^tDsr<%
a \
i W-1
User's Guide for the AMS/EPA Regulatory
Model (AERMOD)
-------
-------
EPA-454/B-23-008
October 2023
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
-------
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.
11
-------
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, 2023a). 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.
111
-------
iv
-------
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 1-2
1.1.3 Management/decision makers 1-2
1.2 Overview of the AERMOD model 1-3
1.2.1 Regulatory applicability 1-3
1.2.2 Basic input data requirements 1-3
1.2.3 Computer hardware requirements 1-4
1.2.4 Dispersion options 1-4
1.2.5 Source options 1-5
1.2.6 Receptor options 1-5
1.2.7 Meteorology options 1-6
1.2.8 Output options 1-6
1.2.9 Source contribution analyses 1-8
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 2-2
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 2-3
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 2-4
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
v
-------
2.1.2.7 TOXX model input files 2-7
2.1.3 Controlling file inputs and outputs (I/O) 2-9
2.1.3.1 Controlling I/O on PCs 2-9
2.2 Description of keyword/parameter approach 2-9
2.2.1 Basic rules for structuring input control files 2-10
2.2.2 Advantages of the keyword approach 2-13
2.3 Regulatory default modeling options 2-14
2.4 Setting up a simple control file 2-15
2.4.1 A simple industrial source application 2-17
2.4.2 Selecting modeling options - CO pathway 2-17
2.4.3 Specifying source inputs - SO pathway 2-20
2.4.4 Specifying a receptor network - RE pathway 2-24
2.4.5 Specifying the meteorological Input - ME pathway 2-25
2.4.6 Selecting output options - OU pathway 2-27
2.4.7 Using the error message file to debug the input control file 2-30
2.4.8 Running the model and reviewing the results 2-35
2.5 Modifying an existing control file 2-44
2.5.1 Modifying modeling options 2-44
2.5.2 Adding or modifying a source or source group 2-44
2.5.3 Adding or modifying a receptor network 2-45
2.5.4 Modifying output options 2-45
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 3-9
3.2.2.5 Output types (CONC, DEPOS, DDEP and/or WDEP) 3-10
vi
-------
3.2.2.6 Deposition depletion options 3-10
3.2.2.7 NO2 conversion options 3-11
3.2.2.8 FASTAREA and FASTALL 3-12
3.2.2.9 Urban transition and NOURBTRAN option 3-14
3.2.2.10 SCREEN mode 3-14
3.2.2.11 SCI VI 3-15
3.2.2.12 Deposition Options 3-16
3.2.2.13 Definition of seasons for gaseous dry deposition 3-18
3.2.2.14 Definition of land use categories for gas dry deposition 3-19
3.2.2.15 Deposition velocity and resistance outputs 3-20
3.2.2.16 Remove displacement height from RLINE wind profile 3-21
3.2.3 Low wind parameters 3-21
3.2.4 Building downwash options 3-23
3.2.4.1 ORD building downwash options 3-25
3.2.4.2 AWMA building downwash options 3-27
3.2.5 Input parameters for NO2 conversion options 3-29
3.2.5.1 Specifying ozone concentrations for PVMRM, OLM, TTRM/TTRM2, and
GRSM options 3-32
3.2.5.2 Specifying NOx background concentrations for the GRSM option 3-37
3.2.5.3 Specifying the ambient equilibrium NCh/NOx ratio (PVMRM, OLM,
TTRV1/TTRV12) 3-42
3.2.5.4 Specifying the default in-stack NO2/NOX ratio (PVMRM, OLM,
TTRV1/TTRV12. GRSM) 3-42
3.2.6 Averaging time options 3-43
3.2.7 Performing multiple year analyses with MULTYEAR option 3-44
3.2.8 Urban modeling option 3-46
3.2.9 Specifying the pollutant type 3-47
3.2.10 Modeling with exponential decay 3-48
3.2.11 Flagpole receptor height option 3-49
3.2.12 Plume Rise from Aircraft Emissions 3-49
3.2.13 To run or not to run 3-50
3.2.14 Generating an input file for EVENT processing 3-51
vii
-------
3.2.15 The model re-start capability 3-52
3.2.16 Processing for particulate matter (PM) NAAQS 3-53
3.2.16.1 Processing for fine particulate matter (PM-2.5) 3-53
3.2.16.2 Processing for particulate matter of 10 microns or less (PM-10) 3-56
3.2.17 Processing for 1-hour NO2 and SO2 NAAQS 3-57
3.2.18 Debugging output options 3-58
3.2.19 Detailed error listing file 3-60
3.3 Source pathway inputs and options 3-61
3.3.1 Identifying source types and locations 3-62
3.3.2 Specifying source release parameters 3-67
3.3.2.1 POINT, POINTHOR, and POINTCAP source inputs 3-67
3.3.2.2 VOLUME source inputs 3-68
3.3.2.3 AREA source type 3-70
3.3.2.4 AREA source inputs 3-70
3.3.2.5 AREAPOLY source inputs 3-74
3.3.2.6 AREACIRC source inputs 3-75
3.3.2.7 OPENPIT source inputs 3-76
3.3.2.8 LINE source inputs 3-78
3.3.2.9 RLINE and RLINEXT source inputs 3-79
3.3.2.10 BUOYLINE source inputs 3-85
3.3.2.11 SWPOINT source inputs 3-88
3.3.3 Specifying gas deposition parameters 3-90
3.3.3.1 Source parameters for gas deposition (dry and/or wet) 3-90
3.3.3.2 Option for specifying the deposition velocity for gas dry deposition 3-91
3.3.4 Specifying source parameters for particle deposition 3-92
3.3.4.1 Specifying particle inputs for Method 1 3-92
3.3.4.2 Specifying particle inputs for Method 2 3-93
3.3.5 Specifying Emission and Output Units 3-94
3.3.6 Source input parameters for NO2 conversion options 3-95
3.3.6.1 Specifying in-stack NO2/NOX ratios by source for PVMRM, OLM,
TTRM/TTRM2, and GRSM 3-95
viii
-------
3.3.6.2 Specifying combined plumes for OLM 3-96
3.3.6.3 Specifying ambient NCh/NOx ratios for the ARM2 option 3-97
3.3.7 Modeling NO2 increment credits with PVMRM 3-98
3.3.7.1 Increment consuming and baseline sources 3-99
3.3.7.2 Calculating increment consumption under the PSDCREDIT option 3-99
3.3.7.3 Specifying source groups under the PSDCREDIT option 3-101
3.3.7.4 Model outputs under the PSDCREDIT option 3-103
3.3.8 Background concentrations 3-103
3.3.8.1 Defining background concentration sectors 3-104
3.3.8.2 Specifying the background concentration 3-104
3.3.8.3 Specifying background concentration units 3-108
3.3.9 Specifying building downwash information 3-109
3.3.10 Specifying urban sources 3-114
3.3.11 Specifying variable emission factors (EMISFACT) 3-115
3.3.12 Specifying an hourly emission rate file (HOUREMIS) 3-117
3.3.13 Adjusting the emission rate units for output 3-121
3.3.14 Including source data from an external file 3-122
3.3.15 Using source groups 3-123
3.3.16 Specifying platform downwash information (POINT, POINTHOR, POINTCAP
sources ONLY) 3-125
3.3.17 Specifying highly buoyant point sources for HBP option (POINT, POINTHOR,
POINTCAP sources ONLY) 3-126
3.3.18 Specifying aircraft sources (AREA and VOLUME sources ONLY) 3-127
3.4 Receptor pathway inputs and options 3-128
3.4.1 Defining networks of gridded receptors 3-129
3.4.1.1 Cartesian grid receptor networks 3-129
3.4.1.2 Polar grid receptor networks 3-133
3.4.2 Using multiple receptor networks 3-137
3.4.3 Specifying discrete receptor locations 3-137
3.4.3.1 Discrete Cartesian receptors 3-137
3.4.3.2 Discrete polar receptors 3-138
IX
-------
3.4.3.3 Discrete Cartesian receptors for evalfile output 3-139
3.4.4 Including receptor data from an external file 3-140
3.5 Meteorology pathway inputs and options 3-141
3.5.1 Specifying the input data files and formats 3-141
3.5.2 Specifying station information 3-144
3.5.3 Specifying the base elevation for potential temperature profile 3-144
3.5.4 Specifying a data period to process 3-145
3.5.5 Correcting wind direction alignment problems 3-147
3.5.6 Specifying wind speed categories 3-147
3.5.7 Specifying SCIM parameters 3-148
3.5.8 Specify the number of years to process 3-149
3.5.9 Specify turbulence treatment options 3-149
3.6 Event pathway inputs and options 3-150
3.6.1 Using events generated by the AERMOD model 3-152
3.6.2 Specifying discrete events 3-154
3.6.3 Including event data from an external file 3-154
3.7 Output pathway inputs and options 3-155
3.7.1 Selecting options for tabular printed outputs 3-155
3.7.2 Selecting options for special purpose output files 3-159
3.7.2.1 MAXIFILE 3-160
3.7.2.2 POSTFILE 3-161
3.7.2.3 PI.Oi l II.Ii 3-163
3.7.2.4 TOXXFILE 3-165
3.7.2.5 R.WKI II.Ii 3-166
3.7.2.6 EVALFILE 3-167
3.7.2.7 SEASONHR 3-168
3.7.2.8 MAXDCONT 3-170
3.7.2.9 Y1AXDAII.Y 3-172
3.7.2.10 MAXDYBYYR 3-172
3.7.3 EVENT processing options 3-173
3.7.4 Miscellaneous output options 3-173
x
-------
4.0 References 4-1
APPENDIX A. Functional keyword/parameter reference A-l
APPENDIX B. Explanation of error message codes B-l
B.l Introduction B-l
B.2 Output message summary B-2
B.3 Description of the message layout B-3
APPENDIX C. Description of file formats C-l
C.l 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-6
C.5 TOXX model input files (TOXXFILE option) C-7
C.6 Maximum values by rank (RANKFILE option) C-8
C.l Arc-maximum values for evaluation (EVALFIL option) C-9
C.8 Results by season and hour-of-day (SEASONHR option) C-l2
C.9 Source group contribution for ranked averaged maximum daily values
(MAXDCONT) C-l 3
C.10 Daily maximum 1-hour values (MAXDAILY) C-16
C.l 1 Maximum daily 1-hour concentration by year (MAXDYBYYR) C-l8
APPENDIX D. Overview of AERMOD revisions in version 23132 D-l
APPENDIX E. Glossary E-7
XI
-------
Figures
Figure Page
Figure 2-1. Example Input File for AERMOD for Sample Problem 2-16
Figure 2-2. Example Input control file for Sample Problem 2-29
Figure 2-3. Example Message Summary Table for AERMOD Execution 2-33
Figure 2-4. Example of Keyword Error and Associated Message Summary Table 2-34
Figure 2-5. Organization of the AERMOD Model Output File 2-37
Figure 2-6. Sample of Model Option Summary Table from an AERMOD Model
Output File 2-40
Figure 2-7. Example Output Table of High Values by Receptor 2-41
Figure 2-8. Example of Result Summary Tables for the AERMOD Model 2-43
Figure 3-1. Relationship of Area Source Parameters for Rotated Rectangle 3-72
Figure 3-2.Fixed Stack location with respect to Building and Wind Flow
Orientation 3-89
Figure 3-3. Schematic Diagram Identifying New Building Data for Prime
Downwash 3-113
Figure 3-4. New platform parameter figure with correct parameter definitions.
Adapted from Petersen (1984) 3-126
Figure B-l. Example of an AERMOD Message Summary B-2
xii
-------
Tables
Table Page
Table 3-1 Summary of Deposition Options 3-17
Table 3-2. Implemented N02 Conversion Options by AERMOD Source Type 3-31
Table 3-3. Summary of Suggested Procedures for Estimating Initial Lateral
Dimensions oyo and Initial Vertical Dimensions ozo for Volume and
Line Sources 3-69
Table A-l. Description of Control Pathway Keywords A-3
Table A-2. Description of Control Pathway Keywords and Parameters A-6
Table A-3. Description of Source Pathway Keywords A-21
Table A-4. Description of Source Pathway Keywords and Parameters A-23
Table A-5. Description of Receptor Pathway Keywords A-31
Table A-6. Description of Receptor Pathway Keywords and Parameters A-32
Table A-7. Description of Meteorology Pathway Keywords A-35
Table A-8. Description of Meteorology Pathway Keywords and Parameters A-3 6
Table A-9. Description of Event Pathways and Keywords A-39
Table A-10. Description of Event Pathway Keywords and Parameters A-40
Table A-l 1. Description of Output Pathway Keywords A-41
Table A-12. Description of Output Pathway Keywords and Parameters A-42
Xlll
-------
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
-------
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 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, 2023a) 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
-------
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.
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, 2023c). 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.
1-3
-------
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
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.
1-4
-------
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
contral 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.
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
1-5
-------
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, 2023c). 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.
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
1-6
-------
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.
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
1-7
-------
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.
1-8
-------
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
-------
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 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, 2023c). 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.
2-2
-------
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.
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.
2-3
-------
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 TMP.FIL. If a single file is used, then the
intermediate results file is overwritten 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.
2-4
-------
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. User-specified units must be
greater than or equal to 34 and are recommended to be less than or equal to 100. For a large
number of files or to ensure there will be no file conflicts, user-specified units could begin at
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 will not
cause any conflict with other file units used by the model for up to nine source groups and up to
nine short-term averaging periods.
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.
2-5
-------
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. User-specified units must be greater
than or equal to 34 and are recommended to be less than or equal to 100. For a large number of
files or to ensure there will be no file conflicts, user-specified units could begin at 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 + IAVE for 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.
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
2-6
-------
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. User-specified units must be
greater than or equal to 34 and are recommended to be less than or equal to 100. For a large
number of files or to ensure there will be no file conflicts, user-specified units could begin at
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 will not
cause any conflict with other file units used by the model for up to nine source groups and up to
nine short-term averaging periods.
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 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 selected by the user is
opened explicitly by the model as an unformatted file. The filenames are provided on the input
control file command. The user may specify the file unit on the TOXXFILE card through the
2-7
-------
optional FUNIT parameter. User-specified units must be greater than or equal to 34 and are
recommended to be less than or equal to 100. For a large number of files or to ensure there will
be no file conflicts, user-specified units could begin at 10,000 and increment by one. If no file
unit is specified, then the file unit is determined internally according to the following formula:
where ITXUNT 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). This formula will not cause
any conflict with other file units used by the model for up to four short-term averaging periods.
The user may also select an option for the AERMOD model to generate an output for use
with the RISK model component of TOXLT. The OU TOXXFILE keyword also controls this
option. The user can specify a separate TOXXFILE for each long-term averaging period and
source group combination. The TOXXFILE option may also be used for PERIOD averages with
the AERMOD model. The structure of the TOXXFILE output for AERMOD is very similar to
the long term PLOTFILE output, except results are output for each individual source in the
specified source group. The structure of the long term TOXXFILE 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 TOXXFILE card through the optional FUNIT parameter. User-
specified units must be greater than or equal to 34 and are recommended to be less than or equal
to 100. For a large number of files or to ensure there will be no file conflicts, user-specified
units could begin at 10,000 and increment by one. If no file unit is specified, then the file unit is
determined internally according to the following formulas:
where ITXUNT and IPXUNT are the Fortran unit numbers, IAVE is the averaging period
number (in the order of months, seasons or quarters, and annual), and IGRP is the source group
number (in the order is which the groups are defined in the SO pathway). This formula will not
cause any conflict with other file units used by the model for up to nine source groups.
ITXUNT = 300 + IAVE
ITXUNT = 500 + IAVE* 10 + IGRP
IPXUNT = 700 + IGRP* 10
for long term averages
for PERIOD averages
2-8
-------
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:
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:
2-9
-------
CO - for specifying overall job COntrol options;
SO - for specifying SOurce information;
RE - for specifying REceptor information;
ME - for specifying MEteorology information;
EV - for specifiying EVent processing;
OU - for specifying OUtput options.
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: 123 4567 8 9 012 345 678 901234567 8 90123 456 7890
CO MODELOPT DFAULT CONG
I 1 -~ 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.
2-10
-------
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.
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: 12345678 9012345 678 901234567 8 901234567890
CO MODELOPT DFAULT CONC
I ' ' Parameters
8-Character Keyword
2 Character Pathway ID
2-11
-------
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 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.
2-12
-------
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 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.
2-13
-------
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.
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
2-14
-------
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.
2-15
-------
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
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 1988 ALBANY,NY
ME
UAIRDATA
14735 1988 ALBANY,NY
ME
SITEDATA
ME
PROFBASE
0.0 METERS
ME
FINISHED
OU
STARTING
OU
RECTABLE
ALIVE FIRST-SECOND
OU
MAXTABLE
ALIVE 50
OU
FINISHED
Figure 2-1. Example Input File for AERMOD for Sample Problem
2-16
-------
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 - Indicates the beginning of inputs for the pathway; this keyword is
mandatory on each of the pathways.
TITLEONE - 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).
MODELOPT - Controls the modeling options selected for a particular run through a
series of secondary keywords.
AVERTIME - Identifies the averaging periods to be calculated for a particular run.
POLLUTED - Identifies the type of pollutant being modeled. At the present time,
this option has no influence on the results.
RUNORNOT - 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.
FINISHED - Indicates that the user is finished with the inputs for this pathway; this
keyword is also mandatory on each of the other pathways.
2-17
-------
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
TITIEONE
A Simple Example Problem for the AERMOD-PRIME Model
CO
MODEIOPT
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 FIAT
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:
2-18
-------
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
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 FLAT
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:
2-19
-------
CO
STARTING
TITLEONE
A Simple Example Problem for the AERMOD-PRIME Model
MODELOPT
CONC FLAT
AVERT IME
3 24 PERIOD
POLLUTID
S02
RIJNORNOT
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 BUTLDWID in our input file.
2-20
-------
The input file for the SO pathway for this example will like the following:
STARTING
LOCATION
STACK1
POINT
0 . 0
0 . 0
0 . 0
SRCPARAM
STACK1
500.0
65.00
425.
15.0
5 . 0
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
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
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
50.00
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
50.00
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
2-21
-------
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 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:
2-22
-------
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
8 9. 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.
2-23
-------
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
2-24
-------
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 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:
2-25
-------
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
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 SITEDATA 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.
2-26
-------
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.
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
2-27
-------
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
ALIAVE 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
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.
2-28
-------
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
SO
* *
Ĥk -k
STARTING
LOCATION STACK1
Point Source
Parameters :
POINT 0.0 0.0 0.0
QS HS TS VS
DS
SO
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 36 10 10
POL1 END
500. 1000.
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
OU STARTING
RECTABLE ALLAVE FIRST-SECOND
MAXTABLE ALLAVE 50
OU FINISHED
Figure 2-2. Example Input control file for Sample Problem
2-29
-------
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
2-30
-------
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 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
Hints
1 1 1 1 1
III | Detailed error/warning message
III 1
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
2-31
-------
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.
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.
2-32
-------
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
****
****
FATAL ERROR
MESSAGES ********
*** NONE
***
0.00 Percent)
WARNING MESSAGES ********
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
2-33
-------
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
8 9. 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
8 9. 95
STACK1
87.58
82.54 75.
00
82.54
87.58
8 9. 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 El 05
15
SETUP
Invalid Keyword Specified. The Troubled Keyword
is
BUILDWTS
SO El10
16
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO El10
17
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO El10
18
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO El10
19
SOCARD
Keyword is
Not
Valid for
This Pathway. Keyword
is
BUILDWTS
SO El10
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
2-34
-------
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:
Path-to-AERMOD.EXE\AERMOD
Pa/h-/o-A ERMOI). EXE A E RM O D runstrearn input Jilename
Path-to-AERMOD.EXE\AERMOD runstr earn inputJilename outputJilename
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
specificed, 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
2-35
-------
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 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.
2-36
-------
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
2-37
-------
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.
2-38
-------
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 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.
2-39
-------
+ + + 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
2-40
-------
AERMOD - VERSION 22112
AERMET - VERSION 22112
A Simple Example Problem for the AERMOD-PRIME Model
MODELOPTs:
NonDFAULT CONC FLAT RURAL SigA&SigW
DIRECTION
(DEGREES)
THE 1ST HIGHEST 3-HR AVERAGE CONCENTRATION VALUES FOR SOURCE GROUP: ALL
INCLUDING SOURCE(S): STACK1
175.00
NETWORK ID: POL1
** CONC OF S02
350.00
; NETWORK TYPE: GRIDPOLR
IN MICROGRAMS/M**3
DISTANCE (METERS)
500.00
1000.00
06/07/22
14:18:02
PAGE 9
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
4 6873
(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 . 687 67
(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
2-41
-------
***
AERMOD -
VERSION
22112 *** *** A Simple
Example Problem
for the AERMOD-PRIME Model
***
06/07/22
***
AERMET -
VERSION
22112 *** ***
***
14:18:02
PAGE 15
***
MODELOPTs
: NonDFAULT CONC FLAT RURAL
SigA&SigW
*** THE
SUMMARY OF MAXIMUM PERIOD ( 96 HRS) RESULTS
***
** CONC OF
S02 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
4TH
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
7TH
HIGHEST
VALUE IS 15.01122 AT
( 939.69,
-342.02, 0.00, 0.
00,
0
.00)
GP
POL1
8TH
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
GROUP 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
***
06/07/22
***
AERMET -
VERSION
22112 *** ***
***
14:18:02
PAGE 17
MODELOPTs
: NonDFAULT CONC FLAT RURAL
SigA&SigW
2-42
-------
*** 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
o
o
o
GP
P0L1
HIGH
2ND
HIGH
VALUE IS 10.09519
ON 88030324:
AT ( 8 66
.03, -500.00,
o
o
o
o
o
o
o
o
o
GP
P0L1
*** RECEPTOR
TYPES
GO
= GRIDCART
GP
= GRIDPOLR
DC
= DISCCART
DP
= DISCPOLR
Figure 2-8. Example of Result Summary Tables for the AERMOD Model
2-43
-------
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.
2-44
-------
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 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.
2-45
-------
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 Titlel 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 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
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.
NOWARN - 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-regualtory 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-
regualtory 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.
OLM-
ARM2-
TTRM -
TTRM2 -
GRSM -
Specifies that the non-regulatory Generic Reaction Set Method (GRSM) will be
used for NO2 conversion (non-regulatory BETA option, requires the BETA
3-4
-------
PSDCREDIT -
FASTALL-
FASTAREA -
DRYDPLT -
NODRYDPLT
WETDPLT -
NOWETDPLT -
NOURBTRAN -
VECTORWS -
N0MIN03 -
RLINEFDH -
keyword and cannot be used with the DFAULT keyword); 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 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, 2023a) 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
3-5
-------
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).
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 DCAYCOEFFor 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
3-6
-------
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).
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 23132 includes the
following ALPHA options:
Prevention of Significant Deterioriation Credie (PSDCREDIT)
Low Wind Parmaters (LOW WIND)
A&WMA Downwash Options (AWMADWNW)
EPA Office of Research and Developtment Downwash Options (ORD DWNW)
Offshore Platform Downwash (PLATFORM, applies to point sources only)
Extended RLINE Source Type (RLINEXT)
Depressed Roadway (RDEPRESS, used only with RLINEXT)
3-7
-------
Roadway Barrier (RBARRIER, used only with RLINEXT)
Removal of Displacement Height from RLINE Wind Profile (RLINEFDH)
Particle Deposition - Method 2 (METHOD2)
Gas deposition (GD SEA SON, 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 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. As with the ALPHA options, BETA options are enabled in the
control file in different ways, depending on the option. Version 23132 includes the following BETA
options:
3-8
-------
Mobile Line Source (RLINE)
Generica Reaction Set Method (GRSM, for Tier 3 NO2 conversion)
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 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
3-9
-------
any further adjustment when downwash is applied, as suggested in Section 6.1 of the AERMOD
Implementation Guide (EPA, 2023b), 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.
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
3-10
-------
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 NO2conversion 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 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
3-11
-------
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 and then updated as a BETA option
beginning with version 22112. 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.
Only one of ARM2, TTRM, OLM, PVMRM, or GRSM options for NO2 conversion can be
specified for a given model run. Alternatively, the TTRM2 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 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
3-12
-------
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 (pyeff) that replicates the centerline concentration based on the full meander
approach. Use of the effective oy allows the model runtime to be optimized by skipping receptors
that are more than 40^ off the plume centerline. Based on tests conducted to date, comparisons of
concentrations based on the FASTALL option for POINT and VOLUME sources with
concentrations using the DFAULT option are similar to comparisons of concentrations for AREA
sources using the FASTAREA option. The average ratio of FASTALL concentrations to DFAULT
values is about 1.02 for high ranked values, showing a slight bias toward over prediction for the
FASTALL option. However, the range of ratios for high ranked values shows both over predictions
and under predictions relative to the DFAULT option, and differences at specific receptors may be
much larger.
The FASTALL option for RLINE and RLINEXT uses an approximation to estimate the
values for the horizontal and vertical dispersion coefficients (py and erz, respectively) and the
effective plume wind 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.
3-13
-------
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, 2023a).
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.
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,
3-14
-------
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 = ICS/NS
where:
C = Calculated concentration
^ Cs = Cumulatibe impacts for the sampled hours
Ns = Number of sampled hours
3-15
-------
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 SCIMBYHR keyword 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
3-16
-------
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.
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.
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).
3-17
-------
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)
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 0. 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.
3-18
-------
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
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
3-19
-------
An optional keyword is available on the Control (CO) pathway to allow the user to override
the default values of the reactivity factor (f0), 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 (f0), 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 1, 3, and 4. A
reactivity factor value of 1 should be input for ozone (O3), titanium tetrachloride (TiCU), 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' 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 Vdg (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.
3-20
-------
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 LOW WIND
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,
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
3-21
-------
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.
Note: The LOW WIND 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.
3-22
-------
In addition to the LOWWIND 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 ADJ U* 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 ADJ U* 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 ORDDWNW 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 downwas in AERMOD.
3-23
-------
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.
3-24
-------
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 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 ORDDWNW 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
3-25
-------
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.
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 ORDDWNW options listed are optional, but at least one
must be included if the ORD_ DWNW keyword is specified in the control file.
3-26
-------
3.2.4.2 AWMA building 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:
CO AWMADWNW AWMAUEFF and/or
AWMAENTRAIN and/or
y : ((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
ORDDWNW option ORDUEFF.
AWMAENTRAIN - AWMAENTRAIN changes beta (B) entrainment coefficient for
PRIME downwash from default value of 0.60 to 0.35.
3-27
-------
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
-------
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 NO2 conversion options
This section provides a description of the AERMOD inputs related to the PVMRM, OLM,
and ARM2 regulatory options for modeling the conversion of NO to NO2, as well as the ALPHA
options, TTRM and TTRM2, and the BETA Tier 3 option, GRSM. 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. 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.
A technical description of the PVMRM algorithm as incorporated within AERMOD is
provided in the AERMOD Model Formulation document (EPA, 2023a). Additional information
regarding the regulatory options for NO2 modeling are provided in Technical Support Document
(TSD) for N02-related AERMOD Modifications (EPA, 2015). Background on the original
development of the PVMRM option is provided by Hanrahan (1999a and 1999b).
3-29
-------
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 NCh/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 NCh/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 and
OLM algorithms have been implemented as regulatory Tier 3 screening options. Therefore, any
one of the three options can be used with the DFAULT keyword. TTRM/TTRM2 and GRSM have
been added as non-regulatory ALPHA and BETA options, respectively, 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 GRSM, 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 N02 model concentrations are calculated based on the net production of N02
from the following: N02 in-stack ratio, ozone entratinment and conversion of NOx to N02,
photolysis of N02 to NO, and time-of-travel of the NOx plume from source to receptor.
3-30
-------
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
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.
3-31
-------
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 03 VALUES 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, 03 VALUES, or
OZONEFIL keyword to use the PVMRM, OLM, TTRM/TTRM2, or GRSM option. The
OZONEVAL or 03 VALUES keyword may also be specified with the OZONEFIL keyword, in
which case the value(s) entered on the OZONEVAL or 03 VALUES 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 03 VALUES 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 03SECT0R 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
3-32
-------
where the 03 Value 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 optional 03 SECTOR keyword for which the 03 Value 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 03SECT0R 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 03 SECTOR
keyword. 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. 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),
3-33
-------
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),
SHRDOW7 - ozone values vary by season, hour-of-day, and the seven days of the week [M, Tu,
W, Th, F, Sat, Sun] (n = 672),
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 03 Values 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 03 VALUES keyword are assumed to be in units of
PPB unless the OZONUNIT keyword is specified.
3-34
-------
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 03 VALUES 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).
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
03SECT0R keyword, then the applicable sector ID needs to be specified, e.g., 'SECT1' 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
3-35
-------
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 T,' '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 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 03 VALUES 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 N0MIN03 keyword. As
with all NO2 options, this option shall be used in agreement with the appropriate reviewing
authority.
3-36
-------
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/N0X 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
NOXVALS keyword on the CO pathway, or as hourly values from a separate data file specified
through the NOXFILE keyword 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 NOX_VALS 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-
3-37
-------
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).
The syntax of the NOX VALS keyword is as follows and is similar to the 03 VALUES
keyword described above in Section 3.2.5.1 for specifying temporally varying ozone background
concentrations:
3-38
-------
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 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
3-39
-------
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 NOXVALS keyword are assumed to be in units of
PPB unless the NOXUNIT keyword is specified.
The syntax of the NOX_UNIT 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 NOX UNIT 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:
3-40
-------
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
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., ' SECT1' 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
3-41
-------
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 or NOX_VALS keywords are used, then the model will
equilibrium of NOx with NO2 for hours with missing NOx data.
3.2.5.3 Specifying the ambient equilibrium NO2/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.
3.2.5.4 Specifying the default in-stackNO?/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.
3-42
-------
This requirement has been carried forward with the addition of the TTRM/TTRM2 and GRSM
options.
The in-stack NCh/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 N02RATI0 keyword to specify a value on a source-by-source
basis. The SO N02RATI0 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:
Syntax:
CO N02STACK N02Ratio
Type:
Optional, Non-repeatable
where the N02Ratio parameter is the default in-stack NO2/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 NO2/NOX 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 .
. TimejV MONTH PERIOD
Syntax:
or
ANNUAL
Type:
Mandatory, Non-repeatable
where the parameters Timel . . . Time# refer to the user-specified short-term averaging periods of
I, 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,
3-43
-------
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-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
3-44
-------
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 1-hour NO2 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 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
3-45
-------
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.SAV YEAR1.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 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.
3.2.8 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
3-46
-------
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.
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
3-47
-------
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, orPM-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:
CO HALFLIFE Haflif
Syntax: CQ DCAYCqEF 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.
3-48
-------
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 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:
3-49
-------
Syntax:
CO ARCFTOPT (AirportlD)
Type:
Optional, Non-Repeatable
Where AirportlD 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 calculations, or NOT to run
3-50
-------
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 ILEN FLD 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
3-51
-------
RECTABLE keyword and the threshold violations identified by the MAXIFILF. keyword on the
OU pathway.
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: C0 INITFILE (Inifil)
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.
3-52
-------
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.
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
3-53
-------
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.
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
POLLUTED 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 0) to
determine contributions from other source groups to the cumulative modeled design value will not
3-54
-------
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 1 ST) highest value should be requested on the RECTABLE keyword
for 24-hour averages for estimating modeled PM2.5 contributions for compliance
with the 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.
3-55
-------
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-A' /-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) 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 TV
years 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.
3-56
-------
3.2.17 Processing for 1-hour NO2 and SO2 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 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
3-57
-------
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:
3-58
-------
CO DEBUGOPT MODEL fDbefiD
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:
GDEP.DAT 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
3-59
-------
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 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 AFTERTTRM.DBG, AFTEK option.DBG, and TTRM2 MERGE.DBG,
where option is the NO2 conversion option with which TTRM2 is paired, (e.g.,
AFTERPVMRM.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:
3-60
-------
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.
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.
3-61
-------
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:
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. A RE AC IRC. 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. The RLINE source type requires the BETA secondary keyword
with the MODELOPT keyword on the CO pathway, while the RLINEXT source type is an alpha
option and similarly, requires the ALPHA keyword with the MODELOPT keyword. The original
implementation was based on the numerical integration and algorithms in the Research LINE-
3-62
-------
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 the EPA's related TSD
(EPA, 2023d). 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-
analyses).
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. Also, refer to the user's guide for R-LINE
Model Version 1.2 (Snyder and Heist, 2013) and EPA's 2023 TSD (EPA, 2023d) 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. Refer to the BLP user's guide (Schulman and Scire, 1980)
for detailed information about the formulation of the buoyant line source algorithm.
3-63
-------
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 Xsl, Ysl, 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 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.
3-64
-------
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 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
3-65
-------
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 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 LINE1 A, LINE1B, LINE1C, etc.
3-66
-------
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:
SO SRCPARAM STACK 1 16.71 35.0 444.0 22.7 274
3-67
-------
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, BUTLDLEN, 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:
3-68
-------
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
Type of Source
Procedure for Obtaining
Initial Dimension
(a) Initial Lateral Dimension (oy0)
Single Volume Source
Gyo = 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)
Elevated Source (he > 0) on or Adjacent to a
Building
Ozo = vertical dimension of source divided by 2.15
Ozo = building height divided by 2.15
Elevated Source (he > 0) not on or Adjacent to oZ0 = vertical dimension of source divided by 4.3
a Building
3-69
-------
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 ARE APPLY source type may be
used to specify an area source as an irregularly-shaped polygon of up to 20 sides; the A RE AC IRC
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
3-70
-------
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,
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.
3-71
-------
Figure 3-1. Relationship of Area Source Parameters for Rotated Rectangle
3-72
-------
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
3-73
-------
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).
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).
3-74
-------
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 AREA VERT keyword, which applies only
to ARE APPLY sources. The syntax, type and order for the AREA VERT keyword used for
ARE APPLY sources are summarized below:
Syntax:
SO AREA VERT 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 LPCATIPN 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 AERMPD 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 A RE AC IRC source inputs
The A RE AC IRC 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:
3-75
-------
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:
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:
3-76
-------
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 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,
3-77
-------
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.
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),
3-78
-------
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, with the number of points included in the integration determined by
error analysis. Beginning with version 19191, use of the RLINE source type requires use of the
non-regulatory BETA flag for the Control pathway MODELOPT keyword. Because the BETA flag
is required for this source type, it is currently non-regulatory and can not 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).
3-79
-------
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 See Section 3.3.13).
3.3.2.10 RLINEXT source inputs
Beginning with version 19191, use of the RLINEXT source type requires use of the non-
regulatory ALPHA flag for the Control pathway MODELOPT keyword. As with RLINE, the
RLINEXT source type is currently non-regulatory and can not be used with the DFAULT option.
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'.
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.)
3-80
-------
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 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, with the number of points included in the integration determined by
error analysis. RLINE and RLINEXT sources use the same dispersion calculations, but parameter
definition is different for each source type.
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
3-81
-------
model assumes 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 See Section 3.3.13).
The distance from the centerline (DCL) parameter determines the offset from roadway
centerline for a source representing a single lane of traffic. As an example, in the case of 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
distance from the midpoint of the median to the midpoint of each source, i.e., where the endpoints
of the source are located. 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. 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, positive
DCL value, and the westernmost lane having the lowest, 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 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.
The Width parameter indicates 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.
3-82
-------
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:
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,
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:
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:
3-83
-------
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).
As of version 19191, barrier and depressed roadway source configurations can only be used
if the ALPHA flag is present as a MODELOPT.
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.
3-84
-------
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:
3-85
-------
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 - buoyant line group ID,
Blavgblen (L) - average building length (m),
Blavgbhgt (HB) - average building height (m),
Blavgbwid (WB) - average building width (m),
Blavglwid (WM) - average line source width (m) (of the individual lines),
Blavgbsep (DX) - average building separation (m) (between the individual lines),
Blavgfprm (FPRIME) - 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 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.
3-86
-------
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.
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
3-87
-------
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 occures 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:
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:
3-88
-------
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.
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" Stack
Figure 3-2.Fixed Stack location with respect to Building and Wind Flow Orientation
3-89
-------
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 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.
3-90
-------
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:
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
3-91
-------
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 [j,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 [j,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 [j,m in diameter) and the deposition velocity for the
coarse mode (i.e., greater than 2.5 [j,m but less than 10 [j,m in diameter). As described in Section 0,
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:
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
3-92
-------
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 METHOD 2 keyword on the SO
pathway. The syntax, type, and order for the METHOD 2 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).
As of version 21112, optional default Method 2 particle deposition parameters
(FineMassFraction and Dmm) are included for arsenic, cadmium, lead, mercury, and polycyclic
3-93
-------
aromatic hydrocarbons (PAH). There are two requirements to use the default Method 2 particle
deposition parameters. First, the POLLUTED 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
METHOD 2 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
3-94
-------
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 40 characters) for concentration calculations. The default conversion is from g/s to
Hg/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
*lxl09) where lxlO9 is the conversion from g to nanograms.
3.3.6 Source input parameters for NO2 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-stackNCh/NOx 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 NO2/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
NO2/NOX ratios through the optional N02RATIO keyword on the SO pathway. The syntax of the
N02RATIO keyword is as follows:
3-95
-------
Syntax:
SO N02RATI0 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 NCh/NOx ratio for a group of stacks. For example, the following input:
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 STACK1 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
3-96
-------
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 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 3.3.2.10.
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 Mh/NOx 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
3-97
-------
ambient ratio to the 1-hr modeled NOx concentrations based on a formula derived empirically from
ambient monitored ratios of NCh/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.
3.3.7 Modeling NO2 increment credits with PVMRM
Due to the ozonelimiting 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.
3-98
-------
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.
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
3-99
-------
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).
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)
3-100
-------
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
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,
3-101
-------
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.
3-102
-------
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.
3-103
-------
3.3.8.1 Defining background concentration sectors
For applications that include 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
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.
3.3.8.2 Specifying 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:
3-104
-------
SO BACKGRND SECTx BGflag BGvalue(i), i=l, and x < 6
and/or
Syntax: SQ BACKGRND SECTx HOURLY BGfilnam (BGformat), where
x < 6
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
3-105
-------
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).
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
3-106
-------
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).
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).
3-107
-------
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.
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
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.
3-108
-------
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:
BUTLDHGT, BUILDWID, BUTLDLEN, XBADJ, YBADJ. The syntax, type and order for the
BUILDHGT keyword, used to input direction specific building heights, are summarized below:
Syntax:
SO BUILDHGT Srcid (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 STACK1 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
3-109
-------
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 VENT 1 A-VENT 1C. However, VENT2 does not fall within the range of
VENT1A to VENT3B, since the third part of VENT2 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 from north), and incrementing by 10 degrees in a clockwise direction. Some
examples of building height inputs are presented below:
3-110
-------
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 BUTLDWID 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:
3-111
-------
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.
3-112
-------
Flow
J
Stack w
Xbadj
\
\ Ybadi +X (along How
*
J
^Bujldiert_^
Projected
Building
Figure 3-3. 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.
3-113
-------
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.
3-114
-------
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:
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 -
MONTH-
HROFDY -
WSPEED -
SEASHR -
HRDOW -
HRDOW7 -
SHRDOW-
SHRDOW7 -
3-115
emission rates vary seasonally (n=4),
emission rates vary monthly (n=12),
emission rates vary by hour-of-day (n=24),
emission rates vary by wind speed (n=6),
emission rates vary by season and hour-of-day (n=96),
emission rates vary by hour-of-day, and day-of-week [M-F, Sat, Sun] (n=72),
emission rates vary by hour-of-day, and the seven days of the week [M, Tu, W, Th,
F, Sat, Sun] (n=168),
emission rates vary by season, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n=288),
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 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:
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
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.
3-116
-------
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 0.5 11*1.0 0.5 6*0.3
**
Saturdays
Hrs: 1-5 6 7-17 18 19-24
so
EMISFACT
STK1
HRDOW
5*0.3 0.5 11*1.0 0.5 6*0.3
**
Sundays:
Hrs: 1-5 6 7-17 18 19-24
so
EMISFACT
STK1
HRDOW
5*0.3 0.5 11*1.0 0.5 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 0.5 11*1.0 0.5 6*0.3
**
Tuesdays:
Hrs: 1-5 6 7-17 18 19-24
so
EMISFACT
STK1
HRDOW7
5*0.3 0.5 11*1.0 0.5 6*0.3
**
Saturdays
Hrs: 1-5 6 7-17 18 19-24
so
EMISFACT
STK1
HRDOW7
5*0.3 0.5 11*1.0 0.5 6*0.3
**
Sundays:
Hrs: 1-5 6 7-17 18 19-24
so
EMISFACT
STK1
HRDOW7
5*0.3 0.5 11*1.0 0.5 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
24*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
24*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
24*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.
8 24*0.6 24*0.8
**
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.
8 24*0.6 24*0.8
**
Saturdays
so
EMISFACT
STK1
MHRDOW7
24*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
MHRDOW7
24*1.0 24*0.8 24*0.6 24*0.8 24*1.0 24*0.
8 24*0.6 24*0.8
3.3.12 Specifying an hourly emission rate file (HOUREMIS)
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:
3-117
-------
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:
3-118
-------
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)
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 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.
3-119
-------
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.
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
3-120
-------
so
HOUREMIS 8£
3
1
3
VOL1
500.0
2.0
N)
O
O
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.
3.3.13 Adjusting the emission rate units for output
The default emission rate units for the AERMOD model are grams per second for
POINT/POINTHOR/POINTCAP and VOLUME sources, grams per second per meter for
RLINEXT sources, and grams per second per square meter squared for AREA, LINE, OPENPIT,
and RLINE sources. By default, the model converts these input units to output units of micrograms
per cubic meter 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
3-121
-------
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 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:
3-122
-------
Syntax:
SO 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
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 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 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
3-123
-------
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 3.3.2.10. 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 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 indivual lines by specifying the source IDs from
the LOCATION keyword for those lines that should make up the SRCGROUP.
3-124
-------
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:
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 enterd 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.
3-125
-------
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 3-4. The platform downwash influence
is not adjusted for platform dimension normal to the wind, the influce will be identical for all
wind directions.
Figure 3-4. 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.
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.
3-126
-------
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
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.
3-127
-------
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 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).
3-128
-------
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:
3-129
-------
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 Zflaal 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
3-130
-------
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:
3-131
-------
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
3-132
-------
above. The model 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
3-133
-------
select the options for defining the receptor locations that make up the network. The syntax and type
of the GRIDPOLR keyword are summarized below:
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
Dirnum
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
3-134
-------
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.
3-135
-------
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.
3-136
-------
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:
3-137
-------
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:
3-138
-------
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 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
3-139
-------
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 reference elevation (e.g., mean sea level) used for source elevations. The Zflag parameter
is the 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. 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 terrain height and flagpole height inputs are ignored if the appropriate options are
not specified on the CO TERRHGHT and CO FLAGPOLE cards.
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:
3-140
-------
Syntax:
RE 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
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 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:
3-141
-------
Syntax:
ME SURFFILE Sfcfil (Format)
ME PROFFILE Profil (Format)
Type:
Optional, Repeatable
where the Srcfil and Profil parameters are character fields of up to 40 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)
Day of Month (1-31)
Julian Day (Day of Year) (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)
Bo wen Ratio
Albedo
Reference Wind Speed (m/s)
Reference Wind Direction (degrees)
Reference Height for Wind (m)
Ambient Temperature (K)
3-142
-------
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 M (m/s)
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.
3-143
-------
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 SITEDATA Stanum Year (Name) (Xcoord) (Ycoord)
Type:
Mandatory, Non-repeatable for SURFDATA and UAIRDATA
Optional, Non-repeatable for SITEDATA
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:
3-144
-------
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.
3-145
-------
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:
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 RangcS ... Rangc/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
3-146
-------
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 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: ME WDROTATE 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:
3-147
-------
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:
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 1. 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).
3-148
-------
3.5.8 Specify 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 0), 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.
3.5.9 Specify turbulence treatment options
Beginning with version 21112, the user can prompt AERMOD to set non-missing values for
turbulence (oe or ow) 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 meterological 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, 2023b). 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 owto missing for all hours
NOTURB ST: set oe and ow for stable hours only
NOTURBCO: set go and ow for convective hours only
NOSA: set oe to missing for all hours
NOSW: set ow to missing for all hours
3-149
-------
NOSAST: set oe to missing for stable hours only
NOSWST: set ow to missing for stable hours only
NOSACO: set oe to missing for convective hours only
NOSWCO set Ow 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.
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:
3-150
-------
Syntax:
EV EVENTPER Evname Aveper Grpid Date
Syntax:
EV EVENTLOC Evname XR= Xr YR= Yr (Zclcv) (Zflas)
Or Evname RNG= Rna DIR= Dir (Zelev) (Zflag)
Type:
Mandatory, Repeatable
where the parameters are as follows:
3-151
-------
Evname - event name (an alphanumeric string of up to 8 characters),
Aveper - averaging period for the event (e.g., I, 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.)
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
3-152
-------
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
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.
3-153
-------
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 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.
3-154
-------
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 1-hour NO2 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:
3-155
-------
OU RECTABLE Aveper FIRST SECOND
. . . SIXTH ... TENTH and/or
Syntax:
1ST 2ND ... 6TH .... 10TH
and/or
1 2 ... 6 ... 10 .... N ....
999
Type:
Optional, Repeatable
where the Aveper parameter is the short-term averaging period (e.g., I, 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.
3-156
-------
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., I, 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:
3-157
-------
OU MAXTABLE ALLAVE 50
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 Avper// parameters are the short-term averaging periods (e.g., I, 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,
3-158
-------
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:
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 - Output values, including arc-maximum normalized concentrations,
suitable for model evaluation studies;
SEASONHR -
MAXDCONT
MAXDAILY -
Output values by season and hour-of-day;
Ranked values for individual source groups to
determine source contributions for 24-hour PM25, 1-
hourN02 and 1-hour SO2 standards;
Daily maximu 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
MAXDYBYYR - 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.
3-159
-------
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.
The user-specified file unit must be in the range of 30-100, inclusive. 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 3.7.2).
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
3-160
-------
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 40 characters in
length. It should also be noted that only one MAXIFILE card may be used for each averaging
period/source group combination. 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
3-161
-------
file unit for the output file. The user-specified file unit must be in the range of 30-100, inclusive.
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.
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
3-162
-------
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
17 # 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, 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. The user-specified file unit must be in the range of 30-100, inclusive.
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
3-163
-------
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 7 5
ou
PLOTFILE
3
PLANT
1ST
C:\PLOTS\PLT3HR.FIL
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.
3-164
-------
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., I, 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. The user-specified file unit must be in the range of 30-
100, inclusive. 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.
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
3-165
-------
when full. The size of the arrays is controlled by the NPAIR PARAMETER defined in MODULE
MAIN1 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 40 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.
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
3-166
-------
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 40 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. The user-specified file unit must be in the range of 30-100, inclusive.
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 + LAVE
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).
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 40 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. The user-specified file unit must be in the range of 30-100, inclusive.
By specifying the same filename and unit for more than one EVALFILE card, results for different
3-167
-------
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.
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 and must be in
the range 30-100, inclusive. 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:
3-168
-------
*
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,
14, 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.
3-169
-------
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 PM2.5, 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
3-170
-------
(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. 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.
3-171
-------
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.
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.
3-172
-------
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.
3-173
-------
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.
3-174
-------
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.
3-175
-------
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., Stocker, 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
http://www.cleanairinfo.com/regionalstatelocalmodelingworkshop/archive/2007/presentatio
ns/Tuesdav%20-
%20Mav%2015%202007/AERMQD Modeling System Update.pdfhttp://www.epa.gov/tt
n/scram/7thconf/aermod/aermod implmtn guide 19March2009.pdf
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.
4-1
-------
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.
EPA, 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.
EPA, 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.
EPA, 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
EPA, 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.
EPA. 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, 2017b: Guideline on Air Quality Models, Appendix W to 40 CFR Part 51. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
https://www.epa.gov/sites/production/files/2020-09/documents/appw_17.pdf.
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, 2023a: AERMOD Model Formulation. EPA-454/B-23-010. U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina 27711.
EPA, 2023b: AERMOD Implementation Guide (Revised June 2022). EPA-454/B-23-009. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
4-2
-------
EPA, 2023c: User's Guide for the AERMOD Meteorological Preprocessor (AERMET). EPA-
454/B-23-005. U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711.
EPA, 2023d: 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.
Hanna, S.R., Dicristofaro, D.C., 1988. Development and Evaluation of the OCD/API (Offshore and
Coastal Dispersion / American Petroleum Institute) Model.
Hanrahan, P.L., 1999a. "The plume volume molar ratio method for determining M^/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 M^/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 atEPA/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
StratificationBoundary-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/j.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.
4-3
-------
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.
Snyder, M.G., Venkatram, A., Heist, D.K., Perry, S.G., Petersen, W.B. and Isakov, V., 2013.
RLINE: 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: 10.1016/13 52-2310(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.
4-4
-------
Note: Many of the references listed can be found on the U.S. EPA SCRAM website at the following url:
h tips://www, epa.gov/scram.
4-5
-------
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
A-l
-------
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-2
-------
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-3
-------
and GRSM options; can be used with the OZONEFIL, OZONEVAL, and
03VALUES options
OZONEFIL
O-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
O-N
Option to specify units for temporally varying ozone concentrations for the
03VALUES keyword
FLAGPOLE
O-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
O-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
O-N
Specifies whether to generate an input file for EVENT model
SAVEFILE3
O-N
Option to store intermediate results for restart of model after user or system
interrupt
INITFILE3
O-N
Option to initialize model from intermediate results generated by SAVEFILE
option
MULTYEAR3
O-N
Option to process multiple years of meteorological data (one year per run) and
accumulate high short-term values across years
DEBUGOPT
O-N
Option to generate detailed result and meteorology files for debugging purposes
ERRORFIL
O-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
A-4
-------
defined by the RECTABLE and MAXIFILE keywords on the OU pathway and are placed in the
EVENT pathway.
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
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-5
-------
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 specifVine the kevword FLAT in
place of the source elevation field on the SO LOCATION
A-6
-------
Keyword
Parameters
ELEV
NOSTD
NOCHKD
WARNCHKD
NOWARN
SCREEN
SCIM
PVMRM
OLM
ARM2
TTRM
keyword (cannot be used simultaneously with the DFAULT
keyword); the RLINE and RLINEXT source types require
FLAT to be used.
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) forN02
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-regualtory
alpha option, requires the ALPHA keyword and cannot be
used with the DFAULT keyword); cannot be used with
A-7
-------
Keyword
Parameters
TTRM2
GRSM
PSDCREDIT
FASTALL
FASTAREA
DRYDPLT
NODRYDPLT
WETDPLT
NOWETDPLT
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 OLM, PVMRM, or ARM2 for
NO2 conversion (non-regualtory 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 non-regulatory Generic Reaction Set Method
(GRSM) will be used for NO2 conversion (non-regulatory
option, requires the BETA keyword and cannot be used with
the DFAULT keyword); 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
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.
A-8
-------
Keyword
Parameters
NOURBTRAN
VECTORWS
N0MIN03
RLINEFDH
AREAMNDR
HBP
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, 2023a) 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 . . . Timc/v' 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.
A-9
-------
Keyword
Parameters
URBANOPT
For multiple urban areas:
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 1.0m; 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 of N02 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.
A-10
-------
Keyword
Parameters
HALFLIFE
Haflif
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.
A-ll
-------
Keyword
Parameters
LOWWIND
SVmin (WSmin) or
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
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-12
-------
Keyword
Parameters
ORDCAV
Redefines the initial vertical dispersion, erz. 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).
N02STACK
N02Ratio
where:
N02Ratio
Default in-stack ratio of NO2/NOX for PVMRM, OLM, TTRM,
and GSRM options, which may be overridden by the
N02RATI0 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 TV 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
A-13
-------
Keyword
Parameters
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 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 speed
cateaorv; 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=l2: HROFDY. n=24:
WSPEED. n=6: SEASHR. n=96: HRDOW. n=72:
HRD0W7. n=168: SHRDOW. Ğ=288; SHRD0W7. Ğ=672;
MHRDOW. Ğ=864: MHRD0W7. Ğ=2016.
NOTE: Background ozone values input through the
03 VALUES 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.
A-14
-------
Keyword
Parameters
The following keywords: NOXSECTR, NOX_FILE, NOXVALUE, NOX_VALS, and NOXJJNIT,
are only applicable to the GRSM NO-to-NCh Conversion Option. The BETA and GRSM options
must both be specified as MODELOPTs on the CO pathway.
NOXSECTR
StartSectl StartSect2 . . . StartSect/V, where TV 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 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)
A-15
-------
Keyword
Parameters
where:
SECTx
NOXFlag
NOXvalues
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
monthly; HROFDY for hour-of-dav; WSPEED for wind speed
cateaorv; 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=l2: HROFDY. n=24:
WSPEED. n=6: SEASHR. n=96: HRDOW. n=72:
HRD0W7. Ğ=168: SHRDOW. Ğ=288: SHRD0W7. Ğ=672:
MHRDOW. Ğ=864: MHRD0W7. 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)
Identifies the filename to be used to generate a file for input to
EVENT model (Default=EVENTFIL INP).
A-16
-------
Keyword
Parameters
(Evopt)
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).
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 (Dbefil) and/or METEOR (Dbmfil) and/or PRIME (Prmfil)
and/or
AWMADW (AwmaDwfil)
and/or
PLATFORM (PlatfinDbeFiD
and/or
DEPOS (Dbefil)
and/or
[AREA (AreaDbFil) or LINE (LineDbFil)l
and/or
RLINE (RlincDbsFil)
and/or
BLPDBUG (BLPDbFil)
and/or
URBANDB (UrbanDbFil)
and/or
fPVMRM (DbDvfil) (and TTRM2) or
OLM (OLMfiD (and TTRM2) or
ARM2 (ARM2fil) (and TTRM2) or
TTRM (TTRMfil) or GSRM (GSRMfil)l
and/or
A-17
-------
Keyword
Parameters
SWPOINT (SWfil)
and/or
HBPDBG fHBPfiD
and/or
AIRCRAFT (DbARCFTfil)
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 METEORoloaical 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.
(Pimfil)
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 debuaaina output will be aenerated.
using default filenames of 'GDEP.DAT' for gas deposition
and 'PDEP.DAT' for particle deposition.
AREA or LINE
Specifies that AREA or LINE debuaaina 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 dbugging 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
A-18
-------
Keyword
Parameters
filename, respectively. Default filenames: URBDBUG.DBG,
URBDBUG1 DBG, and URBDBUG2.DBG.
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
HBPDEBUG.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-19
-------
ERRORFIL
(Errfil)
where:
(Errfil)
Specifies name of detailed error listing file (default =
ERRORS.LST).
A-20
-------
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 METHOD 2 particle deposition
A-21
-------
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-22
-------
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 Srctvp Xs Ys (Zs) Tfor all Srctvps except LINE.
BUOYLINE. RLINE. and RLINEXT1
or
(FLAT) Tfor 'FLAT & ELEV' ootionl
or
SrcID SrctvD Xs 1 Ys 1 Xs2 Ys2 (Zs) Tfor LINE. RLINE. or BUOYLINE Srctvol
or
(FLAT) Tfor 'FLAT & ELEV' ODtionl
or
SrcID SrctvD Xs 1 Ys 1 Zs 1 Xs2 Ys2 Zs2 (Zs) Tfor RLINEXT Srctvol
or
(FLAT) Tfor 'FLAT & ELEV' ootionl
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 tvoe: 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 Stktmp Stkvel Stkdia (POINT. POINTCAP.
POINTHOR source)
Vlemis Relhat Svinit Szinit (VOLUME source)
Aremis Relhat Xinit (Yinit) (Angle) (Szinit) (AREA source)
Aremis Relhat Nverts (Szinit) (AREAPOLY source)
Aremis Relhat Radius (Nverts) (Szinit) (AREACIRC source)
A-23
-------
Keyword
Parameters
Lnemis Relhet Width (Szinit) (LINE or RLINE source)
Openiis Relhet 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-24
-------
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 of Ys 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-25
-------
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.Sat.Sun); 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-26
-------
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 NC^/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-27
-------
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 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.
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 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 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. n=24: WSPEED. n=6: SEASHR. n=96:
HRDOW. n=72: HRDOW7. Ğ=168; SHRDOW. Ğ=288;
SHRDOW7. n=672; 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-28
-------
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 icroeram s/cubic-mete r.
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-29
-------
Keyword
Parameters
SrcRange's
Note: Card mav be repeated with same Grpid if more space 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 PSDGrpID if more space 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-30
-------
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
0 - 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-31
-------
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 Zflae 1 Zflae2 ZflaeS ... 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 subpathwav. repeat for each new Netid.
GRIDPOLR
Netid STA
ORIG Xinit Yinit.
or ORIG Srcid
A-32
-------
Keyword
Parameters
DIST Rinel Rine2 Rine3 ... RineN
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 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).
(Zflag)
Receptor height (flagpole) above local terrain (optional), used only with
FLAGPOLE keyword.
DISCPOLR
Srcid Dist Direct (Zelev Zhill) (Zflag)
A-33
-------
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 kevword.
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 (optional), used
onlv for ELEV terrain.
Hill height scale (m).
Receptor height (flagpole) above local terrain (optional), 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-34
-------
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
NOTURBST
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-35
-------
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 beginning
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-36
-------
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 ... Rangc/v'
where:
Range1
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
NOTURBST
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.
A-37
-------
Keyword
Parameters
WINDCATS
Wsl Ws2 Ws3 Ws4 Ws5
where:
Wsl
Ws2
Ws3
Ws4
Ws5
Upper bound of first wind speed category (m/s).
Upper bound of second wind speed category (m/s).
Upper bound of third wind speed category (m/s).
Upper bound of fourth wind speed category (m/s).
Upper bound of fifth wind speed category (m/s).
(sixth category is assumed to have no upper bound).
A-38
-------
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-39
-------
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 (Zclcv 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-40
-------
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-41
-------
Table A-12. Description of Output Pathway Keywords and Parameters
Keyword
Parameters
RECTABLE
Aveper FIRST SECOND . . . SIXTH . . . TENTH and/or
Aveper 1ST 2ND . . . 6TH . . . 10TH and/or
Aveper 1 2 ... 6 ... 10 ... N ... 999
where:
Aveper
FIRST
SECOND
SIXTH
1ST
2ND
6TH
N
Averaging period to summarize with high values (keyword
ALLAVE specifies all short-term averaaina periods).
Select summaries of FIRST hiahest values bv receptor.
Select summaries of SECOND hiahest values bv receptor.
Select summaries of SIXTH hiahest values bv receptor.
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 iV-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-42
-------
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
averages. PERIOD for period averages.
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
averages. PERIOD for period averages, etc.
Specifies source group to be output to file.
Specifies rank to be included in high value summary (e.g.. 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., 1 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
Specifies the source group ID to be output to file.
A-43
-------
Keyword
Parameters
FileName
(FileUnit)
Specifies filename for output file.
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 ThreshValue FileName (FileUnit)
where:
GrpID
UpperRank
LowerRank
THRESH
ThreshValue
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 ThreshValue
NOTE: The ThreshValue 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 ThreshValue 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
SummFileName
where:
SummFileName
Specifies filename of output summary file
FILEFORM
EXP or FIX
A-44
-------
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 . . . FilcTvpc/v'
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-45
-------
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
-------
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
-------
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
-------
Pi# Txix LLLL raxnsran; MESSAGE Hints
Detailed message for this code {22:71)
: . . e 1 e ru::.. which the
line nuirji-er c f
the irn:
ut runf-r
e fiic.
_:v r.
j-p
he v.
r^n^er"'-! rhe
runtir.r
ligy file
Ĥ o
cri"
en i *? i *.2)
Numeric message code (a 3-digit number) (5:7)
Message type (Eğ 1*1, I) {4:4)
r a*h"-:av I j {C'J,
, ?E t Z-3L t ET f : r 17 <
i. - : 11 or
MX r:-r rr.e~e:r:L
; i
7 c. X Ilf.Tft rXTIcrTl'in,
i - . -
r:r
- -s ^ - -
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
-------
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:
READ() 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, 2023c) 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
C-l
-------
Data records:
READ()
FORMAT statement will need to be revised with additional terms to read beyond the
version date to retrieve the flags from the header record.
year, month, day, j day, hour, H, u*, w*, VPTG, Zic, Zim, L, z0 , B0 , r, Ws, Wj, zref,
temp, ztemp, ipcode, pamt, rh, pres, ccvr, WSADJ
FORMAT
where
J
H
u*
w*
VPTG
Zic
Zim
L
zo
Bo
r
Ws
Wd
Zref
temp
Ztemp
ipcode
pamt
rh
pres
ccvr
WSAD.J
(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)
= Julian day
= sensible heat flux (W/m2)
= surface friction velocity (m/s)
= convective velocity scale (m/s)
= vertical potential temperature gradient above Zic (K/m)
= height of convectively-generated boundary layer (m)
= height of mechanically-generated boundary layer (m)
= Monin-Obukhov length (m)
= surface roughness length (m)
= Bowen ratio
= Albedo
= reference wind speed (m/s)
= reference wind direction (degrees)
= reference height for wind (m)
= reference temperature (K)
= reference height for temperature (m)
= precipitation type code (0=none, ll=liquid, 22=frozen,
99=missing)
= precipitation amount (mm/hr)
= relative humidity (percent)
= station pressure (mb)
= cloud cover (tenths)
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;
C-2
-------
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;
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)
top= 1, if this is the last (highest) level for this hour, or 0 otherwise
WD nn = wind direction at the current level (degrees)
WS nn = wind speed at the current level (m/s)
TTnn = temperature at the current level (°C)
SA nn = oe (degrees)
SW nn = o (m/s)
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
C-3
-------
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,
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,13
IX,A8,IX,18
.8,2(IX,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
C-4
-------
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 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 (IX,F13.5),3 (1X,F8.2),2X
,A6,2X,A8
H
CO
CO
,A8)
*
X
Y AVERAGE CONC
ZELEV
ZHILL
ZFLAG
AVE
GRP
NUM HRS
NET ID
30 .38843
172.34136 0.21576
o
o
o
1
o
o
o
o
o
o
PERIOD
ALL
00000096
POL1
60.77686
344.68271 0.53162
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
POL1
86.82409
492.40388 0.85993
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
POL1
173 . 64818
984.80775 1.39778
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
POL1
59.85353
164.44621 0.20861
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
POL1
119.70705
328.89242 0.67388
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
POL1
C-5
-------
171.01007
469 . 84631
1.27452
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
342.02014
939.69262
2 . 45702
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
87.50000
151.55445
0.20576
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
175 .00000
303 .10889
0 . 64322
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
250 .00000
433.01270
1.20422
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
500 .00000
866.02540
2.28880
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
112 .48783
134 . 05778
0.20172
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
224.97566
268.11556
0 .48027
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
321.39380
383 .02222
0.76067
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
642.78761
766.04444
1.19405
o
o
o
o
o
o
o
o
o
PERIOD
ALL
00000096
P0L1
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 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:
C-6
-------
*
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,I8)
*
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.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
C-7
-------
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, IDUM2, IDUM3 = dummy integer variables, arbitrarily set equal to zero
CUTOFF = User-specified threshold for outputting results (g/m3)
RDUM1, ..., 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 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
C-8
-------
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:
* 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 4 0 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,F7.2),2X,A8)
* RANK AVERAGE CONG DATE X Y ZELEV ZHILL ZFLAG GRP
1 329.96009 88030112 433.01270 -250.00000 0.00 0.00 0.00 ALL
2 278.47891 88030115 469.84631 -171.01007 0.00 0.00 0.00 ALL
3 124.30430 88030118 433.01270 -250.00000 0.00 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
C-9
-------
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)
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(IX,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-ll
-------
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 14 4
RECEPTORS.
*
FORMAT :
(2(IX,F13.5)
,1(IX,F13.8),3
(IX,F7.
2) , 2X,A8
,2X,3(14
2X),A8)
*
X
Y
AVERAGE CONG
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-12
-------
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, ncluding: 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-13
-------
*
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,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
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 .28291
-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-14
-------
*
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
2 4-HR
ALL
2ND
P0L1
0 .00000
0. 00000
0. 00000
C-15
-------
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-16
-------
*
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(IX,
F8.2),2X,A6,
2X
A8,2X,I4,2X,I3,2X,I8
. 8,2X,A8)
*
X
Y
AVERAGE CONC
ZELEV
ZHILL
ZFLAG
AVE
GRP
J DAY
HR
DATE
NET ID
100 .00000
0 .00000
50.00000
35.00
o
o
o
o
o
1-HR
ALL
1
13
99010113
POL 1
300 .00000
0 .00000
50.00159
35.00
o
o
o
o
o
1-HR
ALL
1
13
99010113
POL 1
1000 . 00000
0 .00000
50.20117
35.00
o
o
o
o
o
1-HR
ALL
1
13
99010113
POL 1
3000.00000
0 .00000
50.12314
35.00
o
o
o
o
o
1-HR
ALL
1
13
99010113
POL 1
0 .00000
-100.00000
50 . 00000
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
POL 1
0 .00000
-300 .00000
50.00259
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
POL 1
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
o
o
o
o
o
1-HR
ALL
1
7
99010107
P0L1
-100.00000
-0 .00000
50 . 00000
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
POL 1
-300.00000
-0 .00000
50 . 00258
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
POL 1
-1000.00000
-0 .00000
50.2007 9
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-3000.00000
-0 .00000
50. 12262
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-0.00000
100 .00000
50 . 00000
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-0.00000
300 .00000
50.00159
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-0.00000
1000 .00000
50.20117
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
P0L1
-0.00000
3000 .00000
50.12314
o
o
o
o
o
o
o
1-HR
ALL
1
13
99010113
P0L1
100.00000
0 .00000
50.00000
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
300.00000
0 .00000
50.00001
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
1000.00000
0 .00000
50.00008
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
3000.00000
0 .00000
50 . 00280
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
0 .00000
-100.00000
50.00000
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
0 .00000
-300 .00000
50.00001
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
0.00000
1000 .00000
50.00009
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
0.00000
3000 .00000
50 . 00285
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
-100.00000
-0 .00000
50 . 00000
o
o
o
o
o
o
o
1-HR
ALL
2
13
99010213
P0L1
C-17
-------
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 MAXDATT Yr
output file for which ranks 4, 8 12, and 50 were specified on the MAXDCONT keyword.
C-18
-------
*
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(IX,
F8.2),2X,A6,
2X,A8,2X,I4,2X,I3,2X,I8
8,2X,A8)
*
X
Y
AVERAGE CONC
ZELEV
ZHILL
ZFLAG
RANK
GRP
J DAY
HR
DATE
NET ID
100 .00000
0 .00000
76.74205
o
o
o
o
o
o
o
4TH
ALL
236
14
99082414
P0L1
300 .00000
0 .00000
174.62886
o
o
o
o
o
o
o
4TH
ALL
136
14
99051614
POL 1
1000.00000
0 .00000
146.90191
o
o
o
o
o
o
o
4TH
ALL
147
14
99052714
P0L1
3000.00000
0 .00000
91.97719
35.00
o
o
o
o
o
4TH
ALL
104
13
99041413
POL 1
0 .00000
-100.00000
99.52361
o
o
o
o
o
o
o
4TH
ALL
252
15
99090915
P0L1
0 .00000
-300 .00000
171.76063
o
o
o
o
o
o
o
4TH
ALL
107
11
99041711
P0L1
0.00000
1000 .00000
152.93801
o
o
o
o
o
o
o
4TH
ALL
65
13
99030613
P0L1
0.00000
3000.00000
111.73167
35.00
o
o
o
o
o
4TH
ALL
293
16
99102016
POL 1
-100.00000
-0.00000
91.59388
35.00
o
o
o
o
o
4TH
ALL
62
14
99030314
P0L1
-300.00000
-0.00000
154.65265
o
o
o
o
o
o
o
4TH
ALL
62
15
99030315
P0L1
-1000.00000
-0.00000
131.73020
35.00
o
o
o
o
o
4TH
ALL
360
13
99122613
POL 1
-3000 .00000
-0.00000
86.11262
o
o
o
o
o
o
o
4TH
ALL
312
16
99110816
P0L1
-0 .00000
100.00000
80 . 06381
35.00
o
o
o
o
o
4TH
ALL
203
8
99072208
POL 1
-0 .00000
300.00000
166.86210
o
o
o
o
o
o
o
4TH
ALL
139
16
99051916
P0L1
-0 .00000
1000.00000
156.54681
35.00
o
o
o
o
o
4TH
ALL
110
15
99042015
POL 1
-0 .00000
3000.00000
102.04635
o
o
o
o
o
o
o
4TH
ALL
23
15
99012315
P0L1
100 .00000
0 .00000
65.46639
35.00
o
o
o
o
o
8TH
ALL
250
17
99090717
POL 1
300 .00000
0 .00000
164 . 95260
o
o
o
o
o
o
o
8TH
ALL
147
14
99052714
P0L1
1000 .00000
0 .00000
137.02622
o
o
o
o
o
o
o
8TH
ALL
145
16
99052516
P0L1
3000 .00000
0 .00000
79.71649
o
o
o
o
o
o
o
8TH
ALL
102
19
99041219
P0L1
0 .00000
-100.00000
90.20572
35.00
o
o
o
o
o
8TH
ALL
175
9
99062409
P0L1
0 .00000
-300.00000
167.99537
35.00
o
o
o
o
o
8TH
ALL
81
14
99032214
P0L1
0.00000
1000.00000
147.76997
35.00
o
o
o
o
o
8TH
ALL
107
18
99041718
POL 1
0.00000
3000.00000
108.50074
35.00
o
o
o
o
o
8TH
ALL
272
17
99092917
POL 1
-100.00000
-0.00000
86.21569
35.00
o
o
o
o
o
8TH
ALL
251
12
99090812
P0L1
-300 .00000
-0.00000
147 . 43347
35.00
o
o
o
o
o
8TH
ALL
63
13
99030413
P0L1
-1000.00000
-0.00000
113.23071
35.00
o
o
o
o
o
8TH
ALL
144
8
99052408
POL 1
-3000.00000
-0.00000
80 . 46493
35.00
o
o
o
o
o
8TH
ALL
251
12
99090812
P0L1
-0 .00000
100.00000
62.77470
35.00
o
o
o
o
o
8TH
ALL
213
15
99080115
POL 1
-0 .00000
300.00000
164.12251
35.00
o
o
o
o
o
8TH
ALL
212
12
99073112
P0L1
-0 .00000
1000 . 00000
147.60345
35.00
o
o
o
o
o
8TH
ALL
84
15
99032515
POL 1
C-19
-------
-0.00000
3000 .00000
92 .37244
o
o
o
o
o
o
o
8TH
ALL
264
19
99092119
P0L1
100 .00000
0 .00000
63.04954
35.00
o
o
o
o
o
12TH
ALL
213
15
99080115
POL 1
300 .00000
0 .00000
158 . 05318
o
o
o
o
o
o
o
12TH
ALL
182
15
99070115
POL1
1000 .00000
0 .00000
132.45210
o
o
o
o
o
o
o
12TH
ALL
123
15
99050315
POL1
3000 .00000
0 .00000
75 . 06520
35.00
o
o
o
o
o
12TH
ALL
56
14
99022514
POL 1
0 .00000
-100 . 00000
81.79820
o
o
o
o
o
o
o
12TH
ALL
230
14
99081814
POL1
0 .00000
-300.00000
163.58691
o
o
o
o
o
o
o
12TH
ALL
150
13
99053013
POL1
0 .00000
-1000.00000
143.66477
o
o
o
o
o
o
o
12TH
ALL
63
11
99030411
POL1
0 .00000
-3000.00000
103.84510
35.00
o
o
o
o
o
12TH
ALL
359
10
99122510
POL 1
-100.00000
-0.00000
66.87945
o
o
o
o
o
o
o
12TH
ALL
210
13
99072913
POL1
-300.00000
-0.00000
134.34226
35.00
o
o
o
o
o
12TH
ALL
192
11
99071111
POL 1
-1000 .00000
-0.00000
112.42027
o
o
o
o
o
o
o
12TH
ALL
90
10
99033110
POL1
-3000 .00000
-0.00000
69.14045
o
o
o
o
o
o
o
12TH
ALL
70
12
99031112
POL 1
-0 .00000
100.00000
57.29793
35.00
o
o
o
o
o
12TH
ALL
80
13
99032113
POL 1
-0 .00000
300.00000
161.46688
35.00
o
o
o
o
o
12TH
ALL
46
12
99021512
POL 1
-0 .00000
1000 .00000
141.04997
o
o
o
o
o
o
o
12TH
ALL
165
14
99061414
POL1
-0 .00000
3000.00000
89.51271
35.00
o
o
o
o
o
12TH
ALL
109
19
99041919
POL 1
100 .00000
0 .00000
51.04396
35.00
o
o
o
o
o
5 OTH
ALL
132
13
99051213
POL 1
300 .00000
0 .00000
126.14782
o
o
o
o
o
o
o
50TH
ALL
175
15
99062415
POL1
1000.00000
0 .00000
105.50261
o
o
o
o
o
o
o
50TH
ALL
267
17
99092417
POL1
3000 .00000
0 .00000
56.90880
o
o
o
o
o
o
o
50TH
ALL
236
14
99082414
POL1
0 .00000
-100.00000
56.69467
o
o
o
o
o
o
o
50TH
ALL
287
13
99101413
POL1
0 .00000
-300.00000
137 .18380
o
o
o
o
o
o
o
50TH
ALL
204
13
99072313
POL1
0 .00000
-1000.00000
120.65746
o
o
o
o
o
o
o
50TH
ALL
268
13
99092513
POL1
0 .00000
-3000 .00000
85.42463
35.00
35.00
o
o
o
5 OTH
ALL
156
1
99060501
POL 1
-100.00000
-0.00000
51.20790
o
o
o
o
o
o
o
50TH
ALL
169
14
99061814
POL1
-300.00000
-0.00000
72 . 61516
o
o
o
o
o
o
o
5 OTH
ALL
32
13
99020113
POL 1
-1000 .00000
-0.00000
72 .1447 6
o
o
o
o
o
o
o
50TH
ALL
270
10
99092710
POL1
-3000 .00000
-0.00000
52 .15505
35.00
o
o
o
o
o
5 OTH
ALL
265
13
99092213
POL 1
-0 .00000
100.00000
50.39602
35.00
o
o
o
o
o
5 OTH
ALL
180
14
99062914
POL 1
-0 .00000
300.00000
125 . 74471
35.00
o
o
o
o
o
5 OTH
ALL
247
14
99090414
POL 1
-0 .00000
1000.00000
117.67662
o
o
o
o
o
o
o
50TH
ALL
143
1
99052301
POL1
-0 .00000
3000.00000
70 . 84420
o
o
o
o
o
o
o
50TH
ALL
127
2
99050702
POL1
C-20
-------
APPENDIX D. Overview of AERMOD revisions in version 23132
Model Change Bulletin (MCB) 17
AERMOD version 23132 (April 22, 2022)
Changes are listed by type and with each change are the affected pollutants and source types:
Bug Fixes
Item
Modification
Pollutants
Source Types
1
Logic updated that interprets the 2-digit year from
the surface file to be in the 1900s if the year is
>=50 and in the 2000s if < 50. This update is
needed when year specified on the SURFDATA in
the ME pathway does not match the year recorded
in the SFC meteorological file.
All
All
2
Updated initialized value of N02STACK from 0.1
to -9.0 which is outside of the valid range or 0.0-
1.0. This ensures N02STACK cannot be set
erroneously from within the code to a valid but
unspecified value.
N02
All
3
Event processing with the BUOYLINE source
type updated to correct conflicts with source group
id prevent when multiple source types are defined
on the SO pathway.
ALL
BUOYLINE
4
Corrected recursive subroutines which caused
runtime error when compiled with gfortran
compiler with fcheck-recursive or fcheck-all flag
set. Two subroutines were identified, RECSIZ in
aermod.f and RECARD in reset.f.
All
All
5
Added logic to the URBCALC subroutine in
METEXT.f to cycle the urban source loop if the no
urban transition option (NOURBTRAN) is chosen
in AERMOD. This eliminates possible "Nan" in
the urban debug file.
All
All
6
Add header to BUOYLINE debug file
All
BUOYLINE
D-l
-------
7
Variable DHP3PLAT, associated with penetrated
plumes and the alpha option for platform
downwash was declared in modules.f but never
initialized and assumed to be zero. DHP3PLAT is
a placeholder variable for future updates and
should be zero.
All
POINT
POINTCAP
POINTHOR
(offshore
platform
sources only)
8
Corrected a false warning message "Julian Day
Out of Range" that was issued when using
DAYRANGE keyword. Logic statement in meset.f
referenced incorrect variable JDAY. Code was
updated to replace JDAY with JDAYB and
JDAYE.
All
All
9
Corrected logic to require ALPHA flag when
RLINEXT source type is specified.
All
RLINEXT
10
Corrected logic to generate error message rather
than a warning message when N0MIN03 is used
with ARM2. N0MIN03 turns off minimum
background ozone concentration which does not
apply to ARM2.
N02
All
11
Correction when AREACIRC sources are listed in
an INCLUDED file. Sources were being
overwritten when multiple reads of AREACIRC
sources caused memory conflicts between array
sizing and id assignments. Bug fix enables correct
AREACIRC source ID and NVERTs tracking for
multiple AREACIRC sources.
All
AREACIRC
12
Updated the logic for ARMRATIO minimum and
maximum values to match the ranges provided in
the AERMOD User's Guide when based on
whether the DFAULT keyword is specified
N02
All
13
Updated code to initialize variable I ALPHA in
INTERPCOEFFS subroutine to avoid runtime
error encountered by 64-bit executable in some
circumstances.
All
RLINE
14
Add warning message when an N02 conversion
method is used with a source type for which it has
not been implemented. Model run will complete
but list a warning indicating the N02 option was
not applied to a source type.
N02
All
D-2
-------
15
A warning message was added when the SCREEN
option is used with RLINE, RLINEXT,
BUOYLINE, SWPOINT, AREA, or LINE
sources.
All
RLINE
RLINEXT
AREA
AREAPOLY
AREAC IRC
LINE
BUOYLINE
SWPOINT
16
Added a warning message that receptor ZHILL
and ZELEV values are ignored for source when
FLAT is used in the place of the source elevation
field on the SO LOCATION field.
All
All
17
Correction to code logic in bline.f, rline.f, and
soset.f causing inconsistent results for
BUOYLINE, RLINE, and RLINEXT source types
depending on how FLAT terrain was specified.
All
BUOYLINE
RLINE
RLINEXT
18
Correction for SWPOINT source array. Incorrectly
allocated.
All
SWPOINT
Enhancements
Item
Modification
Pollutants
Source Types
1
Added capability to use elevated terrain (ELEV) to
RLINE and RLINEXT sources. In previous
versions, RLINE and RLINEXT required the
FLAT terrain flag be specified for those source
types. NOTE: When modeling project level
conformity and hot-spot analyses, refer to the
Office of Transportation and Air Quality
(OTAQ) for current guidance for modeling
roadway sources.
All
RLINE
RLINEXT
2
Added new debug file for urban sources that
reports temperature and vertical potential
temperature profiles.
All
All
Formulation updates - Regulatory
None
D-3
-------
Formulation updates - BETA
Item
Modification
Pollutants
Source Types
1
Proposed Regulatory Update
Original implementation of the RLINE source type
was reformulated to bring the RLINE source type
into better agreement with other AERMOD source
types and simultaneously not degrade the previous
evaluation database results. There were three main
aspects of the reformulation: (1) Wind Speed
calculation, (2) Harmonization with AERMOD
sources, and (3) Dispersion Coefficients. The
modifications were made in this order, with the
wind speed and harmonization changes made first,
then the reexamination of the parameters used in
the vertical and lateral dispersion calculations.
Refer to the following for details on the
reformulation which can be found on the EPA
SCRAM website:
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, RTP, NC.
All
RLINE
RLINEXT
2
Proposed Regulatory Update
Formulation of the GRSM N02 conversion option
updated. Refer to the following for details on the
reformulation which can be found on the EPA
SCRAM website:
Environmental Protection Agency, 2023.
Technical Support Document (TSD) for Adoption
of the Generic Reaction Set Method (GRSM) as a
Regulatory Non-Default Tier-3 N02 Screening
Option, Publication No. EPA-454/R-23-009.
Office of Air Quality Planning & Standards,
Research Triangle Park, NC.
N02
POINT
POINTHOR
POINTCAP
AREA
AREAPOLY
AREAC IRC
LINE
VOLUME
OPENPIT
D-4
-------
Proposed Regulatory Update
All
All
The COARE algorithm for processing marine-
based meteorological data for modeling offshore
sources was added to AERMET v23132. This
update to AERMET has been proposed as an
update to the formulation of AERMET for
regulatory modeling applications. AERMET
writes the string 'COARE' in the SFC file header
when the COARE algorithm is used. The
AERMOD source code was updated to require the
BETA flag in the AERMOD control file if
'COARE' is found in the SFC file header. The
presence of 'COARE' in the SFC file header
without the inclusion of the BETA flag in the
AERMOD control file will result in an error
message.
Formulation updates - ALPHA
Item
Modification
Pollutants
Source Types
1
Meander added to AREA source types. Current
implementation computes meander for downwind
receptors only.
All
AREA
AREAPOLY
AREAC IRC
LINE
2
AREA and VOLUME sources were updated to
accept additional parameters to characterize
aircraft sources. A new keyword ARCFTOPT
must specified, and aircraft sources must be
identified with the new ARCFTSRC keyword.
New aircraft parameters (for AREA and/or
VOLUME sources) must be provided in an hourly
emissions file.
All
AREA
AREAPOLY
AREAC IRC
LINE
VOLUME
3
Added ALPHA option for highly buoyant plumes
(HBP) when plume penetrates the top of the mixed
layer. Limited to point source types (POINT,
POINTHOR, POINTCAP)
All
POINT
POINTHOR
POINTCAP
D-5
-------
Documentation Updates Only
Item
Modification
1
Update Section 3.2.5 of AERMOD User's Guide to clarify that ARM2 is only
applied to SRCGROUP ALL. If at least one source group is defined and is not
ALL, AERMOD will assume SRCGROUP ALL and apply ARM2.
2
Updated Section 5.9 in the Model Formulation Document (MFD) to state that
Equation 109 leads to Equation 110. MFD previously stated that Equation 103
leads to Equation 110.
3
Updated the AERMOD User's Guide Section 3.3.1 to define Zs and effective
depth for the OPENPIT source.
4
Added the equation for the buoyancy flux calculation to the AERMOD User's
Guide Section 3.3.2.11.
5
Updated Section 5.5.1.1 of MFD to correct definition of X term Eqn 77 to
X = av x/uzi.
D-6
-------
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.
E-7
-------
EV EVent, the 2-character pathway ID for input control file commands used to specify event
inputs for the Short-Term EVENT model.
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.
E-8
-------
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
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.
E-9
-------
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.
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.
E-10
-------
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.
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.
E-ll
-------
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-12
-------
United States Office of Air Quality Planning and Standards Publication No. EPA-454/B-23-008
Environmental Protection Air Quality Assessment Division October 2023
Agency Research Triangle Park, NC
13
------- |