a range of 0.0 to 3.0 m/s.
Time period (BigT) used to calculate the time scale TRAN,
within a range of 0.5 to 48.0 hours.
Minimum value for meander factor, within a range of 0.0 to 1.0
but must be less than or equal to FRANmax.
Alternate momentum balance approach to determine plume
meander which overrides the default energy balance approach.
AWMADWNW
AWMAUEFF and/or
AWMAENTRAIN and/or
((AWMAUTURB or AWMAUTURBHX) w/wo STREAMLINE(D))
The ALPHA option must be specified as a MODELOPT on the CO pathway to use
the AWMADWNW keyword.
where:
AWMAUEFF
AWMAENTRAIN
AWMAUTURB
AWMAUTURBHX
STREAMLINE
Redefines the height at which the wind speed is taken from the
profile wind speed used in the calculation of concentrations
from the primary plume.
Changes beta (B) entrainment coefficient for PRIME downwash
from default value of 0.60 to 0.35.
Uses alternative formulations for turbulence enhancement and
velocity deficit calculations.
Uses distance-based plume rise at the downwind distance X for
calculations.
Reduces dispersion in the wake of streamlined structures such as
storage tanks and cooling towers.
ORDDWNW
ORDUEFF and/or ORDTURB and/or ORDCAV
The ALPHA option must be specified as a MODELOPT on the CO pathway to use
the ORD DWNW keyword.
where:
ORDUEFF
ORDTURB
ORDCAV
Redefines the height at which the wind speed is taken from the
profile wind speed used in the calculation of concentrations
from the primary plume.
Redefines the maximum value of the ambient turbulence
intensity in the wake, reduced from 0.07 to 0.06.
A-ll
-------
Keyword
Parameters
Redefines the initial vertical dispersion, az. of the re-emitted
plume at the cavity boundary to equal the az of the cavity
plume.
N02EQUIL
N02Equil
where:
N02Equil
Equilibrium ratio ofN02/NOx for the PVMRM, OLM, and
TTRM options; between 0.1 and 1.0, inclusive (default is 0.9).
N02 STACK
N02Ratio
where:
N02Ratio
Default in-stack ratio of NO2/NOX for PVMRM, OLM, TTRM,
and GSRM options, which may be overridden by the
N02RATIO keyword on SO pathway.
NOTE: Beainnina with version 11059. AERMOD no lonaer
assumes a default in-stack ratio of 0.1 for the OLM option.
ARMRATIO
ARM2 Min ARM2 Max For ARM2 Option
where:
ARM2 Min
ARM2_Max
Minimum ARM2 ambient ratio, with a default value of 0.50.
Maximum ARM2 ambient ratio, with a default value of 0.90.
03 SECTOR
StartSectl StartSect2 . . . StartSect/V, where N is < 6
where:
StartSectl
StartSect2
StartSect/V
Starting direction for the first sector.
Starting direction for the second sector.
Starting direction for the last sector.
NOTE: The minimum sector width allowed is 30 dearees. and
warning messages will be issued for sector widths less than
60 degrees. Sector-varying O3 concentrations will be selected
based on the flow vector, i.e., the downwind direction based
on the wind direction specified in the surface meteorological
data file.
OZONEFIL
03FileName (03Units) (03Format) (without 03SECTORs)
or
SECTx 03FileName (03Units) (03Format) (with 03SECTORs)
where:
SECTx
03FileName
(03Units)
(03Format)
Applicable sector (x = 1 to 6) defined on the CO 03 SECTOR
keyword, if specified.
Filename for hourly ozone data file (YR, MN, DY, HR,
03 Value).
Units of ozone data (PPM, PPB, or UG/M3); default is UG/M3.
Fortran format statement to read ozone file; default is FREE-
format, i.e., comma or space-delimited data fields (Yr Mn Dy
Hr 03Value). The 03Format parameter must include open
and close parentheses, the date variables must be read as
integers (Fortran I format), and the 03Value must be read as
real (Fortran F, E, or D format), e.g., '(412,F8.3)'. The year
A-12
-------
Keyword
Parameters
may be specified as a 2-digit or 4-digit year, and the data
period in the OZONEFIL must match the data period in the
meteorological data files.
OZONEVAL
03Value (03Units ) (without 03SECTORs)
or
SECTx 03Value (03Units) (with 03SECTORs)
where:
SECTx
03Value
(03Units)
Applicable sector (x = 1 to 6) defined on the CO 03 SECTOR
keyword, if specified.
Background ozone concentration; also used to substitute for
missing data in OZONEFIL.
Units of ozone value (PPM, PPB, or UG/M3); default is UG/M3.
03VALUES
03Flag 03values(i), i=l, n (without 03SECTORs)
or
SECTx 03Flag 03values(i), i=l, n (with 03SECTORs)
where:
SECTx
03Flag
03values
Applicable sector (x = 1 to 6) defined on the CO 03 SECTOR
keyword, if specified.
Background ozone values flag:
ANNUAL for annual; SEASON for seasonal; MONTH for
monthlv; HROFDY for hour-of-dav; WSPEED for wind soeed
category: SEASHR for season-bv-hour; HRDOW for
emission rates vary by hour-of-day, and day-of-week [M-F,
Sat. Sunl; HRD0W7 for emission rates varv bv hour-of-dav.
and the seven days of the week [M, Tu, W, Th, F, Sat, Sun];
SHRDOW for season bv hour-of-dav bv dav-of-week
(M-F.Sat.Sun); SHRD0W7 for season bv hour-of-dav bv dav-
of-week (M.Tu.W.Th.F.Sat.Sun): MHRDOW for month bv
hour-of-dav bv dav-of-week (M-F.Sat.Sun); MHRD0W7 for
month by hour-of-day by day-of-week
(M,Tu,W,Th,F, Sat, Sun).
Arrav of background concentrations, for: ANNUAL. n= 1;
SEASON. n=4: MONTH. n=12; HROFDY. Ğ=24;
WSPEED. n=6: SEASHR. n=96: HRDOW. Ğ=72:
HRD0W7. Ğ=168: SHRDOW. Ğ=288: SHRD0W7. Ğ=672:
MHRDOW. Ğ=864; MHRD0W7. Ğ=2016.
NOTE: Background ozone values input through the
03VALUES keyword are assumed to be in units of PPB,
unless modified by the OZONUNIT keyword.
OZONUNIT
OzoneUnits
where:
OzoneUnits
Ozone concentration units for 03VALUES, specified as PPB for
parts-per-billion. PPM for parts-per-million. or UG/M3 for
micrograms/cubic-meter.
The following keywords: NOXSECTR, NOX_FILE, NOXVALUE, NOX_VALS, and NOXJJNIT,
are only applicable to the GRSM NO-to-NCh Conversion Option.
A-13
-------
Keyword
Parameters
NOXSECTR
StartSectl StartSect2
. . . StartSect/V, where N is < 6
where:
StartSectl
StartSect2
Starting direction for the first sector.
Starting direction for the second sector.
StartSect/V
Starting direction for the last sector.
NOTE: The minimum sector width allowed is 30 dearees. and
warning messages will be issued for sector widths less than 60
degrees. Sector-varying NOX concentrations will be selected
based on the flow vector, i.e., the downwind direction based on
the wind direction specified in the surface meteorological data
file.
NOX FILE
NOXFileName (NOXUnits) (NOXFormat) (without NOXSECTRs)
or
SECTx NOXFileName (NOXUnits) (NOXFormat) (with NOXSECTRs)
where:
SECTx
NOXFileName
(NOXUnits)
(NOXFormat)
Applicable sector (x = 1 to 6) defined on the CO 03 SECTOR
keyword, if specified.
Filename for hourly NOX data file (YR, MN, DY, HR,
NOXValue).
Units of NOX data (PPM, PPB, or UG/M3); default is UG/M3.
Fortran format statement to read NOX file; default is FREE-
format, i.e., comma or space-delimited data fields (Yr Mn Dy
Hr NOXValue). The NOXFormat parameter must include
open and close parentheses, the date variables must be read as
integers (Fortran I format), and the NOXValue must be read as
real (Fortran F, E, or D format), e.g., '(412,F8.3)'. The year
may be specified as a 2-digit or 4-digit year, and the data
period in the NOX FILE must match the data period in the
meteorological data files.
NOXVALUE
NOXValue (NOXUnits) (withoutNOXSECTRs)
or
SECTx NOXValue (NOXUnits) (with NOXSECTRs)
where:
SECTx
NOXValue
(NOXUnits)
Applicable sector (x = 1 to 6) defined on the CO NOXSECTR
keyword, if specified.
Background ozone concentration; also used to substitute for
missing data in OZONEFIL.
Units of ozone value (PPM, PPB, or UG/M3); default is UG/M3.
NOX VALS
NOXFlag NOXvalues(i), i=l, n (without NOXSECTRs)
or
SECTx NOXFlag NOXvalues(i), i=l, n (with NOXSECTRs)
where:
SECTx
NOXFlag
Applicable sector (x = 1 to 6) defined on the CO 03 SECTOR
keyword, if specified.
Background ozone values flag:
A-14
-------
Keyword
Parameters
NOXvalues
ANNUAL for annual; SEASON for seasonal; MONTH for
monthly; HROFDY for hour-of-dav; WSPEED for wind speed
category; SEASHR for season-bv-hour; HRDOW for
emission rates vary by hour-of-day, and day-of-week [M-F,
Sat. Sunl; HRDOW7 for emission rates varv bv hour-of-dav.
and the seven days of the week [M, Tu, W, Th, F, Sat, Sun];
SHRDOW for season bv hour-of-dav bv dav-of-week
(M-F.Sat.Sun); SHRDOW7 for season bv hour-of-dav bv dav-
of-week (M.Tu.W.Th.F.Sat.Sun); MHRDOW for month bv
hour-of-dav bv dav-of-week (M-F.Sat.Sun); MHRDOW7 for
month by hour-of-day by day-of-week
(M,Tu,W,Th,F, Sat, Sun).
Arrav of background concentrations, for: ANNUAL. n= 1;
SEASON. n=4: MONTH. n=12; HROFDY. n=24:
WSPEED. n=6: SEASHR. n=96: HRDOW. Ğ=72;
HRDOW7. Ğ=168; SHRDOW. Ğ=288; SHRDOW7. Ğ=672;
MHRDOW. Ğ=864; MHRDOW7. Ğ=2016.
NOTE: Background NOX values input through the
NOXVALUES keyword are assumed to be in units of PPB,
unless modified by the NOX_UNIT keyword.
NOX UNIT
NOXUnits
where:
NOXUnits
NOX concentration units for NOX VALS, specified as PPB for
parts-per-billion. PPM for parts-per-million. or UG/M3 for
micrograms/cubic-meter.
FLAGPOLE
(Flagdf)
where:
(Flagdf)
Default value for height of (flagpole) receptors above local
ground, a default value of 0.0 m is used if this optional
parameter is omitted.
ARCFTOPT
(AirportID)
where:
(AirportID)
Optional alphanumeric character string to identify the airport
where aircraft sources are located.
RUNORNOT
RUN or NOT
where:
RUN
NOT
Indicates to run full model calculations.
Indicates to process setup data and report errors, but to not run
full model calculations.
EVENTFIL
(Evfile) (Evopt)
where:
(Evfile)
(Evopt)
Identifies the filename to be used to generate a file for input to
EVENT model (Default=EVENTFIL.INP).
Optional parameter to specify the level of output detail selected
for the EVENT model: either SOCONT or DETAIL (default is
DETAIL if this parameter is omitted).
A-15
-------
Keyword
Parameters
SAVEFILE
(Savfil) (Dayinc) (Savfl2)
where:
(Savfil)
(Dayinc)
(Savfl2)
Specifies name of disk file to be used for storing intermediate
results (default = SAVE.FIL); file is overwritten after each
dump.
Number of days between dumps (optional: default is 1).
Optional second disk filename to be used on alternate
dumps - eliminates risk of system crash during the dump. If
blank, file is overwritten each time.
INITFILE
(Inifil)
where:
(Inifil)
Specifies name of disk file of intermediate results to be used for
initializing run (default = SAVE.FIL).
MULTYEAR
(H6H) Savfil (Inifil)
where:
(H6H)
Savfil
(Inifil)
Optional field formerly used to specify that High-Sixth-High is
being calculated for use in PM10 processing; no longer
required.
Specifies name of file to be used for storing results at the end of
the year.
Optional name of file used for initializing the results arrays from
previous year(s). The Inifil parameter is not used for the first
year in the multi-year run.
DEBUGOPT
MODEL (DbefiD and/or METEOR (Dbmfil) and/or PRIME (Prmfil)
and/or
AWMADW (AwmaDwfil)
and/or
PLATFORM (PlatfmDbeFil)
and/or
DEPOS (Dbefil)
and/or
[AREA (AreaDbFiD or LINE (LincDbFiDI
and/or
RLINE (RlincDbeFil)
and/or
BLPDBUG (BLPDbFiD
and/or
URBANDB (UrbanDbFiD
and/or
fPVMRM (Dbovfil) (and TTRM2) or
OLM (OLMfil) (and TTRM2) or
ARM2 (ARM2fiD (and TTRM2) or
TTRM (TTRMfiD or GSRM (GSRMfil)l
and/or
SWPOINT (SWfil)
and/or
HBPDBG (HBPfil)
and/or
A-16
-------
Keyword
Parameters
AIRCRAFT (DbARCFTfiD
where:
MODEL
Specifies that MODEL debugging output will be generated.
(Dbgfil)
Optional filename for the model calculation debug file (a default
filename of 'MODEL.DBG' will be used if omitted).
METEOR
Specifies that METEORoloeical profile data file will be
generated.
(Dbmfil)
Optional filename for the meteorological profile data file (a
default filename of 'METEOR.DBG' will be used if omitted).
PRIME
Specifies that PRIME debugging output will be generated.
(Prmfil)
Optional filename for PRIME debug file (a default filename of
'PRIME.DBG' will be used if omitted).
AWMADW
Specifies the debug out will be generated for AWMA Downwash
options.
(AwmaDwfil)
Optional filename for AWMADW debug file (a default filename
of 'AWMADW.DBG' will be used if omitted).
PLATFORM
Specifies the debug out will be generated for PLATFORM
Downwash options.
(PlatfmDbgfil)
Optional filename for PLATFORM downwash debug file, (a
default filename of 'PLATFORM.DBG' will be used if
omitted).
DEPOS
Specifies that DEPOSition debugging output will be generated,
using default filenames of 'GDEPDAT for gas deposition and
'PDEPDAT for particle deposition.
AREA or LINE
Specifies that AREA or LINE debugging output will be
generated, including debugging outputs for OPENPIT sources,
if included in the modeling.
(AreaDbfil)
Optional filename for AREA debug file (a default filename of
'AREA.DBG' will be used if omitted).
RLINE
Specifies that RLINE debugging output will be generated.
(RLineDbgFil)
Optional filename for RLINE debug file (a default filename of
'RLINE.DBG' will be used if omitted).
BLPDBUG
Debug information for the BUOYLINE source.
(BLPDbFil)
Optional filename for BLPDBUG debug file (a default filename
of 'BLPDBUG.DBG' will be used if omitted).
URBANDB
Debug information from the URBANDB option. This will
produce 3 output files, one for the surface meteorology and
two for the profile meteorology.
(UrbanDbFil)
Optional filename for URBANDB debug files This will produce
three output files, one for the surface meteorology, two for the
profile meteorology. If the filename is specified by the user,
then the filename will be used for the surface meteorology
debug file. The same name will be assigned for the two
profile debug files with a "1" and "2" appended to the
filename, respectively. Default filenames: URBDBUG.DBG,
URBDBUG1 DBG, and URBDBUG2.DBG.
A-17
-------
Keyword
Parameters
PVMRM
Specifies that PVMRM debuaaina output will be aenerated
(Dbpvfil)
Optional filename for PVMRM debug file (a default filename of
'PVMRM.DBG' will be used if omitted).
OLM
Specifies that OLM debuaaina output will be aenerated
(OLMfil)
Optional filename for OLM debug file (a default filename of
'OLM.DBG' will be used if omitted).
ARM2
Specifies that ARM2 debuaaina output will be aenerated
(ARM261)
Optional filename for ARM2 debug file (a default filename of
'ARM2.DBG' will be used if omitted).
TTRM
Specifies that TTRM debuaaina output will be aenerated
(TTRMfil)
Optional filename for TTRM debug file (a default filename of
'TTRM.DBG'will be used if omitted).
TTRM2
Specifies that TTRM2 debugging output will be generated.
TTRM2 can only be used with ARM2, PVMRM, or OLM and
only if specified with the MODELOPT keyword along with
one of those options. A user-defined debug filename cannot be
specified for the TTRM2 debug option.
GRSM
Specifies that GRSM debuaaina output will be aenerated.
(GSRMfil)
Optional filename for GRSM debug file (a default filename of
'GRSM.DBG' will be used if omitted).
SWPOINT
Specifies debugging output for the SWPOINT (sidewash) source
type will be generated.
(SWfil)
Optional filename for SWPOINT debug file (a default filename
of SWPOINT.DBG will be used if omitted).
Note: The user can specifV anv of the applicable debua
options for a particular model run, and the options can be
specified in any order. However, the optional filenames
must be specified immediately after the keyword option
associated with the filename. Also note that debugging
information that was written to the main 'aermod.out' file
for the MODEL debua option prior to version 13350 is
now written to the applicable debua file (either MODEL
or PRIME) and beainnina with version 14134 debua
information for AREA/LINE/OPENPIT sources is written
to the AREA debua file.
HBPDBG
Specifies debugging output for the HBP (highly buoyant plume)
sources will be generated.
(HBPfil)
Optional filename for HBP debug file (a default filename of
HBP DEBUG.DBG will be used if omitted).
AIRCRAFT
Specifies debugging output for AREA and VOLUME aircraft
sources.
(DbARCFTfil)
Optional filename for the AIRCRAFT debug file (a default
filename of AIRCRAFT.DBG will be used if omitted).
A-18
-------
ERRORFIL
(Errfil)
where:
(Errfil)
Specifies name of detailed error listing file (default =
ERRORS.LST).
A-19
-------
Table A-3. Description of Source Pathway Keywords
SO Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of SOURCE pathway inputs
ELEVUNIT
O-N
Defines input units for source elevations (defaults to meters), must be first
keyword after SO STARTING if used.
LOCATION
M-R
Identifies coordinates for particular source
RLEMCONV
O-N
Optional emission units conversion that changes the input units for the
RLINE and RLINEXT sources to grams/hour/link
SRCPARAM
M-R
Identifies source parameters for a particular source
BUILDHGT
0 - R
Building height values for each wind sector
BUILDLEN
0 - R
Building projected length values for each wind sector
BUILDWID
0 - R
Building projected width values for each wind sector
XBADJ
0 - R
Along-flow distances from the stack to the center of the upwind face of the
projected building
YBADJ
0 - R
Across-flow distances from the stack to the center of the upwind face of the
projected building
AREAVERT
M-R
Specifies location of vertices for an AREAPOLY source type (mandatory if
AREAPOLY source is used)
RBARRIER
0 - R
Specifies RLINEXT barrier source configuration
The ALPHA option must be specified as a MODELOPT on the CO
pathway to use the RBARRIER keyword.
RDEPRESS
0 - R
Specifies RLINEXT depressed roadway source configuration
The ALPHA option must be specified as a MODELOPT on the CO
pathway to use the RDEPRESS keyword.
BLPINPUT
M-R
Buoyant line group parameters representative of the buoyant line group
URBANSRC
0 - R
Identifies which sources to model with urban effects
EMISFACT
0 - R
Optional input for variable emission rate factors
EMISUNIT
O-N
Optional unit conversion factors for emissions, concentrations
CONCUNIT
O-N
Optional conversion factors for emissions and concentrations
DEPOUNIT
O-N
Optional conversion factors for emissions and depositions
PARTDIAM
0 - R
Input variables for optional input of particle size (microns)
MASSFRAX
0 - R
Optional input of mass fraction for each particle size category
PARTDENS
0 - R
Optional input of particle density (g/cm3) for each size category
METHOD 2
0 - R
Optional input of parameters for METHOD2 particle deposition
A-20
-------
SO Keywords
Type
Keyword Description
The ALPHA option must be specified as a MODELOPT on the CO
pathway to use the METHOD 2 keyword.
GASDEPOS
0 - R
Optional input of gas deposition parameters
The ALPHA option must be specified as a MODELOPT on the CO
pathway to use the GASDEPOS keyword.
N02RATI0
0 - R
Option to specify in-stack N02/N0x equilibrium ratio for OLM and
PVMRM options by source
HOUREMIS
0 - R
Option for specifying hourly emission rates in a separate file
BGSECTOR
O-N
Specifies optional wind sectors for use in varying background
concentrations by wind direction for the pollutant being modeled, as
specified on the BACKGRND keyword
BACKGRND
0 - R
Option to specify temporally varying background concentrations
BACKUNIT
O-N
Option to specify units for background concentrations
INCLUDED
0 - R
Option to include data from a separate file in the runstream
OLMGROUP
0 - R
Specifies sources to combine for OLM option to account for merging
plumes
BLPGROUP2
M-R
Associates individual buoyant lines with a buoyant line source group
PSDGROUP1
0 - R
Specifies source groups for PSDCREDIT option with PVMRM
HBPSRCID
M-R
Identification of HBP (highly buoyant plume) sources. Mandatory when
HBP option is used
ARCFTSRC
M-R
Identification of aircraft sources. Mandatory when the ARCFTOPT option is
used
SRCGROUP1
M-R
Identification of source groups
PLATFORM
0 - R
Optional input for POINT and POINTHOR sources on a platform.
The ALPHA option must be specified as a MODELOPT on the CO
pathway to use the PLATFORM keyword.
FINISHED
M-N
Identifies the end of SOURCE pathway inputs
1) The PSDGROUP or SRCGROUP keywords must be the last keyword within the SO pathway
before the FINISHED keyword. The SRCGROUP keyword is mandatory, unless the
PSDCREDIT option is used, which requires the PSDGROUP option instead.
2) The BLPGROUP keyword(s) must be after the BLPINPUT keyword(s)
A-21
-------
Table A-4. Description of Source Pathway Keywords and Parameters
Keyword
Parameters
ELEVUNIT
METERS or FEET
where:
METERS
FEET
Specifies input units for source base elevations of meters (default if
ELEVUNIT is omitted).
Specifies input units for source elevations of feet.
Note: This kevword applies to source base elevations onlv.
LOCATION
SrcID SrctvD Xs Ys (Zs) 1 for all Srctvos exccot LINE.
BUOYLINE. RLINE. and RLINEXT1
or
(FLAT) Tfor ' FLAT & ELEV' ODtionl
or
SrcID SrctvD Xs 1 Ys 1 Xs2 Ys2 (Zs) Tfor LINE. RLINE. or BUOYLINE Srctvol
or
(FLAT) Tfor 'FLAT & ELEV' ootionl
or
SrcID SrctvD Xs 1 Ys 1 Zs 1 Xs2 Ys2 Zs2 (Zs) Tfor RLINEXT Srctvol
or
(FLAT) Tfor 'FLAT & ELEV' ODtionl
where:
SrcID
Srctyp
Xs
Ys
Xsl, Xs2
Ysl, Ys2
Zsl, Zs2
(Zs)
(FLAT)
Source identification code (unique alphanumeric string of up to 12
characters).
Source tvpe: POINT. POINTCAP. POINTHOR. VOLUME. AREA.
AREAPOLY. AREACIRC. OPENPIT. LINE. BUOYLINE. RLINE. or
RLINEXT.
x-coord of source location, corner for AREA. AREAPOLY. and
OPENPIT. center for AREACIRC (m).
v-coord of source location, corner for AREA. AREAPOLY. and
OPENPIT. center for AREACIRC (m).
x-coords of midpoint for start and end of LINE. RLINE. RLINEXT. or
BUOYLINE source (m).
v-coords of midpoint for start and end of LINE. RLINE. RLINEXT. or
BUOYLINE source (m).
z-coords of midpoint for start and end of RLINEXT source (m).
Optional z-coord of source location (elevation above mean sea level,
defaults to 0.0 if omitted).
Optional keyword to indicate non-DFAULT option to specify source to
model with FLAT terrain.
SRCPARAM
SrcID Ptemis Stkhat Stktnro Stkvel Stkdia (POINT. POINTCAP.
POINTHOR source)
Vlemis Relhat Svinit Szinit (VOLUME source)
Aremis Relhat Xinit (Yinit) (Anale) (Szinit) (AREA source)
Aremis Relhat Nverts (Szinit) (AREAPOLY source)
Aremis Relhat Radius (Nverts) (Szinit) (AREACIRC source)
A-22
-------
Keyword
Parameters
Lnemis Relhgt Width (Szinit) (LINE or RLINE source)
Oocmis Relhat Xinit Yinit Pitvol (Angle) (OPENPIT source)
Blemis Relhgt (BUOYLINE source)
Rlemis DCL Width Szinit (RLINEXT source)
where:
SrcID
Emis
Hgt
Stktmp
Stkvel
Stkdia
Syinit
Szinit
Xinit
Yinit
Angle
Nverts
Radius
Width
Pitvol
Blemis
DCL
Source identification code.
Source emission rate: in g/s for Ptemis, Vlemis, and Blemis; g/(s-m2) for
Aremis, Lnemis, and Opemis; g/m/s for Rlemis.
Source physical release height above ground (center of height for
VOLUME, height above base of pit for OPENPIT).
Stack gas exit temperature (K).
Stack gas exit velocity (m/s).
Stack inside diameter (m).
Initial lateral dimension of VOLUME source (m).
Initial vertical dimension of VOLUME. AREA. LINE. RLINE. or
RLINEXT source (m).
Length of side of AREA source in X-direction (m).
Length of side of AREA source in Y-direction (m) (optional parameter,
assumed to be equal to Xinit if omitted).
Orientation angle (deg) of AREA or OPENPIT source relative to N
measured positive clockwise, rotated around the source location,
(Xs,Ys) (optional parameter, assumed to be 0.0 if omitted).
Number of vertices used for AREAPOLY or AREACIRC source
(optional for AREACIRC sources).
Radius of circular area for AREACIRC source (m).
Width of LINE. RLINE. or RLINEXT source (m).
Volume of OPENPIT source (m3).
Buovant line emission rate in g/(s) for the individual line of BUOYLINE
source.
Distance from roadwav centerline for RLINEXT source (m).
BUILDHGT
SrcID (or SrcRange) Dsbh(i), i=l, 36
where:
SrcID
SrcRange
Dsbh
Source identification code.
Range of sources (inclusive) for which building dimensions apply,
entered as two alphanumeric strings separated by a
Array of direction-specific building heights (m) beginning with 10-
degree flow vector and incrementing by 10 degrees clockwise.
BUILDLEN
SrcID (or SrcRange) Dsbl(i), i=l, 36
where:
SrcID
SrcRange
Dsbl
Source identification code.
Range of sources (inclusive) for which building dimensions apply.
Array of direction-specific building lengths (m) beginning with 10
degree flow vector and incrementing by 10 degrees clockwise.
BUILDWID
SrcID (or SrcRange) Dsbw(i), i=l, 36
where:
SrcID
SrcRange
Source identification code.
Range of sources (inclusive) for which building dimensions apply.
A-23
-------
Keyword
Parameters
Dsbw
Array of direction-specific building widths (m) beginning with 10
degree flow vector and incrementing by 10 degrees clockwise.
XBADJ
SrcID (or SrcRange) Xbadj(i), i=l, 36
where:
SrcID
SrcRange
Xbadj(i)
Source identification code.
Range of sources (inclusive) for which XBADJ distances apply.
Array of direction-specific along-wind distances beginning with 10
degree flow vector and incrementing by 10 degrees clockwise.
YBADJ
SrcID (or SrcRange) Ybadj(i), i=l, 36
where:
SrcID
SrcRange
Ybadj(i)
Source identification code.
Range of sources (inclusive) for which YBADJ distances apply.
Array of direction-specific across-wind distances beginning with 10
degree flow vector and incrementing by 10 degrees clockwise.
AREAVERT
SrcID Xv(l) Yv(l) Xv(2) Yv(2) ... Xv(i) Yv(i)
where:
SrcID
Xv(l)
Yv(l)
Xv(i)
Yv(i)
Source identification code.
X-coordinate of the first vertex of an AREAPOLY source (must be the
same as the value of Xs for that source defined on the SO LOCATION
card).
Y-coordinate of the first vertex of an AREAPOLY source (must be the
same as the value ofYs for that source defined on the SO LOCATION
card).
X-coordinate for the ith vertex of an AREAPOLY source.
Y-coordinate for the ith vertex of an AREAPOLY source.
RBARRIER
SrcID Htwall DCLwall (Htwall2 DCLwall2)
where:
SrcID
Htwall
DCLwall
Htwall2
DCLwall2
Source identification code.
Height of the wall (or barrier 1) near roadway (m).
Distance from the roadway centerline to the wall (m).
Height of the second wall (or barrier 2) near roadway (m).
Distance from the roadway centerline to the second wall (m).
RDEPRESS
SrcID Htwall DCLwall Depth Wtop Wbottom
where:
SrcID
Depth
Wtop
Wbottom
Source identification code.
Depth of the depression containing the roadway (m).
Width of the top of the depression containing the roadway (m).
Width of the bottom of the depression containing the roadway (m).
BLPINPUT
(BLPGrpID) Blavgllen Blavgbhgt Blavgbwid Blavglwid Blavgbsep Blavgfprm
where:
BLPGrpID
Blavgllen
Blavgbhgt
Blavgbwid
Blavglwid
Blavgsep
Blavgfprm
Buoyant line group ID following parameters apply to
Average buoyant line length (m)
Average building height (m)
Average building width (m)
Average buoyant line width (m)
Average building separation (m)
Average buoyancy parameter (m4/s3)
A-24
-------
Keyword
Parameters
URBANSRC
For multiple urban areas:
UrbanID SrcID's and/or SrcRng's
For single urban areas:
SrcID's and/or SrcRng's
User may also specify 'ALL' for SrcID's to assign all sources as urban.
where:
UrbanID
SrcID
SrcRange
Specifies the alphanumeric urban ID (up to eight characters).
Specifies which source(s) will be modeled with urban effects.
Specifies a range of sources that will be modeled with urban effects.
EMISFACT
SrcID (or SrcRange) Qflag Qfact(i), i=l,n
where:
SrcID
SrcRange
Qflag
Qfact
Source identification code.
Range of sources (inclusive) for which emission rate factors apply.
Variable emission rate flag:
SEASON for seasonal; MONTH for monthly; HROFDY for
hour-of-dav; WSPEED for wind speed cateaorv; SEASHR for
season-bv-hour; HRDOW for emission rates varv bv hour-of-dav. and
dav-of-week 1M-F. Sat. Sunl; HRDOW7 for emission rates varv bv
hour-of-day, and the seven days of the week [M, Tu, W, Th, F, Sat,
Sunl; SHRDOW for season bv hour-of-dav bv dav-of-week
(M-F.Sat.Sun); SHRDOW7 for season bv hour-of-dav bv dav-of-
week (M.Tu.W.Th.F.SatSun); MHRDOW for month bv hour-of-dav
bv dav-of-week (M-F.Sat.Sun); MHRDOW7 for month bv hour-of-
day by day-of-week (M,Tu,W,Th,F,Sat,Sun).
Array of scalar emission rate factors, for:
SEASON. n=4; MONTH. n=12; HROFDY. n=24;
WSPEED. n=6; SEASHR. n=96; HRDOW. n=72;
HRDOW7. n=168; SHRDOW. n=288; SHRDOW7. n=672;
MHRDOW. n=864; MHRDOW7. n=2016
EMISUNIT
Emifac Emilbl Outlbl
where:
Emifac
Emilbl
Outlbl
Emission rate factor used to adjust units of output (default value is
1.0E06 for CONC for grams to micrograms; default value is 3600 for
grams/sec to grams/m2/hr for deposition).
Label to use for emission units (default is grams/sec).
Label to use for output units; applies to first output type if more than one
output type is generated (default is micrograms/m**3 for
concentration and grams/m**2 for deposition).
RLEMCONV
No parameters or secondary keywords
Changes the expected emission units for the RLINE (Lemis) and RLEINXT
(Rlemis)emissions to grams/hour/link.
CONCUNIT
Emifac Emilbl Conlbl
where:
Emifac
Emission rate factor used to adjust units of output (default value is
1.0E06 for concentration for grams to micrograms).
A-25
-------
Keyword
Parameters
Emilbl
Conlbl
Label to use for emission units (default is grams/sec).
Label to use for concentrations (default is micrograms/m3).
DEPOUNIT
Emifac Emilbl Deplbl
where:
Emifac
Emilbl
Deplbl
Emission rate factor used to adjust units of output for deposition (default
value is 3600 for grams/sec to grams/m2/hr).
Label to use for emission units (default is grams/sec).
Label to use for deposition (default is grams/m2).
PARTDIAM
SrcID (or SrcRange) Pdiam(i), i=l,Npd
where:
SrcID
SrcRange
Pdiam
Source identification code.
Range of sources (inclusive) for which size categories apply.
Array of particle diameters (microns).
MASSFRAX
SrcID (or SrcRange) Phi(i), i=l,Npd
where:
SrcID
SrcRange
Phi
Source identification code.
Range of sources (inclusive) for which mass fractions apply.
Array of mass fractions for each particle size category.
PARTDENS
SrcID (or SrcRange) Pdens(i), i=l,Npd
where:
SrcID
SrcRange
Pdens
Source identification code.
Range of sources (inclusive) for which particle densities apply.
Array of particle densities (g/cm3) for each size category.
METHOD 2
SrcID (or SrcRange) FineMassFraction Dmm
where:
SrcID
FineMassFra
ction
Dmm
Source identification code.
Fraction (between 0 and 1) of particle mass emitted in fine mode, less
than 2.5 microns.
Representative mass mean particle diameter in microns.
GASDEPOS
SrcID (or SrcRange) Da Dw rcl Henry
where:
SrcID
Da
Dw
rcl
Henry
Source identification code.
Diffusivity in air for the pollutant being modeled (cm2/s).
Diffusivity in water for the pollutant being modeled (cm2/s).
Cuticular resistance to uptake by lipids for individual leaves (s/cm).
Henry's Law constant (Pa m3/mol).
N02RATI0
SrcID (or SrcRange) N02Ratio
where:
SrcID
SrcRange
N02Ratio
Source identification code.
Source ID range for specified ratio.
In-stack ratio of NCh/NOx.
HOUREMIS
Emifil SrcID's SrcRange's
where:
Emifil
SrcID's
SrcRange's
Specifies name of the hourly emission rate file.
Discrete source IDs that are included in the hourly emission file.
Source ID ranges that are included in the hourly emission file.
BGSECTOR
StartSectl StartSect2 . . . StartSect/V, where N is < 6
A-26
-------
Keyword
Parameters
where:
StartSectl
StartSect2
Starting direction for the first sector.
Starting direction for the second sector.
StartSect/v'
Starting direction for the last sector.
NOTE: The minimum sector width allowed is 30 dearees. and warning
messages will be issued for sector widths less than 60 degrees.
Sector-varying background concentrations will be selected based on
the flow vector, i.e., the downwind direction, based on the wind
direction specified in the surface meteorological data file.
BACKGRNd
BGflag BGvalue(i), i=l, n (without BGSECTORs)
and/or
HOURLY BGfilnam (BGformat)
or
SECTx BGflag BGvalue(i), i=l, n (with BGSECTORs)
and/or
SECTx HOURLY BGfilnam (BGformat)
where:
SECTx
Applicable sector (x = 1 to 6) defined on the SO BGSECTOR keyword,
if specified.
BGflag
BGvalue
Variable background concentration flag:
ANNUAL for annual; SEASON for seasonal; MONTH for monthlv;
HROFDY for hour-of-dav; WSPEED for wind soeed cateaorv;
SEASHR for season-bv-hour; HRDOW for emission rates varv bv
hour-of-dav. and dav-of-week 1M-F. Sat. Sunl; HRDOW7 for
emission rates vary by hour-of-day, and the seven days of the week
1M. Tu. W. Th. F. Sat. Sunl; SHRDOW for season bv hour-of-dav bv
dav-of-week (M-F.Sat.Sun); SHRDOW7 for season bv hour-of-dav
bv dav-of-week (M.Tu.W.Th.F.Sat.Sun); MHRDOW for month bv
hour-of-dav bv dav-of-week (M-F.Sat.Sun); MHRDOW7 for month
by hour-of-day by day-of-week (M,Tu,W,Th,F,Sat,Sun).
Array of background concentrations; for:
ANNUAL. n=l: SEASON. n=4: MONTH. n=l2:
HROFDY. Ğ=24; WSPEED. n=6: SEASHR. n=96:
HRDOW. Ğ=72; HRDOW7. Ğ=168; SHRDOW. Ğ=288;
SHRDOW7. n=612: MHRDOW. n=864;
MHRDOW7. Ğ=2016
HOURLY
Flag indicating that hourly background concentrations are specified in a
separate data file; data period must match the meteorological data
period being processed; no missing values are allowed in the hourly
file, unless temporally varying background concentrations are also
specified through the BGflag parameter, which are used to substitute
for missing hourly values.
A-27
-------
Keyword
Parameters
BGfilnam
(BGformat)
Filename for hourly background concentrations.
Optional Fortran format of hourly background concentration file; the
default format is FREE format, i.e., comma or space-delimited data
fields (Yr Mn Dy Hr BGvalue). The BGformat parameter must
include open and close parentheses, the date variables must be read as
integers (Fortran I format), and the BGvalue must be read as real
(Fortran F, E, or D format), e.g., '(412,F8.3)'. The year may be
specified as a 2-digit or 4-digit year, and the data period in the
HOURLY background file must match the data period in the
meteorological data files. The BGformat parameter cannot include any
blank spaces, unless the field in enclosed by double quotes.
NOTE: Background concentrations specified on the BACKGRND
keyword are currently assumed to be in units of PPB for NO2 and
SO2, PPM for CO, and UG/M3 for all other pollutants, unless
otherwise specified on the SO BACKUNIT keyword.
Background concentrations can be included with any source group,
including group 'ALL', by including a "SrcID" of
'BACKGROUND' on the SRCGROUP keyword. Note that
background concentrations are automatically included with
group ALL by default; however, background concentrations
can be excluded from group ALL by including
NOBACKGROUND (or NOBACKGRND) on the SRCGROUP
ALL keyword.
BACKUNIt
BGunits
where:
BGunits
Background concentration units, specified as PPB for parts-per-billion,
PPM for parts-per-million. or UG/M3 for 111 icroerams/cubic-meter.
Background concentrations input in units of PPB or PPM are
converted to micrograms/cubic-meter based on reference temperature
(25 C) and pressure (1013.25 mb).
Note: Units of PPB and PPM can onlv be used with the N02. S02.
and CO POLLUTID.
INCLUDED
Incfil
where:
SrcIncFile
Filename for the included source file, up to 200 characters in length;
double quotes (") may be used as delimiters for the filename to allow
for embedded spaces; and quotes don't count toward the limit of 200.
OLMGROUP
OLMGrpID SrcID's SrcRange's
or
ALL
where:
OLMGrpID
SrcID's
Group ID (Grpid = ALL specifies group including all sources).
Discrete source IDs to be included in group.
Source ID ranges to be included in group.
A-28
-------
Keyword
Parameters
SrcRange's
Note: Card mav be repeated with same Groid if more soace is needed
to specify sources.
BLPGROUP
BLPGrpID SrcID's SrcRange's
where:
BLPGrpID
SrcID's
SrcRange's
Buoyant line group ID.
Discrete BUOYLINE source IDs to be included in group.
BUOYLINE source ID ranges to be included in group.
PSDGROUP
PSDGrpID SrcID's SrcRange's
where:
PSDGrpID
SrcID's
SrcRange's
PSD GrpID for PSDCREDIT option, must be one of the following:
INCRCONS - increment-consuming sources,
NONRBASE - non-retired baseline sources, or
RETRBASE - retired (increment-expanding) baseline sources.
Discrete source IDs to be included in group.
Source ID ranges to be included in group.
Note: Card mav be repeated with same PSDGroID if more soace is
needed to specify sources
HBPSRCID
SrcID's and/or SrcRange's or ALL
where:
SrcID's
SrcRange's
ALL
Discrete source IDs to be included.
Source ID ranges to be included.
Note: Card mav be repeated if more space is needed to specifv sources.
Includes all sources modeled that are source type POINT, POINTHOR,
and POINTCAP.
ARCFTSRC
SrcID's and/or SrcRange's or ALL
where:
SrcID's
SrcRange's
ALL
Discrete source IDs to be included.
Source ID ranges to be included.
Note: Card mav be repeated if more space is needed to specifV sources.
Applies aircraft plume rise option (ARCFTOPT) to all AREA and
VOLUME source types modeled.
SRCGROUP
SrcGrpID SrcID's SrcRange's
where:
SrcGrpID
SrcID's
Group ID (Grpid = ALL specifies group including all sources).
Discrete source IDs to be included in group; a "SrcID" of
'BACKGROUND' (or 'BACKGRND') can be used to include
background concentrations, based on the BACKGRND keyword.
Also note that background concentrations are automatically included
with group ALL; however, background concentrations can be
A-29
-------
Keyword
Parameters
SrcRange's
excluded from group ALL by specifying 'NOBACKGROUND' on the
SRCGROUP ALL keyword.
Source ID ranges to be included in group.
Note: Card mav be repeated with same Grpid if more space is needed to
specify sources.
BLPINPUT
Blavgblen Blavgbhgt Blavgbwid Blavglwid Blavgbsep Blavgfprm
where:
Blavgblen
Blavgbhgt
Blavgbwid
Blavglwid
Blavgbsep
Blavgfprm
Average building length (m).
Average building height (m).
Average building width (m).
Average line source width (m) (of the individual lines).
Average building separation (m) (between the individual lines).
Average buoyancy parameter (m4/s3).
Table A-5. Description of Receptor Pathway Keywords
RE Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of RECEPTOR pathway inputs
ELEVUNIT
O-N
Defines input units for receptor elevations (defaults to meters), must be first
keyword after RE STARTING if used.
GRIDCART
O1 -R
Defines a Cartesian grid receptor network
GRIDPOLR
O1 -R
Defines a polar receptor network
DISCCART
O1 -R
Defines the discretely placed receptor locations referenced to a Cartesian
system
DISCPOLR
O1 -R
Defines the discretely placed receptor locations referenced to a polar system
EVALCART
O1 -R
Defines discrete Cartesian receptor locations for use with EVALFILE output
option
INCLUDED
0 - R
Identifies an external file containing receptor locations to be included in the
inputs
FINISHED
M-N
Identifies the end of RECEPTOR pathway inputs
1) At least one of the following must be present: GRIDCART, GRIDPOLR, DISCCART,
DISCPOLR, or EVALCART, unless the INCLUDED keyword is used to include receptor inputs
from an external file. Multiple receptor networks can be specified in a single run, including
both Cartesian and polar.
A-30
-------
Table A-6. Description of Receptor Pathway Keywords and Parameters
Keyword
Parameters
ELEVUNIT
METERS or FEET
where:
METERS
Specifies input units for receptor elevations of meters.
FEET
Specifies input units for receptor elevations of feet.
Note: This keyword applies to receptor elevations only.
GRIDCART
Netid STA
XYINC Xinit Xnum Xdelta Yinit YnumYdelta
or XPNTS Gridxl Gridx2 Gridx3 .... GridxN. and
YPNTS Gridvl Gridv2 Gridv3 .... GridvN
ELEV
Row Zelev 1 Zelev2 Zelev3 ...ZelevN
HILL
Row Zhill 1 Zhill2 Zhill3 ... ZhillN
FLAG Row Zflael Zflae2 Zflae3 ...ZflaeN
END
where:
Netid
Receptor network identification code (up to eight alphanumeric
characters).
STA
Indicates STArt of GRIDCART subpathwav. repeat for each new Netid.
XYINC
Keyword identifying grid network generated from x and y increments.
Xinit
Starting local x-axis grid location in meters.
Xnum
Number of x-axis receptors.
Xdelta
Spacing in meters between x-axis receptors.
Yinit
Starting local y-axis grid location in meters.
Ynum
Number of y-axis receptors.
Ydelta
Spacing in meters between y-axis receptors.
XPNTS
Keyword identifying grid network defined by series of x and y
coordinates.
Gridxl
Value of first x-coordinate for Cartesian grid.
GridxN
Value of'nth' x-coordinate for Cartesian grid.
YPNTS
Keyword identifying grid network defined by series of x and y
coordinates.
Gridyl
Value of first y-coordinate for Cartesian grid.
GridyN
Value of'nth' y-coordinate for Cartesian grid.
ELEV
Keyword to specify that receptor elevations follow.
Row
Indicates which row (y-coordinate fixed) is being input.
Zelev
An array of receptor terrain elevations for a particular Row.
HILL
Keyword to specify that hill height scales follow.
Row
Indicates which row (y-coordinate fixed) is being input.
Zhill
An array of hill height scales for a particular Row.
FLAG
Keyword to specify that flagpole receptor heights follow.
Row
Indicates which row (y-coordinate fixed) is being input.
Zflag
An array of receptor heights above local terrain elevation for a particular
Row (flagpole receptors).
END
Indicates END of GRIDCART subDathwav. repeat for each new Netid.
GRIDPOLR
Netid STA
ORIG Xinit Yinit.
or ORIG Srcid
A-31
-------
Keyword
Parameters
DIST Rinsl Rins2 Rins3 ... RinsN
DDIR Dirl Dir2 Dir3 ... DirN,
or GDIR Dirnum Dirini Dirinc
ELEV Dir Zelevl Zelev2 Zelev3 ... ZelevN
HILL Dir Zhilll Zhill2 Zhill3 ... ZhillN
FLAG Dir Zflagl Zflag2 Zflag3 ... ZflagN
END
where:
Netid
Receptor network identification code (up to eight alphanumeric
characters).
STA
Indicates STArt of GRIDPOLR subpathway, repeat for each new Netid
ORIG
Optional keyword to specify the origin of the polar network (assumed to
be at x=0, y=0 if omitted).
Xinit
local x-coordinate for origin of polar network (m).
Yinit
local y-coordinate for origin of polar network (m).
Srcid
Source ID of source used as origin of polar network.
DIST
Keyword to specify distances for the polar network.
Ringl
Distance to the first ring of polar coordinates (m).
RingN
Distance to the 'nth' ring of polar coordinates (m).
DDIR
Keyword to specify discrete direction radials for the polar network.
Dirl
First direction radial in degrees (1 to 360).
DirN
The 'nth' direction radial in degrees (1 to 360).
GDIR
Keyword to specify generated direction radials for the polar network.
Dirnum
Number of directions used to define the polar system.
Dirini
Starting direction of the polar system.
Dirinc
Increment (in degrees) for defining directions.
ELEV
Keyword to specify that receptor elevations follow.
Dir
Indicates which direction is being input.
Zelev
An array of receptor terrain elevations for a particular direction radial.
HILL
Keyword to specify that hill height scales follow.
Row
Indicates which row (y-coordinate fixed) is being input.
Zhill
An array of hill height scales for a particular Row Keyword to specify that
flagpole receptor heights follow.
FLAG
Keyword to specify that flagpole receptor heights follow.
Dir
Indicates which direction or direction number is being input.
Zflag
An array of receptor heights above local terrain elevation for a particular
direction (flagpole receptors).
END
Indicates END of GRIDPOLR subpathwav. repeat for each new Netid.
DISCCART
Xcoord Ycoord (Zelev Zhill) (Zflag)
where:
Xcoord
local x-coordinate for discrete receptor location (m).
Ycoord
local y-coordinate for discrete receptor location (m).
(Zelev)
Elevation above sea level for discrete receptor location (optional), used
onlv for ELEV terrain.
(Zhill)
Hill height scale (optional), used onlv for ELEV terrain.
(Zflag)
Receptor height (flagpole) above local terrain (optional), used only with
FLAGPOLE kevword.
DISCPOLR
Srcid Dist Direct (Zelev Zhill) (Zflag)
A-32
-------
Keyword
Parameters
where:
Srcid
Dist
Direct
(Zelev)
(Zhill)
(Zflag)
Specifies source identification for which discrete polar receptor locations
apply (used to define the origin for the discrete polar receptor).
Downwind distance to receptor location (m).
Direction to receptor location, in degrees clockwise from North.
Elevation above sea level for receptor location (optional), used only for
ELEV terrain.
Hill height scale (optional).
Receptor height (flagpole) above local terrain (optional), used only with
FLAGPOLE keyword.
EVALCART
Xcoord Ycoord Zelev Zhill Zflag Arcid (Name)
where:
Xcoord
Ycoord
Zelev
Zhill
Zflag
Arcid
(Name)
Local x-coordinate for discrete receptor location (m).
Local y-coordinate for discrete receptor location (m).
Elevation above sea level for discrete receptor location, used only for
ELEV terrain.
Hill height scale (m). used onlv for ELEV terrain.
Receptor height (flagpole) above local terrain, used only with
FLAGPOLE kevword.
Receptor arc ID used to group receptors along an arc or other grouping
(up to eight characters).
Optional name for receptor (up to eight characters).
INCLUDED
RecIncFile
where:
RecIncFile
Identifies the filename for the included receptor file, up to 200 characters
in length; double quotes (") may be used as delimiters for the filename
to allow for embedded spaces; quotes don't count toward the limit of
200.
A-33
-------
Table A-7. Description of Meteorology Pathway Keywords
ME Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of METEOROLOGY pathway inputs
SURFFILE
M-N
Describes input meteorological surface data file
PROFFILE
M-N
Describes input meteorological profile data file
SURFDATA
M-N
Describes surface meteorological station
UAIRDATA
M-N
Describes upper air meteorological station
SITEDATA
O-N
Describes on-site meteorological station
PROFBASE
M-N
Specifies the base elevation for the potential temperature profile
STARTEND
O-N
Specifies start and end dates to be read from input meteorological data file
(default is to read entire file)
DAYRANGE
0 - R
Specifies days or ranges of days to process (default is to process all data)
NOSA
O-N
Specifies to set oe to missing for all hours in profile data file
NOSACO
O-N
Specifies to set oe to missing for convective hours only in profile data file
NOSAST
O-N
Specifies to set oe to missing for stable hours only in profile data file
NOSW
O-N
Specifies to set ow to missing for all hours in profile data file
NOSWCO
O-N
Specifies to set ow to missing for convective hours only in profile data file
NOSWST
O-N
Specifies to set ow to missing for stable hours only in profile data file
NOTURB
O-N
Specifies to set oe and ow to missing for all hours in profile data file
NOTURBCO
O-N
Specifies to set oe and ow to missing for convective hours only in profile
data file
NOTURB ST
O-N
Specifies to set oe and ow to missing for stable hours only in profile data
file
SCIMBYHR
O-N
Specifies the parameters for the SCIM (Sampled Chronological Input
Model) option (see CO MODELOPT)
WDROTATE
O-N
May be used to correct for alignment problems of wind direction
measurements, or to convert wind direction from to flow vector
WINDCATS
O-N
Input upper bounds of wind speed categories, five values input - sixth
category is assumed to have no upper bound (used for WSPEED option on
the EMISFACT keyword)
FINISHED
M-N
Identifies the end of METEOROLOGY pathway inputs
A-34
-------
Table A-8. Description of Meteorology Pathway Keywords and Parameters
Keyword
Parameters
SURFFILE
Sfcfil
where:
Sfcfil
Specify filename for surface meteorological input file
Note: FREE format is used for all SURFFILE reads beainnina
with version 09292.
PROFFILE
Profil
where:
Profil
Specify filename for profile meteorological input file
Note: FREE format is used for all PROFFILE reads beainnina
with version 09292.
SURFDATA
Stanum Year (Name) (Xcoord Ycoord)
where:
Stanum
Year
(Name)
(Xcoord)
(Y coord)
Station number, e.g., 5-digit WBAN number for NWS station.
Year of data being processed (four digits).
Station name (optional).
x-coordinate of station location (m) (optional).
y-coordinate of station location (m) (optional).
UAIRDATA
Stanum Year (Name) (Xcoord Ycoord)
where:
Stanum
Year
(Name)
(Xcoord)
(Y coord)
Station number, e.g., 5-digit WBAN number for NWS station.
Year of data being processed (four digits).
Station name (optional).
x-coordinate of station location (m) (optional).
y-coordinate of station location (m) (optional).
SITEDATA
Stanum Year (Name) (Xcoord Ycoord)
where:
Stanum
Year
(Name)
(Xcoord)
(Y coord)
Station number for on-site meteorological data station.
Year of data being processed (four digits).
Station name (optional).
x-coordinate of station location (m) (optional).
y-coordinate of station location (m) (optional).
PROFBASE
BaseElev (Units)
where:
BaseElev
(Units)
Base elevation (above MSL) for the potential temperature profile.
Units of BaseElev: METERS or FEET (default is METERS).
STARTEND
Strtyr Strtmn Strtdy (Strthr) Endyr Endmn Enddy (Endhr)
where:
Strtyr
Strtmn
Strtdy
(Strthr)
Endyr
Endmn
Enddy
(Endhr)
Year of first record to be read.
Month of first record to be read.
Day of first record to be read.
Hour of first record to be read (optional).
Year of last record to be read.
Month of last record to be read.
Day of last record to be read.
Hour of last record to be read (optional).
A-35
-------
Keyword
Parameters
Note: File read begins with hour 1 of the start date and ends with
hour 24 of the end date if Stahr and Endhr are omitted.
DAYRANGE
Range 1 Range2 Range3 ... RangeiV
where:
Range 1
Rangc/v'
First range of days to process, either as individual day (XXX) or as
range (XXX-YYY); days may be input as Julian dates (XXX) or
as month and day (XX/YY).
The 'N-th' range of days to process.
NUMYEARS
NumYrs
where:
NumYrs
Specifies the number of years of meteorological data being
processed for purposes of allocating array storage for the OU
MAXDCONT option. A default value of 5 years is assumed if the
optional NUMYEARS keyword is omitted.
NOSA
or
NOSACO
or
NOSAST
or
NOSW
or
NOSWCO
or
NOSWST
or
NOTURB
or
NOTURBCO
or
NOTURB ST
No parameters or secondary keywords
SCIMBYHR
NRegStart NReglnt (SfcFilnam PflFilnam)
where:
NReg Start
NReglnt
(SfcFilnam)
(PflFilnam)
Specifies the first hour to be sampled with the SCIM option;
required to have a value from 1 to 24.
Specifies the sampling interval, in hours.
Optional output file name to list the surface meteorological data for
the sampled hours.
Optional output file name to list the profile meteorological data for
the sampled hours.
WDROTATE
Rotang
where:
Rotang
Specifies angle (in degrees) to rotate wind direction measurements
to correct for alignment problems; value of Rotang is subtracted
from WD measurements, i.e., rotation is counterclockwise.
WINDCATS
Wsl Ws2 Ws3 Ws4 Ws5
A-36
-------
Keyword
Parameters
where:
Wsl
Upper bound of first wind speed category (m/s).
Ws2
Upper bound of second wind speed category (m/s).
Ws3
Upper bound of third wind speed category (m/s).
Ws4
Upper bound of fourth wind speed category (m/s).
Ws5
Upper bound of fifth wind speed category (m/s).
(sixth category is assumed to have no upper bound).
Table A-9. Description of Event Pathways and Keywords
EV Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of EVENT pathway inputs
EVENTPER
M-R
Describes data and averaging period for an event
EVENTLOC
M-R
Describes receptor location for an event
INCLUDED
0 - R
Identifies an external file containing EVENT data to be included in the
inputs
FINISHED
M-N
Identifies the end of EVENT pathway inputs
A-37
-------
Table A-10. Description of Event Pathway Keywords and Parameters
Keyword
Parameters
EVENTPER
Evname Aveper Grpid Date Cone
where:
Name
Grpid
Aveper
Date
Cone
Specify name of event to be processed (e.g., H002H24ALL), (up to
ten alphanumeric characters).
Specify source group ID for event.
Specify averaging period for event.
Specify data period for event (ending YYMMDDHH for averaging
period).
Specifies the concentration value generated during the initial non-
EVENT processing.
EVENTLOC
Evname XR= Xr YR= Yr (Zelev Zhill) (Zflas)
or
RNG= Rna DIR= Dir (Zelev Zhill) (Zflas)
where:
Evname
XR=
YR=
RNG=
DIR=
(Zelev)
(Zhill)
(Zflag)
Specify name of event to be processed (e.g., H002H24ALL), (up to
ten alphanumeric characters).
X-coordinate for event (discrete Cartesian receptor).
Y-coordinate for event (discrete Cartesian receptor).
Distance range for event (discrete polar receptor).
Radial direction for event (discrete polar receptor).
Terrain elevation for event (optional).
Hill height scale (optional).
Receptor height above ground for event (optional).
INCLUDED
EventlncFile
where:
EventlncFile
Identifies the filename for the included EVENT file, up to 200
characters in length; double quotes (") may be used as delimiters for
the filename to allow for embedded spaces; and quotes don't count
toward the limit of 200.
Note: EVENT locations can be input as either discrete Cartesian receptors (XR=. YR=) or as
discrete polar receptors (RNG=. DIR=). Events that are specified in the file generated by
the AERMOD model (CO EVENTFIL card) are always given as discrete Cartesian
coordinates. Discrete polar receptors are assumed to be relative to an origin of (0,0).
A-38
-------
Table A-ll. Description of Output Pathway Keywords
OU Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of OUTPUT pathway inputs
RECTABLE
0 - R
Option to specify value(s) by receptor for output
MAXTABLE
0 - R
Option to summarize the overall maximum values
DAYTABLE
O-N
Option to print summaries for each averaging period for each day processed.
MAXIFILE
0 - R
Option to list events exceeding a threshold value to file (if CO
EVENTFIL option is used, these events are included in the input file
generated for the EVENT model).
POSTFILE1
0 - R
Option to write results to a mass storage file for postprocessing.
PLOTFILE1
0 - R
Option to write certain results to a storage file suitable for
input to plotting routines
TOXXFILE
0 - R
Option to write results to a storage file suitable for input to the
TOXX model component of TOXST or the RISK
RANKFILE
0 - R
Option to output file of ranked values for Q-Q plots (must be used
with the MAXTABLE keyword)
EVALFILE
0 - R
Option to output file of normalized arc maxima from EVALCART
receptors for model evaluation studies
SEASONHR
0 - R
Option to output results by season and hour-of-day
MAXDAILY
0 - R
Option to output file of daily maximum 1-hour values for each day
processed; only applicable for 1-hour NO2 and 1-hour SO2 NAAQS
MXDYBYYR
0 - R
Option to output file of daily maximum 1-hour values by year, for each year
processed; only applicable for 1-hour NO2 and 1-hour SO2 NAAQS
MAXDCONT
0 - R
Option to output contributions of each source group to ranked values
averaged across years for a reference source group, paired in time and space;
only applicable for 24-hour PM2.5 1-hour NO2, and 1-hour SO2 NAAQS
SUMMFILE
O-N
Option to output summary of high ranked values to separate file
FILEFORM
O-N
Specify fixed or exponential format for output results files
NOHEADER
O-N
Option to suppress file headers for output file options, e.g., POSTFILE,
PLOTFILE, MAXDCONT, etc.
EVENTOUT
M-N
Specifies the level of output information provided for EVENT
Processing [EVENT Only]
FINISHED
M-N
Identifies the end of OUTPUT pathway inputs
1) POSTFILE is used to output concurrent concentration values for particular source groups and
averaging times across the receptor network suitable for postprocessing. PLOTFILE is used to
output specific design values, such as second high concentrations, across the receptor network,
suitable for plotting concentration contours.
A-39
-------
Table A-12. Description of Output Pathway Keywords and Parameters
Keyword
Parameters
RECTABLE
Aveoer FIRST SECOND . . . SIXTH . . . TENTH and/or
Aveper 1ST 2ND . . . 6TH . . . 10TH and/or
Aveper J_ 2 ... 6 ... 10 . . . N 999
where:
Aveper
FIRST
Averaging period to summarize with high values (keyword
ALLAVE specifies all short-term averaaina periods).
Select summaries of FIRST highest values bv receptor.
SECOND
SIXTH
Select summaries of SECOND hiahest values bv receptor.
Select summaries of SIXTH hiahest values bv receptor.
1ST
2ND
6TH
E
Select summaries of 1ST highest values by receptor.
Select summaries of 2ND hiahest values bv receptor.
Select summaries of 6TH highest values by receptor.
Select summaries of /v'-th highest values by receptor (up to 999-th
highest values).
Note:
If two parameters are input separated by a dash (e.g.
FIRST-THIRD or 4-12). then summaries of all hiah
ranked values within that range (inclusive) are provided.
If the CO EVENTFIL keyword is exercised, then the
events generated by the RECTABLE keyword are included
in the input file for EVENT model.
The range of ranks specified on the RECTABLE keyword
(but not the individual ranks specified) also determines
the range of ranks that may be considered with the
MAXDCONT option.
MAXTABLE
Aveper Maxnum
where:
Aveper
Maxnum
Averaging period to summarize with overall maximum values
(keyword ALLAVE specifies all averaging periods).
Specifies number of overall maximum values to summarize .
DAYTABLE
Avperl Avper2 Avper3 . . .
where:
Avperl
Averaging period, e.g., 24 for 24-hr averages, to summarize with
values by receptor for each day of data processed (keyword
ALLAVE for first parameter specifies all averaging periods).
MAXIFILE
Aveper GrpID Thresh Filnam (Funit)
where:
Aveper
GrpID
Thresh
Filnam
Funit
Specifies averaging period for list of values equal to or exceeding a
threshold value.
Specifies source group to be output to file.
Threshold value (e.g., NAAQS) for list of exceedances.
Name of disk file to store maximum values.
Optional parameter to specify the file unit.
A-40
-------
Keyword
Parameters
Note:
If the CO EVENTFIL keyword is exercised, then the events
generated by the MAXIFILE keyword are included in the input
file for EVENT processing.
POSTFILE
Aveper GrpID Format Filnam (Funit)
where:
Aveper
GrpID
Format
Filnam
Funit
Specifies averaging period to be output to file, e.g., 24 for 24-hr
averaaes. PERIOD for period averaaes.
Specifies source group to be output to file.
Specifies format of file, either UNFORM for unformatted files or
PLOT for formatted files for plotting.
Specifies filename for output file.
Optional parameter to specify the file unit.
PLOTFILE
Aveper GrpID Hivalu Filnam (Funit) (Short-Term values)
Aveper GrpID Filnam (Funit) (PERIOD or ANNUAL averages)
where:
Aveper
GrpID
Hivalu
Filnam
Funit
Specifies averaging period to be output to file, e.g., 24 for 24-hr
averaaes. PERIOD for period averaaes. etc.
Specifies source group to be output to file.
Specifies rank to be included in hiah value summarv (e.a.. FIRST.
SECOND. 1ST. 2ND. etc.) to be output to file (the rank must be
included on the RECTABLE card).
Specifies filename for output file.
Optional parameter to specify the file unit.
TOXXFILE
Aveper Cutoff Filnam (Funit)
where:
Aveper
Cutoff
Filnam
Funit
Specifies averaging period to be output to file, e.g., ! for 1-hr
averages.
Specifies cutoff (threshold) value in g/m3 for outputting results for
AERMOD model.
Specifies filename for output file.
Optional parameter to specify the file unit.
RANKFILE
Aveper Hinum Filnam (Funit)
where:
Aveper
Hinum
Filnam
Funit
Specifies averaging period to be output to file, e.g., 24 for 24-hr
averages.
Specifies the number of high values to be ranked.
Specifies filename for output file.
Optional parameter to specify the file unit.
EVALFILE
SrcID Filnam (Funit)
where:
SrcID
Filnam
Funit
Specifies the source ID to be output to file.
Specifies filename for output file.
Optional parameter to specify the file unit.
SEASONHR
GrpID FileName (FileUnit)
where:
GrpID
FileName
Specifies the source group ID to be output to file.
Specifies filename for output file.
A-41
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Keyword
Parameters
(FileUnit)
Optional parameter to specify file unit.
MAXDAILY
GrpID FileName (FileUnit)
where:
GrpID
FileName
(FileUnit)
Specifies the source group ID to be output to file.
Specifies filename for output file.
Optional parameter to specify file unit.
MXDYBYYR
GrpID FileName (FileUnit)
where:
GrpID
FileName
(FileUnit)
Specifies the source group ID to be output to file.
Specifies filename for output file.
Optional parameter to specify file unit.
MAXDCONT
GrpID UpperRank LowerRank FileName (FileUnit)
or
GrpID UpperRank THRESH Thresh Value FileName (FileUnit)
where:
GrpID
UpperRank
LowerRank
THRESH
Thresh Value
FileName
(FileUnit)
Specifies the source group ID to be output to file.
Upper bound of ranks to evaluate for contributions.
Lower bound of ranks to evaluate for contributions (note that lower
rank refers to lower concentrations and higher rank refers to
higher concentrations).
NOTE: The UpperRank and LowerRank values must be within
the range of ranks specified on the RECTABLE keyword.
AERMOD will analyze each rank within the range, regardless
of whether the rank is specified explicitly on the RECTABLE
keyword.
Indicates that a threshold concentration (ThreshValue) will be
specified as a limit on the lower bound rank to process.
Lower threshold value for evaluating contributions; processing will
stop after the first ranked value that is below Thresh Value
NOTE: The Thresh Value analvsis will be limited to the range
of ranks specified on the RECTABLE keyword (but not the
individual ranks that are specified). A warning message is
generated if the Thresh Value is not reached within the range of
ranks analyzed.
Specifies filename for output file.
Optional parameter to specify file unit.
Note:
The range of ranks specified on the RECTABLE keyword
(but not the individual ranks specified) also determines
the range of ranks that may be considered with the
MAXDCONT option, even with the THRESH option.
SUMMFILE
SummF ileN ame
where:
SummF ileN ame
Specifies filename of output summary file
FILEFORM
EXP or FIX
A-42
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Keyword
Parameters
where:
EXP
FIX
Specifies that the output results files will use EXPonential-
formatted values.
Specifies that the output results files will use FIXed-formatted
values (fixed-formatted values will be used if FILEFORM is
omitted).
NOHEADER
FileTypel FileType2 FileType3 . . . FileTypeiV
or
ALL
where:
FilcTvpc/v'
ALL
Specifies the output file type(s) for which header records will be
suppressed; includes the following file types:
POSTFILE, PLOTFILE, MAXIFILE, RANKFILE,
SEASONHR, MAXDAILY, MXDYBYYR, and MAXDCONT.
Specifies that header records will be suppressed for ALL applicable
output file types.
EVENTOUT
SOCONT or DETAIL TEVENT Onlvl
where:
SOCONT
DETAIL
Provide source contribution information only in the event output.
Include hourly concentrations for each source and hourly
meteorological data in the event output
A-43
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APPENDIX B. Explanation of error message codes
B.l Introduction
Prior to AERMOD beginning the intensive processing to calculate predicted values specified by the
user (e.g., concentrations, deposition), AERMOD runs a series of checks on the input control file to identify
issues that would prevent AERMOD from completing successfully. Some of these checks include the control
file structure and syntax, proper use or use of undefined keywords or parameters, missing required keywords,
and conflicting options. Also, a great deal of effort has been made to eliminate the possibility of run time
errors, such as "divide by zero" and to identify questionable input data.
Error messages are reported to the user in two ways. A summary of messages is provided in the
main output result file. The user can also request a detailed message file.
Message Summary: Whether the user selects a detailed message file or not, the AERMOD model
outputs a summary of messages within the output result file. This message table gives the number of
messages of each type, together with a detailed list of all the fatal errors and warning messages. During setup
processing, if no errors or warnings are generated, then the model simply reports to the user that "SETUP
Finishes Successfully."
Detailed Message File: The AERMOD model provides the option of saving a detailed list of all
messages generated by the model in a separate output file. The user can select this option by specifying the
keyword "ERRORFIL" followed by a filename inside the COntrol pathway. For example, the following
statements will save all the error messages to an ASCII text file named "errormsg.out":
CO STARTING
ERRORFIL errormsg.out
CO FINISHED
B-l
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B.2 Output message summary
There are two message summaries provided in the standard output file of the AERMOD model. The
first one is located after the echo of input control file options and before the input data summary. This
summary will take one of two forms, depending on whether any fatal error or non-fatal warning messages
were generated and depending on whether the option to RUN or NOT to run was selected on the CO
RUNORNOT card. If there are no errors or warnings generated during the setup processing, and the RUN
option was selected, then the model simply reports that "SETUP Finishes Successfully." If any fatal errors or
warning messages were generated during the setup processing or if the option NOT to run was selected, then
a more detailed summary is provided. This summary provides a message count for each type of message and
a detailed listing of each fatal error and warning message generated. The second message summary table is
located at the very end of the standard output result file, and it sums up the messages generated by the
complete model run - both setup processing and run-time processing. An example of a setup processing
message summary is shown in Figure B-l.
*** Message Summary For The AERMOD Model Setup ***
Summary of Total Messages
A Total of 0 Fatal Error Message(s)
A Total of 0 Warning Message(s)
A Total of 0 Information Message(s)
******** FATAL ERROR MESSAGES ********
* * * NONE * * *
******** WARNING MESSAGES ********
* * * NONE * * *
***********************************
*** SETUP Finishes Successfully ***
Figure B-l. Example of an AERMOD Message Summary
B-2
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B.3 Description of the message layout
Three types of messages can be produced by the model during the processing of input control file
commands and during model calculations. These are described briefly below:
Errors that will halt any further processing, except to identify additional error conditions
(type E);
Warnings that do not halt processing but indicate possible errors or suspect conditions
(type W); and
Informational messages that may be of interest to the user but have no direct bearing on
the validity of the results (type I).
The messages have a consistent structure which contains the pathway ID, indicating which pathway
the messages are generated from; the message type followed by a three-digit message number; the line
number of the input control file command file for setup messages (or the meteorology hour number for
runtime messages); the name of the module (e.g., the subroutine name) from which the message is generated;
a detailed message corresponding to the message code; and an 8-character simple hint to help the user spot
the possible source of the problem.
The following is an example of a detailed message generated from the CO pathway:
CO E1008 EXPATH: Invalid Pathway Specified. The Troubled Pathway is FF
The message syntax is explained in more detail below (values in parentheses give the column numbers
within the message line for each element):
B-3
-------
PW Txxx LLLL imnnnmm: MESSAGE Hints
Hints to help you determine the
nature of errors (keyword, pathway
where the error occurs, ... etc.)
(73:80)
Detailed message for th:
;ode (2:
'1)
Name of the code module from which the
message is generated (14:19)
The line number of the input runstream
image file where the message occurs; If
message occurs in runtime operation, the
hour number of the meteorology file is
given (9:12)
Numeric message code (a 3-digit number)
Message type (E, W, I) (4:4)
Pathway ID (CO, SO, RE, ME, EV, or OU) (1:2) oi
MX for meteorological data extraction, or CN
for calculation messages
If an error occurs during processing of an included file (either SO INCLUDED or RE INCLUDED),
the line number will represent the line number of the included file. The line number of the control file is
saved before processing the included data, and then restored when processing returns to the main control file.
The three message types are identified with the letters E (for errors), W (for warnings), and I (for
informational messages).
B-4
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APPENDIX C. Description of file formats
C.l AERMET meteorological data
Two files are produced for input to the AERMOD dispersion model by the AERMET meteorological
preprocessor. The surface OUTPUT contains observed and calculated surface variables, one record per hour.
The PROFILE file contains the observations made at each level of an on-site tower, or the one level
observations taken from NWS data, one record per level per hour. The contents and format of each of these
files is described below:
SURFACE OUTPUT
Header record:
READQ latitude, longitude, UA identifier, SF identifier, OS identifier, Version date, AERMETflags
FORMAT (2(2X,A8), 8X,' UA ID: ',A8,' SF ID: ',A8,' OS ID: ',A8, T85, 'VERSION:', A6 )
where
latitude =
UA identifier
SF identifier
OS identifier
Version date
AERMET flags
latitude specified in Stage 1 for primary surface station
= longitude specified in Stage 1 for primary surface station
= station identifier for upper air data; usually the WBAN number used
to extract the data from an archive data set
= station identifier for hourly surface observations; usually the
WBAN number used in extracting the data
= site-specific identifier
= AERMET version date; this date also appears in the banner on
each page of the summary reports
= One or more of the following flags may be included in the header
record after the version date, based on either the source of the data
or option(s) used in AERMET to process the data for input to
AERMOD: CCVR Sub, TEMP Sub, THRESH1MIN speed,
Adjust_u*, MMIF version, BULKRN, and COARE, where speed is
the threshold wind speed and version is the MMIF version used.
Refer to the AERMET User's Guide (EPA, 2024e) for information
on each of these flags.
Note 1: The 'cc_ID:' fields in the FORMAT statement above where cc can be UA for
upper air, SF for surface, and OS for onsite or site-specific, include two spaces before the
2-character pathway ID and one space after the colon.
Note 2: The FORMAT statement above will read the header record through the version
date. One or more flags may follow the version date to identify either the data source or
option(s) used to preprocess the data with AERMET for input to AERMOD. The
FORMAT statement will need to be revised with additional terms to read beyond the
version date to retrieve the flags from the header record.
C-l
-------
Data records:
READ() year, month, day, jday, hour, H,u* ,w*, VPTG, Zic, Zim, L, z0 , B0 , r, Ws, Wd, zref,
temp, ztemp, ipcode, pamt, rh, pres, ccvr, WSADJ
FORMAT (3(12,IX), 13,IX, 12,IX, F6.1,1X, 3(F6.3,1X), 2(F5.0,1X), F8.1,1X, F7.4,1X,
2(F6.2,1X), F7.2,1X, F5.0, 3(1X,F6.1), IX,15, 1X,F6.2, 2(1X, F6.0), IX, 15, IX,
A7)
where j day = Julian day
H = sensible heat flux (W/m2)
u * = surface friction velocity (m/s)
w * = convective velocity scale (m/s)
VPTG = vertical potential temperature gradient above Zic (K/m)
Zic = height of convectively-generated boundary layer (m)
Zim = height of mechanically-generated boundary layer (m)
L = Monin-Obukhov length (m)
zo = surface roughness length (m)
Bo = Bowen ratio
r = Albedo
Ws = reference wind speed (m/s)
Wd = reference wind direction (degrees)
Zref = reference height for wind (m)
temp = reference temperature (K)
ztemp = reference height for temperature (m)
ipcode = precipitation type code (0=none, 11 =liquid, 22=frozen,
99=missing)
pamt = precipitation amount (mm/hr)
rh = relative humidity (percent)
pres = station pressure (mb)
ccvr = cloud cover (tenths)
WSADJ = wind speed adjustment and data source flag
When site-specific data are included in the data base, the definition of the reference height wind
speed and direction are subject to the following restrictions:
the wind speed, Ws, must be greater than or equal to the site-specific data threshold wind
speed;
the measurement height must be at or above 7*zo, where zo is the surface roughness length;
the height must be less than or equal to 100 meters;
C-2
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If AERMET is run only with NWS data, i.e., no site-specific data are in the data base, then the
restrictions above do not apply and the reference winds are taken to be the NWS winds independent of the
height at which the winds were measured.
Ambient air temperature is subject to a similar, but less restrictive, selection process:
the measurement height must be above zo; and
the height must be less than or equal to 100 meters.
The sensible heat flux, Bowen ratio and albedo are not used by AERMOD, but are passed through by
AERMET for information purposes only.
PROFILE OUTPUT
READ() year, month, day, hour, height, top, WDnn, WSnn, TTnn, SAnn, SWnn
FORMAT (4(12,IX), F7.1,1X, II,IX, F7.1,1X, F8.2,1X, F8.2,1X, F8.2,1X, F8.2)
where, height = measurement height (m)
C.2 Threshold violation files (MAXIFILE option)
The OU MAXIFILE card for the AERMOD model allows the user the option to generate a file or
files of threshold violations for specific source group and averaging period combinations. The file consists of
several header records, each identified with an asterisk (*) in column one. The header information includes
the model name and version number, the first line of the title information for the run, the list of modeling
option keywords applicable to the results, the averaging period and source group included in the file, and the
threshold value. Any value equal to or exceeding the threshold value will be included in the file. The header
also includes the format used for writing the data records, and column headers for the variables included in
the file. The variables provided on each data record include the averaging period, the source group ID, the
date (YYMMDDHH) for the end of averaging period, the X and Y coordinates of the receptor location,
WDĞĞ
WS nn
TTnn
SA nn
SWnn
top
1, if this is the last (highest) level for this hour, or 0 otherwise
wind direction at the current level (degrees)
wind speed at the current level (m/s)
temperature at the current level (°C)
oe (degrees)
aw (m/s)
C-3
-------
receptor terrain elevation, hill height scale, flagpole receptor height, and the concentration value that violated
the threshold. The following example from a threshold file identifies the contents of the MAXIFILE:
*
AERMOD (
15181) : A Simple Example Problem for the
AERMOD-PRIME Model
06/09/16
*
AERMET (
15181) :
17:03:34
*
MODELING
OPTIONS USED:
NonDFAULT CONC FLAT
RURAL
*
MAXI-FILE FOR
3-HR VALUES >= A THRESHOLD
OF 50.00
*
FOR SOURCE GROUP: ALL
*
FORMAT: (IX,I 3
IX,A8,IX,18.8,2(1X,F13.5) ,
3(IX,F7.2),IX,F13.5)
*
AVE GRP
DATE
X Y
ZELEV ZHILL ZFLAG
AVERAGE CONC
3 ALL
88030112
344.68271 -60.77686
0.00 0.00 0.00
71 36678
3 ALL
88030112
492.40388 -86.82409
0.00 0.00 0.00
73.20689
3 ALL
88030112
984.80775 -173.64818
0.00 0.00 0.00
50.65556
3 ALL
88030112
164.44621 -59.85353
0.00 0.00 0.00
112.74896
C.3 Postprocessor files (POSTFILE option)
The OU POSTFILE card for the AERMOD model allows the user the option of creating output files
of concurrent concentration values suitable for postprocessing. The model offers two options for the type of
file generated - one is an unformatted file, and the other is a formatted file of X, Y, CONC values suitable for
inputting to plotting programs.
The unformatted POSTFILE option generates a separate unformatted data record of concurrent
values for each averaging period and source group specified. The averaging period and source group
combinations may be written to separate files or combined into a single file. Each record begins with the date
variable for the end of the averaging period (an integer variable of the form YYMMDDHH), the averaging
period (e.g., an integer value of 3 for 3-hour averages), and the source group ID (eight characters).
Following these three header variables, the record includes the concentration values for each receptor
location, in the order in which the receptors are defined on the RE pathway. The results are output to the
unformatted file or files as they are calculated by the model.
The formatted plot file option for the POSTFILE keyword includes several lines of header
information, each identified with an asterisk (*) in column one. The header information includes the model
C-4
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name and version number, the first line of the title information for the run, the list of modeling option
keywords applicable to the results, the averaging period and source group included in the file, and the
number of receptors included. The header also includes the format used for writing the data records, and
column headers for the variables included in the file. The variables provided on each data record include the
X and Y coordinates of the receptor location, the concentration value for that location, receptor terrain
elevation, hill height scale, flagpole receptor height, the averaging period, the source group ID, the date
variable for the end of the averaging period (in the form of YYMMDDHH) for short-term averages or the
number of hours in the period for PERIOD averages, and the receptor network ID. The following example
from a formatted postprocessor file for PERIOD averages identifies the contents of the POSTFILE:
*
AERMOD ( 15181):
A Simple Example
Problem
for the AERMOD-PRIME
Model
06/09/16
*
AERMET ( 15181):
16:58
19
*
MODELING OPTIONS
USED: NonDFAULT
CONC
FLAT
RURAL
*
POST/PLOT FILE OF PERIOD
VALUES FOR SOURCE
GROUP: ALL
*
FOR A TOTAL OF 144 RECEPTORS.
*
FORMAT:
(3 (1X,F13.5),3(IX
,F8.2),2X
,A6,2X,A8
,2X,18.8,2X
,A8)
*
X
Y AVERAGE CONC
ZELEV
ZHILL
ZFLAG
AVE
GRP
NUM HRS
NET ID
30.38843
172.34136
0.21576
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
60 . 77 686
344.68271
0.53162
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
86.82409
492.40388
0.85993
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
173 . 64818
984.80775
1.39778
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
59.85353
164.44621
0.20861
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
119.70705
328.89242
0.67388
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
171.01007
469.84631
1.27452
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
342 . 02014
939.69262
2 . 45702
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
87.50000
151.55445
0.20576
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
175 . 00000
303.10889
0 . 64322
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
250 . 00000
433.01270
1.20422
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
500.00000
866.02540
2.28880
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
112.48783
134.05778
0.20172
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
224.97566
268.11556
0 .48027
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
321.39380
383.02222
0.76067
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
642.78761
766.04444
1.19405
0 .00
0 .00
0 .00
PERIOD
ALL
00000096
POL 1
C.4 High value results for plotting (PLOTFILE option)
The OU PLOTFILE card for the AERMOD model allows the user the option of creating output files
of highest concentration values suitable for importing into graphics software to generate contour plots. The
C-5
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formatted plot files generated by the PLOTFILE include several lines of header information, each identified
with an asterisk (*) in column one. The header information includes the model name and version number,
the first line of the title information for the run, the list of modeling option keywords applicable to the
results, the averaging period and source group included in the file, the high value (e.g., 2ND highest)
included for plotting, and the number of receptors included. The header also includes the format used for
writing the data records, and column headers for the variables included in the file. The variables provided on
each data record include the X and Y coordinates of the receptor location, the concentration value for that
location, receptor terrain elevation, hill height scale, flagpole receptor height, averaging period, the source
group ID, the high value included for short-term averages or the number of hours in the period for PERIOD
averages, and the receptor network ID. For short-term averages, the PLOTFILE also includes the date
variable for the end of the averaging period (in the form of YYMMDDHH). The PERIOD average
PLOTFILE uses the same format for the data records as the PERIOD average formatted POSTFILE shown
in the previous section. The following example from a plot file for high second highest 24-hour averages
identifies the contents of the PLOTFILE:
*
AERMOD ( 15181): A Simple Example Problem
for the AERMOD-PRIME Model
06/09/16
*
AERMET ( 15181):
17:07:58
*
MODELING OPTIONS USED: NonDFAULT CONC
FLAT
RURAL
*
PLOT FILE OF HIGH 2ND HIGH 24-HR VALUES
FOR SOURCE
GROUP: ALL
*
FOR A TOTAL OF 144 RECEPTORS.
*
FORMAT: (3(1X,F13.5),3(1X,F8.2),3X
,A5,2X,A8
,2X,A5,5X,
A8,2X,18)
*
X Y AVERAGE CONC
ZELEV
ZHILL
ZFLAG AVE
GRP
RANK NET ID
DATE(CONC)
30.38843 172.34136 0.34726
0 .00
0 .00
0.00 24-HR
ALL
2ND POL1
88030324
60.77686 344.68271 0.75187
0 .00
0 .00
0.00 24-HR
ALL
2ND POL1
88030124
86.82409 492.40388 1.18649
0 .00
0 .00
0.00 24-HR
ALL
2ND POL1
88030124
173.64818 984.80775 1.19837
0 .00
0 .00
0.00 24-HR
ALL
2ND POL1
88030124
The PLOTFILE output also includes a flag ('**') identifying the receptor with the highest
concentration. For short-term averages, the flag precedes the date field. For period averages, the flag
precedes the field with the number of hours in the period.
C-6
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C.5 TOXX model input files (TOXXFILE option)
The OU TOXXFILE card for the AERMOD model allows the user the option to generate an
unformatted file or files of threshold violations for a specific averaging period for use with the TOXX model
component of TOXST. The file consists of three header records, including the first line of the title
information for the run, the number of source groups, receptors and averaging periods, information on the
type of receptor network, and the threshold cutoff value. Following the header records are pairs of records
identifying the specific averaging period, source group and receptor location and corresponding
concentration value for the values exceeding the user- specified threshold. If any source group exceeds the
threshold for a given averaging period and receptor location, then the concentrations for all source groups are
output for that period and receptor. The structure of the unformatted file for the AERMOD model
TOXXFILE option is described below:
Record # Description
1 Title (80 characters)
2 IYEAR, NUMGRP, NUMREC, NUMPER, ITAB, NXTOX, NYTOX, IDUM1,
IDUM2, IDUM3
3 CUTOFF, RDUM1, . . ., RDUM9
where: TITLE = First line of title (80 characters)
IYEAR = Year of simulation
NUMGRP = No. of source groups
NUMREC = Total no. of receptors
NUMPER = No. of averaging periods (e.g., number of hours in the year)
ITAB = 1 for polar grid; 2 for Cartesian grid; 0 for discrete receptors or
mixed grids
NXTOX = No. of x-coordinates (or distances) in receptor network
NYTOX = No. of y-coordinates (or directions) in receptor network
IDUM1 = dummy integer variable, arbitrarily set equal to zero
IDUM2 = dummy integer variable, arbitrarily set equal to zero
IDUM3 = dummy integer variable, arbitrarily set equal to zero
CUTOFF = User-specified threshold for outputting results (g/m3)
RDUM1 = Dummy real variables (nine), arbitrarily set equal to zero
RDUM9 = Dummy real variables (nine), arbitrarily set equal to zero
Following the header records, the file consists of pairs of records including an ID variable identifying the
data period, source group number and receptor number, and the corresponding concentration values. The
C-7
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number of values included in each record is controlled by the NPAIR PARAMETER, which is initially set at
100 in MODULE MAIN1. The identification variable is determined as follows:
IDCONC = IPER* 100000 + IGRP* 1000 + IREC
where: IPER = the hour number for the year corresponding to the concentration value
IGRP = the source group number (the order in which the group was defined on the SO
pathway)
IREC = the receptor number (the order in which the receptor was defined on the RE pathway)
C.6 Maximum values by rank (RANKFILE option)
The OU RANKFILE card for the AERMOD model allows the user the option of creating output files
of the maximum concentration values by rank, suitable for generating Q-Q or quantile plots. The data
contained in the RANKFILE output is based on the MAXTABLE arrays, except that only one occurrence per
data period is included. The formatted data files generated by the RANKFILE include several lines of
header information, each identified with an asterisk (*) in column one. The header information includes the
model name and version number, the first line of the title information for the run, the list of modeling option
keywords applicable to the results, the averaging period included in the file, and the number of ranked values
included. The header also includes the format used for writing the data records, and column headers for the
variables included in the file. The variables provided on each data record include the rank, concentration
value, X and Y coordinates of the receptor location, receptor terrain elevation, hill height scale, flagpole
receptor height, and the source group ID. Each RANKFILE includes results for all of the source groups for a
particular averaging period. Since the RANKFILE only include one occurrence per data period, the file may
not include the number of ranked values requested, especially for evaluation data bases of limited duration.
The following example identifies the contents of the RANKFILE:
C-8
-------
*
AERMOD
( 15181): A
Simple Example Problem for the AERMOD-PRIME Model
06/09/16
*
AERMET
( 15181):
17:11:08
*
MODELING OPTIONS USED: NonDFAULT CONG FLAT RURAL
*
RANK-FILE OF UP TO 40 TOP 3-HR VALUES FOR 1
SOURCE
GROUPS
*
INCLUDES OVERALL MAXIMUM VALUES WITH DUPLICATE DATA
PERIODS REMOVED
*
FORMAT: (IX
,16,IX,F13.5,IX,18.8,2(IX,F13.5),3(IX,F7
X*
0\]
0\]
00
<
*
RANK
AVERAGE CONG
DATE X Y
ZELEV
ZHILL ZFLAG
GRP
1
329 . 96009
88030112 433.01270 -250.00000
o
o
o
0.00 0.00
ALL
2
278.47891
88030115 469.84631 -171.01007
o
o
o
0.00 0.00
ALL
3
124.30430
88030118 433.01270 -250.00000
o
o
o
0.00 0.00
ALL
C.7 Arc-maximum values for evaluation (EVALFIL option)
The OU EVALFILE card for the AERMOD model allows the user the option of creating output files
of the arc-maximum concentration values for individual sources suitable for use in model evaluation studies.
The data contained in the EVALFILE output is based on the maximum value along arcs of receptors,
identified using the RE EVALCART card. Receptors may be grouped on arcs based on their distance from
the source, or other logical grouping. The formatted EVALFILE output includes five records of information
for each selected source and each hour of meteorological data. The information provided is as follows:
1. Source ID (12 characters)
2. Date (YYMMDDHH)
3. Arc ID (eight characters)
4. Arc maximum P/Q
5. Emission rate for arc maximum (including unit conversions)
6. Crosswind integrated concentration based on true centerline concentration
7. Normalized non-dimensional crosswind integrated concentration
8. Downwind distance corresponding to arc maximum (m)
9. Effective wind speed corresponding to arc maximum (m/s)
10. Effective Fv corresponding to arc maximum (m/s)
11. Effective Fw corresponding to arc maximum (m/s)
12. Fy corresponding to arc maximum (m)
13. Effective plume height corresponding to arc maximum (m)
14. Monin-Obukhov length for current hour (m)
C-9
-------
15. Mixing height for current hour (m)
16. Surface friction velocity for current hour (m/s)
17. Convective velocity scale for current hour if unstable (m/s) or Fz for current hour if stable
18. Buoyancy flux for current hour (m4/s3)
19. Momentum flux for current hour (m4/s2)
20. Bowen ratio for current hour
21. Plume penetration factor for current hour
22. Centerline P/Q for direct plume
23. Centerline P/Q for indirect plume
24. Centerline P/Q for penetrated plume
25. Nondimensional downwind distance
26. Plume height/mixing height ratio
27. Non-dimensional buoyancy flux
28. Source release height (m)
29. Arc centerline P/Q
30. Developmental option settings place holder (string of 10 zeroes)
31. Flow vector for current hour (degrees)
32. Effective height for stable plume reflections (m)
The following Fortran WRITE and FORMAT statements are used to write the results to the
EVALFILE output:
WRITE(IELUNT(ISRC),9000) SRCID(ISRC), KURDAT, ARCID(I),
&
&
&
&
&
&
&
ARCMAX(I) , QMAX(I), CWIC, CWICN,
DXMAX(I), UOUT, SVMAX(I),
SWMAX(I), SYOUT, HEMAX(I),
OBUOUT, ZI, USTAR, PWSTAR, FB, FM,
BOWEN, PPF, CHIDML(I), CHINML(I), CHI3ML(I)
XNDIM, HEOZI, FSTAR, AHS(ISRC), ARCCL(I),
AFV, HSBLMX(I)
9000 FORMAT(1X,A12,IX,18.8,IX,A8,4(1X,G12.6),
& 9X, 6 (IX, G12 . 4 ) , 9X, 6 (IX, G12 . 4 ) ,
& 9X,6(IX,G12.4),9X,4(1X,G12.4),IX,'0000000000'
& IX, G12 . 4, IX, G12 . 4 )
C-10
-------
C.8 Results by season and hour-of-day (SEASONHR option)
The SEASONHR option is used to output a file containing the average results by season and hour-
of-day. The formatted data files generated by the SEASONHR option include several lines of header
information, each identified with an asterisk (*) in column one. The header information includes the model
name and version number, the first line of the title information for the run, the list of modeling option
keywords applicable to the results, the source group included in the file, and the number of receptors. The
header also includes the format used for writing the data records, and column headers for the variables
included in the file. The variables provided on each data record include the X and Y coordinates of the
receptor location, the average concentration value, receptor terrain elevation, hill height scale, flagpole
receptor height, source group ID, number of non-calm and non-missing hours used to calculate the season-
by-hour-of-day averages (the NHRS column), season index (the SEAS column with 1 for winter, 2 for
spring, 3 for summer, and 4 for fall), the hour-of-day for the concentration value, and the receptor network
ID. A sample from a SEASONHR output file is shown below:
*
AERMOD 15181) :
A Simple Example Problem
for the
AERMOD-PRIME Model
06/09/16
*
AERMET 14134):
17
27 : 43
*
MODELING OPTIONS
USED: NonDFAULT CONG
FLAT
RURAL
*
FILE OF
SEASON/HOUR VALUES FOR SOURCE GROUP
: ALL
*
FOR A TOTAL OF 144 RECEPTORS.
*
FORMAT:
(2(IX,F13.5),1(IX,F13.8),
3(IX,F7.
2)
,2X,A8,2X,3(14
,2X),A8)
*
X
Y AVERAGE CONC
ZELEV
ZHILL ZFLAG
GRP
NHRS
SEAS
HOUR
NET ID
30.38843
172.34136 34.14568783
0.00
0.00 0.00
ALL
65
1
1
POL1
60.77686
344.68271 39.19676801
0.00
0.00 0.00
ALL
65
1
1
POL1
86.82409
492.40388 34.59785413
0.00
0.00 0.00
ALL
65
1
1
POL1
173.64818
984.80775 16.14253303
0.00
0.00 0.00
ALL
65
1
1
POL1
59.85353
164.44621 32.93762092
0.00
0.00 0.00
ALL
65
1
1
POL1
119.70705
328.89242 41.97750583
0.00
0.00 0.00
ALL
65
1
1
POL1
C-ll
-------
C.9 Source group contribution for ranked averaged maximum daily values (MAXDCONT)
The OU MAXDCONT card of the AERMOD model allows the user to create output files that
provide source contributions for the 24-hour PM2.5, 1-hour NO2 and 1-hour SO2 standards in which the
design value is based on averages of ranked values across multiple years. Ranked concentrations and source
contributions are based on a target source group specified by the user. The user can define the ranks to
include or a range of ranks and an optional minimum threshold concentration value. The MAXDCONT
output file includes several lines of header information, each identified with an asterisk (*) in column one,
including: the model name and version number, the first line of the title information, the list of modeling
option keywords, the highest rank specified, the averaging period, target source group, and threshold value if
applicable. The header also includes the total number of receptors and source groups and the Fortran format
statement used to write the data records. The variables provided on each data record include the X and Y
coordinates of the receptor location, the concentration value for the target source group at the receptor
location, receptor terrain elevation, hill height scale, flagpole receptor height, averaging period, the source
group ID, rank, receptor network ID, and the source contribution for each source modeled. The data records
are grouped by rank in ascending order. Concentrations are displayed for all receptors for the highest rank,
then the next highest rank, etc. The following example is a partial MAXDCONT file with a minimum
threshold value of 35 (ig/m3 was specified for ranks 1 through 50. Results for the first two ranks are
displayed for four the source groups that were modeled.
C-12
-------
*
AERMOD 15181):
PM-2.5 Test
Case for the
AERMOD
Model using
single
met file
07/
30/15
*
AERMET 13350):
13 :
50: 57
*
MODELING OPTIONS
USED: NonDFAULT CONC
FLAT
RURAL
*
MAXDCONT
FILE OF
1ST
-HIGHEST 24-
HR VALUES
AVERAGED
OVER 5
YEARS
FOR SOURCE
GROUP:
ALL
; ABOVE
THRESH =
35.00000
*
FOR A TOTAL OF
16
RECEPTORS AND 3
SOURCE GROUPS; WITH
CONTRIBUTIONS FROM OTHER SOURCE
GROUPS PAIRED IN TIME & SPACE
*
FORMAT:
(3(IX,F13 . 5
) ,3
(IX,F8.2) ,2X
,A6,2X,
z\8
2X,A5,5X,
A8,2X,
3 (F13
5,2X:))
*
X
Y
AVERAGE CONC
ZELEV
ZHILL
ZFLAG
AVE
GRP
RANK
NET
ID CONT
STACK1
CONT STACK2
CONT ALL
200.00000
0.00000
9. 76902
0. 00
0 .00
0 .00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
500.00000
0.00000
25.61401
0. 00
0 .00
0 .00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
1000.00000
0.00000
26.86548
0. 00
0 .00
0 .00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
3000.00000
0.00000
8.85979
0. 00
0 .00
0 .00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
0.00000
-200.00000
20.50162
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
0.00000
-500.00000
51.65594
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
21.15838
30.49757
51.65594
0.00000
1000.00000
52 . 82753
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
13.99357
38 .83396
52 .82753
0.00000
3000.00000
19.91409
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
-200.00000
-0.00000
8.64428
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
-500.00000
-0.00000
14.58084
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
-1000.00000
-0.00000
11.59131
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
-3000.00000
-0.00000
12.28970
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
-0.00000
200.00000
67.53734
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
67 . 53733
0 .00002
67 .53734
-0.00000
500.00000
67.83252
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
64 . 45844
3 .37408
67 .83252
-0.00000
1000.00000
52.28291
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
28.94476
23.33815
52 .282 91
-0.00000
3000.00000
29.08609
0. 00
0 .00
0. 00
24-HR
ALL
1ST
POL1
0. 00000
0 .00000
0 .00000
*
AERMOD 15181) :
PM-2.5 Test
Case for the
AERMOD
Model using
single
met file
07/
30/15
*
AERMET 13350) :
13 :
50: 57
*
MODELING OPTIONS
USED: NonDFAULT CONC
FLAT
RURAL
*
MAXDCONT
FILE OF
2ND
-HIGHEST 24-
HR VALUES
AVERAGED
OVER 5
YEARS
FOR SOURCE
GROUP:
ALL
; ABOVE
THRESH =
35.00000
C-13
-------
*
FOR A
TOTAL OF
16 RECEPTORS AND
3 SOURCE GROUPS; WITH
CONTRIBUTIONS
FROM OTHER
SOURCE
GROUPS PAIRED IN TIME &
SPACE
*
FORMAT
: (3(IX,F13 . 5
),3(IX,F8.2),2X,
A6,2X,A8
2X,A5,5X
A8,2X,
3(F13.
5,2X:))
*
X
Y
AVERAGE CONC
ZELEV
ZHILL
ZFLAG
AVE
GRP
RANK
NET
ID
CONT STACK1 CONT
STACK2
CONT ALL
200.00000
0.00000
7 . 91782
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0.00000
0 .00000
0 .00000
500.00000
0.00000
22 . 53064
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0.00000
0 .00000
0 .00000
1000.00000
0.00000
24.26451
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0 .00000
0.00000
3000.00000
0.00000
8.10584
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0 .00000
0.00000
0.00000
-200.00000
16.96505
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0 .00000
0 .00000
0.00000
-500.00000
43.25276
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
14.36197
28.89079
43.25276
0.00000
-1000.00000
43.82672
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
10.92254
32.90417
43.82672
0.00000
-3000.00000
17.32480
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0 .00000
0 .00000
-200.00000
-0.00000
6. 77421
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0 .00000
0 .00000
-500.00000
-0.00000
11.56687
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0 .00000
0 .00000
-1000.00000
-0.00000
9. 7222 9
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0.00000
0 .00000
-3000.00000
-0.00000
8.03098
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0.00000
0 .00000
-0.00000
200.00000
51.19765
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
51.19763
0.00002
51.19765
-0.00000
500.00000
59.15581
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
57 . 67153
1.48428
59.15581
-0.00000
1000.00000
41.49519
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
18 . 49276
23 . 00243
41.49519
-0.00000
3000.00000
23.24160
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
P0L1
0. 00000
0.00000
0 .00000
C-14
-------
C.10 Daily maximum 1-hour values (MAXDAILY)
The OU MAXDAILY card of the AERMOD model generates a file of daily maximum 1-hour
concentrations for a specified source group, useful for analyzing the 1-hour NO2 and SO2 NAAQS. The
MAXDAILY file includes several lines of header information, each identified with an asterisk (*) in column
one, including: the model name and version number, the first line of the title information, the list of modeling
option keywords, and the source group. The header also includes the total number of receptors and the
Fortran format statement used to write the data records. The variables provided on each data record include
the X and Y coordinates of the receptor location, the concentration value for the target source group at the
receptor location, receptor terrain elevation, hill height scale, flagpole receptor height, averaging period, the
source group ID, day of the year, hour, date, and receptor network ID. The following example is a sample
from a MAXDAILY output file.
C-15
-------
*
AERMOD 15181):
AERMOD OLM/OLMGROUP ALL
Test Case,
with BACKGROUND
07/30/15
-
AERMET 13350) :
13
o
CO
-
MODELING OPTIONS
USED: NonDFAULT CONC
FLAT
OLM
RURAL
-
MAXDAILY
FILE OF DAILY MAXIMUM 1
-HR VALUES
BY DAY FOR
SOURCE
GROUP:
ALL
-
FOR A TOTAL OF 16
RECEPTORS.
-
FORMAT:
(3(IX,F13.5)
,3(1X,F8.2),2X,A6,2X,A8
,2X,14,2X,
13,2X,18
.8,2X,A8)
*
X
Y
AVERAGE CONC
ZELEV
ZHILL
ZFLAG
AVE
GRP
JDAY
HR
DATE
NET ID
100 .00000
0.00000
50 .00000
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
300 .00000
0.00000
50 .00159
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
1000 .00000
0.00000
50 .20117
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
3000 .00000
0.00000
50 .12314
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
0 .00000
-100.00000
50 .00000
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
0 .00000
-300.00000
50 .00259
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
0.00000
1000 . 00000
50 .22100
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
0.00000
3000.00000
68 .29389
o
o
35.00
o
o
o
1-HR
ALL
1
7
99010107
P0L1
-100.00000
-0.00000
50 .00000
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-300 .00000
-0.00000
50 .00258
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-1000 .00000
-0.00000
50.20079
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-3000.00000
-0.00000
50.12262
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-0 . 00000
100.00000
50 .00000
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-0 . 00000
300.00000
50 .00159
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-0 . 00000
1000.00000
50 .20117
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-0 . 00000
3000.00000
50 .12314
o
o
35.00
o
o
o
1-HR
ALL
1
13
99010113
P0L1
100.00000
0 .00000
50 .00000
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
300.00000
0 .00000
50 .00001
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
1000.00000
0 .00000
50 .00008
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
3000.00000
0 .00000
50 .00280
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
0 . 00000
-100.00000
50 .00000
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
0.00000
-300.00000
50 .00001
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
0.00000
1000 . 00000
50 .00009
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
0.00000
3000.00000
50 .00285
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
-100.00000
-0.00000
50 .00000
o
o
35.00
o
o
o
1-HR
ALL
2
13
99010213
P0L1
C-16
-------
C.ll Maximum daily 1-hour concentration by year (MAXDYBYYR)
The OU MAXDYBYYR card of the AERMOD model generates a file with a summary of daily
maximum 1-hour concentrations by year for each rank specified on the RECTABLE keyword for a specified
source group. This is another output file type that is applicable to the 1-hour NO2 and 1-hour SO2 NAAQS.
The ranks included in the MXDYBYYR file are the ranks used in the MAXDCONT postprocessing option.
The MAXDYBYYR file includes several lines of header information, each identified with an asterisk (*) in
column one, including: the model name and version number, the first line of the title information, the list of
modeling option keywords, and the source group. The header also includes the total number of receptors and
the Fortran format statement used to write the data records. The variables provided on each data record
include the X and Y coordinates of the receptor location, the concentration value for the target source group
at the receptor location, receptor terrain elevation, hill height scale, flagpole receptor height, rank, the source
group ID, day of the year, hour, date, and receptor network ID. The data records are grouped by rank in
ascending order. Concentrations are displayed for all receptors for the highest rank, then the next highest
rank, etc. The following example is a sample from a MAXDAILY output file for which ranks 4, 8 12, and 50
were specified on the MAXDCONT keyword.
C-17
-------
*
AERMOD 15181):
AERMOD OLM/OLMGROUP ALL
Test Case,
with BACKGROUND
07/30/15
-
AERMET 13350) :
13
o
CO
-
MODELING OPTIONS
USED: NonDFAULT CONC
FLAT
OLM
RURAL
-
MXDYBYYR FILE OF RANKED DAILY MAXIMUM 1-HR
VALUES BY
YEAR FOR
SOURCE GROUP:
ALL
-
FOR A TOTAL OF 16
RECEPTORS.
-
FORMAT:
(3(IX,F13.5)
,3 (1X,F8.2),2X,A6,2X,A8
2X,14,2X,
13,2X,18.
8,2X,A8)
*
X
Y
AVERAGE CONC
ZELEV
ZHILL
ZFLAG
RANK
GRP
JDAY
HR
DATE
NET ID
100.00000
0.00000
76.74205
o
o
35.00
1
o
o
o
4TH
ALL
236
14
99082414
P0L1
300 .00000
0.00000
174 . 62886
o
o
35.00
o
o
o
4TH
ALL
136
14
99051614
P0L1
1000 .00000
0.00000
146 . 90191
o
o
35.00
o
o
o
4TH
ALL
147
14
99052714
P0L1
3000 .00000
0.00000
91.97719
o
o
35.00
o
o
o
4TH
ALL
104
13
99041413
P0L1
0 .00000
-100.00000
99.52361
o
o
35.00
o
o
o
4TH
ALL
252
15
99090915
P0L1
0 .00000
-300.00000
171.76063
o
o
35.00
o
o
o
4TH
ALL
107
11
99041711
P0L1
0.00000
1000.00000
152 . 93801
o
o
35.00
o
o
o
4TH
ALL
65
13
99030613
P0L1
0.00000
3000.00000
111.73167
o
o
35.00
o
o
o
4TH
ALL
293
16
99102016
P0L1
-100.00000
-0.00000
91.59388
o
o
35.00
o
o
o
4TH
ALL
62
14
99030314
P0L1
-300 .00000
-0.00000
154 . 65265
o
o
35.00
o
o
o
4TH
ALL
62
15
99030315
P0L1
-1000 .00000
-0.00000
131. 73020
o
o
35.00
o
o
o
4TH
ALL
360
13
99122613
P0L1
-3000.00000
-0.00000
86.11262
o
o
35.00
o
o
o
4TH
ALL
312
16
99110816
P0L1
-0.00000
100.00000
80 .06381
o
o
35.00
o
o
o
4TH
ALL
203
8
99072208
P0L1
-0 . 00000
300.00000
166.86210
o
o
35.00
o
o
o
4TH
ALL
139
16
99051916
P0L1
-0 . 00000
1000.00000
156.54681
o
o
35.00
o
o
o
4TH
ALL
110
15
99042015
P0L1
-0 . 00000
3000.00000
102 .04635
o
o
35.00
o
o
o
4TH
ALL
23
15
99012315
P0L1
100.00000
0.00000
65 .46639
o
o
35.00
o
o
o
8TH
ALL
250
17
99090717
P0L1
300.00000
0.00000
164.95260
o
o
35.00
o
o
o
8TH
ALL
147
14
99052714
P0L1
1000.00000
0.00000
137 . 02622
o
o
35.00
o
o
o
8TH
ALL
145
16
99052516
P0L1
3000.00000
0.00000
79.71649
o
o
35.00
o
o
o
8TH
ALL
102
19
99041219
P0L1
0 . 00000
-100.00000
90 .20572
o
o
35.00
o
o
o
8TH
ALL
175
9
99062409
P0L1
0 . 00000
-300.00000
167.99537
o
o
35.00
o
o
o
8TH
ALL
81
14
99032214
P0L1
0.00000
1000 . 00000
147.76997
o
o
35.00
o
o
o
8TH
ALL
107
18
99041718
P0L1
0.00000
3000.00000
108 .50074
o
o
35.00
o
o
o
8TH
ALL
272
17
99092917
P0L1
-100.00000
-0.00000
86.21569
o
o
35.00
o
o
o
8TH
ALL
251
12
99090812
P0L1
-300.00000
-0.00000
147 . 43347
o
o
35.00
o
o
o
8TH
ALL
63
13
99030413
P0L1
-1000.00000
-0.00000
113.23071
o
o
35.00
o
o
o
8TH
ALL
144
8
99052408
P0L1
-3000.00000
-0.00000
80.46493
o
o
35.00
o
o
o
8TH
ALL
251
12
99090812
P0L1
-0 . 00000
100 . 00000
62 .77470
o
o
35.00
o
o
o
8TH
ALL
213
15
99080115
P0L1
-0 . 00000
300.00000
164.12251
o
o
35.00
o
o
o
8TH
ALL
212
12
99073112
P0L1
-0 . 00000
1000 . 00000
147.60345
o
o
35.00
o
o
o
8TH
ALL
84
15
99032515
P0L1
-0.00000
3000.00000
92 .37244
o
o
35.00
o
o
o
8TH
ALL
264
19
99092119
P0L1
C-18
-------
100 .00000
0 .00000
63 .04954
o
o
35.00
o
o
o
12 TH
ALL
213
15
99080115
POL1
300 .00000
0 .00000
158.05318
o
o
35.00
o
o
o
12 TH
ALL
182
15
99070115
POL1
1000 .00000
0 .00000
132 . 45210
o
o
35.00
o
o
o
12 TH
ALL
123
15
99050315
POL1
3000 .00000
0 .00000
75 .06520
o
o
35.00
o
o
o
12 TH
ALL
56
14
99022514
POL1
0 .00000
-100.00000
81.79820
o
o
35.00
o
o
o
12TH
ALL
230
14
99081814
POL1
0 .00000
-300.00000
163.58691
o
o
35.00
o
o
o
12TH
ALL
150
13
99053013
POL1
0 .00000
-1000.00000
143.66477
o
o
35.00
o
o
o
12TH
ALL
63
11
99030411
POL1
0 .00000
-3000.00000
103.84510
o
o
35.00
o
o
o
12TH
ALL
359
10
99122510
POL1
-100.00000
-0.00000
66.87945
o
o
35.00
o
o
o
12TH
ALL
210
13
99072913
POL1
-300 .00000
-0.00000
134 .34226
o
o
35.00
o
o
o
12TH
ALL
192
11
99071111
POL1
-1000.00000
-0.00000
112.42027
o
o
35.00
o
o
o
12TH
ALL
90
10
99033110
POL1
-3000.00000
-0.00000
69.14045
o
o
35.00
o
o
o
12TH
ALL
70
12
99031112
POL1
-0.00000
100.00000
57.29793
o
o
35.00
o
o
o
12TH
ALL
80
13
99032113
POL1
-0 . 00000
300.00000
161.46688
o
o
35.00
o
o
o
12TH
ALL
46
12
99021512
POL1
-0.00000
1000.00000
141.04997
o
o
35.00
o
o
o
12TH
ALL
165
14
99061414
POL1
-0 . 00000
3000.00000
89.51271
o
o
35.00
o
o
o
12TH
ALL
109
19
99041919
POL1
100.00000
0 .00000
51.04396
o
o
35.00
o
o
o
5 0 TH
ALL
132
13
99051213
POL1
300.00000
0 .00000
126.14782
o
o
35.00
o
o
o
5 0 TH
ALL
175
15
99062415
POL1
1000.00000
0 .00000
105.50261
o
o
35.00
o
o
o
5 0 TH
ALL
267
17
99092417
POL1
3000.00000
0 .00000
56 . 90880
o
o
35.00
o
o
o
5 0 TH
ALL
236
14
99082414
POL1
0 . 00000
-100.00000
56.69467
o
o
35.00
o
o
o
50TH
ALL
287
13
99101413
POL1
0 . 00000
-300.00000
137 .18380
o
o
35.00
o
o
o
50TH
ALL
204
13
99072313
POL1
0 . 00000
-1000.00000
120 . 65746
o
o
35.00
o
o
o
50TH
ALL
268
13
99092513
POL1
0 . 00000
-3000.00000
85.42463
o
o
35.00
o
o
o
50TH
ALL
156
1
99060501
POL1
-100.00000
-0.00000
51.20790
o
o
35.00
o
o
o
50TH
ALL
169
14
99061814
POL1
-300.00000
-0.00000
72 . 61516
o
o
35.00
o
o
o
50TH
ALL
32
13
99020113
POL1
-1000.00000
-0.00000
72.14476
o
o
35.00
o
o
o
50TH
ALL
270
10
99092710
POL1
-3000.00000
-0.00000
52.15505
o
o
35.00
o
o
o
50TH
ALL
265
13
99092213
POL1
-0 . 00000
100 . 00000
50 .39602
o
o
35.00
o
o
o
50TH
ALL
180
14
99062914
POL1
-0 . 00000
300.00000
125 .74471
o
o
35.00
o
o
o
50TH
ALL
247
14
99090414
POL1
-0.00000
1000 . 00000
117.67662
o
o
35.00
o
o
o
50TH
ALL
143
1
99052301
POL1
-0.00000
3000.00000
70.84420
o
o
35.00
o
o
o
50TH
ALL
127
2
99050702
POL1
C-19
-------
APPENDIX D. Overview of AERMOD revisions in version 24142
Model Change Bulletin (MCB) 18
AERMOD version 24142 (May 21, 2024)
Changes are listed by type and with each change are the affected pollutants and source types:
Bug Fixes
Item
Modification
Pollutants
Source Types
1
Corrected a bug in subroutine
PLUMECONCENTRATION that was causing
mixing height to be potentially reset each time
the subroutine was called.
ALL
RLINE,
RLINEXT
2
Corrected 2-digit year conversion for year 2000
when meteorological data crosses from 1999 to
2000.
ALL
ALL
3
Corrected bug in which EMISUNIT keyword
was not working with the BUOYLINE source
type. EMISUNIT keyword was ignored.
ALL
BUOYLINE
4
GRSM PLUMESIZES and DoGRSMChem
code modified to prevent not-a-number (NaNs)
concentration values for ground releases from
volume, area, and openpit source types.
N02
ALL
Enhancements
Item
Modification
Pollutants
Source Types
1
Updated the warning message for 24-hour
average to state the date and time information
when less than 18 hours of data are used in the
average.
ALL
ALL
2
Add warning messages for 3- and 8-hour
averages. Warning issued if less than 6 hours
used to compute 8-hour average or less than 3
hours used to compute 3-hour average.
ALL
ALL
D-l
-------
Formulation updates - Regulatory
Item
Modification
Pollutants
Source Types
1
Remove BETA flag restriction for RLINE
source type. RLINE promulgated as a regulatory
option in 2024 update to the Guideline (40 CFR
Part51, Appendix W).
ALL
RLINE
2
Remove BETA flag restriction for GRSM N02
conversion option. GRSM promulgated as a
regulatory option in 2024 update to the
Guideline (40 CFR Part51, Appendix W).
ALL
ALL
3
Remove BETA flag restriction for COARE
processing of overwater meteorology in
AERMET. COARE in AERMET promulgated
as a regulatory option in 2024 update to the
Guideline (40 CFR Part51, Appendix W).
ALL
ALL
Formulation updates - BETA
None
Formulation updates - ALPHA
None
D-2
-------
APPENDIX E. Glossary
AERMAP -- AMS/EPA Regulatory Model (AERMOD) Terrain Preprocessor. AERMET ~
AMS/EPA Regulatory Model (AERMOD) Meteorological Preprocessor. AERMOD ~
AMS/EPA Regulatory Model.
ASCII -- American Standard Code for Information Interchange, a standard set of codes used by
computers and communication devices. Sometimes used to refer to files containing only such
standard codes, without any application-specific codes such as might be present in a document
file from a word processor program.
Card -- A single input record within the input control file.
CO -- COntrol, the 2-character pathway ID for input control file commands used to specify overall job
control options.
CO Pathway ~ Collective term for the group of input control file commands used to specify the
overall job control options, including titles, dispersion options, terrain options, etc.
Directory ~ A logical subdivision of a disk used to organize files stored on a disk.
Dispersion Model ~ A group of related mathematical algorithms used to estimate (model) the
dispersion of pollutants in the atmosphere due to transport by the mean (average) wind and
small scale turbulence.
DOS -- Disk Operating System. Software that manages applications software and provides an
interface between applications and the system hardware components, such as the disk drive,
terminal, and keyboard.
Echo of inputs ~ By default, the AERMOD model will echo the input control file commands,
character by character, into the main printed output file. This serves as a record of the inputs
as originally entered by the user, without any rounding of the numerical values. The echoing
can be suppressed with the NO ECHO option.
EOF -- End-of-File.
EPA U. S. Environmental Protection Agency.
Error message ~ A message written by the model to the error/message file whenever an error is
encountered that will inhibit data processing.
Error/Message File ~ A file used for storage of messages written by the model.
EV -- EVent, the 2-character pathway ID for input control file commands used to specify event inputs for
the Short-Term EVENT model.
E-3
-------
EV Pathway ~ Collective term for the group of input control file commands used to specify the event
periods and location for the Short-Term EVENT model.
EVENT Processing ~ An option in the AERMOD model specifically designed to provide source
contribution (culpability) information for specific events of interest, e.g., design values or
threshold violations.
Extended Memory ~ Additional memory on 80386 and 80486 PCs that allows programs to address
memory beyond the 640 KB limit of DOS. Special software is required to utilize this extra
memory.
Fatal Error ~ Any error which inhibits further processing of data by the model. Model continues to read
input images to check for errors during setup and will continue to read input meteorological data
during calculation phase.
Flow Vector ~ The direction towards which the wind is blowing. GMT
-- Greenwich Mean Time, the time at the 0° meridian.
Informational Message ~ Any message written to the error/message file that may be of interest to the user,
but which have no direct bearing on the validity of the results, and do not affect processing.
Input Image ~ User supplied input, read through the default input device, controlling the model options
and data input. A single card or record from the input control file. Each input image consists of a
pathway ID (may be blank indicating a continuation of the previous pathway), a keyword (may
also be blank for continuation of a keyword), and possibly one or more parameter fields.
Input control file ~ The basic input file to the AERMOD model controlling the modeling options, source
data, receptor locations, meteorological data file specifications, and output options. Consists of a
series of input images grouped into functional pathways.
Julian Day ~ The number of the day in the year, i.e., Julian Day = 1 for January 1 and 365 (or 366 for leap
years) for December 31.
KB -- Kilobyte, 1000 bytes, a unit of storage on a disk
Keyword ~ The 8-character codes that follow immediately after the pathway ID in the input run stream
data.
LST -- Local Standard Time.
Math Co-processor ~ A computer chip used to speed up floating point arithmetic in a personal
computer.
MB -- Megabyte, one million bytes, a unit of storage on a disk
E-4
-------
ME -- MEteorology, the 2-character pathway ID for input control file commands used to specify
meteorological data options
ME Pathway ~ Collective term for the group of input control file commands used to specify the input
meteorological data file and other meteorological variables, including the period to process from
the meteorological file for the AERMOD model.
Meteorological Data File ~ Any file containing meteorological data, whether it be mixing
heights, surface observations or on-site data.
Missing Value ~ Alphanumeric character(s) that represent breaks in the temporal or spatial record of an
atmospheric variable.
Mixing Height ~ The depth through which atmospheric pollutants are typically mixed by
dispersive processes.
NCDC -- National Climatic Data Center, the federal agency responsible for distribution of the
National Weather Service upper air, mixing height and surface observation data.
NO ECHO -- Option to suppress echoing of the control file commands to the main printed output file.
NWS -- National Weather Service.
On-site Data ~ Data collected from a meteorological measurement program operated in the
vicinity of the site to be modeled in the dispersion analysis.
OU -- OUtput, the 2-character pathway ID for input control file commands used to specify output
options.
OU Pathway ~ Collective term for the group of input control file commands used to specify the output
options for a particular run.
Overlay ~ One or more subprograms that reside on disk and are loaded into memory only when needed.
Pasquill Stability Categories ~ A classification of the dispersive capacity of the atmosphere,
originally defined using surface wind speed, solar insolation (daytime) and cloudiness
(nighttime). They have since been reinterpreted using various other meteorological
variables.
Pathway ~ One of the six major functional divisions in the input control file for the AERMOD model.
These are COntrol, SOurce, REceptor, MEteorology, EVent, and OUtput (see these entries in this
section for a description).
PC -- Personal Computer, a wide-ranging class of computers designed for personal use, typically small
enough to fit on a desktop.
E-5
-------
Quality Assessment ~ Judgment of the quality of the data.
Quality Assessment Check ~ Determining if the reported value of a variable is reasonable (see also
Range Check).
Quality Assessment Message ~ Message written to the error/message file when a data value is
determined to be suspect.
Quality Assessment Violation ~ Occurrences when data values are determined to be suspect (see also
Range Check Violation).
RAM -- Random Access Memory on a personal computer.
RAMMET -- Meteorological processor program used for regulatory applications capable of processing
twice-daily mixing heights and hourly surface weather observations for use in dispersion models
such as AERMOD, CRSTER, MPTER and RAM.
Range Check ~ Determining if a variable falls within predefined upper and lower bounds.
Range Check Violation ~ Determination that the value of a variable is outside range defined by upper
and lower bound values (see also Quality Assessment Violation).
RE -- REceptor, the 2-character pathway ID for input control file commands used to specify receptor
locations.
RE Pathway ~ Collective term for the group of input control file commands used to specify the
receptor locations for a particular run.
Regulatory Applications ~ Dispersion modeling involving regulatory decision-making as described in
the Guideline on Air Quality Models, which is published as Appendix W of 40 CFR Part 51 (as
revised).
Regulatory Model ~ A dispersion model that has been approved for use by the regulatory offices of the
EPA, specifically one that is included in Appendix A of the Guideline on Air Quality Models, (as
revised), such as the AERMOD model.
R-LINE - Research LINE-source dispersion model for near surface releases.
Control file ~ Collectively, all input images required to process input options and input data for the
AERMOD model.
SCRAM -- Support Center for Regulatory Air Models - part of EPA's website on the internet, used by
EPA for disseminating air quality dispersion models, modeling guidance, and related
information.
Secondary Keyword ~ A descriptive alphabetical keyword used as a parameter for one of the main
control file keywords to specify a particular option.
E-6
-------
SO -- SOurce, the 2-character pathway ID for input control file commands used to specify input
source parameters and source groups.
SO Pathway ~ Collective term for the group of input control file commands used to specify the source
input parameters and source group information.
Station Identification ~ An integer or character string used to uniquely identify a station or site as
provided in the upper air, mixing height, and surface weather data formats available from NCDC.
There are no standard station numbers for on-site data or card image/screening data, and the user
may include any integer string
Subdirectory ~ A directory below the root, or highest level, directory or another subdirectory, used for
organization of files on a storage medium such as a PC hard disk.
Surface Weather Observations ~ A collection of atmospheric data on the state of the atmosphere as
observed from the earth's surface. In the U.S. the National Weather Service collect these data on
a regular basis at selected locations.
Surface Roughness Length ~ Height at which the wind speed extrapolated from a near-surface wind
speed profile becomes zero.
Syntax ~ The order, structure and arrangement of the inputs that make of the input control file,
specifically, the rules governing the placement of the various input elements including pathway
IDs, keywords, and parameters.
Unformatted File ~ A file written without the use of a FORTRAN FORMAT statement,
sometimes referred to as a binary file.
Upper Air Data (or soundings) ~ Meteorological data obtained from balloon- borne instrumentation that
provides information on pressure, temperature, humidity, and wind away from the surface of the
earth.
Vertical Potential Temperature Gradient ~ The change of potential temperature with height, used in
modeling the plume rise through a stable layer, and indicates the strength of the stable temperature
inversion. A positive value means that potential temperature increases with height above ground
and indicates a stable atmosphere.
Warning Message ~ A message written by the model to the error/message file whenever a problem
arises that may reflect an erroneous condition but does not inhibit further processing.
E-7
-------
United States Office of Air Quality Planning and Standards Publication No. EPA-454/B-24-007
Environmental Protection Air Quality Assessment Division November 2024
Agency Research Triangle Park, NC
8
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