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User's Guide for the AMS/EPA Regulatory
Model (AERMOD)
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EPA-454/B-19-027
August 2019
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
Air Quality Modeling Group
Research Triangle Park, NC
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Notice
Mention of trade names, products, or services does not convey, and should not be
interpreted as conveying official EPA approval, endorsement, or recommendation. The
following trademarks appear in this guide:
Microsoft Windows are registered trademarks of the Microsoft Corporation.
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Preface
This User's Guide for the AMS/EPA Regulatory Model (AERMOD) provides user
instructions for the AERMOD model. The technical description of the AERMOD algorithms is
provided in a separate Model Formulation and Evaluation document (EPA, 2018a). Additional
resources provided by the USEPA that may be helpful with regard to the application of
AERMOD can be accessed via the Support Center for Regulatory Atmospheric Modeling
(SCRAM) website at https://www.epa.gov/scram.
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Acknowledgments
The User's Guide for AERMOD was originally prepared by Pacific Environmental
Services, Inc., Research Triangle Park, North Carolina under contract to the US EPA. The user
instructions for AERMOD were developed in part from Volume I of the ISC3 User's Guide
(EPA, 1995a). Incremental updates and revisions to the User's Guide have been prepared under
contract to the US EPA by a variety of contractors, including MACTEC Federal Programs, Inc.,
Research Triangle Park, North Carolina, AMEC and Amec Foster Wheeler, Research Triangle
Park, North Carolina, and Wood, Research Triangle Park, North Carolina.
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Contents
Section Page
1.0 Introduction 1-1
1.1 How to use the AERMOD manuals 1-1
1.1.1 Novice users 1-1
1.1.2 Experienced modelers 1-2
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 1-4
1.2.3 Computer hardware requirements 1-4
1.2.3.1 Dispersion options 1-4
1.2.3.2 Source options 1-5
1.2.3.3 Receptor options 1-6
1.2.3.4 Meteorology options 1-6
1.2.3.5 Output options 1-6
1.2.3.6 Source contribution analyses 1-8
2.0 Getting started - a brief tutorial 2-1
2.1 Description of keyword/parameter approach 2-1
2.1.1 Basic rules for structuring input control files 2-2
2.1.2 Advantages of the keyword approach 2-5
2.2 Regulatory default modeling options 2-6
2.3 Setting up a simple control file 2-7
2.3.1 A simple industrial source application 2-9
2.3.2 Selecting modeling options - CO pathway 2-9
2.3.3 Specifying source inputs - SO pathway 2-12
2.3.4 Specifying a receptor network - RE pathway 2-15
2.3.5 Specifying the meteorological Input - ME pathway 2-17
2.3.6 Selecting output options - OU pathway 2-19
2.3.7 Using the error message file to debug the input control file 2-22
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2.3.8 Running the model and reviewing the results 2-27
2.4 Modifying an existing control file 2-35
2.4.1 Modifying modeling options 2-35
2.4.2 Adding or modifying a source or source group 2-35
2.4.3 Adding or modifying a receptor network 2-36
2.4.4 Modifying output options 2-36
3.0 Detailed keyword reference 3-37
3.1 Overview 3-37
3.2 Control pathway inputs and options 3-38
3.2.1 Title information 3-38
3.2.2 Dispersion options 3-38
3.2.2.1 1)1 Al l. I option 3-41
3.2.2.2 ALPHA options 3-42
3.2.2.3 BETA options 3-43
3.2.2.4 Options for capped and horizontal stack releases 3-43
3.2.2.5 Output types (CONC, DEPOS, DDEP and/or WDEP) 3-45
3.2.2.6 Deposition depletion options 3-45
3.2.2.7 NO2 conversion options 3-46
3.2.2.8 FASTAREA and FASTALL 3-46
3.2.2.9 Urban transition 3-47
3.2.2.10 SCREEN mode 3-48
3.2.2.11 SCIM 3-48
3.2.2.12 Definition of seasons for gas dry deposition 3-51
3.2.2.13 Definition of land use categories for gas dry deposition 3-51
3.2.2.14 Deposition velocity and resistance outputs 3-53
3.2.3 Low wind parameters 3-53
3.2.4 Building downwash options 3-55
3.2.4.1 ORD building downwash options 3-56
3.2.4.2 AWMA building downwash options 3-58
3.2.5 Input parameters forN02 conversion options 3-60
3.2.5.1 Specifying ozone concentrations for PVMRM and OLM options 3-61
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3.2.5.2 Specifying the ambient equilibrium NCh/NOx ratio (PVMRM, OLM) 3-66
3.2.5.3 Specifying the default in-stack NCh/NOx ratio (PVMRM OLM) 3-67
3.2.6 Averaging time options 3-67
3.2.7 Performing multiple year analyses with MULTYEAR option 3-69
3.2.8 Urban modeling option 3-70
3.2.9 Specifying the pollutant type 3-72
3.2.10 Modeling with exponential decay 3-73
3.2.11 Flagpole receptor height option 3-73
3.2.12 To run or not to run - that is the question 3-74
3.2.13 Generating an input file for EVENT processing 3-74
3.2.14 The model re-start capability 3-75
3.2.15 Processing for particulate matter (PM) NAAQS 3-77
3.2.15.1 Processing for fine particulate matter (PM-2.5) 3-77
3.2.15.2 Processing for particulate matter of 10 microns or less (PM-10) 3-80
3.2.16 Processing for 1-hour NO2 and SO2 NAAQS 3-80
3.2.17 Debugging output option 3-82
3.2.18 Detailed error listing file 3-83
3.3 Source pathway inputs and options 3-83
3.3.1 Identifying source types and locations 3-84
3.3.2 Specifying source release parameters 3-88
3.3.2.1 POINT source inputs 3-88
3.3.2.2 VOLUME source inputs 3-90
3.3.2.3 AREA source type 3-91
3.3.2.4 AREA source inputs 3-92
3.3.2.5 AREAPOLY source inputs 3-96
3.3.2.6 AREACIRC source inputs 3-97
3.3.2.7 OPENPIT source inputs 3-98
3.3.2.8 LINE source inputs 3-100
3.3.2.9 RLINE and RLINEXT source inputs 3-101
3.3.2.10 BUOYLINE source inputs 3-105
3.3.3 Specifying gas deposition parameters 3-106
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3.3.3.1 Source parameters for gas deposition (dry and/or wet) 3-106
3.3.3.2 Option for specifying the deposition velocity for gas dry deposition 3-106
3.3.4 Specifying source parameters for particle deposition 3-107
3.3.4.1 Specifying particle inputs for Method 1 3-108
3.3.4.2 Specifying particle inputs for Method 2 3-108
3.3.5 Specifying Emission and Output Units 3-109
3.3.6 Source input parameters for NO2 conversion options 3-110
3.3.6.1 Specifying in-stack NO2/NOX ratios by source for PVMRM and OLM....3-110
3.3.6.2 Specifying combined plumes for OLM 3-111
3.3.6.3 Specifying ambient NO2/NOX ratios for the ARM2 option 3-112
3.3.7 Modeling NO2 increment credits with PVMRM 3-112
3.3.7.1 Increment consuming and baseline sources 3-113
3.3.7.2 Calculating increment consumption under the PSDCREDIT option 3-114
3.3.7.3 Specifying source groups under the PSDCREDIT option 3-116
3.3.7.4 Model outputs under the PSDCREDIT option 3-117
3.3.8 Background concentrations 3-118
3.3.8.1 Defining background concentration sectors 3-118
3.3.8.2 Specifying the background concentration 3-118
3.3.8.3 Specifying background concentration units 3-122
3.3.9 Specifying building downwash information 3-123
3.3.10 Specifying urban sources 3-127
3.3.11 Specifying variable emission factors (EMISFACT) 3-128
3.3.12 Specifying an hourly emission rate file (HOUREMIS) 3-130
3.3.13 Adjusting the emission rate units for output 3-133
3.3.14 Including source data from an external file 3-134
3.3.15 Using source groups 3-135
3.4 Receptor pathway inputs and options 3-137
3.4.1 Defining networks of gridded receptors 3-137
3.4.1.1 Cartesian grid receptor networks 3-138
3.4.1.2 Polar grid receptor networks 3-141
3.4.2 Using multiple receptor networks 3-144
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3.4.3 Specifying discrete receptor locations 3-145
3.4.3.1 Discrete Cartesian receptors 3-145
3.4.3.2 Discrete polar receptors 3-146
3.4.3.3 Discrete Cartesian receptors for evalfile output 3-147
3.4.4 Including receptor data from an external file 3-148
3.5 Meteorology pathway inputs and options 3-149
3.5.1 Specifying the input data files and formats 3-149
3.5.2 Specifying station information 3-151
3.5.3 Specifying the base elevation for potential temperature profile 3-152
3.5.4 Specifying a data period to process 3-152
3.5.5 Correcting wind direction alignment problems 3-154
3.5.6 Specifying wind speed categories 3-154
3.5.7 Specifying SCIM parameters 3-155
3.5.8 Specify the number of years to process 3-156
3.6 Event pathway inputs and options 3-156
3.6.1 Using events generated by the AERMOD model 3-158
3.6.2 Specifying discrete events 3-159
3.6.3 Including event data from an external file 3-159
3.7 Output pathway inputs and options 3-160
3.7.1 Selecting options for tabular printed outputs 3-160
3.7.2 Selecting options for special purpose output files 3-164
3.7.2.1 MAXIFILE 3-165
3.7.2.2 POSTFILE 3-166
3.7.2.3 PI.Oil II.i: 3-168
3.7.2.4 TOXXFILE 3-169
3.7.2.5 RAN Kill.I' 3-171
3.7.2.6 EVALFILE 3-172
3.7.2.7 SEASONHR 3-173
3.7.2.8 MAXDCONT 3-174
3.7.2.9 VI AX DAILY 3-176
3.7.2.10 MAXDYBYYR 3-176
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3.7.3 EVENT processing options 3-177
3.7.4 Miscellaneous output options 3-177
3.8 Controlling input and output files 3-180
3.8.1 Description of AERMOD input files 3-180
3.8.1.1 Input control file 3-180
3.8.1.2 Meteorological data files 3-180
3.8.1.3 Initialization file for model re-start 3-181
3.8.2 Description of AERMOD output files 3-181
3.8.2.1 Main output file 3-182
3.8.2.2 Detailed error message file 3-182
3.8.2.3 Intermediate results file for model re-start 3-183
3.8.2.4 Maximum value/threshold file 3-183
3.8.2.5 Sequential results file for postprocessing 3-184
3.8.2.6 High value summary file for plotting 3-185
3.8.2.7 TOXX model input files 3-186
3.8.3 Controlling file inputs and outputs (I/O) 3-187
3.8.3.1 Controlling I/O on PCs 3-187
3.8.3.2 Controlling I/O on other computer systems 3-188
4.0 References 4-1
APPENDIX A. Alphabetical keyword reference A-l
APPENDIX B. Functional keyword/parameter reference B-l
APPENDIX C. Explanation of error message codes C-l
APPENDIX D. Description of file formats D-l
APPENDIX E. Quick reference for AERMOD E-l
APPENDIX F. Evaluation of modified urban option F-l
APPENDIX G. Overview of AERMOD revisions G-l
GLOSSARY GLOSSARY-1
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Figures
Figure Page
Figure 2-1. Example Input File for AERMOD for Sample Problem 2-8
Figure 2-2. Example Input control file for Sample Problem 2-21
Figure 2-3. Example Message Summary Table for AERMOD Execution 2-25
Figure 2-4. Example of Keyword Error and Associated Message Summary Table 2-26
Figure 2-5. Organization of the AERMOD Model Output File 2-29
Figure 2-6. Sample of Model Option Summary Table from an AERMOD Model
Output File 2-32
Figure 2-7. Example Output Table of High Values by Receptor 2-33
Figure 2- 8. Example of Result Summary Tables for the AERMOD Model 2-34
Figure 3-1. Relationship of Area Source Parameters for Rotated Rectangle 3-94
Figure 3-2. Schematic Diagram Identifying New Building Data for Prime
Downwash 3-126
Figure C-l. Example of an AERMOD Message Summary C-2
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Tables
Table Page
Table 3-1 Summary of Deposition Options 3-50
Table 3-2. Summary of Suggested Procedures for Estimating Initial Lateral
Dimensions oyo and Initial Vertical Dimensions ozo for Volume and Line
Sources 3-90
Table B-l. Description of Control Pathway Keywords B-3
Table B-2. Description of Control Pathway Keywords and Parameters B-5
Table B-3. Description of Source Pathway Keywords B-14
Table B-4. Description of Source Pathway Keywords and Parameters B-16
Table B-5. Description of Receptor Pathway Keywords B-24
Table B-6. Description of Receptor Pathway Keywords and Parameters B-25
Table B-7. Description of Meteorology Pathway Keywords B-28
Table B-8. Description of Meteorology Pathway Keywords and Parameters B-29
Table B-9. Description of Event Pathways and Keywords B-31
Table B-10. Description of Event Pathway Keywords and Parameters B-32
Table B-l 1. Description of Output Pathway Keywords B-33
Table B-12. Description of Output Pathway Keywords and Parameters B-34
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1.0 Introduction
This section provides an overall introduction to the AERMOD model and to the
AERMOD user's guide. Some suggestions are offered on how various users would best benefit
from using the manuals. Also provided is an overview of the model's applicability, range of
options, and basic input data and hardware requirements. The input file needed to run the
AERMOD model 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 in an attempt to meet the needs of
various types of users, depending on their level of experience with the model. This section
describes briefly how different types of users would benefit most from their use of the manual.
1.1.1 Novice users
Novice users are those whose exposure to or experience with the AERMOD model has
been limited. 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 concentrate their review on Section 2.0, which provides a brief tutorial on
setting up an input file that illustrates the most 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. As
the user becomes more familiar with the operation of the model and encounters the need to use
more advanced features of the model, he/she will want to review the contents of Section 3.0,
which provides a more detailed and complete reference of the various options for running the
model.
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1.1.2 Experienced modelers
Experienced modelers will have had considerable experience in applying the AERMOD
model in a variety of situations. They should have basic familiarity with the overall goals and
purposes of regulatory modeling in general, and with the scope of options available in the
AERMOD model in particular. Experienced modelers who are new to the AERMOD model will
benefit from first reviewing the contents of Section 2.0 of this guide, which will give them 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
particular options. The information in Section 3.0 has a functional organization with detailed
descriptions of each of the individual keyword options by functional pathway. Once they are
familiar with most or all of the keywords, they may find the functional keyword reference
provided in APPENDIX B useful to quickly review the proper syntax and available
options/parameters for a particular keyword. They may also find the Quick Reference in
APPENDIX E sufficient as a simple reminder of the available keywords for each pathway and to
ensure the proper order of parameters for each input image.
Experienced modelers may also need to refer to the description of model formulation for
AERMOD (EPA, 2018a) in order 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 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 particular applications.
They may also want to review the brief tutorial provided in Section 2.0 to learn about the nature
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and structure of the input control file, in order to better be able to review the modeling results.
1.2 Overview of the AERMOD model
This section provides an overview of the AERMOD model, including a discussion of the
regulatory applicability of the model, a description of the basic options available for running the
model, and an explanation of the basic input data and hardware requirements needed for
executing the model.
1.2.1 Regulatory applicability
The U.S. Environmental Protection Agency (EPA) maintains a Guideline on Air Quality
Models (EPA, 2017), 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. 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.
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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 type of 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, 2018c). One file consists of surface scalar parameters, and the other file consists
of vertical profiles of meteorological data. These meteorological data files are described briefly
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, 2018d) before input to the AERMOD model.
1.2.3 Computer hardware requirements
The current version of the AERMOD model was developed within the Microsoft
Windows operating system (Windows) and has been designed to run on Windows PCs within a
Command-prompt using command-line arguments to initiate a model run. The amount of storage
space required on the hard disk for a particular application will depend greatly on the output
options selected. Some of the optional output files of concentration data can be rather large.
More information on output file products is provided in Sections 3.7 and 3.8.Overview of
available modeling options
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 in the
AERMOD model.
1.2.3.1 Dispersion options
Since the AERMOD model is especially 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
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averages when calm winds or missing meteorological data occur. The model also includes non-
default options for suppressing the use of stack-tip downwash, deposition modeling, NO2
conversion, special processing for low wind conditions, and to disable the date checking for non-
sequential meteorological data files. The latter option is needed to facilitate evaluation of the
model. The AERMOD model also includes a non-default screening mode added specifically for
integration with the AERSCREEN model interface (EPA, 2016). The user can specify several
short-term averages to be calculated in a single run of the AERMOD model, as well as
requesting the overall period (e.g. annual) averages.
1.2.3.2 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, line sources, or a string of volume sources. If elongated area
sources, the user input required to define the source is simplified from 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. These 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 some or all of the sources included in a
particular model run.
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1.2.3.3 Receptor options
The AERMOD model has considerable flexibility in the specification of receptor
locations. The user has the capability of specifying multiple receptor networks in a single run
and may also mix Cartesian grid receptor networks and polar grid receptor networks in the same
run. This is useful for applications where the user may need a coarse grid over the whole
modeling domain, but a denser grid in 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 in order to model the effects of terrain above
(or below) stack base 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 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, 2018d).
1.2.3.4 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, 2018c). Both of these 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.
1.2.3.5 Output options
The basic types of printed output available with AERMOD are:
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• Summaries of high values (highest, second highest, etc.) by receptor for each
averaging period and source group combination;
• Summaries of overall maximum values (e.g., the maximum 50) for each averaging
period and source group combination; and
• Tables of concurrent values summarized by receptor for each averaging period and
source group combination for each day of data processed. These "raw"
concentration values may also be output to unformatted (binary) files, as described
below.
The tables by receptor and maximum value tables can be output for the source group
values or for the individual source values, or both. 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, or 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 graphics plotting packages to generate contour plots of the
concentration values. Separate files can be specified for all of the averaging period and source
group combinations of interest to the user.
Another output file option of 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
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included. This file may be used to generate Q-Q (quantile) plots of results, where values from
different models and/or observed data are paired by rank. The other type of output file provides
arc maxima results along with detailed information about the plume characteristics associated
with the arc maximum.
Finally, there are output options specifically for comparing model results to the 24-hour
PM2.5, 1-hour NO2 and 1-hour SO2 NAAQS. The form 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.
1.2.3.6 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 in order 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 regard to the PM2.5, NO2 and SO2 standards.
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2.0 Getting started - a brief tutorial
This section provides a brief tutorial for setting up a simple application problem with the
AERMOD model, which serves as an introduction for novice users to the AERMOD model. The
example illustrates the usage of the most 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 leads 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, a general description of the input
file keyword/parameter approach is provided first.
2.1 Description of keyword/parameter approach
The input 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, and 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:
2-1
-------
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: 123456789012345678 9012345678901234567890
CO MODELOPT DFAULT CONC
I I
Parameters
The following sections describe the rules for structuring the input control file and explain
some of the advantages of the keyword/parameter approach.
2.1.1 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.
8-Character Keyword
2-Character Pathway ID
2-2
-------
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 (previously 132 characters). The information on each input image
consists of a "pathway," a "keyword," and one or more "parameters." Each of these "fields" on
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 13through 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:
123456789012345678 9012345678901234567890
CO MODELOPT DFAULT CONC
j ' ¦(— Parameters
8-Character Keyword
^ 2^Character Pathway ID
2-3
-------
Alphabetical characters can be input as either lower case or upper case letters. The model
converts all character input to upper case letters internally, with the exception of 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.
Other keywords are optional and are only needed to exercise particular 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, APPENDIX A, APPENDIX B and the
Quick Reference in APPENDIX E.
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. 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 also to declare the length of all filename and format
variables. This PARAMETER is currently assigned a value of 200 beginning with version 09292
(previously 80), and is in MODULE MAIN1 in MODULES.FOR.
2-4
-------
2.1.2 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, as long as 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 of 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.
2-5
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2.2 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;
• 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 a number of
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 through the use of secondary keywords
associated with the MODELOPT keyword. The MODELOPT keyword is described in more
detail in the Section 3.2.2. Throughout this user's guide, there has been an effort to clearly
distinguish regulatory options that are required to be set by the user and can be used
2-6
-------
simultaneously with the DFAULT keyword from non-regulatory options that cannot be used
along with the DFAULT keyword. These non-regutory options are sometimes referred to as
"non-DFAULT" options since they cannot be used along with the DFAULT keyword.
2.3 Setting up a simple control file
This section goes through a step-by-step description of setting up a simple application
problem, illustrating the most 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 also illustrates some of the flexibility in
structuring the input file.
2-7
-------
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
o
o
o
o
o
. 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
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
2-8
-------
2.3.1 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. We will assume 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.
2.3.2 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
APPENDIX B
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.
POLLUTID - 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.
2-9
-------
The first two keywords are fairly self-explanatory. As discussed above in Section 2.2,
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.
Since the pollutant in this example is SO2, we will probably need to calculate average
values for 3-hour and 24-hour time periods, and we also need to calculate averages for the full
annual time period. Our control file might therefore look something like this after adding two
more keywords:
2-10
-------
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 B, 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 of the inputs are summarized in the output file for the user to
review.
Our complete control file for the CO pathway may look something like this:
CO
STARTING
CO
TITLEONE
A Simple Example Problem for the AERMOD-PRIME Model
CO
MODELOPT
CONC FIAT
CO
AVERTIME
3 24 PERIOD
CO
POLLUTID
S02
CO
RUNORNOT
RUN
CO
FINISHED
The following set of control file options has a more structured look, but it is equivalent to the
example above:
2-11
-------
CO
STARTING
TITLEONE
A Simple Example Problem for the AERMOD-PRIME Model
MODELOPT
CONC FIAT
AVERTIME
3 24 PERIOD
POLLUTID
S02
RIJNORNOT
RUN
CO
FINISHED
Since the pathway ID is required to begin in column 1 (see Section 2.3.8 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.
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.
2.3.3 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 our example problem is influenced by a nearby building,
we also need to include the optional keywords BUILDHGT and BUILDWID in our input file.
2-12
-------
The input file for the SO pathway for this example will look something like this:
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 eight 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 makes reference to that 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
2-13
-------
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 6 values given on each of 6 lines for
each of the building dimensions. There could have been fewer or more lines as long as exactly
36 values were entered before starting with a new keyword. Since all of the building heights
were 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.
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 our example
may look like this, with the same result as above:
2-14
-------
SO STARTING
LOCATION
STACK1
POINT
o
o
o
o
o
. 0
** Point Source
QS
HS TS
VS
DS
** Parameters:
—
—
SRCPARAM
STACK1
500.0
65.0 425.
0 15
. 0
5.0
BUILDHTS
STACK1
36*50
BUILDWTS
STACK1
62.26
72. 64
80.
80
86.51
89.59
89. 95
STACK1
87.58
82.54
75.
00
82.54
87.58
89. 95
STACK1
89.59
86.51
80.
80
72 . 64
62.26
50. 00
STACK1
62.26
72. 64
80.
80
86.51
89.59
89. 95
STACK1
87.58
82.54
75.
00
82.54
87.58
89. 95
STACK1
89.59
86.51
80.
80
72 . 64
62.26
50. 00
XBADJ
STACK1
-47.35
-55.76
-62.
48
-67.29
-70.07
-70.71
STACK1
-69.21
o
IT)
KD
1
-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 B.
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 0 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.
2.3.4 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
2-15
-------
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 starting
and ending of the sub-pathway are identified. The order of secondary keywords within the sub-
pathway is not critical, similar to the main pathways. Each card must be identified with a
network ID (up to eight alphanumeric characters), in this case it is "POLl." Multiple networks
may be specified in a single model run. The model waits until the END secondary keyword is
encountered to set the variables, which may include terrain heights for receptors on elevated
terrain or flagpole receptor heights if those options are being exercised by the user. The use of
these optional secondary keywords is described in detail in Section 3.4.
For this example, the ORIG secondary keyword specifies the location of the origin for the
polar network being defined as being the location of the source STACK1. The origin can also be
specified as X and Y-coordinates. The ORIG keyword is optional, and the model will default to
an origin of (0.0, 0.0) if it is omitted. The DIST keyword identifies the distances along each
direction radial at which the receptors will be located. In this case there are four distances. More
distances could be added by adding values to that input card or by including a continuation card
with the DIST keyword, if needed. The GDIR keyword specifies that the model will Generate
DIRection radials for the network, in this case there will be 36 directions, beginning with the 10-
degree flow vector and incrementing every 10 degrees clockwise. The user may elect to define
2-16
-------
Discrete DIRection radials instead by using the DDIR keyword in place of the GDIR keyword.
2.3.5 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 we will assume that the meteorological data files are for
Albany, NY and that an on-site location called Hudson has also been used. We will also assume
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 something like this:
ME
STARTING
SURFFILE
AERMET2.SFC
PROFFILE
AERMET2.PFL
SURFDATA
14735 1988
ALBANY,NY
UAIRDATA
14735 1988
ALBANY,NY
SITEDATA
99999 1988
HUDSON
PROFBASE
0.0 METERS
ME
FINISHED
2-17
-------
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 2.1.1). 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.
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.
2-18
-------
2.3.6 Selecting output options - OU pathway
All of 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 of these keywords, the user has additional flexibility to specify for which
short-term averaging periods the outputs are selected. For the MAXTABLE keyword the user
can also specify the number of overall maximum values to summarize for each averaging period
selected, up to a maximum number controlled by a parameter in the computer code. In the
example below, the highest and second-highest values by receptor and the maximum 50 values
for all averaging periods are specified.
OU
STARTING
RECTABLE
ALLAVE
FIRST SECOND
MAXTABLE
ALLAVE
50
OU
FINISHED
To simplify the input for users who request the same printed table output options for all
averaging periods, these keywords recognize the secondary keyword "ALLAVE" as the first
parameter for that purpose. In order to obtain the overall maximum 10 values for the 24-hour
averages only, then the OU pathway input would look like this:
OU
STARTING
RECTABLE
ALLAVE FIRST SECOND
MAXTABLE
24 10
OU
FINISHED
2-19
-------
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 in order to improve its
readability. This input file is comparable to the version shown earlier in Figure 2-1, which used
a somewhat different style.
2-20
-------
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
STARTING
LOCATION
STACK1 POINT 0.
0 0.0 0.
0
* *
Point Source QS
HS TS
VS
DS
* -k
Parameters: --
SRCPARAM
STACK1 500.0 65.0 425
. 15 . 0
5.0
BUILDHGT
STACK1 3 6*50.
so
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
so
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
so
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
so
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
POL1 STA
GRIDPOLR
POL1 ORIG
STACK1
GRIDPOLR
POL1 DIST
175. 350. 500.
1000 .
GRIDPOLR
POL1 GDIR
36 10
10
GRIDPOLR
POL1 END
RE
FINISHED
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
2-21
-------
2.3.7 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 most 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 C of this volume provides more
details about the error handling provided by the AERMOD model, including a listing and
explanation of all error and other types of messages generated by the 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
2-22
-------
at the completion of the model calculations, the model rereads the message file and generates a
summary of the messages which is included in the main printed output file. If the processing of
the model setup information indicates no errors or warnings, and the user has selected the option
to RUN the model calculations on the CO RUNORNOT card, then the model will simply write a
statement to the print file that the model setup was completed successfully. Otherwise, the
model will report a summary of the 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
2-23
-------
Since this is a warning message, it would have appeared at the end of the message summary table
in the output file, but it would not have halted processing of the data. The last item on the
message line, "Hints," may include such information as the keyword or parameter name causing
the error, the source ID, group ID or (as in this case) the network ID involved, or perhaps the
date variable identifying when the message occurred during the processing of the meteorological
data, such as an informational message identifying the occurrence of a calm wind.
For new users and for particularly complex applications, it is strongly recommended that
the model first be run with the RUNORNOT keyword (on the CO pathway) set NOT to run. In
this way, the user can determine if the model is being setup properly by the control file before
committing the resources to perform a complete run. The user should make a point of examining
any warning messages carefully to be sure that the model is operating as expected for their
application, since these messages will not halt processing by the model. In most cases, the
detailed messages will provide enough information for the user to determine the location and
nature of any errors in the control file. If the intent of the message is not immediately clear, then
the user should refer to the more detailed descriptions provided in APPENDIX C for the
particular error code generated.
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 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
2-24
-------
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 3.2.18, allows the user to save the complete list
of detailed messages to a user-specified filename.
*** Message Surranary : AERMOD Model Execution ***
Surranary of Total Messages
A Total of
A Total of
A Total of
A Total of
A Total of
A Total of
0 Fatal Error Message(s)
0 Warning Message(s)
0 Informational Message(s)
96 Hours Were Processed
0 Calm Hours Identified
0 Missing Hours Identified ( 0.00 Percent)
******** FATAL ERROR MESSAGES ********
* * * NONE * * *
~k~k~k~k~k~k~k~k
WARNING MESSAGES
* NONE
~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~k~k~k~k~k~k
*** AERMOD Finishes 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
Figure 2-3. Example Message Summary Table for AERMOD Execution
2-25
-------
SO STARTING
LOCATION
STACK1
POINT 0
0 0.0 0.0
** Point Source
QS HS TS
VS
DS
** Parameters:
—
--
SRCPARAM
STACK1
500.0 65
0 425.0
15 . 0
5.0
BUILDHTS
STACK1
36*50.
BUILDWTS
STACK1
62.26
72. 64
80.80
86.51
89.59
89. 95
STACK1
87.58
82.54
75. 00
82.54
87.58
89. 95
STACK1
89.59
86.51
80.80
72 . 64
62.26
50. 00
STACK1
62.26
72. 64
80.80
86.51
89.59
89. 95
STACK1
87.58
82.54
75. 00
82.54
87.58
89. 95
STACK1
89.59
86.51
80.80
72 . 64
62.26
50. 00
XBADJ
STACK1
-47.35
-55.76
-62.48
-67.29
-70.07
-70.71
STACK1
-69.21
-65.60
-60.00
-65.60
-69.21
-70.71
STACK1
-70.07
-67.29
-62.48
-55.76
-47.35
-37.50
STACK1
-35.19
-31.82
-27.48
-22.30
-16.44
-10.09
STACK1
-3.43
3.34
10. 00
3.34
-3.43
-10.09
STACK1
-16.44
-22.30
-27.48
-31.82
-35.19
-37.50
YBADJ
STACK1
34 .47
32.89
30.31
26.81
22.50
17 . 50
STACK1
11. 97
6.08
0. 00
-6.08
-11.97
-17.50
STACK1
-22.50
26.81
-30.31
-32.89
-34.47
-35.00
STACK1
-34.47
-32.89
-30.31
-26.81
-22.50
-17.50
STACK1
-11.97
-6.08
0. 00
6.08
11. 97
17 . 50
STACK1
22.50
26.81
30.31
32 . 89
34 .47
35. 00
SRCGROUP
ALL
SO FINISHED
*** Message Summary For AERMOD Model
Setup
***
Surrmary
of Total Messages
A Total of
9 Fatal Error Message(
s)
A Total of
0 Warning Message(s)
A Total of
0 Informational
Message(s)
~k~k~k~k~k~k~k~,
FATAL ERROR MESSAGES ********
SO El 05
14
SETUP
Invalid
Keyword Specified. The Troubled Keyword
is
BUILDHTS
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 E236
40
SRCQA
Not Enough BUILDHGTs Specified for
SourcelD
STACK1
SO E237
40
SRCQA
Not Enough BUILDWIDs Specified for
SourcelD
STACK1
~k~k~k~k~k~k~k~k
WARNING MESSAGES ********
* * *
NONE * * *
~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
2-26
-------
2.3.8 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 RMO 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 or 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 from which the model is being executed,
only when the control input filename is not specified. The model can also be executed by double
clicking on the executable file from Windows Explorer.
As mentioned above, the SCRAM PC-executable file for AERMOD opens the input and
output files explicitly. One reason for this is to allow for the model to write an update on the
status of processing to the PC terminal screen. For the AERMOD model, the model first
indicates that setup information is being processed and then gives the Julian day currently being
processed. If no status message is displayed, then the model did not load into memory properly.
2-27
-------
If the model stops after completing the setup processing, then either 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.
2-28
-------
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
2-29
-------
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.
2-30
-------
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 second highest values by
receptor for our sample problem. These values are the second 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. The summaries
for all averaging periods have been combined onto a single figure but appear on separate pages
of the actual output file.
2-31
-------
* + * AERMOD - VERSION 15181 A Simple Example Problem for the AERMOD-PRIME Model *
4.** CERMET - VERSION 15181
* *MODELOPTs: NonDFAULT CONC FLAT RURAL
** 05/27/16
*** 09:29:00
PAGE 1
* + * MODEL SETUP OPTIONS SUMMARY
^Model Is Setup For Calculation of Average CONCentration Values.
— DEPOSITION LOGIC —
**N0 GAS DEPOSITION Data Provided.
**N0 PARTICLE DEPOSITION Data Provided.
"*"*¦ Model Uses NO DRY DEPLETION. DRYDPLT = F
"*"*¦ Model Uses NO WET DEPLETION. WETDPLT = F
**Model Uses RURAL Dispersion Only.
**Model Allows User-Specified Options:
1. Stack-tip Downwash.
2. Model Assumes Receptors on FLAT Terrain.
3. Use Calms Processing Routine.
4. Use Missing Data Processing Routine.
5. No Exponential Decay.
¦^Other Options Specified:
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
**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 OPENPIT source(s)
**Model Set To Continue RUNning After the Setup Testing.
**The AERMET Input Meteorological Data Version Date: 15181
**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
2-32
-------
*** AERMOD
- VERSION 15181 ***
* A Simple Example Problem for
the AERMOD-PRIME
Model
***
05/27/16
AERMET -
VERSION 15181 *** ***
***
09:29:00
PAGE 9
*^MODELOPTs :
NonDFAULT
CONC FLAT RURAL
*** THE
1ST HIGHEST
3-HR AVERAGE CONCENTRATION VALUES FOR SOURCE GROUP: ALL
***
INCLUDING SOURCE(S):
STACK1
'
,,,
NETWORK ID:
POL1
; NETWORK TYPE: GRIDPOLR
***
CONC OF
S02
IN MICROGRAMS/N!** 3
* *
DIRECTION |
DISTANCE (METERS)
(DEGREES) |
175
00
350.00
500
. 00
1000
00
10.0 |
1.60637
(88030212)
4.32183 (
88030215
) 9.
87871
(88030215)
20.31341
(88030215)
20.0 |
1.27691
(88030212)
7.75747 (
88030215
) 19.
35471
(88030215)
43.24437
(88030215)
30. 0 |
1.31753
(88030321)
6.80000 (
88030215
) 16.
96932
(88030215)
37 21008
(88030215)
40.0 |
1.37996
(88030321)
2.78658 (
88030215
) 6.
56111
(88030215)
13.02309
(88030215)
50. 0 |
1.41988
(88030321)
2.62563 (
88030115
) 4 .
10823
(88030115)
4 68748
(88030212)
o
o
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 |
7.93417
(88030115)
113.82878 (
88030115
) 143.
17281
(88030115)
83.53515
(88030115)
100.0 |
49.08742
(88030112)
182.84892 (
88030115
) 220.
83950
(88030115)
145.67439
(88030115)
110.0 |
112.74896
(88030112)
242.27760 (
88030112
) 278.
47891
(88030115)
163.85178
(88030115)
120.0 |
133.57958
(88030112)
303.36780 (
88030112
) 329.
9 6 0 0 9
(88030112)
201.18209
(88030112)
130.0 |
84.37449
(88030112)
177.43465 (
88030112
) 193.
23412
(88030112)
123.90900
(88030112)
140.0 |
34.33094
(88030112)
78.48757 (
88030115
) 90.
16432
(88030115)
66.26935
(88030112)
150.0 |
3.26313
(88030112)
28.20306 (
88030115
) 35.
81299
(88030112)
33.54932
(88030112)
160.0 |
1.45757
(88030209)
8.53192 (
88030112
) 13.
46873
(88030112)
12 93284
(88030112)
170.0 |
1.33663
(88030209)
2.92150 (
88030112
) 4 .
70642
(88030112)
9. 87872
(88030415)
180.0 |
1.23781
(88030212)
2.59400 (
88030115
) 4 .
58665
(88030415)
11 25826
(88030415)
190.0 |
1.23781
(88030212)
2.62640 (
88030115
) 4 .
10607
(88030115)
6.95118
(88030415)
200.0 |
1.23781
(88030212)
2.63486 (
88030115
) 4 .
10609
(88030115)
4 68748
(88030212)
210.0 |
1.23781
(88030212)
2.63700 (
88030115
) 4 .
10609
(88030115)
4 68748
(88030212)
220.0 |
1.23783
(88030212)
2.63762 (
88030115
) 4 .
10609
(88030115)
4 68748
(88030212)
230.0 |
1.26732
(88030212)
2.63762 (
88030115
) 4 .
10609
(88030115)
4 68767
(88030212)
240.0 |
1.59395
(88030212)
2.63762 (
88030115
) 4 .
10609
(88030115)
4 .72694
(88030212)
250.0 |
2.39221
(88030212)
2.63762 (
88030115
) 4 .
10609
(88030115)
5.24318
(88030212)
260.0 |
3.44586
(88030212)
3.11001 (
88030212
) 4 .
10609
(88030115)
7 .70339
(88030212)
270.0 |
4.67900
(88030212)
4.53914 (
88030212
) 4 .
60912
(88030212)
13.41550
(88030212)
280.0 |
6.10725
(88030212)
6.15657 (
88030212
) 6.
42897
(88030212)
21.16129
(88030212)
290.0 |
7.47165
(88030212)
7.75530 (
88030212
) 8.
18188
(88030212)
27 .76976
(88030212)
300.0 |
8.45754
(88030212)
8.93592 (
88030212
) 9.
35713
(88030212)
30.22723
(88030212)
310.0 |
8.83767
(88030212)
9.29972 (
88030212
) 9.
54143
(88030212)
27 .40028
(88030212)
320.0 |
8.53526
(88030212)
8.67663 (
88030212
) 8.
65382
(88030212)
20.68075
(88030212)
330.0 |
7.53807
(88030212)
7.17470 (
88030212
) 6.
91694
(88030212)
13.22924
(88030212)
340.0 |
5.96054
(88030212)
5.15139 (
88030212
) 4 .
78244
(88030212)
8 04861
(88030212)
350.0 |
4.10326
(88030212)
3.16494 (
88030212
) 4 .
10609
(88030115)
5.75319
(88030212)
360.0 |
2.52862
(88030212)
2.63762 (
88030115
) 4 .
10609
(88030115)
4 96113
(88030212)
Figure 2-7. Example Output Table of High Values by Receptor
2-33
-------
*** AERMOD -
- VERSION 15181 ***
*** A Simple Example Problem for the AERMOD-PRIME Model
***
05/27
/16
*** AERMET -
VERSION
15181 ***
***
***
09:29:
00
PAGE
15
**MODELOPTs:
NonDFAULT CONC
FLAT RURAL
*** 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
24.85172 AT (
433.01, -250.00,
o
o
o
o
o
o
o
00
GP
P0L1
2ND
HIGHEST
VALUE IS
23.13772 AT (
469.85, -171.01,
o
o
o
o
o
o
o
00
GP
P0L1
3RD
HIGHEST
VALUE IS
21.03526 AT (
303.11, -175.00,
o
o
o
o
o
o
o
00
GP
P0L1
4 TH
HIGHEST
VALUE IS
19.33505 AT (
328.89, -119.71,
o
o
o
o
o
o
o
00
GP
P0L1
5TH
HIGHEST
VALUE IS
17.19043 AT (
383.02, -321.39,
o
o
o
o
o
o
o
00
GP
P0L1
6TH
HIGHEST
VALUE IS
16.86864 AT (
866.03, -500.00,
o
o
o
o
o
o
o
00
GP
P0L1
7 TH
HIGHEST
VALUE IS
15.01122 AT (
939.69, -342.02,
o
o
o
o
o
o
o
00
GP
P0L1
8 TH
HIGHEST
VALUE IS
14.27333 AT (
268.12, -224.98,
o
o
o
o
o
o
o
00
GP
P0L1
9TH
HIGHEST
VALUE IS
12.80321 AT (
492.40, -86.82,
o
o
o
o
o
o
o
00
GP
P0L1
10TH
HIGHEST
VALUE IS
12.38150 AT (
766.04, -642.79,
o
o
o
o
o
o
o
00
GP
P0L1
***
THE SUMMARY OF HIGHEST 3
-HR RESULTS ***
** CONC OF S02
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
329.96009 ON
88030112: AT ( 433.01
-250.00, 0.00
0
. 00,
0.00) GP
P0L1
HIGH
2ND HIGH VALUE IS
261.07802 ON
88030112: AT ( 469.85
-171.01, 0.00
'
0
. 00,
0.00) GP
P0L1
***
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,
Z FLAG)
OF TYPE
GRID-
ID
ALL HIGH
1ST HIGH VALUE IS
88.89511 ON
88030124: AT ( 433.01
-250.00, 0.00
0
. 00,
0.00) GP
P0L1
HIGH
2ND HIGH VALUE IS
10.09519 ON
88030324: AT ( 866.03
-500.00, 0.00
'
0
. 00,
0.00) GP
P0L1
*** RECEPTOR
TYPES:
GC = GRIDCART
GP = GRIDPOLR
DC = DISCCART
DP = DISCPOLR
Figure 2- 8. Example of Result Summary Tables for the AERMOD Model
2-34
-------
2.4 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.
2.4.1 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.
2.4.2 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 2.1.2, 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.
2-35
-------
2.4.3 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.
2.4.4 Modifying output options
Modifying the output options involves many of the same principles that are described above.
In addition, all of 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.
2-36
-------
3.0 Detailed keyword reference
This section of the AERMOD User's Guide provides a detailed reference for all of 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 in order 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 B, and the Quick Reference in APPENDIX E. 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 B 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.
3-37
-------
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:
Syntax:
CO TITLEONE Title 1
CO TITLETWO Title2
Type
TITLEONE - Mandatory, Non-repeatable
TITLETWO - Optional, Non-repeatable
The parameters Title 1 and Title2 are character parameters of length 200, which are read as a single
field starting at column 13. The title information is taken as it appears in the control file without
any conversion of lower case to upper case letters. If the TITLETWO keyword is not included in
the control file, then the second line of the title in the output file will appear blank. Note that in the
output files, only the first 68 characters of TITLEONE and TITLETWO are printed.
3.2.2 Dispersion options
The dispersion options are controlled by the MODELOPT keyword on the CO pathway. The
syntax, type, and order of the MODELOPT keyword are summarized below:
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Syntax:
CO MODELOPT
DFAULT ALPHA BETA CONC AREADPLT FLAT NOSTD NOCHKD NOWARN SCREEN
SCIM
PVMRM
FASTALL
DEPOS and/or or
or
OLM
or
DDEP ELEV WARNCHKD
or
ARM 2
FASTAREA
and/or
WDEP
DRYDPLT
WETDPLT NOURBTRAN VECTORWS PSDCREDIT
or
or
NODRYDPLT
NOWETDPLT
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 - 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);
ALPHA - 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, METHOD
2 particle deposition, gas deposition, and RLINEXT with options for modeling
barriers and depressed roadways);
BETA - 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;
CONC - Specifies that concentration values will be calculated;
DEPPS - Specifies that total deposition flux values (both dry and wet) will be calculated;
DDEP - Specifies that dry deposition flux values will be calculated;
WDEP - Specifies that wet deposition flux values will be calculated;
AREADPLT - 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);
FLAT - 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;
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FLAT sources are identified by specifying the keyword FLAT in place of the
source elevation field on the SO LOCATION keyword (cannot be used
simultaneously with the DFAULT keyword); the RLINE and RLINEXT source
types require FLAT to be used
ELEV - 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 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-
WARNCHKD-
NOWARN -
SCREEN -
SCIM -
PVMRM -
OLM-
ARM2 -
PSDCREDIT -
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);
Specifies that the option for running AERMOD in a screening mode will be
used (cannot be used with the DFAULT keyword);
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) forN02
conversion will be used (regulatory option, can be used simultaneously with
DFAULT);
Specifies that the Ozone Limiting Method (OLM) for NO2 conversion will be
used (regulatory option, can be used simultaneously with DFAULT keyword);
Specifies that the Ambient Ratio Method - 2 (ARM2) for NO2 conversion will
be used (regulatory option, can be used with DFAULT keyword);
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);
FASTALL - 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 and
OPENPIT sources through hybrid approach (formerly associated with TOXICS
option, now controlled by the FASTAREA and FASTALL option, cannot be
used with the DFAULT keyword);
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FASTAREA -
DRYDPLT -
NODRYDPLT-
WETDPLT -
NOWETDPLT -
NOURBTRAN -
VECTORWS -
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;
Option to disable dry depletion (removal) processes associated with dry
deposition algorithms;
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;
Option to disable wet depletion (removal) processes associated with wet
deposition algorithms;
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 and Evaluation Document (EPA, 2018a) will be applied (can be
used with the DFAULT keyword).
3.2.2.1 DFAULT option
As previously discussed, the regulatory DFAULT option in AERMOD includes the use of
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.
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The missing data processing routines that are included in the AERMOD model allow the
model to handle missing meteorological data in the processing of short-term averages. The model
treats missing meteorological data in the same way as the calms processing routine, i.e., it sets the
concentration values to zero for that hour and calculates the short-term averages according to EPA's
calms policy, as set forth in the Guideline. Calms and missing values are tracked separately for the
purpose of flagging the short-term averages. An average that includes a calm hour is flagged with a
'c', an average that includes a missing hour is flagged with an'm', and an average that includes both
calm and missing hours is flagged with a 'b'. If the number of hours of missing meteorological data
exceeds 10 percent of the total number of hours for a given model run, a cautionary message is
written to the main output file, and the user is referred to Section 5.3.2 of "Meteorological
Monitoring Guidance for Regulatory Modeling Applications" (EPA, 2004).
3.2.2.2 ALPHA options
Beginning with version 18081, a new secondary keyword, ALPHA, has been 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 considered to be 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.
Version 19191 includes the following ALPHA options:
• PSDCREDIT
• LOW WIND
• AWMADWNW
• ORDDWNW
• RLINEXT
• RDEPRESS
• RBARRIER
• URBAN when combined with RLINE or RLINEXT
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• METH0D2 particle deposition
• Gas deposition (GDSEASON, GDLANUSE,GASDEPDF, GASDEPOS, GASDEPVD
keywords)
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. We decided to make the options ALPHA
while we evaluate deposition in AERMOD. Note, that METHOD 1 particle deposition is
unaffected and can still be used with AERMOD in default mode.
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. Version 19191 includes the following BETA options:
• RLINE
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 in order 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
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the numerical plume rise calculation, and the initial radius of the plume can significantly influence
plume rise based on the PRIME algorithm. As a result, use of an effective diameter adjusted to
maintain the flow rate is not appropriate and could produce unrealistic results. For PRIME
downwash sources modeled using the options for capped and horizontal releases, the basic premise
of the Model Clearinghouse procedure, i.e. that the vertical momentum is suppressed while the
buoyancy of the plume is conserved, has been adapted for the PRIME numerical plume rise
formulation. For capped stacks the initial radius of the plume is assumed to be 2 times the actual
stack diameter to account for the interaction of the exiting plume with the cap. The initial vertical
velocity of the plume is set at 0.001 m/s, and the initial lateral velocity of the plume is set at 25% of
the initial exit velocity of the plume. For horizontal stacks, the initial vertical velocity of the plume
is set at 0.001 m/s, the total exit velocity of the plume is assigned to the initial lateral velocity, and
the plume is assumed to be emitted in the downwind direction. Although this adaptation of the
Model Clearinghouse procedure to PRIME downwash sources has not been validated by field tracer
or wind tunnel data, analyses have shown that simply setting the exit velocity to 0.001 m/s without
any further adjustment when downwash is applied, as suggested in Section 6.1 of the AERMOD
Implementation Guide (EPA, 2018b), 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 B. The AERMOD model performs the necessary adjustments
internally to account for plume rise and stack-tip downwash. For horizontal releases, the model
currently assumes that the release is oriented with the wind direction, and the model does not
account for directional effects that may occur with horizontal releases. The model also does not
account for stacks oriented at a non-horizontal angle relative to vertical. For PRIME downwash
sources, the user-specified exit velocity for horizontal releases is treated initially as horizontal
momentum in the downwind direction.
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3.2.2.5 Output types (CONC. DEPPS. DDEP and/or WDEP)
The user may select any or all of the output types (CONC, DEPOS, DDEP and/or WDEP) to
be generated in a single model run. The order of these secondary keywords on the MODELOPT
card has no effect on the order of results in the output files - the outputs will always be listed in the
order of CONC, DEPOS, DDEP, and WDEP. Appropriate deposition parameters must be specified
in order to output deposition fluxes using the DEPOS, DDEP, and/or WDEP keywords (see
Sections 3.3.3 and 3.3.4 for more details). Deposition has not been implemented for
RLINE/RLINEXT or BUOYLINE sources, 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/or wet removal (depletion) mechanisms (the
DRYDPLT and WETDPLT options in earlier versions of AERMOD) will automatically be
included in the calculated concentrations or deposition flux values if the dry and/or wet deposition
processes are considered, unless the user specifies the NODRYDPLT and/or NO WETDPLT
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 the effect of 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 or BUOYLINE
sources, thus the user can only run CONC with these source types.
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3.2.2.7 NQ2 conversion options
Beginning with version 16216r, the PVMRM, OLM, ARM2 options for modeling NO2
conversion are regulatory options that can be specified simultaneously with the DFAULT keyword.
Only one of these options for NO2 conversion can be specified for a given model run, and all
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
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. 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.
The FASTALL option for POINT 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 ay 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 based on 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
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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. Note that, as of version 19191, the FASTALL option has not
been implemented for the BUOYLINE, RLINE, or RLINEXT source types.
3.2.2.9 Urban transition
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 APPENDIX F.
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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,
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, 2016) 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).
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
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where:
C = Calculated concentration
^ C-s = Cumulatibe impacts for the sampled hours
Ns = Number of sampled hours
To use the SCIM option, the user must include the SCIM keyword on the CO MODELOPT
card, and also specify 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.Deposition Parameters
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, 2017), 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 considered to be 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 option 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
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the same as for the particle deposition algorithm in the ISCST3 model. For "Method 2" particle
deposition, the user must define the fraction of the particle mass in the fine particle category (less
than 2.5 microns) and a representative mass mean diameter for the particles. Table 3-1 summarizes
the required keywords for the various deposition options within AERMOD and whether they are
allowed under the DFAULT option. For all keywords associated with METHOD 2 or gas
deposition, the ALPHA option must be used 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
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, 2017).
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The user should be aware that one or more of the following meteorological parameters are
needed for deposition: precipitation code, precipitation rate, relative humidity, surface pressure, and
cloud cover.
3.2.2.12 Definition of seasons for gas 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.
3.2.2.13 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):
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Land Use Category
Description
Urban land, no vegetation
Agricultural land
Rangeland
Forest
Suburban areas, grassy
Suburban areas, forested
Bodies of water
Barren land, mostly desert
Non-forested wetlands
1
2
3
4
5
6
7
8
9
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:
where a numeric value from 1 to 9 is entered for each of the 36 direction sectors (every 10
degrees) to associate it with the land use definitions given above. This keyword is optional for the
model, but mandatory when applying the gas deposition algorithms, unless the GASDEPVD option
for user-specified deposition velocity is used. The first value, Seel, corresponds with the land use
category, downwind of the application site, for winds blowing toward 10 degrees, plus or minus 5
degrees. The downwind sectors are defined in clockwise order, with Sec36 corresponding to winds
blowing toward 360 degrees (North) and should generally reflect conditions downwind relative to
the source location. The user can specify "repeat values" by entering a field such as "36*3" as a
parameter for the GDLANUSE keyword. The model will interpret this as "36 separate entries, each
with a value of 3." Since the model must identify this as a single parameter field, there must not be
any spaces between the repeat-value and the value to be repeated. Option for overriding default
parameters for gas dry deposition
An optional keyword is available on the Control (CO) pathway to allow the user to override
the default values of the reactivity factor (/<>), and the fraction (F) of maximum green leaf area index
(LAI) for seasonal categories 2 (autumn/unharvested cropland) and 5 (transitional spring), for use
with the gas dry deposition algorithms.
Syntax: CO GDLANUSE Seel Sec2 Sec3 ... Sec36
Type: Optional, Non-repeatable
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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).
3.2.2.14 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 3.2.17. 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 Vd for each source and for each hour modeled. The particle outputs are
labeled as being based on either Method 1 or Method 2. For Method 1, results are output for each
particle size category. The filename and file units for these data files are hardcoded in the model,
and the files are overwritten each time the model is executed. Since these files include data for each
source for each hour, file sizes may become large.
3.2.3 Low wind parameters
An ALPHA option, LOWWIND (see Section3.2.3), is included in AERMOD (beginning
with the version dated 18081) related to concerns regarding model performance under low wind
speed conditions. The LOW WIND keyword has been added to the CO pathway to allow users to
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adjust the minimum sigma-v value (SVmin) within a range of 0.01 to 1.0 m/s) and the minimum
wind speed value (WSmin) within a range from 0.01 to 1.0 m/s. Inclusion of the LOWWIND
keyword is intended to facilitate further testing and evaluation of AERMOD in low wind conditions
in order to better understand the relationships of certain variables and potentially develop additional
regulatory low wind options that will improve AERMOD's performance in low wind conditions.
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) with SVmin=0.2. The LOW WIND keyword also allows users to adjust
the maximum value for the meander factor (FRANmax), within a range of 0.0 to 1.0, inclusive. The
default value for FRANmax is 1.0. The syntax and type of the LOW WIND keyword are:
s . CO LOW WIND SVmin [WSmin]
Syntax: CO LOW WIND SVmin WSmin [FRANmax]
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, within a range of 0.01 to 1.0 m/s, and FRANmax is the maximum meander
factor, within a range of 0.0 to 1.0, inclusive. The WSmin and FRANmax parameters on the
LOW WIND keyword are optional. However, a value for WSmin must also be included in order to
specify a value for FRANmax.
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.
In addition to the LOW WIND ALPHA option, an option has been incorporated in the
AERMET meteorological processor (first as a BETA option beginning with version 12345 and a
regulatory option in version 16216) to address concerns regarding model performance under low
wind conditions. The ADJU* option in AERMET adjusts the surface friction velocity (U*) under
low-wind/stable conditions based on Qian and Venkatram (2011). The ADJ U* option may be used
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as a regulatory option in AERMET with NWS data or with site-specific data that does not include
turbulence (i.e., sigma-w and/or sigma-theta). When the ADJU* option is used in the absence of
turbulence data, AERMOD can accept the data with the regulatory DFAULT option enabled.
Beginning with version 16216 of AERMET, an adjustment to U* under the ADJ U* option is also
available as a regulatory option for applications utilizing the Bulk Richardson Number (BULKRN)
method, based on Luhar and Raynor (2009) (see also AECOM (2010)) when used with site-specific
data that does not include turbulence parameters. The ADJ U* option, when used with site-specific
data that does include tublulence 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.
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
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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. 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 completly 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 dependancies between options are noted
in the sections below.
3.2.4.1 ORD building downwash options
The first is an initiative led by the EPA's Office of Research and Development (ORD). ORD
has performed wind tunnel experiments and embedded large eddy simulations (LES) to better
understand how to parameterize buildings that are elongated and angled relative to the wind flow
and the parameterization of the plume in the cavity and far wake regions. The ORD studies are
concentrated on single rectangular buildings, specifically investigating changes in plume parameters
at discrete downwind distances from the building and source, longitudinal and lateral plume
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profiles, the lateral plume shift on the lee side of rotated buildings, and building characterization in
BPIPPRM (Heist et al., 2016; Monbureau et al., 2018). To date, this research has led to
recommended changes to the building preproc essor, 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
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
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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 ORD DWNW options listed are optional, but at least one
must be included if the ORD_ DWNW keyword is specified in the control file.
3.2.4.2 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.
Three ALPHA building downwash options developed by the AWMA have been
implemented in AERMOD and require the ALPHA secondary keyword included with the
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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:
Syntax:
CO AWMADWNW AWMAUEFF
and/or
[AWMAUTURB
with/without STREAMLINE(D)]
Type:
Optional, Non-repeatable
where:
AWMAUEFF - Redefines the height at which the wind speed is taken from the profile
wind speed used in the calculation of concentrations from the primary
plume. The PRIME algorithm currently uses the wind speed at the stack
height. AWMAUEFF uses the wind speed at the height of the plume
centerline.
NOTE: AWMAUEFF cannot be used in combination with the
ORD DWNW option ORDUEFF.
AWMAUTURB - Defines new lower and upper bounds for calculating effective
parameters iueff, sweff, svejf, and tgeff).
STREAMLINE(D) -Reduces dispersion in the wake of streamlined structures such as
storage tanks and cooling towers. Uses the alternate formulations for
turbulence enhancement and velocity deficit associated with the
AWMUTURB option with modifications for streamlined structures.
NOTE: The STREAMLINE option can only be specified in
conjunction with the AWMAUTURB option. When specified,
AERMOD assumes all buildings defined in the input control file
are streamlined structures.
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NOTE: Each of the three AWMADWNW options listed are optional, but at least one
must be included if the AWMADWNW is used. As noted above, STREAMLINE (or
STREAMLINED) can only be used in conjunction with the AWMAUTURB option.
Refer to Section 3.2.17 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 options for modeling the conversion of NO to NO2. 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 and Evaluation Document (EPA, 2018a)).
Additional information regarding 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).
The ARM2 option is based on work sponsored by API (API, 2013) to develop a method to
adjust the modeled NOx concentrations based on an empirical relationship between ambient NOx
and ambient NO2 concentrations. A key difference between the PVMRM and OLM methods, as
compared to the ARM2 method, is that ARM2 does not require the user to input background ozone
(O3) concentrations or in-stack NO2/NOX ratios, as required by PVMRM and OLM; however, the
default minimum ratio utilized in the ARM2 method may not be appropriate in cases where the
sources being modeled are known to have relatively high in-stack Mh/NOx ratios.
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. It is important to note that the
OLM, PVMRM, and ARM2 options are NOT applied to the background NO2 concentrations input
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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. For Tier 2 applications involving temporally-varying background
NO2 concentrations, the ARM2 option in AERMOD should be used to ensure that the ambient
ratios are applied only to the modeled NO2 concentrations before adding the contribution from
background NO2 concentrations.
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.
Note that beginning with version 19191, ARM2 has been implemented for all source
types (POINT, AREA, VOLUME, LINE, BUOYLINE, RLINE and RLINEXT) while
PVMRM and OLM have not been implemented for the BUOYLINE, RLINE and RLINEXT
sources.
3.2.5.1 Specifying ozone concentrations for PVMRM and OLM options
The background ozone concentrations for the PVMRM and OLM 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 in order to
use the PVMRM or OLM options. 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. 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 .
. StartSectN, where N < 6
Type:
Optional, Non-Repeatable
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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 SECTn 03Value (03Units) (w/ sectors)
Type: Optional, Non-repeatable
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 SECTn refers to the user-specified sector
defined on the optional 03 SECTOR keyword for which the 03 Value inputs are applied. 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).
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 SECTn 03Flag 03values(i), i=l,n (w/sectors)
Type: Optional, Repeatable
where the SECTn parameter specifies the applicable sector as defined on the optional 03 SECTOR
keyword, and where 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):
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ANNUAL - annual ozone value (n=l); 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),
HRDOW7 - 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
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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.
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 SECTn 03FileName (03Units) (03Format) (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
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03SECTOR keyword, then the applicable sector ID needs to be specified, e.g., 'SECTT indicates
that values are specified for the first sector. The 03FileName can be up to 200 characters in length
based on the default parameters in AERMOD. Double quotes (") at the beginning and end of the
filename can also be used as field delimiters to allow filenames with embedded spaces.
The hourly ozone file must include the year, month, day, and hour, followed by the ozone
concentration, in that order (unless specified differently through the 03Format parameter). The year
can be specified as either a 2-digit or 4-digit year. If an optional Fortran format is specified using
the 03Format parameter, the year, month, day, and hour variables must be read as integers using the
Fortran 'I' format specifier, and the ozone concentration must be read as a real variable, using the
Fortran 'F,' 'E,' or 'D' format specifiers, e.g., (412,F8.3). Note that ozone values that do not include
decimal places can be read as Fx.O, where x is the length of the data field. However, ozone values
that to not include decimal places may be read incorrectly if the 03Format specified for reading the
data includes decimal places. For example, a value of' 1234' would be interpreted as ' 123.4' if a
format of F4.1 was used. The 03Format parameter must include the open and close parentheses as
shown in the example and may also include embedded spaces if double quotes (") are used to
delimit the field. A warning message will be generated if the specified format does not meet these
requirements, and AERMOD may also issue a fatal error message when reading the file in cases
where real variables are read with an integer format, or vice versa.
If the optional 03Format parameter is missing, then the model will read the ozone data using
a Fortran 'free' format, i.e., assuming that 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
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data.
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 3.2.5.3, 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 NO2/NOX and/or emissions rates are defined. This behavior does not apply to the
AERMOD PVMRM method.
3.2.5.2 Specifying the ambient equilibrium NO2/NOX ratio (PVMRM. OLM)
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. A Mh/NOx equilibrium
ratio other than 0.90 can be specified for either the PVMRM or OLM option through the optional
N02EQUIL keyword on the CO pathway. The syntax of the N02EQUTL 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.
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3.2.5.3 Specifying the default in-stack NCh/NOx ratio (PVMRM OLM)
The PVMRM and OLM 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.
The in-stack NO2/NOX ratio can be specified for the PVMRM or OLM options by using
either the CO N02STACK keyword to specify a default value to be used for all sources, or by using
the SO N02RATIO keyword to specify a value on a source-by-source basis. The SO N02RATIO
keyword can also be used to override the default value for specific sources if the CO N02STACK
keyword has been specified. The syntax of the N02STACK keyword is as follows:
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 N02RATIO 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 and PVMRM options require the user to specify an
in-stack NO2/NOX ratio for each source, using either the CO N02STACK or SO N02RATIO
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 .
. TimeN MONTH PERIOD
Syntax:
or
ANNUAL
Type:
Mandatory, Non-repeatable
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where the parameters Timel . . . TimeN refer to the user-specified short-term averaging periods of
L 2., 3, 4, 6, 8, 12, and/or 24 hours, the secondary keyword MONTH refers to monthly averages (for
calendar months), the secondary keyword PERIOD refers to the average for the entire data period,
and the secondary keyword ANNUAL refers to an annual average. Any of the short-term averaging
periods listed above may be selected for a given run. Since the monthly averages are treated as
short-term averages, the user can select appropriate output options, such as the second highest
values by receptor, on the OU pathway. The location of the PERIOD or ANNUAL keyword in the
parameter list is not critical. The order of the short-term averaging periods (including MONTH) is
also not critical, although it does control the order of the averaging period result tables in the main
output file. Generally, it is recommended that the short-term averaging periods be input in
increasing order, unless there is a clear advantage in doing otherwise.
The user may specify either the PERIOD keyword or the ANNUAL keyword, but not both.
For concentration calculations for a single year data file, the PERIOD and ANNUAL keywords
produce the same results. However, the ANNUAL average option applies only to complete
years of data, and for multi-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.
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3.2.7 Performing multiple year analyses with MULTYEAR option
The MULTYEAR keyword on the CO pathway provides an option for the user to perform a
multiple year analysis such as would be needed to determine the "high-sixth-high in five years"
design value for determining PM-10 impacts without the need for postprocessing of multiple
concentration files, and for multiple year analyses associated with the 24-hour PM2.5 NAAQS and
1-hour NO2 and SO2 NAAQS which are based on concentrations averaged across the number of
years processed. More information regarding the 24-hour PM2.5 and 1-hour NO2 and SO2 NAAQS
is provided in Sections 3.2.15 and 3.2.16. Since the multiple year option makes use of the model
re-start capabilities described in the Section 3.2.14, 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.
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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 of the applicable modeling options, the source
inventory data, the receptor locations, the meteorology options for the first year and the output file
options. To obtain the PM-10 design value, be sure to include the SIXTH highest value on the OU
RECTABLE card (see Section 3.7.1). For the CO MULTYEAR card for the first year, the user
would only specify the Savfil parameter, and may use a card such as:
CO MULTYEAR YEAR1. SAY
For the subsequent years, the user could copy the input file created for Year-1 and edit the files to
change the year parameters and meteorology filename on the ME pathway (and possibly in the title
information) and edit the MULTYEAR cards. For the subsequent years, both the Savfil and Inifil
parameters must be specified, with the Savfil for Year-1 becoming the Inifil for Year-2, and so on.
The MULTYEAR cards (one for each AERMOD run) might look like this:
CO MULTYEAR YEAR1.SAV (First year)
CO MULTYEAR YEAR2.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
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may be applicable for large domains that encompass more than one identifiable urban area where
the separation is large enough to warrant separate treatment of the urban boundary layer effects.
Use of the option for multiple urban areas eliminates the need for post-processing for such
applications. The urban area(s) are defined using one or more instances of the URBANOPT
keyword on the CO pathway. The sources that are to be modeled with urban effects and the urban
area that will be applied to each source are identified using the URBANSRC keyword on the SO
pathway (see Section 3.3.10). The syntax and type of the URBANOPT keyword are summarized
below:
For Multiple Urban Areas:
CO URBANOPT UrbanID UrbPop (UrbName) (UrbRoughness)
Syntax:
For Single Urban Areas:
CO URBANOPT UrbPop (UrbName) (UrbRoughness)
Type:
Optional, Repeatable for multiple urban areas
where the UrbanID parameter is the alphanumeric urban ID defined by the user (up to eight
characters) when multiple urban areas are defined, the UrbPop parameter specifies the population of
the urban area, the optional UrbName parameter may be used to identify the name of the urban area,
and the optional UrbRoughness parameter may be used to specify the urban surface roughness
length. Note the UrbName must be specified if the user wants to specify the urban roughness
length. A default value of 1.0 meter will be used for the urban roughness length if the
UrbRoughness parameter is omitted. Beginning with version 09292, any value for the urban
roughness length other than 1.0 meter will be treated as a non-regulatory option. Caution should be
used when specifying a non-default urban roughness length, and use of a non-default value should
be clearly documented and justified. Note that the syntax of the URBANOPT keyword for single
urban areas has not changed from previous versions of AERMOD, so that existing input files will
not require modification.
Beginning with version 19191, the urban modeling option has been incorporated as an
ALPHA option for the BUOYLINE, RLINE, and RLINEXT source types.
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3.2.9 Specifying the pollutant type
The POLLUTID keyword is used to identify the type of pollutant being modeled for a
particular run. The syntax, type, and order of the POLLUTID keyword are summarized below:
Syntax:
CO POLLUTID Pollut (H1H or H2H or INC)
Type:
Mandatory, Non-repeatable
where the Pollut parameter may be a pollutant name of up to eight characters. Examples include
SQ2. NOX. CO. PM10. TSP. and OTHER. Some pollutant names, by themselves or in
combination with other model options, have special meaning and will affect how AERMOD
computes the final results based on the current NAAQS. The parameters H1H, H2H, and INC
disable the special processing requirements associated the 1-hr NO2 and SO2 NAAQS and the 24-hr PM2.5
NAAQS. Specifying one of these keywords will allow for modeling PM2.5 24-hr increments which are based
on the H2H value, and also allow evaluating NO2 options in AERMOD based on incomplete years of field
measurements. The pollutants names with special meaning that will affect how AERMOD computes
the results include:
• PM10 (orPM-10) with the multi-year option for generating the high-sixth-high in five
years (see Section 3.2.15.2),
• PM25 (or PM-2.5. PM2.5. orPM-25^) (see Section 3.2.15.11
• NQ2 when computing 1-hour averages (See Sections 3.2.7 and 3.2.16),
• N02 is required when using OLM or PVMRM options for simulating the conversion
of NO to NO2 (see Section 3.2.2.7),
• S02 when computing 1-hour averages (see Sections 3.2.7 and 3.2.16),
• S02 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.
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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.
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.
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NOTE: Flagpole receptors are not applicable to the buoyant line sources defined with
the source type keyword BUOYLINE. (See Sections 3.3.1 and 3.3.2.10 for more information
about the integration of buoyant line sources and their use in AERMOD). All receptors are
assumed to be at ground-level (surface) when computing concentrations from BUOYLINE
source types. Collocated receptors at different flagpole heights will be treated as ground-level
receptors and the contributions from BUOYLINE sources will be identical for those
receptors.
3.2.12 To run or not to run - that is the question
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
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
3.2.13 Generating an input file for EVENT processing
The AERMOD model contains the EVENTFIL keyword on the CO pathway to control
whether or not the AERMOD model will generate an input file for EVENT processing. The syntax
and type of the EVENTFIL keyword are summarized below:
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Syntax:
CO EVENTFIL (Evfile) (Evopt)
Type:
Optional, Non-repeatable
where the optional Evfile parameter specifies the name of the EVENT input file to be generated (the
maximum length of the file name is set by the ILENFLD parameter in MODULE MAIN1), and
the optional parameter, Evopt, specifies the level of detail to be used in the EVENT output file.
Valid inputs for the Evopt parameter are the secondary keywords of SOCONT and DETAIL (see
the EVENTOUT keyword on the OUtput pathway, Section 3.7.2). The default filename used if no
parameters are specified is EVENTS.INP, and the default for the level of detail is DETAIL. If only
one parameter is present, then it is taken to be the Evfile, and the default will be used for Evopt.
The primary difference between routine AERMOD and EVENT processing is in the
treatment of source group contributions. The AERMOD model treats the source groups
independently. EVENT processing is designed to provide source contributions to particular events,
such as the design concentrations determined from AERMOD, or user specified events. The user
may specify the "events" to process using the EVent pathway, which lists specific combinations of
receptor location, source group, and averaging period. By specifying the EVENTFIL keyword, an
input control file will be generated that can be used directly for EVENT processing. The events
included in the generated EVENT processing input file are the design concentrations defined by the
RECTABLE keyword and the threshold violations identified by the MAXIFILE keyword on the
OU pathway.
3.2.14 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: CO INITFILE (Inifil)
Type: Optional, Non-repeatable
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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 that the
power failure or interrupt might occur while the temporary file is open and the intermediate results
are being copied to it. In such a case, the temporary results file would be lost.
The optional Dayinc parameter allows the user to specify the number of days between
successive dumps. The default is to dump values at the end of each day, i.e., Dayinc = 1. For larger
modeling runs, where the SAVEFILE option is most useful, the additional execution time required
to implement this option is very small compared to the total runtime. To be most effective, it is
recommended that results be saved at least every 5 days.
If no parameters are specified for the SAVEFILE keyword, then the model will store
intermediate results at the end of each day using a default filename of TMP.FIL.
The INITFILE keyword works in conjunction with the SAVEFILE keyword and instructs
the model to initialize the results arrays from a previously saved file. The optional parameter, Inifil,
identifies the unformatted file of intermediate results to use for initializing the model. If no Inifil
parameter is specified, then the model assumes the default filename of TMP.FIL. If the file doesn't
exist or if there are any errors encountered in opening the file, then a fatal error message is
generated, and processing is halted.
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.
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3.2.15 Processing for particulate matter (PM) NAAQS
3.2.15.1 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, 2014) 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, 2017) for use of 5 years of National Weather Service (NWS) data, and the
5-year average of modeled impacts serves as an unbiased estimate of the 3-year average for
purposes of modeling demonstrations of compliance with the NAAQS.
Based on EPA's May 2014 draft recommendations, the 24-hour modeled contribution to the
design value for purposes of modeling demonstrations of compliance with the PM-2.5 NAAQS is
based on the highest of the eighth-highest (H8H) concentrations at each receptor, if one year of site-
specific meteorological data is input to the model, or the highest of the multi-year average of the
eighth-highest (H8H) concentrations at each receptor, if more than one year of meteorological data
is input to the model. In other words, the model calculates the eighth-highest 24-hour concentration
at each receptor for each year modeled, averages those eighth-highest concentrations at each
receptor across the number of years of meteorological data, and then selects the highest, across all
receptors, of the N-year averaged eighth-highest values.
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Similar to the 24-hour averages, an unbiased estimate of the 3-year average annual mean is
simply the annual mean, if only one year of site-specific meteorological data is input to the model,
or the multi-year average of the annual means if multiple years of meteorological data are used.
The annual design value for PM-2.5 is then based on the highest annual average across the receptor
domain for single-year meteorological data input, or the highest of the multi-year averaged annual
means across the receptor domain for multi-year meteorological data input.
The special processing of the 24-hour and annual averages for the PM-2.5 NAAQS is
triggered by specifying a pollutant ID of 'PM25', 'PM-2.5', 'PM2.5' or 'PM-25' on the CO
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
3.7.2.8) to determine contributions from other source groups to the cumulative modeled design
value will not work with the MULTYEAR option or with separate meteorological data files for
each year.) Processing the average of the individual annual mean values across multiple years for
PM-2.5 also requires use of the ANNUAL average option on the AVERTIME keyword, rather than
PERIOD average. The PERIOD option computes a single multi-year average concentration for
each receptor, which may give slightly different results than the multi-year average of individual
ANNUAL mean concentrations due to differences in the number of calms and/or missing data from
year to year.
In order 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
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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.
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
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EVENTFIL option will be ignored.
3.2.15.2 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.
3.2.16 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; and EPA, 2011). 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
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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
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 S02 or N02 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 a 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).
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3.2.17 Debugging output option
The DEBUGOPT keyword on the CO pathway allows the user to request detailed files of
intermediate calculation results for debugging purposes. There are a number of 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. 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:
CO DEBUGOPT MODEL (DbefiD
and/or
METEOR (Dbmfil)
and/or
PRIME (Prmfil)
and/or
Syntax:
AWMADW (AwmaDwfil)
and/or
DEPOS
and/or
[AREA (AreaDbFil) or LINE (LineDbFil)]
and/or
[PVMRM (Dbpvfil) or OLM (OLMfil) or ARM2 (ARM2fil)l
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
• DEPOS: Deposition debug information. Only default filenames will be used:
GDEP.DAT for gas deposition and PDEP.DAT for particle deposition.
• AREA, (AreaDbFil) or LINE, (LineDbFil): Area or Line source debugging data
(includes OPENPIT). May only specify one.
• PVMRM, (Dbpvfil) or OLM, (OLMfil) or ARM2 (ARM2fil): NO to NO2 conversion
debug data. Default filenames: PVMRM.DBG, OLM.DBG, ARM2.DBG,
respectively. May only specify one, consistent with the N02 conversion option
specified with the MODELOPT keyword.
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Use the DEBUGOPT keyword with CAUTION: it can produce very large files! Note that the
model will overwrite the debug files, without warning, if they already exist.
3.2.18 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 also any
informational messages (such as occurrences of calm winds) and quality assurance messages that
are generated. The syntax and type of the ERRORFIL keyword are summarized below:
Syntax: CO ERRORFIL (Errfil)
Type: Optional, Non-repeatable
where the Errfil parameter is the name of the detailed message file. If the optional Errfil parameter
is left blank, then the model will use a default filename of ERRORS.LST. A complete description
of the error and other types of messages generated by the model is provided in APPENDIX C.
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 five source types identified as point, volume,
area sources (including non-buoyant line and open pit sources), non-bouyant line (e.g., roadway
sources), and buoyant line sources. 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
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discussed in the sections specific to applicable keywords. The user may group all of 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 eight characters.
The number of sources is allocated dynamically at the time AERMOD is run. This value, in
concert with the other dynamically allocated arrays and input requirements, is limited only by the
amount of available memory.
3.3.1 Identifying source types and locations
The LOCATION keyword is used to identify the source type and the location of each source
to be modeled. The LOCATION card must be the first card entered for each source since it
identifies the source type, and dictates which parameters are needed and/or accepted. The syntax,
type and order of the LOCATION keyword are summarized below:
When Srctyp = POINT, VOLUME, AREA, AREAPOLY, AREACIRC, or OPENPIT
SO LOCATION Srcid Srctyp Xs Ys (Zs)
When Srctyp = LINE, RLINE, or BUOYLINE
Syntax: 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 eight
characters), Srctyp is the source type, which is identified by one of the secondary keywords -
POINT. VOLUME. AREA. AREAPOLY. AREACIRC. OPENPIT. LINE. RLINE. RLINEXT. or
BUOYLINE. Xs and Ys, are the x and y coordinates of the source location in meters for POINT,
VOLUME, AREA, AREAPOLY, AREACIRC, and OPENPIT 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
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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.
Beginning with version 19191, the RLINE and RLINEXT source types were added to the
SO pathway for roadway sources. The current implementation is based on the numerical
integration and algorithms in the Research LINE-source model, version 1.2, for near-surface
releases (Snyder et al., 2013). The R-LINE model was formulated for flat terrain, and thus requires
FLAT to be in the MODELOPT line of the input file. If FLAT and ELEV are MODELOPTs then
the RLINE or RLINEXT source must have Zs=0.0 or ='FLAT'. 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. Refer to the User's Guide for R-LINE Model Version 1.2 (Snyder and Heist, 2013) for
detailed information about the formulation of RLINE source algorithms.
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. As in BLP, only a single buoyant line source,
comprised of one or multiple lines, can be modeled. Multiple lines are assumed to be parallel,
though each line can have a different length, height, and base elevation. However, 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.
Note that beginning with version 18081, ARM2 has been implemented for all source
types (POINT, AREA, VOLUME, LINE, BUOYLINE, etc.) while PVMRM and OLM have
not been implemented for BUOYLINE sources. ARM2 has been implemented for RLINE and
RLINEXT sources beginning with version 19191.
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
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the buoyant line source algorithm in AERMOD. As stated above, AERMOD can only model a
single buoyant line source, but the source can be comprised of one or multiple lines. 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. 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. Anomalous behavior has been observed in AERMOD (confirmed also in BLP) if
the endpoints of all lines are not entered in the same way. This has been confirmed to be a bug in
BLP that was carried over to AERMOD.
The three area source types, 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 ARE APPLY 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). Beginning with version 12345, a LINE source type was added to
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the SO pathway. 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 and LINE source types do not include the horizontal meander
component in AERMOD. 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 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
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
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are for the center of the source for POINT. VOLUME, and AREACIRC 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 eight 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.
3.3.2 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 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
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card for POINT 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 STACK1 16.71 35.0 444.0 22.7 2.74
where the source ID is STACK1, the emission rate is 16.71 g/s, the release height is 35.0 m, the exit
temperature is 444.0 K, the exit velocity is 22.7 m/s, and the inside stack diameter is 2.74 m. All of
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.
Since the AERMOD model uses direction-specific building dimensions for all sources
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subject to building downwash, there are no building parameters entered on the SRCPARAM card.
Building dimensions are entered on the BUILDHGT, BUILDWID, BUILDLEN, XBADJ, and
YBADJ cards described below in Section 3.3.9.
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. The syntax,
type and order for the SRCPARAM card for VOLUME sources are summarized below:
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.
The following table, 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 3-2. Summary of Suggested Procedures for Estimating Initial Lateral Dimensions oyo
and Initial Vertical Dimensions ozo for Volume and Line Sources
Procedure for Obtaining
Type of Source
Initial Dimension
(a) Initial Lateral Dimension (oy0)
Single Volume Source
Gyo = length of side divided by 4.3
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Line Source Represented by Adjacent Volume oy0= length of side divided by 2.15
Sources (see Figure 1-8 (a) in EPA, 1995a)
Line Source Represented by Separated Volume oy0 = center to center distance divided by 2.15
Sources (see Figure l-8(b) in EPA, 1995a)
(b) Initial Vertical Dimension (oZ0)
Surface-Based Source (he ~ 0) oZ0 = vertical dimension of source divided by 2.15
Elevated Source (he > 0) on or Adjacent to a oZ0 = building height divided by 2.15
Building
Elevated Source (he > 0) not on or Adjacent to oZ0 = vertical dimension of source divided by 4.3
a Building
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 AREACIRC
source keyword may be used to specify a circular-shaped area source (modeled as an equal-area
polygon of 20 sides); and the OPENPIT source type can be used to model open rectangular pits
such as surface coal mines and rock quarries. The OPENPIT source type also includes an optional
rotation angle. The source parameter inputs for each of the area source types is described below.
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3.3.2.4 AREA source inputs
The rotation angle for rectangular AREA sources is specified relative to the vertex used to
define the source location on the SO LOCATION card (e.g., the southwest corner). The syntax,
type and order for the SRCPARAM card for AREA sources are summarized below:
Syntax: SO SRCPARAM Srcid Aremis Relhgt Xinit (Yinit) (Angle) (Szinit)
Type: Mandatory, Repeatable
Order: Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a
particular source, and the other parameters are as follows:
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
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vertex defined on the SO LOCATION card for this source. Figure 3-1 illustrates the relationship
between the Xinit, Yinit, and Angle parameters and the source location, (Xs,Ys), for a rotated
rectangle. The Xinit dimension is measured from the side of the area that is counterclockwise along
the perimeter from the vertex defined by (Xs,Ys), while the Yinit dimension is measured from the
side of the area that is clockwise from (Xs,Ys). The Angle parameter is measured as the orientation
relative to North of the side that is clockwise from (Xs,Ys), i.e. the side with length Yinit. The
Angle parameter may be positive (for clockwise rotation) or negative (for counterclockwise
rotation), and a warning message is generated if the absolute value of Angle is greater than 180
degrees. The selection of the vertex to use for the source location is not critical, as long as the
relationship described above for the Xinit, Yinit, and Angle parameters is maintained.
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Figure 3-1. Relationship of Area Source Parameters for Rotated Rectangle
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By making the Yinit and Angle parameters optional, the area source input data for the
previous versions of the ISC model can be used with the AERMOD model. The aspect ratio (i.e.,
length/width) for area sources should generally be less than about 100 to 1. If this is exceeded, then
the model will generate a non-fatal warning message, and the user should consider subdividing the
area to achieve a 100 to 1 aspect ratio (or less) for all subareas.
The optional Szinit parameter may be used to specify an initial vertical dimension to the area
source plume, similar to the use of the Szinit parameter for volume sources. This parameter may be
important when the area source algorithm is used to model mechanically generated emission
sources, such as mobile sources. In these cases, the emissions may be turbulently mixed near the
source by the process that is generating the emissions, and therefore occupy some initial depth. For
more passive area source emissions, such as evaporation or wind erosion, the Szinit parameter may
be omitted, which is equivalent to using an initial sigma-z of zero.
An example of a valid SRCPARAM input card for a rectangular area source is given
SO SRCPARAM SLAGPILE 0.00155.0 50.0 100.0 30.0
where the source ID is SLAGPILE, the emission rate is 0.0015 g/(s-m2), the release height is 5.0 m,
the X-dimension is 50.0 m, the Y-dimension is 100.0 m, and the orientation angle is 30.0 degrees
clockwise from North.
Since the numerical integration algorithm can handle elongated areas with aspect ratios of
up to 100 to 1, the AERMOD area source algorithm may be useful for modeling certain types of
line sources. User's now have the option of specifying a line-type source as either AREA or LINE.
There are no restrictions on the placement of receptors relative to area sources for the AERMOD
model. Receptors may be placed within the area and at the edge of an area. The AERMOD model
will integrate over the portion of the area that is upwind of the receptor. However, since the
numerical integration is not performed for portions of the area that are closer than 1.0 meter upwind
of the receptor, caution should be used when placing receptors within or adjacent to areas that are
less than a few meters wide. More technical information about the application of the AERMOD
area source algorithm is provided in Sections 1.2.3 and 2.2.3 of the ISC Model User's Guide -
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Volume II (EPA, 1995b).
3.3.2.5 AREAPOLY source inputs
The AREAPOLY source type may be used to specify an area source as an arbitrarily-
shaped polygon of between 3 and 20 sides (the number of sides allowed may be increased by
modifying the NVMAX parameter in MODULE MAIN1). This source type option provides the
user with considerable flexibility for specifying the shape of an area source. The syntax, type and
order for the SRCPARAM card for AREAPOLY sources are summarized below:
Syntax:
SO SRCPARAM Srcid Aremis Relhgt Nverts (Szinit)
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a
particular source, and the other parameters are as follows:
Aremis - area emission rate in g/(s-m2),
Relhgt - release height above ground in meters,
Nverts - number of vertices (or sides) of the area source polygon,
Szinit - initial vertical dimension of the area source plume in meters (optional).
As with AREA sources, the emission rate for the source is an emission rate per unit area, which is
different from the point and volume source emission rates, which are total emissions for the source.
The locations of the vertices are specified by use of the AREA VERT keyword, which applies only
to AREAPOLY sources. The syntax, type and order for the AREA VERT keyword used for
AREAPOLY sources are summarized below:
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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 LOCATION card, Xs
and Ys. The remaining vertices may be defined in either a clockwise or counter- clockwise order
from the point used for defining the source location.
Receptors may be placed within the area and at the edge of an area. The AERMOD model
will integrate over the portion of the area that is upwind of the receptor. However, since the
numerical integration is not performed for portions of the area that are closer than 1.0 meter upwind
of the receptor, caution should be used when placing receptors within or adjacent to areas that are
less than a few meters wide.
3.3.2.6 AREACIRC source inputs
The AREACIRC source type may be used to specify an area source as a circular shape. The
model will automatically generate a regular polygon of up to 20 sides to approximate the circular
area source. The polygon will have the same area as that specified for the circle. The syntax, type
and order for the SRCPARAM card for AREACIRC sources are summarized below:
Syntax:
SO SRCPARAM Srcid Aremis Relhgt Radius (Nverts) (Szinit)
Type:
Mandatory, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a
particular source, and the other parameters are as follows:
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Aremis - area emission rate in g/(s-m2),
Relhgt - release height above ground in meters,
Radius - radius of the circular area in meters,
Nverts - number of vertices (or sides) of the area source polygon (optional, 20 sides
will be used if omitted),
Szinit - initial vertical dimension of the area source plume in meters (optional).
As with AREA sources, the emission rate for the source is an emission rate per unit area, which is
different from the point and volume source emission rates, which are total emissions for the source.
3.3.2.7 OPENPIT source inputs
The AERMOD model accepts rectangular pits with an optional rotation angle specified
relative to a north-south orientation and the vertex used to define the source location on the SO
LOCATION card (e.g., the southwest corner). The syntax, type and order for the SRCPARAM
card for OPENPIT sources are summarized below:
Syntax: SO SRCPARAM Srcid Opemis Relhgt Xinit Yinit Pitvol (Angle)
Type: Optional, Repeatable
Order: Must follow the LOCATION card for each source input
where the Srcid parameter is the same source ID that was entered on the LOCATION card for a
particular source, and the other parameters are as follows:
Opemis - open pit emission rate in g/(s-m2),
Relhgt - average release height above the base of the pit in meters,
Xinit - length of X side of the open pit (in the east-west direction if Angle is 0 degrees) in
meters,
Yinit - length of Y side of the open pit (in the north-south direction if Angle is 0 degrees) in
meters,
Pitvol - volume of open pit in cubic meters, and
Angle - orientation angle for the rectangular open pit in degrees from North, measured positive
in the clockwise direction (optional).
The same emission rate is used for both concentration and deposition calculations in the
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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,
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:
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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),
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. 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.
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3.3.2.9 RLINE and RLINEXT source inputs
Beginning with version 19191, use of the RLINE and RLINEXT source types require use of
the non-regulatory BETA and ALPHA flags, respectively for the Control pathway MODELOPT
keyword. As the BETA flag is required for RLINE and the ALPHA flag is required for RLINEXT,
the RLINE and RLINEXT source types are currently non-regulatory and can not be used with the
DFAULT option. In addition, the FLAT MODELOPT flag is also required if any RLINE or
RLINEXT sources are included in the AERMOD run. If FLAT and ELEV are used, Zs for all
RLINE and RLINEXT sources needs to be =0.0 or ='FLAT'. As RLINE was formulated as a flat
terrain model, receptor flagpole heights are used as receptor heights, while elevation and hill heights
are currently ignored.
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 calulations, but parameter
definition is different for each source type.
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:
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),
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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 calcualtions by simply changing the source type from LINE to RUNE. The
syntax, type and order for the SRCPARAM card for RLINEXT sources are summarized below:
Syntax:
SO SRCPARAM Srcid Qemis 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:
Qemis3 - roadway source emission rate in g/s/m,
DCL - 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 - width for each source in meters (e.g., for a one lane source, Width would be the width of
the lane),
Szinit - initial vertical dimension of the line source in meters.
All parameters are required for an RLINEXT source type, however, the user may enter "0"
for any unused parameters. The RLINEXT source emission rate is in grams/second/meter and the
model assumes 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
RLINE and RLINEXT sources should be in g/hr/link.
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
3 Alternatively, the user may specify emissions units of grams per link per hour for the RLINE and RLINEXT source
types using the RLEMCONV keyword on the SO pathway (See Section 3.3.13.)
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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.
Optionally, RLINEXT sources can also contain source configurations to represent solid
barriers or a depressed location. A roadside barrier is specified with the the RBARRIER keyword.
The syntax, type and order for the RBARRIER card for RLINEXT sources are summarized below:
Syntax:
SO RBARRIER Srcid Htwall DCLwall
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
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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,
A roadside located in a depression is specified with the 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:
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 conifgurations 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.
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
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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.
3.3.2.10 BUOYLINE source inputs
The syntax, type and order for the SRCPARAM card for BUOYLINE source is 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 .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, issus a warning message, and continues
processing.
The buoyant line source also requires the user to enter average values representative of the
source as a whole and not for the individual lines that comprise the buoyant line source. These are
entered as parameters on the BLPINPUT keyword:
Syntax:
SO BLPINPUT Blavgblen Blavgbhgt Blavgbwid Blavglwid Blavgbsep Blavgfprm
Type:
Mandatory, Non-Repeatable
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):
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Blavgblen (L) -
Blavgbhgt (HB) -
Blavgbwid (WB) -
Blavglwid (WM) -
Blavgbsep (DX) -
Blavgfprm (FPRIME)
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).
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 mVmol). Values of the physical
parameters for several common pollutants may be found in the appendices to the ANL report
(Wesely, et. al, 2002).
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
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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
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 [^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 [^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.
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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
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
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pathway. The syntax, type, and order for the METHOD2 keyword are summarized below:
Syntax:
SO METHOD 2 Srcid (or Srcrng) FineMassFraction Dmm
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Srcid or Srcrng identify the source or sources for which the inputs apply, the parameter
FineMassFraction is the fraction (between 0 and 1) of particle mass emitted in the fine mode, less
than 2.5 microns, and Dmm is the representative mass-mean aerodynamic particle diameter in
microns. Estimated values of fine particle fractions and mass mean diameters for various pollutants
are provided in Appendix B of the ANL report (Wesely, et al, 2002).
3.3.5 Specifying Emission and Output Units
Since the AERMOD model allows for both concentration and deposition to be output in the
same model run, the EMISUNIT keyword (see Section 3.3.13) cannot be used to specify emission
unit factors if more than one output type is being generated. The AERMOD model therefore allows
for concentration and deposition units to be specified separately through the CONCUNIT and
DEPOUNIT keywords, respectively. The syntax and type of the CONCUNIT keyword are
summarized below:
Syntax:
SO CONCUNIT Emifac Emilbl Conlbl
Type:
Optional, Non-repeatable
where the parameter Emifac is the factor to convert emission rate input units to the desired output
units, Emilbl is the label for the emission input units (up to 40 characters), and Conlbl is the output
unit label (up to 40 characters) for concentration calculations. 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
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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.
3.3.6 Source input parameters for NO2 conversion options
Note that beginning with version 18081, ARM2 has been implemented for all source
types (POINT, AREA, VOLUME, LINE, BUOYLINE, etc.) while PVMRM and OLM have
not been implemented for BUOYLINE sources. Beginning with version 19191, ARM2 has
been implemented for the RLINE and RLINEXT source types while PVMRM and OLM have
not been implemented for the RLINE and RLINEXT source types.
3.3.6.1 Specifying in-stack NCh/NOx ratios by source for PVMRM and OLM
As noted above, the PVMRM, and OLM 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:
Syntax:
SO N02RATIO SrcID or SrcRange N02Ratio
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the SrcID or SrcRange identify the source or sources for which the inputs apply, and where
the N02Ratio parameter specifies the in-stack ratio. In this way, the user can specify a single
in-stack NO2/NOX ratio for a group of stacks. For example, the following input:
SO N02RATIO 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 N02RATIO card will override the default ratio, if any,
specified on the CO N02STACK card. Users should note that while SO N02RATIO is an optional
keyword, the PVMRM and OLM options require the user to specify an in-stack NO2/NOX ratio for
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each source, using either the CO N02STACK (Section 3.2.5.3) or SO N02RATI0 cards, or both.
3.3.6.2 Specifying combined plumes for OLM
The OLM option for modeling NO2 conversion includes an option for specifying which
sources are to be modeled as combined plumes, i.e., where the NOx within the plumes competes for
the available ambient ozone. Sources which are not specified for modeling as combined plumes
will be modeled as individual plumes, i.e., where all of the ambient ozone is available for
conversion of NO to NO2. The selection of individual or combined plume option for OLM is
specified through the OLMGROUP keyword on the SO pathway. The syntax of the OLMGROUP
card is as follows:
Syntax:
SO OLMGROUP OLMGrpID SrcID's and/or SrcRange's
or
SO OLMGROUP ALL
Type:
Optional, Repeatable (except for OLMGROUP ALL)
Order:
Must follow the LOCATION card for each source input;
OLMGROUP ALL must follow the LOCATION card for all sources
where OLMGrpID identifies a group to be treated as a combined plume with OLM, and the SrcID's
and/or SrcRange's identify the sources to be included in the OLM group. As with the SO
SRCGROUP card, individual source IDs and source ranges may be used on the same record, and if
more than one input card is needed to define the sources for a particular OLM group, then
additional records may be input by repeating the pathway, keyword and OLM group ID. A user can
also specify an OLMGrpID of ALL, which means that OLM will be applied on a combined plume
basis to all sources. However, unlike the SO SRCGROUP card, the results will not be output for a
specific OLM group unless the same group of sources is also identified on a SRCGROUP card.
Another constraint for the OLMGROUP keyword is that a source cannot be included in more than
one OLM group.
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
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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 NO2/NOX ratios for the ARM2 option
The ARM2 option in AERMOD is based on applying an ambient ratio of NO2/NOX to a
modeled NOx concentration to estimate ambient NO2 concentrations. The ARM2 option applies an
ambient ratio to the 1-hr modeled NOx concentrations based on a formula derived empirically from
ambient monitored ratios of NO2/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 ozone-limiting effects of the PVMRM option, the predicted concentrations of
NO2 are not linearly proportional to the emission rate. Therefore, the approach of modeling NO2
increment consumption with PSD credits through the use of a negative emission rate for credit
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sources cannot be used with the PVMRM option. However, the ALPHS 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 option is specified, and no comparable option is available for modeling increment
credits with the OLM option. The user should check with the appropriate reviewing authority for
further guidance on modeling increment credits for NO2.
A general discussion of concepts related to modeling increment consumption is provided
below, followed by a description of inputs required to use the ALPHA PSDCREDIT option for
PVMRM.
3.3.7.1 Increment consuming and baseline sources
Increment is the maximum allowable increase in concentration of a pollutant above a
baseline concentration for an area defined under the Prevention of Significant Deterioration (PSD)
regulations. The PSD baseline area can be an entire State or a subregion of a State such as a county
or group of counties. Increment standards exist for three pollutants: SO2 (3-hr, 24-hr, and annual
averages), NO2 (annual average), and PM-10 (24-hr and annual average). 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
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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
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
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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)
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. In order 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.
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3.3.7.3 Specifying source groups under the PSDCREDIT option
The PSDCREDIT option introduces limitations on grouping sources in order 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
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
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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 ID's 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.
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
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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.
3.3.8.1 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:
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SO BACKGRND BGflag BGvalue(i), i=l,n
Syntax:
and/or
SO BACKGRND HOURLY BGfilnam (BGformat)
Type:
Optional, Repeatable
where the BGflag parameter is the variable background concentration flag, BGvalue is the array of
background concentration values associated with BGflag, HOURLY indicates use of an hourly
background file, BGfilnam is the filename for the hourly background data, and BGformat is the
optional Fortran format of the hourly background file ('free' format is used by default). The
BGfilnam can be up to 200 characters in length based on the default parameters in AERMOD.
Double quotes (") at the beginning and end of the filename can also be used as field delimiters to
allow filenames with embedded spaces.
For applications that include sector-varying background concentrations, the syntax of the
BACKGRND keyword is as follows:
SO BACKGRND SECTn BGflag BGvalue(i), i=l,n
Syntax:
and/or
SO BACKGRND SECTn HOURLY BGfilnam (BGformat)
Type:
Optional, Repeatable
where the SECTn parameter identifies the applicable sector as defined on the SO BGSECTOR
keyword, and 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
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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 that commas or spaces separate the data fields, and that
the fields are in the order given above. The date sequence in the background data file must also
match the date sequence in the hourly meteorological data files.
Note that the HOURLY option and an option to specify values based on the BGflag
parameter can both be specified in the same model run. This allows the user to specify background
concentrations on a temporally-varying basis, such as SEASHR. that can be used to substitute for
missing values in an hourly background file. NOTE: AERMOD will issue a fatal error message
and abort processing if missing data are encountered in an HOURLY background file unless
the user provides other temporally-varying background concentrations (e.g., SEASHR, etc.)
to substitute for missing data. Background concentration units can be specified using the
BACKLNIT keyword, described below. If the BACKLNIT 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.
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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 8.3.4.2 of the Guideline, EPA, 2017), which is implemented
within the AERMOD model. 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
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MHRD0W7 - background values vary by month, hour-of-day, and the seven days of the week [M,
Tu, W, Th, F, Sat, Sun] (n=2,016).
The seasons are defined in the following order: Winter (Dec., Jan., Feb.), Spring (Mar.,
Apr., May), Summer (Jun., Jul., Aug.), and Fall (Sep., Oct., Nov.).4 The wind speed categories used
with the WSPEED option may be defined using the ME WINDCATS keyword. If the WINDCATS
keyword is not used, the default wind speed categories are defined by the upper bound of the first
five categories as follows (the sixth category is assumed to have no upper bound): 1.54, 3.09, 5.14,
8.23, and 10.8 m/s. The BACKGRND keyword may be repeated as many times as necessary to
input all of the background values, and repeat values may be used for the numerical inputs,
e.g., 12*25.6 can be used to specify a value of 25.6 for 12 adjacent "cells" within the array of
values.
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).
4 Note that the seasons are based on northern hemisphere seasons. For applications in the southern hemisphere using
the seasonal factors (SEASHR, SHRDOW, and SHRDOW7), background concentrations that would be associated with
the southern hemisphere winter, for example, should be assigned to the summer seasonal background concentrations
input to AERMOD. Similarly, spring southern hemisphere concentrations should be assigned to the fall season
background concentrations input to AERMOD.
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3.3.9 Specifying building downwash information
As noted above, the AERMOD model include algorithms to model the effects of buildings
downwash on emissions from nearby or adjacent point sources. The building downwash algorithms
do not apply to volume or area sources. For a technical description of the building downwash
algorithms in AERMOD, the user is referred to Schulman, et. al. (2000). The AERMOD model uses
direction-specific information for all building downwash cases.
There are five keywords that are used to specify building downwash information:
BUILDHGT, BUILDWID, BUILDLEN, XBADJ, YBADJ. The syntax, type and order for the
BUILDHGT keyword, used to input direction specific building heights, are summarized below:
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 in order for the source ID to be included. If there is no
numeric part, then the ID consists of only one alphabetical part. If the ID begins with a numeric
character, then the initial alphabetical part defaults to a single blank. If there is no trailing
alphabetical part, then the third part also defaults to a single blank part. If the trailing part consists
of more than one alphabetical or numeric field, it is all lumped into one character field. For
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example, the source ID 'STACK2' consists of the parts 'STACK' plus '2' plus a single trailing blank,
''. By comparing the separate parts of the source IDs, it can be seen that STACK2 falls between the
range 'STACK1-STACK10.' For a three-part example, it can also be seen that VENT1B falls
within the range of VENT1A-VENT1C. However, VENT2 does not fall within the range of
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 also 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:
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
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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:
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 3-2 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
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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 3-2 shows the relationship of the projected building to these
distances.
Flow w
1*
J
K
4
Xbadj
k
1
Stack ^
Y rx talong flow;
f
L
P
^Buildleri ^
Projected
Building
Figure 3-2. 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= 1,36
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
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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.
3.3.10 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
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changed from the previous version of AERMOD, so that existing input files will not require
modification. However, beginning with version 12060, users can specify that all sources are to be
treated as urban sources by specifying 'ALL' on the SO URBANSRC keyword for applications
with a single urban area. Since the URBANSRC ALL option is identified during the pre-SETUP
phase, there are no restrictions on the order of the URBANSRC ALL keyword within the SO
pathway.
3.3.11 Specifying variable emission factors (EMISFACT)
The AERMOD model provides the option of specifying variable emission rate factors for
individual sources or for groups of sources. The syntax, type and order of the EMISFACT keyword
are summarized below:
Syntax:
SO EMISFACT SrcID or SrcRange Qflag Qfact(i), i=l,n
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the SrcID parameter is the same source ID that was entered on the LOCATION card for a
particular source. The user also has the option of using the SrcRange parameter for specifying a
range of sources for which the emission rate factors apply, instead of identifying a single source.
This is accomplished by two source ID character strings separated by a dash, e.g., STACK1-
STACK10. The use of the SrcRange parameter is explained in more detail in the description of the
BUILDHGT keyword (see Section 3.3.9).
The parameter Qflag is the variable emission rate flag, and must be specified as one of the
following secondary keywords (the number in parentheses indicates the number of values required
for each option):
SEASON - emission rates vary seasonally (n=4),
MONTH - emission rates vary monthly (n=12),
HROFDY - emission rates vary by hour-of-day (n=24),
WSPEED - emission rates vary by wind speed (n=6),
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SEASHR - emission rates vary by season and hour-of-day (n=96),
HRDOW - emission rates vary by hour-of-day, and day-of-week [M-F, Sat, Sun] (n=72),
HRDOW7 - emission rates vary by hour-of-day, and the seven days of the week [M, Tu, W, Th,
F, Sat, Sun] (n=168),
SHRDOW - emission rates vary by season, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n=288),
SHRDOW7 - emission rates vary by season, hour-of-day, and the seven days of the week [M, Tu,
W, Th, F, Sat, Sun] (n=672),
MHRDOW - emission rates vary by month, hour-of-day, and day-of-week [M-F, Sat, Sun]
(n=864), and
MHRDOW7 - emission rates vary by month, hour-of-day, and the seven days of the week [M, Tu,
W, Th, F, Sat, Sun] (n=2,016).
The Qfact array is the array of factors, where the number of factors is shown above for each
Qflag option. The seasons are defined in the following order: Winter (Dec., Jan., Feb.), Spring
(Mar., Apr., May), Summer (Jun., Jul., Aug.), and Fall (Sep., Oct., Nov.).5 The wind speed
categories used with the WSPEED 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.
3-129
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SO
EMISFACT
STK1
HRDOW
enter 24
hourly scalars for each of the "days"
, first
for Weekdays
(Monday-Friday), then for Saturdays, and 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, and final
ly 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
f
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:
3-130
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Syntax:
SO HOUREMIS Emifil Srcid's (and/or Srcrng's)
Type:
Optional, Repeatable
Order:
Must follow the LOCATION card for each source input
where the Emifil parameter specifies the filename for the hourly emission file, and Srcid or Srcrng
identify the source or sources for which hourly emission rates are included. The Emifil filename
can be up to 200 characters in length based on the default parameters in AERMOD. Double quotes
(") at the beginning and end of the filename can also be used as field delimiters to allow filenames
with embedded spaces. Source ranges, which are described in more detail in Section 3.3.9, are
input as two source IDs separated by a dash, e.g., STACK1-STACK10. The user may include more
than one HOUREMIS card in a control file, if needed to specify additional sources, but there can be
only one hourly emissions file, and therefore the filename must be the same on all HOUREMIS
cards.
The format of each record of the hourly emissions file includes a pathway and keyword (SO
HOUREMIS), followed by the Year, Month, Day, Hour, Source ID, and emission rate (in the
appropriate units). For POINT sources, the stack gas exit temperature (K), and stack gas exit
velocity (m/s) are also specified. Beginning with version 09292, the release heights and initial
dispersion coefficients can also be varied on an hourly basis for AREA, AREAPOLY, AREACIRC,
and VOLUME sources using the HOUREMIS option. 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
3-131
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hour using the buoyancy values specified for each individual line that comprises the buoyant line
source.
The hourly emissions file is processed using the same routines used to process the control
file, therefore each of the parameters must be separated by at least one space, but otherwise the
format is flexible. It is also not necessary to include the SO HOUREMIS on each line, as long as the
parameters (Year, Month, etc.) do not begin before column 13. The data in the hourly emission file
must also include the exact same dates as are included in the meteorological input files, and the
source IDs must correspond to the source IDs defined on the SO LOCATION cards and be in the
same order as defined in the 'aermod.inp' file.
The model will check for a date mismatch between the hourly emissions file and the
meteorological data, and also for a source ID mismatch. 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:
3-132
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so
HOUREMIS 8i
3
1
1
VOL1
500.0
2.0
2.0
2.0
so
HOUREMIS 8i
3
1
1
AREA1
5.000
2.0
2.0
so
HOUREMIS 8i
3
1
2
VOL1
500.0
2.0
2.0
3.0
so
HOUREMIS 8i
3
1
2
AREA1
5.000
2.0
3.0
so
HOUREMIS 8i
3
1
3
VOL1
500.0
2.0
2.0
4.0
so
HOUREMIS 8i
3
1
3
AREA1
5.000
2.0
4.0
For POINT 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
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
3-133
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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 19191
to 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:
3-134
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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 C). 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 2.3.8), 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
3-135
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where the Grpid parameter is an alphanumeric string of up to eight characters that identifies the
group name. The Srcid's and Srcrng's are the individual source IDs and/or source ranges that make
up the group of sources. Source ranges, which are described in more detail in the description of the
BUILDHGT keyword (Section 3.3.9), are input as two source IDs separated by a dash, e.g.,
STACK1-STACK10. Individual source IDs and source ranges may be used on the same card. If
more than one input card is needed to define the sources for a particular group, then additional cards
may be input, repeating the pathway, keyword and group ID.
A special group ID has been reserved for use in specifying the group of all sources. When
Grpid = ALL, the model will automatically setup a source group called ALL that includes all
sources modeled for that particular run. If desired, the user can setup a group of all sources with a
different group ID by explicitly specifying all sources on the input card(s).
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 1.2.3.6 and 3.2.13, 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 regard 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.
3-136
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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).
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
3-137
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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 ST Art 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:
RE GRIDCART Netid STA
XYINC Xinit Xnum Xdelta Yinit Ynum Ydelta
XPNTS Gridxl Gridx2 Gridx3 .... Gridxn. and
Syntax:
or YPNTS Gridvl Gridv2 Gridv3 .... Gridvn
ELEV Row Zelevl Zelev2 Zelev3 ... Zelevn
HILL Row Zhilll Zhill2 Zhill3 ... Zhilln
FLAG Row Zflael Zflae2 Zflae3 ... Zflaen
END
Type:
Optional, Repeatable
where the parameters are defined as follows:
Netid
Receptor network identification code (up to eight alphanumeric characters)
STA
Indicates the STArt of GRIDCART inputs for a particular network, repeated for each
new Netid
XYINC
Xinit
Xnum
Xdelta
Yinit
Ynum
Ydelta
Keyword identifying uniform grid network generated from x and y increments
Starting x-axis grid location in meters
Number of x-axis receptors
Spacing in meters between x-axis receptors
Starting y-axis grid location in meters
Number of y-axis receptors
Spacing in meters between y-axis receptors
3-138
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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
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.
3-139
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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:
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. 100
. 20C
. 400
. 500.
YPNTS
-500.
-250.
250
. 500
ELEV
1
8*10.
HILL
1
8*50.
FLAG
1
8*10.
ELEV
2
8*20.
HILL
2
8*60.
FLAG
2
8*20.
ELEV
3
8*30.
HILL
3
8*70 .
FLAG
3
8*30.
ELEV
4
8*40.
HILL
4
8*80.
FLAG
4
8*40.
RE
GRIDCART
CAR1
END
The Row parameter on the ELEV. HILL, and FLAG inputs may be entered as either the row
number, i.e., 1, 2, etc., or as the actual y-coordinate value, e.g., -500., -250., etc. in the example
above. The model 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:
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RE GRIDCART CAR1 STA
XPNTS
-500.
-400
YPNTS
-500.
-250
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
-200.
250 .
-100 .
500.
100.
200 .
400. 500.
Of course, one must use either the row number or y-coordinate value consistently within each
network to have the desired result.
The following simple example illustrates the use of the XYINC secondary keyword to
generate a uniformly spaced Cartesian grid network. The resulting grid is 11 x 11, with a uniform
spacing of 1 kilometer (1000. meters), and is centered on the origin (0., 0.). No elevated terrain
heights or flagpole receptor heights are included in this example.
RE
GRIDCART
CGI
STA
XYINC
-5000.
11 1000.
-5000.
11 1000.
RE
GRIDCART
CGI
END
3.4.1.2 Polar grid receptor networks
Polar receptor networks are defined by use of the GRIDPOLR keyword. The GRIDPOLR
keyword may also be thought of as a "sub-pathway," in that there are a series of secondary
keywords that are used to define the start and the end of the inputs for a particular network, and to
select the options for defining the receptor locations that make up the network. The syntax and type
of the GRIDPOLR keyword are summarized below:
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RE GRIDPOLR Netid STA
ORIG Xinit Yinit,
or ORIG Srcid
DIST Ringl Ring2 Ring3 ... Ringn
DDIR Dirl Dir2 Dir3 ... Dim,
Syntax. or GDIR Dirnum Dirini Dirinc
ELEV Dir Zelevl Zelev2 Zelev3 ... Zelevn
HILL Dir Zhilll Zhill2 Zhill3 ... Zhilln
FLAG Dir Zflagl Zflag2 Zflag3 ... Zflagn
END
Type: Optional, Repeatable
where the parameters are defined as follows:
Netid
Receptor network identification code (up to eight alphanumeric characters)
STA
Indicates STArt of GRIDPOLR inputs for a particular network, repeat for each
new Netid
ORIG
Xinit
Yinit
Srcid
Keyword to specify the origin of the polar network (optional)
x-coordinate for origin of polar network
y-coordinate for origin of polar network
Source ID of source used as origin of polar network
DIST
Ringl
Ringn
Keyword to specify distances for the polar network
Distance to the first ring of polar coordinates
Distance to the 'nth' ring of polar coordinates
DDIR
Dirl
Dim
Keyword to specify discrete direction radials for the polar network
First direction radial in degrees (1 to 360)
The 'nth' direction radial in degrees (1 to 360)
GDIR
Dimum
Dirini
Dirinc
Keyword to specify generated direction radials for the polar network
Number of directions used to define the polar system
Starting direction of the polar system
Increment (in degrees) for defining directions
ELEV
Dir
Zelev
Keyword to specify that receptor elevations follow (optional)
Indicates which direction is being input
An array of receptor terrain elevations for a
particular direction radial (default units of meters may be
changed to feet by use of RE ELEVUNIT keyword),
number of entries per radial equals the number of distances for
that network
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HILL
Dir
Zelev
Keyword to specify that hill height scales follow (optional)
Indicates which direction is being input
An array of receptor hill height scales for a
particular direction radial (default units of meters may be
changed to feet by use of RE ELEVUNIT keyword),
number of entries per radial equals the number of distances for
that network
FLAG
Dir
Zflag
Keyword to specify that flagpole receptor heights follow (optional)
Indicates which direction is being input
An array of receptor heights above local terrain
elevation for a particular direction (flagpole
receptors)
END
Indicates END of GRIDPOLR subpathwav. repeat for each new Netid
The ORIG secondary keyword is optional for the GRIDPOLR inputs. If omitted, the model
assumes a default origin of (0.,0.) in x,y coordinates. The ELEV. HILL, and FLAG keywords are
also optional inputs, and are only needed if elevated terrain or flagpole receptor heights are to be
used. If elevated terrain is being used, then both the ELEV and HILL inputs are needed for each
receptor. If the ELEV and HILL keywords are used and the model is being run with the flat terrain
option (see Section 3.2.2), then the elevated terrain height inputs will be ignored by the model, and
a non-fatal warning message will be generated. If the elevated terrain option is selected, and no
elevated terrain heights are entered, the elevations will default to 0.0 meters, and warning messages
will also be generated. The model handles flagpole receptor height inputs in a similar manner.
As with the GRIDCART keyword described above, the order of cards within the
GRIDPOLR subpathway is not important, as long as all inputs for a particular network are
contiguous and start with the STA secondary keyword and end with the END secondary keyword. It
is not even required that all ELEV cards be contiguous, although the input file will be more
readable if a logical order is followed. The network ID is also not required to appear on each
control file command (except for the STA card). The model will assume the previous ID if none is
entered, similar to the use of continuation cards for pathway and keywords.
The following example of the GRIDPOLR keyword generates a receptor network consisting
of 180 receptor points on five concentric distance rings centered on an assumed default origin of
(0.,0.). The receptor locations are placed along 36 direction radials, beginning with 10. degrees and
incrementing by 10. degrees in a clockwise fashion.
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RE
GRIDPOLR
POL1
STA
DIST
100. 300. 500.
1000.
2000.
GDIR
36 10. 10.
RE
GRIDPOLR
POL1
END
Another example is provided illustrating the use of a non-zero origin, discrete direction
radials and the specification of elevated terrain and flagpole receptor heights:
RE
GRIDPOLR
POL1
STA
ORIG
500.
500
DIST
100.
300
500.
1000. 2000.
DDIR
90.
180
270.
360 .
ELEV
90.
5.
10
15.
20.
25.
ELEV
180.
5.
10
15.
20.
25.
ELEV
270.
5.
10
15.
20.
25.
ELEV
360.
5.
10
15.
20.
25.
HILL
90.
50.
60
75.
80.
95.
HILL
180.
50.
60
75.
80.
95.
HILL
270.
50.
60
75.
80.
95.
HILL
360.
50.
60
75.
80.
95.
FLAG
90.
5.
10
15.
20.
25.
FLAG
180.
5.
10
15.
20.
25.
FLAG
270.
5.
10
15.
20.
25.
FLAG
360.
5.
10
15.
20.
25.
RE
GRIDPOLR
POL1
END
The user has the option of specifying the radial number (e.g. 1, 2, 3, etc.) on the ELEV.
HILL, and FLAG inputs, or the actual direction associated with each radial.
For purposes of model calculations, all receptor locations, including those specified as polar,
are stored in the model arrays as x, y and z coordinates and flagpole heights. For the purposes of
reporting the results by receptor in the main print file, the tables are labeled with the polar inputs,
i.e., directions and distances.
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
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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:
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.
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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 the third parameter will always be used as
Zelev, and it is not possible to use a default value for Zelev while entering a specific value for the
Zflag parameter.
3.4.3.2 Discrete polar receptors
Discrete polar receptors are defined by use of the DISCPOLR keyword. The syntax and
type of this keyword are summarized below:
Syntax:
RE DISCPOLR Srcid Dist Direct (Zelev Zhill) (Zflag)
Type:
Optional, Repeatable
where the Srcid is the alphanumeric source identification for one of the sources defined on the SO
pathway which will be used to define the origin for the polar receptor location. The Dist and Direct
parameters are the 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 hill top 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
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(Section 3.2.11) are used, then the optional parameters are ignored if present. If only the elevated
terrain height option is used (no flagpoles), then the third parameter (the field after the Ycoord) is
read as the Zelev parameter. If only the flagpole receptor height option is used (no elevated
terrain), then the third parameter is read as the Zflag parameter. If both options are used, then the
parameters are read in the order indicated for the syntax above. If the optional parameters are left
blank, then default values will be used. The default value for Zelev is 0.0, and the default value for
Zflag is defined by the CO FLAGPOLE card (see Section 3.2.11). Note: If both the elevated
terrain and flagpole receptor height options are used, then fourth parameter will always be used as
Zelev, and it is not possible to use a default value for Zelev while entering a specific value for the
Zflag parameter.
3.4.3.3 Discrete Cartesian receptors for evalfile output
The EVALCART keyword is used to define discrete Cartesian receptor locations, similar to
the DISCCART keyword, but it also allows for grouping of receptors, e.g., along arcs. It is
designed to be used with the EVALFILE option, described later for the output pathway, which
outputs arc maxima values to a separate file for evaluation purposes. The EVALCART keyword
can be used without the use of the EVALFILE option, in which case the receptor groupings are
ignored. The syntax and type for the modified EVALCART keyword are summarized below:
Syntax:
RE EVALCART Xcoord Ycoord Zelev Zhill Zflag Arcid (Name)
Type:
Optional, Repeatable
where the Xcoord and Ycoord parameters are the x-coordinate and y-coordinate (m), respectively,
for the receptor location. The Zelev parameter is the terrain elevation (m) for the receptor and Zhill
is the corresponding hill top 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.
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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:
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 C). 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 2.3.8), 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.
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3.5 Meteorology pathway inputs and options
The MEteorology pathway contains keywords that define the input meteorological data for a
particular model run.
3.5.1 Specifying the input data files and formats
The AERMOD model uses hourly meteorological data from separate surface and profile
data files as one of the basic model inputs. These input meteorological data filenames for
AERMOD are identified by the SURFFILE and PROFFILE keywords on the ME pathway. The
syntax and type of these keywords are summarized below:
Syntax:
ME SURFFILE Sfcfil (Format)
ME PROFFILE Profil (Format)
Type:
Optional, Repeatable
where the Srcfil and Profil parameters are character fields of up to 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)
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• Hour of Day (1 - 24)
• Heat Flux (W/m2)
• Surface Friction Velocity, u* (m/s)
• Convective Velocity Scale, w* (m/s)
• Lapse Rate above Mixing Height (K/m)
• Convective Mixing Height (m)
• Mechanical Mixing Height (m)
• Monin-Obukhov Length, L (m)
• Surface Roughness Length, zo (m)
• Bowen Ratio
• Albedo
• Reference Wind Speed (m/s)
• Reference Wind Direction (degrees)
• Reference Height for Wind (m)
• Ambient Temperature (K)
• Reference Height for Temperature (m)
• Precipitation Code (0-45)
• Precipitation Amount (mm)
• Relative Humidity (%)
• Surface Pressure (mb)
• Cloud Cover (tenths)
• Wind Speed Adjustment and Data Source Flag
The sensible heat flux, Bowen ratio and albedo are not used by the AERMOD model but are passed
through by AERMET for information purposes only.
The profile meteorological data file consists of one or more records for each hour of data. As
with the surface data file, the data are delimited by at least one space between each element and
may be read as Fortran free format. The contents of the profile meteorological data file are as
follows:
• Year
• Month (1 - 12)
• Day (1-31)
• Hour (1 - 24)
• Measurement height (m)
• Top flag = 1, if this is the last (highest) level for this hour,
0, otherwise
• Wind direction for the current level (degrees)
• Wind speed for the current level (m/s)
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• Temperature at the current level (K)
• Standard deviation of the wind direction, o2 (degrees)
• Standard deviation of the vertical wind speed, cw (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.
3.5.2 Specifying station information
Three keywords are used to specify information about the meteorological stations,
SURFDATA for the surface meteorological station, UAIRDATA for the upper air station, and the
optional SITED ATA for any on-site meteorological data that may be used. The syntax and type of
these keywords are summarized below:
Syntax:
ME SURFDATA Stanum Year (Name) (Xcoord) (Ycoord)
Syntax:
ME UAIRDATA Stanum Year (Name) (Xcoord) (Ycoord)
Syntax:
ME SITED ATA Stanum Year (Name) (Xcoord) (Ycoord)
Type:
Mandatory, Non-repeatable for SURFDATA and UAIRDATA
Optional, Non-repeatable for SITED ATA
where Stanum is the station number, e.g. the 5-digit WBAN number for NWS stations, Year is the
year of data being processed (either 2 or 4 digits), Name is an optional character field (up to 40
characters with no blanks) specifying the name of the station, and Xcoord and Ycoord are optional
parameters for specifying the x and y coordinates for the location of the stations. Note: The Year
should indicate the first year of data that are present in the meteorological data regardless if
only a subset of complete temporal period will be modeled by AERMOD using the
STARTEND keyword (Section 3.5.4). At the present time, the station locations are not utilized in
the model. Therefore, no units are specified for Xcoord and Ycoord at this time, although meters
are suggested in order to be consistent with the source and receptor coordinates. The AERMOD
model compares the station numbers input using these keywords with the numbers included in the
header record of the surface meteorological data file, and issues non-fatal warning messages if there
are any mismatches.
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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 PROFB ASE
keyword. The syntax and type for the PROFB ASE keyword are summarized below:
Syntax: ME PROFB ASE 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. The default for the model is to read the entire meteorological data file (up to a full year)
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
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be used to specify the start and end hours for the data period to be read. If either Strthr or Endhr is
to be specified, then both must be specified. Any records in the data file that occur before the start
date are ignored, as are any records in the data file that occur after the end date. In fact, once the end
date has been reached, the model does not read any more data from the meteorological file. If Strthr
and Endhr are not specified, then processing begins with hour 1 of the start date, and ends with hour
24 of the end date, unless specific days are selected by the DAYRANGE card described below.
Any PERIOD averages calculated by the model will apply only to the period of data actually
processed. Therefore, if someone wanted to calculate a six-month average, they could select
PERIOD averages on the CO AVERTIME card, and then specify the period as follows:
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 Range3 ... Rangen
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.
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As with the STARTEND keyword, any PERIOD averages calculated by the model will
apply only to the period of data actually processed. If the STARTEND keyword is also used, then
only those days selected on the DAYRANGE cards that fall within the period from the start date to
the end date will be processed. Thus, if the ME pathway included the following two cards:
ME
STARTEND
87 02 01
87 12 31
ME
DAYRANGE
1-31
then no data would be processed, since the days 1 through 31 are outside the period 2/1 to 12/31.
3.5.5 Correcting wind direction alignment problems
The WDROTATE keyword allows the user to correct the input meteorological data for wind
direction alignment problems. All input wind directions or flow vectors are rotated by a user-
specified 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
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for the wind speed categories are as follows: 1.54, 3.09, 5.14, 8.23, and 10.8 m/s. The syntax and
type of the WINDCATS keyword, which may be used to specify different category boundaries, are
summarized below:
Syntax:
ME WINDCATS Wsl Ws2 Ws3 Ws4 Ws5
Type:
Optional, Non-repeatable
where the Wsl through Ws5 parameters are the upper bound wind speeds of the first through fifth
categories in meters per second. The upper bound values are inclusive, i.e., a wind speed equal to
the value of Wsl will be placed in the first wind speed category.
3.5.7 Specifying SCIM parameters
The SCIM parameters on the SCIMBYHR card specify the starting hour and sampling
interval for the regular sample and an optional file name. The syntax and type of the SCIMBYHR
keyword are summarized below:
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
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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).
3.5.8 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 3.7.2.8), with a default value of five (5) years being assumed if the optional
NUMYEARS keyword is omitted. The syntax of the optional NUMYEARS keyword is
summarized below:
Syntax: ME NUMYEARS NumYrs
Type: Optional, Non-repeatable
where NumYrs specifies the number of (full) years of meteorological data being processed.
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.
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The syntax and type of the EVENTPER and EVENTLOC keywords are summarized below:
Syntax: EV EVENTPER Evname Aveper Grpid Date
EV EVENTLOC Evname XR= Xr YR= Yr (Zelev) (Zflag)
ax' Or Evname RNG= Rig DIR= Dir (Zelev) (Zflag)
Type: Mandatory, Repeatable
where the parameters are as follows:
Evname - event name (an alphanumeric string of up to 8 characters),
Aveper - averaging period for the event (e.g. J_, 3, 8, 24 hr)
Grpid - source group ID for the event (must be defined on SO pathway),
Date - date for the event, input as an eight-digit integer for the ending hour of the
data period (YYMMDDHH), e.g. 84030324 defines a data period ending at
hour 24 on March 3, 1984. The length of the period corresponds to Aveper.
XR= - X-coordinate (m) for the event location, referenced to a Cartesian coordinate
system
YR= - Y-coordinate (m) for the event location, referenced to a Cartesian coordinate
system
RNG= - distance range (m) for the event location, referenced to a polar coordinate
system with an origin of (0., 0.)
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).
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3.6.1 Using events generated by the AERMOD model
The AERMOD model has an option (CO EVENTFIL described in Section 3.2.13) to
generate an input file for the AERMOD EVENT processing. When this option is used, the
AERMOD model copies relevant inputs from the AERMOD control input file to the Event
processing input file and generates the inputs for the EVent pathway from the results of the
modeling run. These events are the design concentrations identified by the OU RECTABLE
keyword (see Section 3.8.1.1), such as the highest and high-second-high 24-hour averages, etc., and
any threshold violations identified by the OU MAXIFILE keyword (see Section 3.8.1.2). 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
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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 MAXIFILF. option.
3.6.2 Specifying discrete events
The user can specify discrete events by entering the EVENTPER and EVENTLOC cards as
described above. The averaging period and source group selected for the event must be among
those specified on the CO AVERTIME and SO SRCGROUP cards. If the EVENT processing input
file was generated by the AERMOD model, the user may include additional events for those
averaging periods and source groups used in the original AERMOD model run. They may also add
averaging periods or define new source groups in the Event processing input file in order to define
additional events.
3.6.3 Including event data from an external file
The user has the option of including event data from an external file by using the
INCLUDED keyword on the source (EV) pathway. An EV INCLUDED card may be placed
anywhere within the event pathway, after the STARTING card and before the FINISHED card (i.e.,
the EV STARTING and EV FINISHED cards cannot be included in the external file). The data in
the included file will be processed as though it were part of the control file. The syntax and type of
the INCLUDED keyword are summarized below:
Syntax:
EV INCLUDED Incfil
Type:
Optional, Repeatable
where the Incfil parameter is a character field of up to 40 characters that identifies the filename for
the included file. The contents of the included file must be valid control file commands for the
event pathway. If an error is generated during processing of the included file, the error message
will report the line number of the included file (see APPENDIX C). 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 2.3.8), then the control file commands in the included file must be offset by the same
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amount.
3.7 Output pathway inputs and options
The OUtput pathway contains keywords that define the output options for the model runs.
Beginning with version 11059, a number of enhancements have been incorporated in AERMOD to
more fully support the form of more recent 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:
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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. J_, 3, 8 or 24 hr or MONTH) for
which the receptor table is selected, and the secondary keywords, FIRST. SECOND, etc., indicate
which high values are to be summarized by receptor for that averaging period. The RECTABLE
card may be repeated for each averaging period. For cases where the user wants the same
RECTABLE options for all short-term averaging periods being modeled, the input may be
simplified by entering the secondary keyword ALLAVE for the Aveper parameter.
In order to support the implementation of recent guidance regarding modeling to
demonstrate compliance with these NAAQS, the RECTABLE keyword had been modified to allow
user-specified ranks of short-term averages (for all pollutants) up to the 999th highest value. The
previous version of AERMOD was limited to the lOth-highest value and also restricted the rank for
the 24-hour PM2.5 NAAQS to the 8th highest value (corresponding to the 98th percentile of daily
values during a year).
The following example will select summaries of the highest, second highest and third
highest values by receptor for all averaging periods:
OU RECTABLE ALLAVE FIRST SECOND THIRD
The model will also recognize a range of high values on the RECTABLE input card, and therefore
the following card will have the effect:
OU RECTABLE ALLAVE FIRST-THIRD
The output file will include tables for only the high values selected. Tables for all source
groups for a particular averaging period are grouped together, and the averaging periods are output
in the order that they appear the CO AVERTIME card. For each averaging period and source group
combination, the tables of high values for the receptor networks (if any) are printed first, followed
by any discrete Cartesian receptors, and any discrete polar receptors.
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If the CO EVENTFIL keyword has been used to generate an input file for EVENT
processing, then the design values identified by the RECTABLE options, e.g., the high-second-high
24-hour average, are included in the events that are defined in the EVENT processing input file.
If the PLOTFILE (3.7.2.3) and/or MAXDCONT (3.7.2.8) 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 3.7.2.8, 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:
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OU MAXTABLE ALLAVE 5 0
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,
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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 PM2.5, 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 N02 and S02 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.
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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 26-100, 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 3.2.13 and 3.8). 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
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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 2 4
OU MAXIFILE 2 4
OU MAXIFILE 3
OU MAXIFILE 3
ALL 364.0 MAX24ALL. OUT
PSD 91.0 MAXPSD.OUT 50
PSD 3 65.0 MAXPSD.OUT 5 0
PLANT 25.0 C:\OUTPUT\MAXI3HR.FIL
ALL 10.0 MAXMONTH. OUT
OU MAXIFILE MONTH
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
file unit for the output file. The user-specified file unit must be in the range of 26-100, inclusive.
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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 3.8.2).
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
2 4 ALL
UNFORM
PST24ALL.BIN
ou
POSTFILE
24 PSD
UNFORM
PST24PSD.BIN
ou
POSTFILE
3 PLANT
UNFORM
C:\BINOUT\PST3HR.FIL
ou
POSTFILE
MONTH ALL
PLOT
PSTMONTH.PLT
ou
POSTFILE
PERIOD ALL
PLOT
PSTANN.PLT
where the 3-hour example illustrates the use of a DOS pathname for the PC, and the last example
illustrates the use of monthly averages. The Filnam parameter may be up to 200 characters in
length. The use of separate files for each averaging period/source group combination allows the
user flexibility to select only those results that are needed for post-processing for a particular run,
and also makes the resulting unformatted files manageable. Note: The POSTFILE option can
produce very large files and should be used with some caution. For a file of hourly values for a full
year (8760 records) and 400 receptors, the resulting file will use about 14 megabytes of disk space.
To estimate the size of the file (in bytes), use the following equation:
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#Hrs/Yr
File Size (bytes) = - * (# Rec + 4) * 4
J # 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 26-100, 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 3.8.2).
Note: The averaging period and high value for which a PLOTFILE is generated must
also be included on the RECTABLE keyword (see Section 3.7.1). The RECTABLE keyword
entry must be specified on the OU pathway prior to the PLOTFILE entry. However, a
RECTABLE entry is not required for a PLOTFILE generated for the ANNUAL or PERIOD
average.
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The PLOTFILE card may be repeated for each combination of averaging period, source
group, and high value, and a different filename should be used for each file. The resulting
formatted file includes several records with header information identifying the averaging period,
source group and high value number of the results, and then a record for each receptor which
contains the x and y coordinates for the receptor location, the appropriate high value at that location,
and the averaging period, source group and high value number. The data are written to the file in
the order of x-coord, y-coord, concentration so that the file can easily be imported into a graphics
package designed to generate contour plots. Many such programs will read the PLOTFILEs
directly without any modification, ignoring the header records, and produce the desired plots.
The following examples illustrate the use of the PLOTFILE option:
ou
PLOTFILE
24
ALL
FIRST
PLT24ALL.FST
ou
PLOTFILE
24
ALL
SECOND
PLT24ALL.SEC
ou
PLOTFILE
24
PSD
2ND
PLTPSD.OUT 75
ou
PLOTFILE
3
PSD
2ND
PLTPSD.OUT 75
ou
PLOTFILE
3
PLANT
1ST
C:\PLOTS\PLT3HR.FIL
ou
PLOTFILE
MONTH
ALL
THIRD
PLTMONTH.OUT
ou
PLOTFILE
PERIOD
ALL
PSTANN.PLT
where the 3-hour example illustrates the use of a DOS pathname for the PC, and the last example
illustrates the use of monthly averages. As illustrated by the second and third examples, the high
value parameter may also be input as secondary keywords using the standard abbreviations of 1ST.
2ND. 3RD . . . 10TH. The Filnam parameter may be up to 40 characters in length. The use of
separate files for each averaging period, source group, high value combination allows the user
flexibility to select only those results that are needed for plotting from a particular run.
3.7.2.4 TOXXFILE
The syntax and type for the TOXXFILE keyword are summarized below:
Syntax:
OU TOXXFILE Aveper Cutoff Filnam (Funit)
Type:
Optional, Repeatable
where the Aveper parameter is the short-term averaging period (e.g. J_, 3, 8, 24 for 1, 3, 8 and 24-
hour averages, or MONTH for monthly averages) for which the TOXXFILE option has been
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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 26-
100, inclusive. If the Funit parameter is omitted, then the model will dynamically allocate a unique
file unit for this file (see Section 3.8.2). 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
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 3.8.2 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:
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ou
TOXXFILE
1
1.OE-5
TOXXlHR.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
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 26-100, 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:
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IRKUNT = 100 + IAVE
where IRKUNT is the Fortran unit number and IAVE is the averaging period number (the order of
the averaging period as specified on the CO AVERTIME card).
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 26-100, inclusive.
By specifying the same filename and unit for more than one EVALFILE card, results for different
sources may be combined into a single file. If the Funit parameter is omitted, the model will
dynamically allocate a unique file unit for this file according to the following formula:
IELUNT = 400 + ISRC*5
where IELUNT is the Fortran unit number and I SRC 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
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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 26-100, 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:
*
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
1—1
NO
X
1—1
2X,A8
*
*
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
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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.
3.7.2.8 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),
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THRESH indicates that the lower bound rank is determined based on a lower concentration
threshold, ThreshValue is the user-specified concentration threshold for GrpID impacts which
serves as a lower bound on the range of ranks analyzed, FileName is the output file name, and
(FileUnit) is the optional file unit. The filename can be up to 200 characters in length based on the
default parameters in AERMOD. Double quotes (") at the beginning and end of the filename can
also be used as field delimiters to allow filenames with embedded spaces. 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 N02 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 N02 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 3.2.14) on the
CO pathway, or with the MULTYEAR option (Section 3.2.7) on the CO pathway.
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3.7.2.9 MAXDAILY
The MAXDAILY option, introduced with version 11059, is applicable to 1-hour NO2 and 1-
hour SO2 NAAQS and generates a file of daily maximum 1-hour concentrations for a specified
source group, for each day in the data period processed. The MAXDAILY file provides an interim
output that may be useful for analyzing the 1-hour NO2 and SO2 NAAQS. The syntax, type and
order of the optional MAXDAILY keyword are summarized below:
Syntax: OU MAXDAILY GrpID FileName (FileUnit)
Type: Optional, Non-repeatable
where GrpID is the source group selected for daily maximum 1-hour values, FileName is the name
of the MAXDAILY output file, and FileUnit is the optional file unit. The filename can be up to 200
characters in length based on the default parameters in AERMOD. Double quotes (") at the
beginning and end of the filename can also be used as field delimiters to allow filenames with
embedded spaces.
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.
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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.
The syntax, type and order of the optional SUMMFILE keyword are summarized below:
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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.
The syntax, type and order of the optional NOHEADER keyword are summarized below:
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OU NOHEADER FileTypel FileType2 FileType3 ... FileTypeN
Syntax:
or
OU NOHEADER ALL
Type:
Optional, Non-repeatable
where FileTypeN identifies the keywords for formatted output files for which the file headers will
be suppressed, which may include the includes the following file types: POSTFILE, PLOTFILE,
MAXIFILE, RANKFILE, SEASONHR, MAXDAILY, MXDYBYYR, and MAXDCONT. The
keyword ALL may be used to specify that header records will be suppressed for ALL applicable
output file types.
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3.8 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.
3.8.1 Description of AERMOD input files
The two basic types of input files needed to run all of the AERMOD model are the input
control file containing the modeling options, source data and receptor data, and the two input
meteorological data files. Each of these is discussed below, as well as a special file that may be
used to initialize the AERMOD model with intermediate results from a previous run.
3.8.1.1 Input control file
The input control file contains the user-specified options for running the various AERMOD
model (called 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 B.
For the PC-executable version of the model available on the SCRAM website, the control
file is explicitly opened by the model using a Fortran OPEN statement, and the integer variable,
INUNIT, specifies the unit number for the file. The variable INUNIT is initialized to a value of 7 in
a DATA statement in MODULE MAIN1, and is therefore available to all of the necessary
subroutines.
3.8.1.2 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 format 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,
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2018c). The data are read from formatted ASCII files of hourly sequential records.
The meteorological data files are explicitly opened by the model using Fortran OPEN
statements, and the integer variables MFUNIT for the surface/scalar file and MPUNIT for the
profile file are used to specify the unit numbers for the files. The variable MFUNIT is initialized to
a value of 19 and MPUNIT is initialized to a value of 16 in a DATA statement in MODULE
MAIN1, and are therefore available to all of the necessary subroutines.
3.8.1.3 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. The initialization file is explicitly opened by the AERMOD model, and the
integer variable, IRSUNT, specifies the unit number for the file. The variable IRSUNT is
initialized to a value of 15 in a DATA statement in MODULE MAIN1, and is therefore available to
all of the necessary subroutines.
3.8.2 Description of AERMOD output files
The AERMOD model produce a variety of output files, including the main print 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 in detail
below.
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3.8.2.1 Main output file
The AERMOD model produces a main output file of model results called AERMOD.OUT.
The contents and organization of this file were shown in Figure 2-5. This file includes an echo of
the input control file commands at the beginning of the file (up until a NO ECHO input is
encountered). 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 and on the particular
model being run. 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.
For the PC-executable version of the model available on the SCRAM website, the main
output file is explicitly opened by the model using a Fortran OPEN statement, and the integer
variable, IOUNIT, specifies the unit number for the file. The variable IOUNIT is initialized to a
value of 8 in a DATA statement in MODULE MAIN1, and is therefore available to all of the
necessary subroutines.
3.8.2.2 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 C. 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.
The error message file is explicitly opened by the model using a Fortran OPEN statement,
and the integer variable, IERUNT, specifies the unit number for the file. The variable IERUNT is
initialized to a value of 10 in a DATA statement in MODULE MAIN1, and is therefore available to
all of the necessary subroutines.
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3.8.2.3 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. The main save file is explicitly opened by the AERMOD model, and the
integer variable, IDPUNT, specifies the unit number for the file. The variable IDPUNT is
initialized to a value of 12 in a BLOCK DATA subprogram of the model. If a second save file is
used, then it is also opened explicitly, and the integer variable IDPUN2, initialized to a value of 14,
specifies the unit number.
3.8.2.4 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.
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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 26, and are recommended to be less than or equal to 100. 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 9 source groups and up to 9 short-term
averaging periods.
3.8.2.5 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 cone files into a graphics package for plotting. For the unformatted file
option, each file consists of sequential unformatted records of values at each receptor location for
every averaging period calculated. For the plot file format option, each file consists of formatted
records listing the x-coordinate, y-coordinate and concurrent concentration values for each receptor
and for all averaging periods calculated. For certain applications, these files may become quite
large, and should only be used when needed, especially when using the plot format.
The structure of both types of postprocessing file is described in more detail in APPENDIX
C. Each of the postprocessing files selected by the user is opened explicitly by the model as either
an unformatted or a formatted file, depending on the option selected. The filenames are provided
on the input control file command. The user may specify the file unit on the POSTFILE card
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through the optional FUNIT parameter. User-specified units must be greater than or equal to 26, and
are recommended to be less than or equal to 100. 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.
3.8.2.6 High value summary file for plotting
The user may select an option for the AERMOD model to generate a file or files of the
highest concentration values at each receptor suitable for importing into a graphics package in order
to generate contour plots. The OU PLOTFILE keyword controls this option. The user may select
separate files for each averaging period, source group and high value combination for which a plot
file may be needed. Each file includes several records with header information identifying the
averaging period, source group and high value number of the results, and then a record for each
receptor which contains the x and y coordinates for the receptor location, the appropriate high value
at that location, and the averaging period, source group and high value number.
The structure of the plot file is described in more detail in APPENDIX C. Each of the plot
files selected by the user is opened explicitly by the model as a formatted file. The filenames are
provided on the input control file command. The user may specify the file unit on the PLOTFILE
card through the optional FUNIT parameter. User-specified units must be greater than or equal to
26, and are recommended to be less than or equal to 100. 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
IPPUNT = 300 + IGRP* 10
for short-term averages
for PERIOD averages
3-185
-------
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 9 source groups and up to 9 short-term
averaging periods.
3.8.2.7 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
optional Funit parameter. User-specified units must be greater than or equal to 26 and are
recommended to be less than or equal to 100. If no file unit is specified, then the file unit is
determined internally according to the following formula:
ITXUNT = 300 + IAVE
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 4 short-term averaging periods.
3-186
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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 that 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 26 and are recommended to be less than or equal to 100. 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 9 source groups.
3.8.3 Controlling file inputs and outputs (I/O)
3.8.3.1 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, respectively. Therefore, a standard command
line to execute the AERMOD model might look something like this:
where the "DOS prompt" has been given as "C:\>", but may look different on different systems, or
may include a subdirectory specification. The output file generated by the DOS version includes
page feeds that are written directly to the file as part of the header for each page, rather than using
ITXUNT = 500 + IAVE* 10 + IGRP
IPXUNT = 700 + IGRP* 10
for long term averages
for PERIOD averages
C:\> AERMOD
3-187
-------
the Fortran carriage control of'1'. This is accomplished by including a compiler- specific parameter
to set CARRIAGECONTROL = 'Fortran' on the OPEN statement for the output file.
3.8.3.2 Controlling I/O on other computer systems
Since the main input control file and the main output print file are specified internally by
AERMOD, control of I/O on other computer systems will be the same.
3-188
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4.0 References
AECOM, 2010: AERMOD Low Wind Speed Evaluation Study Results, AECOM Environment,
Westford, MA.
API, 2013: Ambient Ratio Method Version 2 (ARM2) for use with AERMOD for 1-hr N02
Modeling: Development and Evaluation Report. American Petroleum Institute, Washington,
DC. http://www.epa.gov/ttn/scram/models/aermod/ARM2 Development and Evaluation Report-
September 20 2013.pdf.
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.
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.
4-1
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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, 2014: 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.
http://www.epa.gov/ttn/scram/guidance/guide/Guidance for PM25 Permit Modeling.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. 2016: AERSCREEN User's Guide. December 2016. Publication No. EPA-454/B-16-004^
Office of Air Quality Planning & Standards, Research Triangle Park, NC.
EPA, 2017: Guideline on Air Quality Models, Appendix W to 40 CFR Part 51. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
http://www.epa.gov/ttn/scram/guidance/guide/appw 17.pdf.
EPA, 2018a: AERMOD Model Formulation and Evaluation Document. EPA-454/R-18-003. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
EPA, 2018b: AERMOD Implementation Guide (Revised March 2018). EPA-454/B-18-003. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
EPA, 2018c: User's Guide for the AERMOD Meteorological Preprocessor (AERMET).
EPA454/B-18-002. U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711.
EPA, 2018d: 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.
Hanrahan, P.L., 1999a. "The plume volume molar ratio method for determining NO2/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 Mh/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.
4-2
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Luhar, A.K., and K. N. Rayner, 2009: "Methods to Estimate Surface Fluxes of Momentum and
Heat from Routine Weather Observations for Dispersion Applications under Stable
Stratification", Boundary-Layer Meteorology., 132, 437-454.
Monbureau, E. M., Heist, D. K., Perry, S. G., Brouwer, L. H., Foroutan, H., Tang, W.,
2018: "Enhancements of AERMOD's building downwash algorithms based on wind tunnel
and Embedded-LES modeling " Atmospheric Environment, 179, 321-330.
Murray, D. R., and N. E. Bowne, 1988: Urban power plant plume studies. EPRI Report No.
EA-5468, Research Project 2736-1, Electric Power Research Institute, Palo Alto, CA.
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.
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.
4-3
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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.
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
Note: Many of the references listed can be found on the U.S. EPA SCRAM website at the following url:
httv://www.eya. sov/ttn/scram/
4-4
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APPENDIX A. Alphabetical keyword reference
This appendix provides an alphabetical listing of all of the primary keywords used by the
AERMOD model. Each keyword is identified as to the pathway for which it applies, the keyword
type (either mandatory or optional, and either repeatable or non-repeatable), and with a brief
description of the function of the keyword. For a more complete description of the primary
keywords, including a list of associated secondary keywords and parameters, refer to the Detailed
Keyword Reference in Section 3.0 or the Functional Keyword/Parameter Reference in APPENDIX
B.
A-l
-------
Keyword
Path
Type
Keyword Description
AREAVERT
SO
M-R
Specifies location of vertices for an AREAPOLY source type
(mandatory if AREAPOLY source is used)
ARMRATIO
CO
O-N
Option to override default minimum and maximum (equilibrium)
ratios for the ARM2 option
AVERTIME
CO
M-N
Averaging time(s) to process
AWMADWNW
CO
O-N
Specifies downwash options developed by AWMA
BACKGRND
so
0 - R
Option to specify temporally varying background concentrations
BACKUNIT
so
O-N
Option to specify units for background concentrations
BGSECTOR
so
O-N
Option to specify wind sectors for use in varying background
concentrations of the pollutant being modeled by wind direction.
BUILDHGT
so
0 - R
Building height values for each wind sector
BUILDLEN
so
0 - R
Building projected length values for each wind sector
BUILDWID
so
0 - R
Building projected width values for each wind sector
CONCUNIT
CO
O-N
Optional conversion factors for emission input units and
concentration output units
DAYRANGE
ME
0 - R
Specifies days or ranges of days to process (default is to process all
data)
DAYTABLE
ou
O-N
Option to provide summaries for each averaging period for each
day processed.
DCAYCOEF
CO
O-N
Optional decay coefficient for exponential decay
DEBUGOPT
CO
O-N
Option to generate detailed result and meteorology files for
debugging purposes
DEPOUNIT
so
O-N
Optional conversion factors for emission input units and deposition
output units
DISCCART
RE
0 - R
Defines discretely placed receptors referenced to a Cartesian
system
DISCPOLR
RE
0 - R
Defines discretely placed receptors referenced to a polar system
ELEVUNIT
SO
RE
Z; Z;
i i
o o
Defines input units for receptor elevations (RE path), or source
elevations (SO path) (defaults to meters)
EMISFACT
SO
0 - R
Optional input for variable emission rate factors
EMISUNIT
SO
O-N
Optional conversion factors for emission units and concentration
units
ERRORFIL
CO
O-N
Option to generate detailed error listing file (error file is mandatory
for CO RUNORNOT NOT case)
EVALCART
RE
0 - R
Defines discretely placed receptor locations referenced to a
Cartesian system, grouped by arc for use with the EVALFILE
output option
A-2
-------
Keyword
Path
Type
Keyword Description
EVALFILE
OU
0 - R
Option to output file of normalized arc maxima for model
evaluation studies
EVENTFIL
CO
O-N
Specifies whether to generate an input file for EVENT model
EVENTLOC
EV
M-R
Describes receptor location for an event
EVENTOUT
OU
M-N
Specifies level of output information provided by the EVENT
model
EVENTPER
EV
M-R
Describes data and averaging period for an event
FILEFORM
OU
O-N
Specify fixed or exponential format for output results files
FINISHED
ALL
M-N
Identifies the end of inputs for a particular pathway
FLAGPOLE
CO
O-N
Specifies whether to accept receptor heights above local terrain (m)
for use with flagpole receptors, and allows for a default flagpole
height to be specified
GASDEPDF
CO
O-N
Option to override default parameters for gas dry deposition
GASDEPOS
SO
0 - R
Specify source parameters for gas deposition algorithms
GASDEPVD
CO
O-N
Option to specify deposition velocity for gas dry deposition
GDLANUSE
CO
O-N
Specify land use categories by sector for gas dry deposition
GDSEASON
CO
O-N
Specify seasonal definitions for gas dry deposition
GRIDCART
RE
0 - R
Defines a Cartesian grid receptor network
GRIDPOLR
RE
0 - R
Defines a polar receptor network
HALFLIFE
CO
O-N
Optional half-life for exponential decay
HOUREMIS
SO
0 - R
Option for specifying hourly emission rates in a separate file
INCLUDED
SO,
RE,
EV
0 - R
Option to include input data from a separate file in the control
filefor the SO and/or RE pathways, or for the EV pathway for
EVENTS
INITFILE
CO
O-N
Option to initialize model from file of intermediate results
generated by SAVEFILE option
LOCATION
SO
M-R
Identifies coordinates for particular source location
LOWWIND
CO
O-N
ALPHA option for low wind conditions that allows user to specify
values for minimum sigma-v, minimum wind speed, and maximum
meander factor
MASSFRAX
SO
0 - R
Optional input of mass fraction for each particle size category
MAXDAILY
OU
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
MAXDCONT
OU
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
A-3
-------
Keyword
Path
Type
Keyword Description
MAXIFILE
OU
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)
MAXTABLE
OU
0 - R
Option to summarize the overall maximum values
METHOD 2
SO
0 - R
Specify optional source parameters for METHOD 2 option for
particle deposition
MODELOPT
CO
M-N
Job control and dispersion options
MULTYEAR
CO
O-N
Specifies that run is part of a multi-year run, e.g., for PM-10 H6H
in five years
MXDYBYYR
OU
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
S02 NAAQS
NOHEADER
OU
O-N
Option to suppress file headers for output file options, e.g.,
POSTFILE, PLOTFILE, MAXDCONT, etc
N02EQUIL
CO
O-N
Option to override default NO2/NOX equilibrium ratio for PVMRM
or OLM
N02RATI0
so
0 - R
Option to specify in-stack NO2/NOX equilibrium ratio for OLM and
PVMRM options by source
N02STACK
CO
O-N
Option to specify default in-stack NO2/NOX equilibrium ratio for
OLM and PVMRM options; may be overridden by N02RATI0
NUMYEARS
ME
O-N
Option to specify the number of years of meteorological data being
processed for purposes of allocating array storage for the OU
MAXDCONT option
OLMGROUP
SO
0 - R
Specifies sources to combine for OLM option for merging plumes
ORDDWNW
CO
O-N
Specifies downwash options developed by ORD
OZONEFIL
CO
O-N
Specifies hourly ozone file for OLM and PVMRM options
OZONEVAL
CO
O-N
Specifies background value of ozone for OLM and PVMRM
options
OZONUNIT
CO
O-N
Option to specify units for temporally-varying ozone
concentrations for the 03VALUES keyword.
03SECT0R
CO
O-N
Option to specify wind sectors for use in varying background ozone
(03) concentrations by wind direction for use with OLM and
PVMRM options.
03VALUES
CO
0 - R
Option to specify temporally varying ozone concentrations for use
with OLM and PVMRM options for estimating NO2
PARTDENS
so
0 - R
Specifies particle density by size category for particle deposition
PARTDIAM
so
0 - R
Specifies particle diameters by size category for particle deposition
PLOTFILE
OU
0 - R
Option to write certain results to a storage file suitable for input to
plotting routines
A-4
-------
Keyword
Path
Type
Keyword Description
POLLUTID
CO
M-N
Identifies pollutant being modeled
POSTFILE
OU
0 - R
Option to write results to a mass storage file for postprocessing
PROFBASE
ME
M-N
Specifies the base elevation for the potential temperature profile
PROFFILE
ME
M-N
Describes input profile meteorological data file
PSDGROUP
SO
0 - R
Specifies source groups for PSDCREDIT option with PVMRM
RANKFILE
OU
0 - R
Option to produce output file of ranked values for Q-Q plots
RECTABLE
OU
0 - R
Option to output high ranked value(s) by receptor
RLEMCONV
SO
0 - N
Option to specify RLINE and RLIENXT emissions in grams per
hour per link
RBARRIER
SO
0 - R
Specifies RLINEXT source configuration parameters for barriers.
RDEPRESS
SO
0 - R
Specifies RLINEXT source configuration parameters for depressed
roadways.
RUNORNOT
CO
M-N
Identifies whether to run model or process setup information only
SAVEFILE
CO
O-N
Option to store intermediate results for later restart of the model
after user or system interrupt
SCIMBYHR
ME
O-N
Specifies sampling parameters for the SCIM option
SEASONHR
OU
0 - R
Option to output values by season and hour-of-day
SITEDATA
ME
O-N
Describes on-site meteorological station
SRCGROUP
SO
M-R
Identification of source groups
SRCPARAM
SO
M-R
Identifies source parameters for a particular source
STARTEND
ME
O-N
Specifies start and end dates to be read from input meteorological
data file (default is to read entire file)
STARTING
ALL
M-N
Identifies the start of inputs for a particular pathway
SUMMFILE
OU
O-N
Option to output summary of high ranked values to separate file
SURFDATA
ME
M-N
Surface meteorological station
SURFFILE
ME
M-N
Describes input surface meteorological data file
TITLEONE
CO
M-N
First line of title for output
TITLETWO
CO
O-N
Optional second line of output title
TOXXFILE
OU
0 - R
Creates output file for use with TOXX model component of
TOXST
UAIRDATA
ME
M-N
Upper air meteorological station
URBANOPT
CO
0 - R
Option to specify population for urban option
URBANSRC
SO
0 - R
Option to specify use of urban option by source
WDROTATE
ME
O-N
Wind direction rotation adjustment
WINDCATS
ME
O-N
Upper bound of wind speed categories
A-5
-------
Keyword
Path
Type
Keyword Description
XBADJ
SO
0 - R
Along-flow distances from the stack to the center of the upwind
face of the projected building
YBADJ
SO
0 - R
Across-flow distances from the stack to the center of the upwind
face of the projected building
Type: M - Mandatory
O - Optional
N - Non-repeatable
R - Repeatable
A-6
-------
APPENDIX B. 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, and within each pathway the order of the
keywords is based on the function of the keyword within the model. The pathways used by the
model are as follows, in the order in which they appear in the control file and in the tables that
follow:
CO - for specifying overall job COntrol options;
SO - for specifying SOurce information;
RE - for specifying REceptor information;
ME - for specifying MEteorology information and options;
EV - for specifying EVent information and options;
OU - for specifying OUtput options.
The pathways and keywords are presented in the same order as in the Detailed Keyword
Reference in Section 3.0, and in the Quick Reference at the end of the manual.
Two types of tables are provided for each pathway. The first table lists all of the
keywords for that pathway, identifies each keyword as to its type (either mandatory or optional
and either repeatable or non-repeatable), and provides a brief description of the function of the
keyword. The second type of table, which takes up more than one page for most pathways,
presents the parameters for each keyword, in the order in which they should appear in the control
file where order is important, and describes each parameter in detail.
The following convention is used for identifying the different types of input parameters.
Parameters corresponding to secondary keywords which should be input "as is" are listed on the
tables with all capital letters and are underlined, although none of the inputs to AERMOD are
treated as case-sensitive. Other parameter names are given with an initial capital letter and are
not input "as is." In all cases, the parameter names are intended to be descriptive of the input
variable being represented, and they often correspond to the Fortran variable names used in the
AERMOD code. Parentheses around a parameter indicate that the parameter is optional for that
keyword. The default that is taken when an optional parameter is left blank is explained in the
B-l
-------
discussion for that parameter.
B-2
-------
Table B-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
O-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
O-N
Optional half life used for exponential decay
DCAYCOEF1
O-N
Optional decay coefficient
GASDEPDF
O-N
Option to override default parameters for gas dry deposition
GASDEPVD
O-N
Option to specify deposition velocity for gas dry deposition
GDLANUSE
O-N
Specify land use categories by sector for gas dry deposition
GDSEASON
O-N
Specify seasonal definitions for gas dry deposition
LOWWIND
O-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
O-N
Specifies downwash options developed by AWMA
ORDDWNW
O-N
Specifies downwash options developed by ORD
N02EQUIL
O-N
Option to override default N02/N0X equilibrium ratio for PVMRM or OLM
N02STACK
O-N
Option to specify default in-stack NO2/NOX equilibrium ratio for OLM and
PVMRM options; may be overridden by N02RATI0 option on SO pathway
ARMRATIO
O-N
Option to override default minimum and maximum (equilibrium) ratios for the
ARM2 option
03SECT0R
O-N
Specifies optional wind sectors for use in varying background ozone (03)
concentrations by wind direction for use with OLM and PVMRM options; can be
used with the OZONEFIL, OZONEVAL, and 03VALUES options.
OZONEFIL
0 - R
Specifies filename for hourly ozone file for use with OLM and PVMRM options
OZONEVAL
0 - R
Specifies background value of ozone for use with OLM and PVMRM options
03VALUES
0 - R
Option to specify temporally varying ozone concentrations for use with OLM and
PVMRM 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
RUNORNOT
M-N
Identifies whether to run model or process setup information only
B-3
-------
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 or not to generate an input file for EVENT processing.
The primary difference between AERMOD "regular" processing and EVENT processing by
AERMOD is in the treatment of source group contributions. The AERMOD model treats the source
groups independently, whereas EVENT processing determines individual source contributions to
particular events, such as the design concentrations determined from AERMOD, or user-specified
events. By specifying the EVENTFIL keyword, an input control file will be generated that can be
used directly for EVENT processing. The events included in the generated EVENT processing input
file are defined by the RECTABLE and MAXIFILE keywords on the OU pathway, and are placed in
the EVent pathway.
3) The SAVEFILE and INITFILE keywords work together to implement the model's re-start
capabilities. Since the MULTYEAR option utilizes the re-start features in a special way to
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.
B-4
-------
Table B-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 PVMRM or
DEPOS and/or or OLM or
DDEP ELEV WARNCHKD ARM2
and/or
WDEP
FASTALL DRYDPLT WETDPLT NOURBTRAN VECTORWS PSDCREDIT
or or or
FASTAREA NODRYDPLT NOWETDPLT
where:
DFAULT
ALPHA
BETA
CONC
DEPOS
DDEP
WDEP
AREADPLT
FLAT
ELEV
NOSTD
NOCHKD
Specifies that regulatory default options will be used; specification of
DFAULT option will override non-regulatory options that may be
specified
Non-regularory option that allows for experimental options for
review and evaluation by the user community; includes
LOW WIND, PSDCREDIT, ORDDWNW. ORDDWNW, and
RLINEXT with options for barriers depressed roadways (cannot
be used when the DFAULT keyword is specified)
Non-regulatory option that identifies options that have been vetted
through the scientific community and are waiting to be
promulgated as regulatory options (cannot be used when the
DFAULT keyword is specified)
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)
Non-regulatory option of assuming flat terrain will be used (cannot
be used when the DFAULT keyword is specified)
Default option of assuming elevated terrain will be used;
Note: Both FLAT and ELEV mav be specified in the same model
run to allow specifying the non-rceulatorv FLAT terrain option on
a source-by-source basis (see the SO LOCATION keyword for
specifying FLAT sources)
Non-regulatory option of no stack-tip downwash will be used
(cannot be used when the DFAULT keyword is specified)
B-5
-------
Keyword
Parameters
WARNCHKD
NOWARN
SCREEN
SCIM
PVMRM
OLM
ARM2
PSDCREDIT
FASTALL
FASTAREA
DRYDPLT
NODRYDPLT
WETDPLT
NOWETDPLT
NOURBTRAN
VECTORWS
Non-regulatory option of suspending date checking will be used for
non-sequential meteorological data files, also implemented when
SCREEN option is specified (cannot be used when the DFAULT
keyword is specified)
Specifies option for issuing warning messages rather than fatal errors
for non-sequential meteorological data files
Option to suppress detailed listing of warning messages in the main
output file will be used
Non-regulatory option for running AERMOD in a screening mode
for AERSCREEN will be used (cannot be used when the
DFAULT keyword is specified)
Non-regulatory Sampled Chronological Input Model (SCIM) option;
applies to ANNUAL averages only; SCIM sampling parameters
must be specified on the ME pathway (cannot be used when the
DFAULT keyword is specified)
Plume Volume Molar Ratio Method (PVMRM) for NO2 conversion
will be used (PVMRM is regulatory Tier 3 screening option that
can be used simultaneouly with the DFAULT keyword)
Ozone Limiting Method (OLM) for NO2 conversion will be used
(OLM is regulatory Tier 3 screening option that can be used
simultaneouly with the DFAULT keyword)
Ambient Ratio Method - 2 (ARM2) for NO2 conversion will be used
(ARM2 is a regulatory Tier 2 option that can be used
simultaneouly with the DFAULT keyword)
Non-regulatory ALPHA test option to calculate the increment
consumption with PSD credits using the PVMRM option (cannot
be used when the DFAULT keyword is specified)
Non-regulatory option to optimize model runtime for POINT,
VOLUME and AREA sources (AREA optimizations formerly
associated with TOXICS option) (cannot be used when the
DFAULT keyword is specified)
Non-regulatory option to optimize model runtime for AREA sources
(formerly associated with TOXICS option) (cannot be used when
the DFAULT keyword is specified)
Option to incorporate dry depletion (removal) processes associated
with dry deposition algorithms; dry depletion will be used by
default if dry deposition algorithms are invoked
Option to disable dry depletion (removal) processes
Option to incorporate wet depletion (removal) processes associated
with wet deposition algorithms; wet depletion will be used by
default if wet deposition algorithms are invoked
Option to disable wet depletion (removal) processes.
Non-regulatory option to revert to the urban option as implemented
prior to version 11059 (see Section 3.2.2) (cannot be used when
the DFAULT keyword is specified).
Option to specify that input wind speeds are vector mean (or
resultant) wind speeds, rather than scalar means (see Section
3.2.2). The VECTORWS option can be used simultaneously with
B-6
-------
Keyword
Parameters
the DFAULT keyword.
AVERTIME
Timel Time2 . . . TimeN MONTH PERIOD
or
ANNUAL
where:
TimeN
MONTH
PERIOD
ANNUAL
Nth optional averaging time (1, 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 vears);
for multi-year meteorological data files, with and without the
MULTYEAR option, the multi-year average of the ANNUAL
values is reported
URBANOPT
For multiple urban areas:
UrbanID Urbpop (Urbname) (UrbRoughness)
For single urban area:
Urbpop (Urbname) (UrbRoughness)
where:
UrbanID
UrbPop
(UrbName)
(UrbRoughness)
Specifies the alphanumeric urban ID (up to eight characters)
Specifies the population of the urban area
Specifies the name of the urban area (optional)
Specifies the urban surface roughness length, meters (optional,
defaults to 1 .Om; value other than 1,0m treated as non-DFAULT)
POLLUTID
Pollut (H1H or H2H or INC)
where:
Pollut
Identifies type of pollutant being modeled. Any name of up to eight
characters mav be used. e.a.. S02. NOX. CO. PM25. PM-2.5.
PM10. PM-10. TSP or OTHER
NOTE: Some processina 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. triaaers special
processing for the PM-2.5 NAAQS, based on values averaged
across the number of years processed (see Section 3.2.15.1).
Use ofN02 or S02 triaaers special processina 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 3.2.16).
Use ofN02 is required in order to use the OLM and PVMRM
B-7
-------
Keyword
Parameters
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 l-hrN02 and
S02 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 also allow
evaluating N02 options in AERMOD based on incomplete years
of field measurements.
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;
B-8
-------
Keyword
Parameters
3 = Late autumn after harvest or Winter with no snow;
4 = Winter with continuous snow cover; or
5 = Transitional spring/partial green coverage/short annuals)
Dec
Seasonal category for December
LOWWIND
SVmin (WSmin) The ALPHA option must be specified as a
SVmin WSmin (FRANmax) MODELOPT on the CO pathway to use the
LOW WIND keyword
where:
SVmin
(WSmin)
(FRANmax)
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 meander factor, within a range of 0.0 to 1.0
inclusive
AWMADWNW
AWMAUEFF and/or IAWMAUTURB with/without (STREAMLINE) 1
The ALPHA option must be specified as a MODELOPT on the CO pathway to
use the AWMADWNW keyword.
where:
AWMAUEFF
AWMAUTURB
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.
Uses alternative formulations for turbulence enhancement and
velocity deficit calculations.
Reduces dispersion in the wake of streamlined structures such as
storage tanks and cooling towers.
ORDDWNW
ORDUEFF and/or ORDTURB and/or ORDCAV
The ALPHA option must be specified as a MODELOPT on the CO pathway to
use the ORD DWNW keyword.
where:
ORDUEFF
ORDTURB
ORDCAV
Redefines the height at which the wind speed is taken from the
profile wind speed used in the calculation of concentrations from
the primary plume.
Redefines the maximum value of the ambient turbulence intensity in
the wake, reduced from 0.07 to 0.06.
Redefines the initial vertical dispersion, crz, of the re-emitted plume
at the cavity boundary to equal the crz of the cavity plume.
N02EQUIL
N02Equil
where:
N02Equil
Equilibrium ratio ofN02/NOx for the PVMRM and OLM 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 and OLM options,
which may be overridden by N02RATIO keyword on SO
pathway.
B-9
-------
Keyword
Parameters
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 . . . StartSectN, where N is < 6
where:
StartSectl
StartSect2
StartSectN
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 03 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
SECTn 03FileName (03Units) (03Format) (with 03SECT0Rs)
where:
SECTn
03FileName
(03Units)
(03Format)
Applicable sector (n = 1 to 6) defined on the CO 03 SECTOR
keyword, if specified
Filename for hourly ozone data file (YR, MN, DY, HR, 03Value)
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 (Y r Mn Dy Hr
03Value). The 03Format parameter must include open and close
parentheses, the date variables must be read as integers (Fortran I
format), and the 03Value must be read as real (Fortran F, E, or D
format), e.g., '(412,F8.3)'. The year 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
SECTn 03Value (03Units) (with 03SECTOR)
where:
SECTn
03Value
(03Units)
Applicable sector (n = 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
SECTn 03Flag 03values(i), i=l,n) (with 03SECTORs)
B-10
-------
Keyword
Parameters
where:
SECTn
03Flag
03values
Applicable sector (n = 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
category; SEASHR for season-bv-hour; HRDOW for emission
rates vary by hour-of-day, and day-of-week [M-F, Sat, Sun];
HRD0W7 for emission rates varv bv hour-of-dav. and the seven
davs of the week 1M. Tu. W. Th. F. Sat Sunk SHRDOW for
season by hour-of-day by day-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 bv hour-of-
day by day-of-week (M,Tu,W,Th,F,Sat,Sun)
Arrav of background concentrations, for: ANNUAL. n=l;
SEASON. n=4; MONTH. n=12; HROFDY. n=24;
WSPEED. n=6: SEASHR. n=96: HRDOW. n=72:
HRD0W7. n=168: SHRDOW. n=288: SHRD0W7. n=672:
MHRDOW. n=864; MHRD0W7. n=2016
NOTE: Background ozone values input through the 03VALUES
keyword are assumed to be in units of PPB, unless modified by the
OZONUNIT keyword.
OZONUNIT
OzoneUnits
where:
OzoneUnits
Ozone concentration units for 03VALUES, specified as PPB for
parts-per-billion. PPM for parts-per-million. or UG/M3 for
micrograms/cubic-meter.
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
RUNORNOT
RUN or NOT
where:
RUN
NOT
Indicates to run full model calculations
Indicates to process setup data and report errors, but to not run full
model calculations
EVENTFIL
(Evfile) (Evopt)
where:
(Evfile)
(Evopt)
Identifies the filename to be used to generate a file for input to
EVENT model (Default=EVENTFIL.INP)
Optional parameter to specify the level of output detail selected for
the EVENT model: either SOCONT or DETAIL (default is
DETAIL if this parameter is omitted)
SAVEFILE
(Savfil) (Dayinc) (Savfl2)
where:
(Savfil)
Specifies name of disk file to be used for storing intermediate results
(default = SAVE.FIL); file is overwritten after each dump
B-ll
-------
Keyword
Parameters
(Dayinc)
(Savfl2)
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 (Dbafil) and/or METEOR (Dbmfil) and/or PRIME (Prmfil)
and/or
AWMADW (Aw maDwfil)
and/or
DEPOS
and/or
1 AREA (ArcaDbFil) or LINE (LmcDbFil)l
and/or
fPVMRM (Dbpvfil) or OLM (OLMfil) or ARM2 (ARM2fil)|
where:
MODEL
(Dbgfil)
METEOR
Specifies that MODEL debuaaina output will be aenerated
Optional filename for the model calculation debug file (a default
filename of 'MODEL.DBG' will be used if omitted)
Specifies that METEORological profile data file will be generated
(Dbmfil)
PRIME
(Prmfil)
AWMADW
Optional filename for the meteorological profile data file (a default
filename of 'METEOR.DBG' will be used if omitted)
Specifies that PRIME debuaaina output will be aenerated
Optional filename for PRIME debug file (a default filename of
'PRIME.DBG' will be used if omitted)
Specifies the debua out will be aenerated for AWMA DownWash
(AwmaDwfil)
DEPOS
AREA or
LINE
(AreaDbfil)
options
Optional filename for AWMADW debug file (a default filename of
'AWMADW.DBG' will be used if omitted)
Specifies that DEPOSition debuaaina output will be aenerated. usina
default filenames of 'GDEP.DAT' for gas deposition and
'PDEP.DAT' for particle deposition.
Specifies that AREA or LINE debuaaina output will be aenerated.
including debugging outputs for OPENPIT sources, if included in
the modeling.
Optional filename for AREA debug file (a default filename of
'AREA.DBG' will be used if omitted)
B-12
-------
Keyword
Parameters
PVMRM
(Dbpvfil)
OLM
(OLMfil)
ARM2
(ARM261)
Soccifics that PVMRM debuaaina output will be aenerated
Optional filename for PVMRM debug file (a default filename of
'PVMRM.DBG' will be used if omitted)
Specifies that OLM debuaaina output will be aenerated
Optional filename for OLM debug file (a default filename of
'OLM.DBG' will be used if omitted)
Specifies that ARM2 debuaaina output will be aenerated
Optional filename for ARM2 debug file (a default filename of
'ARM2.DBG' will be used if omitted)
Note: The user can specify 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 debug information for AREA/LINE/OPENPIT
sources is written to the AREA debua file.
ERRORFIL
(Errfil)
where:
(Errfil)
Specifies name of detailed error listing file (default = ERRORS.LST)
B-13
-------
Table B-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.
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
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
B-14
-------
SO Keywords
Type
Keyword Description
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
PSDGROUP1
0 - R
Specifies source groups for PSDCREDIT option with PVMRM
SRCGROUP1
M-R
Identification of source groups
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.
B-15
-------
Table B-4. Description of Source Pathway Keywords and Parameters
Keyword
Parameters
ELEVUNIT
METERS or FEET
where:
METERS
FEET
Specifies input units for source base elevations of meters (default if
ELEVUNIT is omitted)
Specifies input units for source elevations of feet
Note: This kevword applies to source base elevations onlv.
LOCATION
SrcID SrctvD Xs Ys (Zs) 1 for all Srctvos exccot LINE.
BUOYLINE. RLINE. and RLINEXT1
or
(FLAT) Tfor 'FLAT & ELEV' ODtionl
or
SrcID SrctvD Xs 1 Ys 1 Xs2 Ys2 (Zs) Tfor LINE. RLINE. or BUOYLINE Srctvol
or
(FLAT) Tfor 'FLAT & ELEV' ootionl
or
SrcID SrctvD Xs 1 Ys 1 Zs 1 Xs2 Ys2 Zs2 (Zs) Tfor RLINEXT Srctvol
or
(FLAT) Tfor 'FLAT & ELEV' ODtionl
where:
SrcID
Srctyp
Xs
Ys
Xsl, Xs2
Ysl, Ys2
Zsl, Zs2
(Zs)
(FLAT)
Source identification code (unique alphanumeric string of up to 12
characters)
Source tvpe: POINT. POINTCAP. POINTHOR. VOLUME.
AREA. AREAPOLY. AREACIRC. OPENPIT. LINE.
BUOYLINE. RLINE. or RLINEXT
x-coord of source location, corner for AREA. AREAPOLY. and
OPENPIT. center for AREACIRC (m)
v-coord of source location, corner for AREA. AREAPOLY. and
OPENPIT. center for AREACIRC (m)
x-coords of midpoint for start and end of LINE. RLINE. RLINEXT.
or BUOYLINE source (m)
v-coords of midpoint for start and end of LINE. RLINE. RLINEXT.
or BUOYLINE source (m)
z-coords of midpoint for start and end of RLINEXT source
(m)Optional z-coord of source location (elevation above mean
sea level, defaults to 0.0 if omitted)
Optional keyword to indicate non-DFAULT option for identifying
sources to model as FLAT terrain
SRCPARAM
SrcID Ptemis Stkhat StktmD Stkvel Stkdia (POINT. POINTCAP.
POINTHOR source)
Vlemis Relhat Svinit Szinit (VOLUME source)
Aremis Relhat Xinit (Yinit) (Anale) (Szinit) (AREA source)
Aremis Relhat Nverts (Szinit) (AREAPOLY source)
Aremis Relhat Radius (Nverts) (Szinit) (AREACIRC source)
B-16
-------
Keyword
Parameters
Lnemis Relhat Width (Szinit) (LINE or RLINE source)
Oocmis Rclhet Xinit Yinit Pitvol (Angle) (OPENPIT source)
Blemis Relhgt (BUOYLINE source)
Qemis 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 Qemis
Source physical release height above ground (center of height for
VOLUME, heiaht 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)
Lenath 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 anale (dea) 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)
Buoyant 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
B-17
-------
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
AREA VERT
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 Depth Wtop Wbottom
where:
SrcID
Htwall
DCLwall
Source identification code
Height of the wall (or barrier) near roadway (m)
Distance from the roadway centerline to the 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)
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.
B-18
-------
Keyword
Parameters
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. Sunk HRDOW7 for emission
rates vary by 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 by hour-of-day by day-of-week (M-F,Sat,Sun);
MHRDOW7 for month bv hour-of-dav bv dav-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 Changes the expected emission units for the RLINE (Lemis) and
RLEINXT (Qemis)emissions to grams/hour/link
CONCUNIT
Emifac Emilbl Conlbl
where:
Emifac
Emilbl
Conlbl
Emission rate factor used to adjust units of output (default value is
1.0E06 for concentration for grams to micrograms)
Label to use for emission units (default is grams/sec)
Label to use for concentrations (default is micrograms/m3)
DEPOUNIT
Emifac Emilbl De
plbl
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)
B-19
-------
Keyword
Parameters
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
FineMassFraction
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 . . . StartSectN, where N is < 6
where:
StartSectl
StartSect2
Starting direction for the first sector
Starting direction for the second sector
StartSectN
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
B-20
-------
Keyword
Parameters
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
and/or
HOURLY BGfilnam (BGformat)
(without BGSECTORs)
or
SECTn BGflag BGvalue(i), i=l,n
and/or
SECTn HOURLY BGfilnam (BGformat)
(with BGSECTORs)
where:
SECTn
BGflag
BGvalue
HOURLY
BGfilnam
(BGformat)
Applicable sector (n = 1 to 6) defined on the SO BGSECTOR
keyword, if specified
Variable background concentration flag:
ANNUAL for annual; SEASON for seasonal; MONTH for
monthly; HROFDY for hour-of-day; WSPEED for wind speed
category; SEASHR for season-by-hour; HRDOW for emission
rates vary by hour-of-day, and day-of-week [M-F, Sat, Sun];
HRDOW7 for emission rates vary by hour-of-day, and the seven
days of the week [M, Tu, W, Th, F, Sat, Sun]; SHRDOW for
season by hour-of-day by day-of-week (M-F,Sat,Sun);
SHRDOW7 for season by hour-of-day by day-of-week
(M,Tu,W,Th,F,Sat,Sun); MHRDOW for month by hour-of-day
by day-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=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
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.
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
B-21
-------
Keyword
Parameters
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
micrograms/cubic-meter. Background concentrations input in
units of PPB or PPM are converted to micrograms/cubic-meter
based on reference temperature (25 C) and pressure (1013.25
mb).
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
SrcRange'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
Note: Card mav be repeated with same Groid if more soace is
needed to specify sources
PSDGROUP
PSDGrpID SrcID's SrcRange's
where:
PSDGrpID
PSD GrpID for PSDCREDIT option, must be one of the following:
B-22
-------
Keyword
Parameters
SrcID's
SrcRange's
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
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 excluded from group ALL by specifying
'NOBACKGROUND' on the SRCGROUP ALL keyword.
SrcRange's
Source ID ranges to be included in group
Note: Card mav be repeated with same Grpid if more space is
needed to specify sources
SRCGROUP
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)
B-23
-------
Table B-5. Description of Receptor Pathway Keywords
RE Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of RECEPTOR pathway inputs
ELEVUNIT
O-N
Defines input units for receptor elevations (defaults to meters), must be first
keyword after RE STARTING if used.
GRIDCART
O1 - R
Defines a Cartesian grid receptor network
GRIDPOLR
O1 - R
Defines a polar receptor network
DISCCART
O1 - R
Defines the discretely placed receptor locations referenced to a Cartesian
system
DISCPOLR
O1 - R
Defines the discretely placed receptor locations referenced to a polar system
EVALCART
O1 - R
Defines discrete Cartesian receptor locations for use with EVALFILE output
option
INCLUDED
0 - R
Identifies an external file containing receptor locations to be included in the
inputs
FINISHED
M-N
Identifies the end of RECEPTOR pathway inputs
1) At least one of the following must be present: GRIDCART, GRIDPOLR, DISCCART,
DISCPOLR, or EVALCART, unless the INCLUDED keyword is used to include receptor
inputs from an external file. Multiple receptor networks can be specified in a single run,
including both Cartesian and polar.
B-24
-------
Table B-6. Description of Receptor Pathway Keywords and Parameters
Keyword
Parameters
ELEVUNIT
METERS or FEET
where:
METERS
Specifies input units for receptor elevations of meters
FEET
Specifies input units for receptor elevations of feet
Note: This keyword applies to receptor elevations only.
GRIDCART
Netid STA
XYINC Xinit Xnum Xdelta Yinit YnumYdelta
or XPNTS Gridxl Gridx2 Gridx3 .... GridxN. and
YPNTS Gridvl Gridv2 Gridv3 .... GridvN
ELEV
Row Zelev 1 Zelev2 Zelev3 ...ZelevN
HILL
Row Zhill 1 Zhill2 Zhill3 ... ZhillN
FLAG Row Zflael Zflae2 Zflae3 ...ZflaeN
END
where:
Netid
Receptor network identification code (up to eight alphanumeric
characters)
STA
Indicates STArt of GRIDCART subpathwav. repeat for each new Netid
XYINC
Keyword identifying grid network generated from x and y increments
Xinit
Starting local x-axis grid location in meters
Xnum
Number of x-axis receptors
Xdelta
Spacing in meters between x-axis receptors
Yinit
Starting local y-axis grid location in meters
Ynum
Number of y-axis receptors
Ydelta
Spacing in meters between y-axis receptors
XPNTS
Keyword identifying grid network defined by series of x and y
coordinates
Gridxl
Value of first x-coordinate for Cartesian grid
GridxN
Value of'nth' x-coordinate for Cartesian grid
YPNTS
Keyword identifying grid network defined by series of x and y
coordinates
Gridyl
Value of first y-coordinate for Cartesian grid
GridyN
Value of'nth' y-coordinate for Cartesian grid
ELEV
Keyword to specify that receptor elevations follow
Row
Indicates which row (y-coordinate fixed) is being input
Zelev
An array of receptor terrain elevations for a particular Row
HILL
Keyword to specify that hill height scales follow
Row
Indicates which row (y-coordinate fixed) is being input
Zhill
An array of hill height scales for a particular Row
FLAG
Keyword to specify that flagpole receptor heights follow
Row
Indicates which row (y-coordinate fixed) is being input
Zflag
An array of receptor heights above local terrain elevation for a particular
Row (flagpole receptors)
END
Indicates END of GRIDCART suboathwav. repeat for each new Netid
GRIDPOLR
Netid STA
ORIG Xinit Yinit.
or ORIG Srcid
B-25
-------
Keyword
Parameters
DIST Rinsl Rins2 Rin23 ... RinsN
DDIR Dirl Dir2 Dir3 ... DirN,
or GDIR Dirnum Dirini Dirinc
ELEV Dir Zelevl Zelev2 Zelev3 ... ZelevN
HILL Dir Zhilll Zhill2 Zhill3 ... ZhillN
FLAG Dir Zflagl Zflag2 Zflag3 ... ZflagN
END
where:
Netid
Receptor network identification code (up to eight alphanumeric
characters)
STA
Indicates STArt of GRIDPOLR subpathway, repeat for each new Netid
ORIG
Optional keyword to specify the origin of the polar network (assumed to
be at x=0, y=0 if omitted)
Xinit
local x-coordinate for origin of polar network (m)
Yinit
local y-coordinate for origin of polar network (m)
Srcid
Source ID of source used as origin of polar network
DIST
Keyword to specify distances for the polar network
Ringl
Distance to the first ring of polar coordinates (m)
RingN
Distance to the 'nth' ring of polar coordinates (m)
DDIR
Keyword to specify discrete direction radials for the polar network
Dirl
First direction radial in degrees (1 to 360)
DirN
The 'nth' direction radial in degrees (1 to 360)
GDIR
Keyword to specify generated direction radials for the polar network
Dirnum
Number of directions used to define the polar system
Dirini
Starting direction of the polar system
Dirinc
Increment (in degrees) for defining directions
ELEV
Keyword to specify that receptor elevations follow
Dir
Indicates which direction is being input
Zelev
An array of receptor terrain elevations for a particular direction radial
HILL
Keyword to specify that hill height scales follow
Row
Indicates which row (y-coordinate fixed) is being input
Zhill
An array of hill height scales for a particular Row Keyword to specify that
flagpole receptor heights follow
FLAG
Keyword to specify that flagpole receptor heights follow
Dir
Indicates which direction 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 kevword
DISCPOLR
Srcid Dist Direct (Zelev Zhill) (Zflag)
B-26
-------
Keyword
Parameters
where:
Srcid
Dist
Direct
(Zelev)
(Zhill)
(Zflag)
Specifies source identification for which discrete polar receptor locations
apply (used to define the origin for the discrete polar receptor)
Downwind distance to receptor location (m)
Direction to receptor location, in degrees clockwise from North
Elevation above sea level for receptor location (optional), used only for
ELEV terrain
Hill height scale (optional)
Receptor height (flagpole) above local terrain (optional), used only with
FLAGPOLE keyword
EVALCART
Xcoord Ycoord Zelev Zhill Zflag Arcid (Name)
where:
Xcoord
Ycoord
Zelev
Zhill
Zflag
Arcid
(Name)
Local x-coordinate for discrete receptor location (m)
Local y-coordinate for discrete receptor location (m)
Elevation above sea level for discrete receptor location (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
B-27
-------
Table B-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
0 - N
Describes on-site meteorological station
PROFBASE
M-N
Specifies the base elevation for the potential temperature profile
STARTEND
0-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)
SCIMBYHR
0-N
Specifies the parameters for the SCIM (Sampled Chronological Input
Model) option (see CO MODELOPT)
WDROTATE
0-N
May be used to correct for alignment problems of wind direction
measurements, or to convert wind direction from to flow vector
WINDCATS
0-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
B-28
-------
Table B-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 WB AN 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)
B-29
-------
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 ... RangeN
where:
Range 1
RangeN
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.
SCIMBYHR
NRegStart NReglnt (SfcFilnam PflFilnam)
where:
NReg Start
NReglnt
(SfcFilnam)
(PflFilnam)
Specifies the first hour to be sampled with the SCIM option;
required to have a value from 1 to 24
Specifies the sampling interval, in hours
Optional output file name to list the surface meteorological data for
the sampled hours
Optional output file name to list the profile meteorological data for
the sampled hours
WDROTATE
Rotang
where:
Rotang
Specifies angle (in degrees) to rotate wind direction measurements
to correct for alignment problems; value of Rotang is subtracted
from WD measurements, i.e., rotation is counterclockwise
WINDCATS
Wsl Ws2 Ws3 Ws4 Ws5
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)
B-30
-------
Table B-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
B-31
-------
Table B-10. Description of Event Pathway Keywords and Parameters
Keyword
Parameters
EVENTPER
Evname Aveper Grpid Date Cone
where:
Name
Grpid
Aveper
Date
Cone
Specify name of event to be processed (e.g. H002H24ALL), (up to
ten alphanumeric characters)
Specify source group ID for event
Specify averaging period for event
Specify data period for event (ending YYMMDDHH for averaging
period)
Specifies the concentration value generated during the initial non-
EVENT processing
EVENTLOC
Evname XR= Xr YR= Yr (Zelev Zhill) (Zflas)
or
RNG= Rna DIR= Dir (Zelev Zhill) (Zflas)
where:
Evname
XR=
YR=
RNG=
DIR=
(Zelev)
(Zhill)
(Zflag)
Specify name of event to be processed (e.g. H002H24ALL), (up to
ten alphanumeric characters)
X-coordinate for event (discrete Cartesian receptor)
Y-coordinate for event (discrete Cartesian receptor)
Distance range for event (discrete polar receptor)
Radial direction for event (discrete polar receptor)
Terrain elevation for event (optional)
Hill height scale (optional)
Receptor height above ground for event (optional)
INCLUDED
EventlncFile
where:
EventlncFile
Identifies the filename for the included EVENT file, up to 200
characters in length; double quotes (") may be used as delimiters for
the filename to allow for embedded spaces; and quotes don't count
toward the limit of 200
Note: EVENT locations can be input as either discrete Cartesian receptors (XR=. YR=) or as
discrete polar receptors (RNG=. DIR=). Events that are specified in the file generated by
the AERMOD model (CO EVENTFIL card) are always given as discrete Cartesian
coordinates. Discrete polar receptors are assumed to be relative to an origin of (0,0).
B-32
-------
Table B-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.
B-33
-------
Table B-12. Description of Output Pathway Keywords and Parameters
Keyword
Parameters
RECTABLE
Aveoer FIRST SECOND . . . SIXTH . . . TENTH and/or
Aveper 1ST 2ND . . . 6TH . . . 10TH and/or
Aveper J_ 2 ... 6 ... 10 . . . N . . . 999
where:
Aveper
FIRST
Averaging period to summarize with high values (keyword
ALLAVE specifies all short-term averasing periods)
Select summaries of FIRST highest values bv receptor
SECOND
SIXTH
1ST
2ND
6TH
E
Select summaries of SECOND highest values bv receptor
Select summaries of SIXTH highest values bv receptor
Select summaries of 1ST highest values by receptor
Select summaries of 2ND highest values bv receptor
Select summaries of 6TH highest values by receptor
Select summaries of /v'-th highest values by receptor (up to 999-th
highest values)
Note:
If two parameters are input separated by a dash (e.g.
FIRST-THIRD or 4-12). then summaries of all high
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
B-34
-------
Keyword
Parameters
Note:
If the CO EVENTFIL keyword is exercised, then the events
generated by the MAXIFILE keyword are included in the input
file for EVENT processing.
POSTFILE
Aveper GrpID Format Filnam (Funit)
where:
Aveper
GrpID
Format
Filnam
Funit
Specifies averaging period to be output to file, e.g., 24 for 24-hr
averaaes. PERIOD for period averaaes
Specifies source group to be output to file
Specifies format of file, either UNFORM for unformatted files or
PLOT for formatted files for dlotting
Specifies filename for output file
Optional parameter to specify the file unit
PLOTFILE
Aveper GrpID Hivalu Filnam (Funit) (Short-Term values)
Aveper GrpID Filnam (Funit) (PERIOD or ANNUAL averages)
where:
Aveper
GrpID
Hivalu
Filnam
Funit
Specifies averaging period to be output to file, e.g., 24 for 24-hr
averaaes. PERIOD for period averaaes. etc.
Specifies source group to be output to file
Specifies rank to be included in hiah value summarv (e.a. FIRST.
SECOND. 1ST. 2ND. etc.) to be output to file (the rank must be
included on the RECTABLE card)
Specifies filename for output file
Optional parameter to specify the file unit
TOXXFILE
Aveper Cutoff Filnam (Funit)
where:
Aveper
Cutoff
Filnam
Funit
Specifies averaging period to be output to file, e.g., J_ 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
B-35
-------
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 ranse
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:
SummF ileN ame
Specifies filename of output summary file
FILEFORM
EXP or FIX
B-36
-------
Keyword
Parameters
where:
EXP
FIX
Specifies that the output results files will use EXPonential-
formatted values
Specifies that the output results files will use FIXed-formatted
values (fixed-formatted values will be used if FILEFORM is
omitted)
NOHEADER
FileTypel FileType2 FileType3 . . . FileTypeiV
or
ALL
where:
FilcTypc/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
B-37
-------
APPENDIX C. Explanation of error message codes
C.l Introduction
The AERMOD input control fileis checked to identify parameters that are missing or
potentially in error, and the input source and meteorological data are checked and flagged for
possible erroneous values.
The AERMOD model uses a "defensive programming" approach to eliminate as much as
possible of the user's work in debugging the input control file. Also, a great deal of effort has been
made to eliminate the possibility of run time errors, such as "divide by zero," and to point out
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, and the user can also request a detailed message
listing file.
Message Summary: Whether the user selects a detailed error listing file or not, the
AERMOD model output 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 Listing File: The AERMOD model provide 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
C-l
-------
C.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 also 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 C-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 C-l. Example of an AERMOD Message Summary
C-2
-------
C.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):
C-3
-------
[xxx I I i: MESSAGE Hints
r. it ;
t: i-
-el/:
:;e:err.me the
7.51" U1
e :r
errors
\key*\"pathvjcsy
vrr.ere
t he
recurs, ... e~:.;
Detailed message for
this code (22:71)
ir.esings gexier ate:i
le fi::.. which the
The lir.e nu.rri:>er of the rnp'
i:. r.: r file "here The :.e::?.
r:e£saje s rn run:me
h:>vir r/jurx-er : f ~he r.erec r:<
TV fxic
Numeric message code (a 3-digit number) (5:7)
Message type (E, W, i) {4:4}
-Atr/way IZ. CO, 5C", FX, ME, ET,
...
or
MM f:r i ,e : e : r : 1: :¦ i: r. I :.h e t r =
.cricr.
11!
=
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). The 3-digit message codes are grouped into general categories
corresponding to the different stages of the processing. Theses categories are:
100 - 199 Input Control file command Structure Processing
200 - 299 Parameter Setup Processing
C-4
-------
300-399 Data and Quality Assurance Processing
400 - 499 Run Time Message Processing
500- 599 Input/Output Message Processing
A listing of each of the message codes currently used in the model is provided in the next section.
C-5
-------
C.4 Listing of the error/message codes
Message
Number
Error/Warning Message
100
Invalid Pathway Specified. The Troubled Pathway is
105
Invalid Keyword Specified. The Troubled Keyword is
109
Too many fields specified on control file command; MAX=
110
Keyword is Not Valid for This Pathway. Keyword is
111
User-specified minimum Sigma-V on LOW_WIND Keyword
112
User-specified minimum WindSpeed on LOW_WIND Keywd
113
User-specified maximum FRAN on the LOW WIND Keywrd
114
User-specified SZCOEF value on LOW WIND Keyword
115
STARTING or FINISHED Out of Sequence: Pathway =
116
Vector Wind Speeds specified on MODELOPT Keyword
119
Missing FINISHED-Control file Incomplete: ISTAT=
120
Pathway is Out of Sequence: Pathway =
130
Missing Mandatory Keyword. The Missing Keyword is
133
LOW WIND Option requires ALPHA option on MODELOPT
135
Nonrepeatable Keyword or Recursed INCLUDED: Keywrd
136
LOW WIND ALPHA option selected on MODELOPT Keyword
140
Invalid Order of Keyword. The Troubled Keyword is
141
Conflicting Options for N02 conversion specified:
142
Following Keyword Invalid Without PVMRM or OLM:
143
Following Keyword Invalid Without PVMRM Option:
144
Following Keyword Invalid Without OLM Option:
145
Following Keyword Invalid Without ARM or ARM2:
146
PSDGROUP Keyword Specified without PSDCREDIT Opt.
147
Following Option is Invalid with PSDCREDIT Option:
148
Both OZONEVAL and 03VALUES keywords are specified
C-6
-------
Message
Number
Error/Warning Message
149
Conflicting options specified on MODELOPT keyword:
150
Conflicting Options: MULTYEAR Option with
151
Non-DFAULT NoUrbTran option selected on MODELOPT
152
ELEVUNIT card must be first for this Pathway:
153
Conflicting Opts: MAXDCONT with Re-Start or MULTYR
154
Conflicting options: SCIM cannot be used with
155
Conflicting Decay Keyword. Inputs Ignored for
156
Option ignored - not valid with SCIM. Option =
157
Wet SCIM Not Supported - Wet SCIM Inputs Ignored
158
EMISUNIT Keyword Used With More Than 1 Output Type
159
EMISUNIT Keyword Used With the Following Keyword:
160
Duplicate ORIG Secondary Keyword for GRIDPOLR:
161
MAXDCONT option already defined for source group:
162
Option only applies to 1-hr N02 or 1-hr S02 NAAQS:
163
Option only applies to 24h PM25, lh N02 or lh S02:
164
NOHEADER selected for non-specified output option:
165
Inconsistent temporally-varying BACKGRND options:
166
BGSECT0R/03SECT0R option invalid w/o BG/03 Inputs:
167
Inconsistent temporally-varying 03VALUES options:
168
Hourly BACKGRND already specified for this sector:
170
Invalid Secondary Keyword for Receptor Grid:
171
Sector ID specified without Sector-varying Option:
175
Missing Secondary Keyword END for Receptor Grid:
180
Conflicting Secondary Keyword for Receptor Grid:
181
BULKRN Delta-T & SolarRad option for SBL was used
182
MMIF-generated meteorological inputs were used
183
Non-DFAULT option for MMIF-generated data without
C-7
-------
Message
Number
Error/Warning Message
184
PROFFILE heights > 999m; inputs could be from MMIF
185
Either No Sources or No Receptors are specified!!!
186
THRESH1MIN 1-min ASOS wind speed threshold used
187
ADJ U* Option for Stable Low Winds used in AERMET
188
Non-DFAULT FLAT required for RLINE/RLINEXT source
189
No Keywords for OU Path and No PERIOD/ANNUAL Aves.
190
Incompatible Option Used With SAVEFILE or INITFILE
191
PM25, lh N02 or S02 w/o MAXIFILE incompatible with
192
FASTALL option also implies use of FASTAREA option
193
Units keyword specified without appropriate option
194
DEBUGOPT input option is invalid or not applicable
195
Incompatible Keyword used with GASDEPVD option
196
Gas deposition algorithms are non-DFAULT options
197
METHOD 2 for particulates is a non-DFAULT option
198
Non-DFAULT ALPHA Option Required for use of
199
Non-DFAULT BETA Option Required for use of
200
Missing Parameter(s). No Options Specified For
201
Not Enough Parameters Specified For the Keyword of
202
Too Many Parameters Specified For the Keyword of
203
Invalid Parameter Specified. Troubled Parameter:
204
Regulatory DFAULT Conflicts with Non-DFAULT Option
205
No Option Parameter Setting. Forced by Default to
206
Regulatory DFAULT Overrides Non-DFAULT Option For
207
No Parameters Specified. Default Values Will Used.
208
Illegal Numerical Field Encountered in
209
Negative Value Appears For Non-negative Variable.
210
Num Ranked values on RANKFILE > MAXTABLE value for
C-8
-------
Message
Number
Error/Warning Message
211
Duplicate Averaging Period Specified for Keyword
212
END Encountered Without (X,Y) Points Properly Set
213
ELEV Input Inconsistent With Option: Input Ignored
214
ELEV Input Inconsistent With Option: Defaults Used
215
FLAG Input Inconsistent With Option: Input Ignored
216
FLAG Input Inconsistent With Option: Defaults Used
217
More Than One Delimiter In A Field for Keyword
218
Number of (X,Y) Points Does Not Match Number of
219
Urban ID field is too long (>8); first 12 char:
220
Missing Origin (Use Default = 0,0) In GRIDPOLR
221
Missing Dist or Direction Setting In Polar Network
222
03 SECTOR or BGSECTOR Value is out of order:
223
Missing Distance or Degree Field in
224
SrcID specified on SRCGROUP keyword not defined:
225
SrcID specified on OLMGROUP keyword not defined:
226
SrcID specified on PSDGROUP keyword not defined:
227
03SECTOR or BGSECTOR Width is out of range:
228
Default(s) Used for Missing Parameters on Keyword
229
Too Many Parameters - Inputs Ignored on Keyword
230
Source ID field is too long (>12); first 12 chars:
231
Too Many Numerical Values Specified for
232
OLMGroup ID field is too long (>8); first 12 char:
233
Building Dimensions Specified for Non-POINT Source
234
Too Many Sectors Input for
235
Num of SRCGRPs exceeds limit for EVT name; Set=999
236
Not Enough BUILDHGTs Specified for SourcelD
237
Not Enough BUILDWIDs Specified for SourcelD
C-9
-------
Message
Number
Error/Warning Message
238
Not Enough BACKGRND Concentration Values Specified
239
Not Enough QFACTs Specified for SourcelD
240
Inconsistent Number of Particle Categories for
241
Not Enough BUILDLENs Specified for SourcelD
242
No Particle Cat. or Gas Depos. Specified for SRCID
243
Wet depos (DEPOS, WDEP, WETDPLT) incompatible with
244
Source parameters are missing or incomplete for
245
SrcGroup ID field is too long (>8); first 12 char:
246
Not Enough XBADJs Specified for SourcelD
247
Not Enough YBADJs Specified for SourcelD
248
Either BGVALs or BGFILE missing for this sector:
249
Source elevation is missing (-9999.0); SRCID =
250
Duplicate XPNT/DIST or YPNT/DIR Specified for GRID
251
Deposition (DEPOS, WDEP, DDEP) incompatible with
252
Duplicate Receptor Network ID Specified. NETID =
253
PSDGROUP ID field is too long (>8); first 12 char:
256
EVALFILE Option Used Without EVALCART Receptors
259
Receptor elevation is missing (-9999.0); IREC =
260
Number of EMISFACT/03VALUES/BACKGRND values > max:
261
Not Enough 03VALUES Ozone Concentrations Specified
262
First Vertex Does Not Match LOCATION for AREAPOLY
264
Too Many Vertices Specified for AREAPOLY Source
265
Not Enough Vertices Specified for AREAPOLY Source
266
Invalid shape defined (area=0) for AREAPOLY source
267
RLINE/RLINEXT requires Zs = 0.0 or FLAT; SRCID=
271
03FILE w/o 03VALs; full conv for hrs with miss 03
272
Upper bound rank > Lower bound rank for MAXDCONT:
C-10
-------
Message
Number
Error/Warning Message
273
Range of ranks for MAXDCONT THRESH Opt is limited:
276
Special proc for lh-N02/S02 24hPM25 NAAQS disabled
277
Specified option not applicable for this pollutant
278
Keyword only applies to RLINEXT source type:
279
Multiple URBANOPT/URBANSRC inputs not allowed for:
280
Number of Output Types Specified Exceeds Max:NTYP=
281
ALPHA required for RLINE/RLINEXT URBANSRC:
282
Following SRCID Included in Multiple OLMGROUPs:
283
OZONEVAL, 03VALUES or OZONEFIL Keyword Needed for
284
Invalid POLLUTID Specified for PVMRM/OLM; Must Use
285
BACKGROUND and BACKGRND are invalid as Source IDs
286
Following SRCID Included in Multiple PSDGROUPs:
287
PSDGROUP ID Must be INCRCONS, RETRBASE or NONRBASE
288
Use of for repeated values not meaningful for
289
Source defined as both particulate and gaseous
290
This array limit exceeded; possible coding error:
291
Filename specified is too long. Maximum length =
292
Potential problem with Fortran format specifier:
293
User-specified met data format not used; use FREE
294
PERIOD and ANNUAL averages are both selected for
295
Invalid Averaging Period Specified for SCREEN Mode
296
Averaging Period .NE. 1-Hr for TOXXFILE Option
297
Aver. Period must be .LE. 24 for EVENT Processing
298
Results reported for source group ALL include
299
SRCGROUP ALL is missing, but is NOT required for
300
Specified SRCID Has Not Been Defined Yet: KEYWORD=
301
Urban Area ID Has Not Been Defined. URBID =
C-ll
-------
Message
Number
Error/Warning Message
302
Following SRCID Included in Multiple Urban Areas:
303
Urban ID has already been defined. URBID =
305
Stack height > or = EPA formula height for SRCID:
310
Attempt to Define Duplicate LOCATION Card for SRC:
313
Attempt to Define Duplicate EVENTPER card for
314
Specified GRP index and SRC index is duplicated:
315
Attempt to Define Duplicate SRCPARAM Card for SRC:
316
Specified SRCID is not included in any SRCGROUP:
317
Specified SRCID not included in any PSDGROUP:
318
No Sources Defined for Urban Area. URBID =
319
No Sources Included in Specified Source Group:
320
Input Parameter May Be Out-of-Range for Parameter
321
BACKGROUND cones are NOT included in any SRCGROUP!
322
Release Height Exceeds Effective Depth for OPENPIT
323
BACKGRND included w/o BACKGRND keyword for SrcGrp:
324
Release Height Exceeds 3000 Meters for SRCID:
325
Negative Exit Velocity (Set=1.0E-5) for SRCID:
330
Mass Fraction Parameters Do Not Sum to 1. for Src
332
Mass Fraction Parameter Out-of-Range for Source
334
Particle Density Out-of-Range for Source
335
Particle Diameter Out-of-Range for Source
336
N02RATIO Missing or Invalid for OLM/PVMRM - SrcID:
338
Neg Emis Rate Cannot be Used with OLM/PVMRM. Src:
340
Possible Error in PROFBASE Input: Value is < 0
341
Emissions in HOUREMIS file < -90; set to 0.0 for
342
Src ID Mismatch in Hourly Emissions File for ID =
344
Missing HOUREMIS fields; EmisRate set = 0. KURDAT=
C-12
-------
Message
Number
Error/Warning Message
345
Problem processing the HOUREMIS file. KURDAT =
346
Too many fields for HOUREMIS file. KURDAT =
350
Julian Day Out Of Range at
352
The "H6H" field is no longer required for MULTYEAR
353
Urban Roughness Length (m) May Be Out-of-Range:
360
2-Digit Year Specified: Valid for Range 1950-2049
361
Multiyear PERIOD/ANNUAL values for N02/S02 require
362
Multiyear lh N02/S02 processing not applicable for
363
Multiyr 24h/Ann PM25 processing not applicable for
365
Year Input is Greater Than 2147
370
Invalid Date: 2/29 In a Non-leap Year.
380
This Input Variable is Out-of-Range:
381
Latitude in Surface File Is Not Valid:
382
Error Decoding Latitude:
383
# buoyant lines does not match # in hourly emiss:
384
Not enough fields specified for HOUREMIS; KURDAT =
385
BLPGROUP keywrd not operational; all BLP lines are
386
PARTDIAM and METHOD 2 specified for same SRCID:
387
METHOD 2 option already specified for this SRCID:
388
Input buoyant line sources not in correct order:
389
Rotated buoyant line sources not in correct order:
390
Aspect ratio (LAV) of LINE source greater than 100
391
Aspect ratio (LAV) of AREA source greater than 100
392
Aspect ratio (LAV) of OPENPIT is greater than 10
394
Met data may be from outdated version of AERMET:
395
Met. Data Error; Incompatible Version of AERMET:
396
AERMET Version Out-dated or Non-standard; Version:
C-13
-------
Message
Number
Error/Warning Message
397
SCREEN option used without use of SCREEN Met Data
398
SCREEN met used without specifying SCREEN option
399
EXP format specified with no applicable file types
400
Output values exceed format limit; use OU FILEFORM
401
Use of turbulence data with ADJ_U* is NonDFAULT
402
Turbulence data being used with ADJ U* w/o DFAULT
403
Turbulence data is being used w/o ADJ_U* option
405
Value of PHEE Exceeds 1.0 on KURD AT =
406
Number of Vertices Exceeds Max (NVMAX) for SRCID:
409
Error Allocating Storage for Setup/Result Arrays!
410
Wind Direction Out-of-Range. KURDAT =
411
Possible ERROR in PVMRM CALC! QSUM=0.0 @ Rec# Date
412
Possible ERROR in PVMRM CALC! QSUM=0.0 @ Evt# Date
413
Number of Threshold Events > 999999 for Ave Period
415
MAXDCONT THRESH not reached within range of ranks
420
Wind Speed Out-of-Range. KURDAT =
430
Ambient Temperature Data Out-of-Range. KURDAT =
432
Friction Velocity Out-of-Range. KURDAT =
435
Surface Roughness Length Out-of-Range. KURDAT =
438
Convective Velocity Data Out-of-Range. KURDAT =
439
Monin-Obukhov Length Out-of-Range. KURDAT =
440
Calm Hour Identified in Meteorology Data File at
441
Vert Pot Temp Grad abv ZI set to min .005, KURDAT=
442
Vert Pot Temp Grad abv ZI exceeds 0.1 K/m, KURDAT=
450
Record Out of Sequence in Meteorological File at:
452
Missing hourly BACKGRND w/o BGSUB, KURDAT/Sector =
453
BGSUB for missing hourly BACKGRND, KURDAT/Sector =
C-14
-------
Message
Number
Error/Warning Message
454
Date/time Mismatch: BACKGRND File, KURDAT/Sector =
455
Date/time Mismatch: Hourly Emission File, KURD AT =
456
Date/time Mismatch on Surface & Profile. KURD AT =
457
Date/time Mismatch: OZONEFIL File, KURDAT/Sector =
458
03 SUB for missing hourly 03 value, KURDAT/Sector =
459
No Hrly 03 & No Sub; Use Full Conversion, KURD AT =
460
Missing Hour Identified in Meteor. Data File at
465
Number of Profile Levels Exceeds Max: MXPLVL =
470
Mixing Height Value is < or = 0.0. KURD AT =
474
WS RefHt invalid (<0.001); Not msg or elm: KURDAT=
475
WS reference height is higher than 100m. KURD AT =
476
# receptors within buoyant line source boundary:
477
Event receptor within buoyant line source for:
479
Potential temperature gradient is out-of-range:
480
Less than lyr for MULTYEAR, MAXDCONT or ANNUAL Ave
481
Data Remaining After End of Year. Number of Hours=
482
Too many years modeled for 24h-PM25 lh-N02 lh-S02:
483
User Start Date is Earlier Than Start of Met File
484
Restart Date < STARTEND date or start of Met File
485
MULTYR DataGap; Restart Date < STARTEND or MetFile
486
MULTYR Date Overlap; STARTEND Date < Restart Date
487
MULTYR Date Overlap; MetFile Start < Restart Date
488
First met HR.ne.l; ST results may not be valid
489
First met HR.ne.l; EV results may not be valid for
490
Problem reading SURFFILE date for EVENTS; MNDYHR =
491
MAXDCONT option requires 1st Hr of met data = 01;
492
SURFDATA YR .NE. 1st YR of file, adj to match file
C-15
-------
Message
Number
Error/Warning Message
493
SURFDATA YR must match 1st YR of file for DAYRANGE
494
Meander factor (FRAN) exceeds max @ YR MN DY ISRC:
495
Surface met file does not include enough variables
496
Total precipitation in SURFFILE is zero (0.0) with
497
Possible code ERROR!!! EVENT mismatch for EVENTID:
498
Possible code ERROR! MAXDCONT mismatch GRP/RNK/REC
499
PRIME plume rise error; check stack parameters for
500
Fatal Error Occurs Opening the Data File of
501
Dup Filename! Fatal Error Opening the Data File of
510
Fatal Error Occurs During Reading of the File of
520
Fatal Error Occurs During Writing to the File of
530
CAUTION! Met Station ID Mismatch with SURFFILE for
531
CAUTION! Met Station ID Missing from SURFFILE for
540
No RECTABLE/MAXTABLE/DAYTABLE for Average Period
550
File Unit/Name Conflict for the Output Option:
555
File Unit/Name conflict across options: GRP# AVE
560
User Specified File Unit .LE. 30 for OU Keyword:
565
Possible Conflict With Dynamically Allocated FUNIT
570
Problem Reading Temporary Event File for Event:
580
End of File Reached Trying to Read the File of
585
Output data file for INITFILE option was not found
590
The INITFILE filename matches a SAVEFILE filename
592
MAXIFILE includes data past start of MULTYEAR run
593
POSTFILE includes data past start of MULTYEAR run
C-16
-------
APPENDIX D. Description of file formats
D.l AI RM I T 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
FORMAT (2(2X,A8), 8X,' UA ID: ',A8,' SF ID: ',A8,' OS ID: ',A8, T85, 'VERSION:', A6 )
where latitude = latitude specified in Stage 1 for primary surface station
longitude = longitude specified in Stage 1 for primary surface station
UA identifier = station identifier for upper air data; usually the WBAN number used
to extract the data from an archive data set
SF identifier = station identifier for hourly surface observations; usually the
WBAN number used in extracting the data
OS identifier = site-specific identifier
Version date = AERMET version date; this date also appears in the banner on
each page of the summary reports
Note that the ' ??_ID: ' fields in the FORMAT statement above include two spaces before
the 2-character pathway ID and one space after the colon.
Data records:
READ() year, month, day, jday, hour, H, u*, w*, VPTG, Zic, Zim, L, z0 , B0 , r, Ws, Wd, zref,
temp, Ztemp, ipcode, pamt, rh, pres, ccvr, WSADJ
FORMAT (3(12,IX), 13,IX, 12,IX, F6.1,1X, 3(F6.3,1X), 2(F5.0,1X), F8.1,1X, F7.4,1X,
2(F6.2,1X), F7.2,1X, F5.0, 3(1X,F6.1), IX,15, 1X,F6.2, 2(1X, F6.0), IX, 15, IX,
A7)
where j day = lulian day
H = sensible heat flux (W/m2)
u - = surface friction velocity (m/s)
D-l
-------
w*
= convective velocity scale (m/s)
VPTG
= vertical potential temperature gradient above Zic (K/m)
Zic
= height of convectively-generated boundary layer (m)
Zim
= height of mechanically-generated boundary layer (m)
L
= Monin-Obukhov length (m)
Zo
= surface roughness length (m)
Bo
= Bowen ratio
r
= Albedo
ws
= reference wind speed (m/s)
wd
= reference wind direction (degrees)
Zref
= reference height for wind (m)
temp
= reference temperature (K)
Ztemp
= reference height for temperature (m)
ipcode
= precipitation type code (0=none, 1 l=liquid, 22=frozen,
99=missing)
pamt
= precipitation amount (mm/hr)
rh
= relative humidity (percent)
pres
= station pressure (mb)
ccvr
= cloud cover (tenths)
WSADJ=
wind speed adjustment and data source flag
When site-specific data are included in the data base, the definition of the reference height
wind speed and direction are subject to the following restrictions:
• the wind speed, Ws, must be greater than or equal to the site-specific data threshold
wind speed;
• the measurement height must be at or above 7*zo, where zo is the surface roughness
length;
• the height must be less than or equal to 100 meters;
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.
D-2
-------
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
READQ
year, month, day, hour, height, top, WDnn, WSnn, YYnn, 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=
WD nn
WS nn
TYnn
SAnn
SW nn
1, if this is the last (highest) level for this hour, or 0 otherwise
= wind direction at the current level (degrees)
= wind speed at the current level (m/s)
= temperature at the current level (°C)
= oe (degrees)
= ow (m/s)
D.2 Threshold violation files (MAXIFILE option)
The OU MAXIFILE card for the AERMOD model allows the user the option to generate a
file or files of threshold violations for specific source group and averaging period combinations.
The file consists of several header records, each identified with an asterisk (*) in column one. The
header information includes the model name and version number, the first line of the title
information for the run, the list of modeling option keywords applicable to the results, the averaging
period and source group included in the file, and the threshold value. Any value equal to or
exceeding the threshold value will be included in the file. The header also includes the format used
for writing the data records, and column headers for the variables included in the file. The variables
provided on each data record include the averaging period, the source group ID, the date
(YYMMDDHH) for the end of averaging period, the X and Y coordinates of the receptor location,
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:
D-3
-------
*
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
D.3 Postprocessor files (POSTFILE option)
The OU POSTFILE card for the AERMOD model allows the user the option of creating
output files of concurrent concentration values suitable for postprocessing. The model offers two
options for the type of file generated - one is an unformatted file, and the other is a formatted file of
X, Y, CONC values suitable for inputting to plotting programs.
The unformatted POSTFILE option generates a separate unformatted data record of
concurrent values for each averaging period and source group specified. The averaging period and
source group combinations may be written to separate files, or combined into a single file. Each
record begins with the date variable for the end of the averaging period (an integer variable of the
form YYMMDDHH), the averaging period (e.g., an integer value of 3 for 3-hour averages), and the
source group ID (eight characters). Following these three header variables, the record includes the
concentration values for each receptor location, in the order in which the receptors are defined on
the RE pathway. The results are output to the unformatted file or files as they are calculated by the
model.
The formatted plot file option for the POSTFILE keyword includes several lines of header
information, each identified with an asterisk (*) in column one. The header information includes
the model 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
D-4
-------
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 (IX
,F8.2),2X
, A6,
2X,A8
,2X,18.8,2X
,A8)
*
X
Y AVERAGE CONC
ZELEV
ZHILL
ZFLAG
AVE
GRP
NUM HRS
NET ID
30 .38843
172.34136
0 .21576
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
60.77686
344.68271
0 .53162
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
86 . 82409
492.40388
0.85993
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
173 . 64818
984.80775
1.39778
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
59 . 85353
164.44621
0.20861
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
119.70705
328.89242
0.67388
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
171. 01007
469.84631
1.27452
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
342 . 02014
939.69262
2.45702
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
87 .50000
151.55445
0 .20576
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
175 .00000
303.10889
0 . 64322
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
250 .00000
433.01270
1.20422
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
500 .00000
866.02540
2.28880
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
112.48783
134 . 05778
0.20172
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
224.97566
268.11556
0.48027
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
321.39380
383 .02222
0.76067
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
642.787 61
766.04444
1.19405
0
.00
0 .
00
0
00
PERIOD
ALL
00000096
POL1
D.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
D-5
-------
date variable for the end of the averaging period (in the form of YYMMDDHH). The PERIOD
average PLOTFILE uses the same format for the data records as the PERIOD average formatted
POSTFILE shown in the previous section. The following example from a plot file for high second
highest 24-hour averages identifies the contents of the PLOTFILE:
*
AERMOD ( 15181):
A Simple Example Problem
for the AERMOD-PRIME
Model
06/09/16
*
AERMET ( 15181):
17 : 07
58
*
MODELING OPTIONS
USED: NonDFAULT CONC
FLAT
RURAL
*
PLOT FILE OF HIGH 2ND HIGH 24-HR VALUES
FOR SOURCE
GROUP: ALL
*
FOR A TOTAL OF 144 RECEPTORS.
*
FORMAT:
(3 (IX,F13.5),3(IX,F8.2),3X
>
>
CO
,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
1
o
o
o
0 .00
24-HR
ALL
2ND
POL1
88030324
60.77686
344.68271 0.75187
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
POL1
88030124
86 . 82409
492.40388 1.18649
o
o
o
o
o
o
o
o
o
24-HR
ALL
2ND
POL1
88030124
173 . 64818
984.80775 1.19837
0 .00
o
o
o
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.
D.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
D-6
-------
3
CUTOFF, RDUM1, ..., RDUM9
where: TITLE = First line of title (80 characters)
IYEAR = Year of simulation NUMGRP = No. of source groups
NUMREC = Total no. of receptors
NUMPER = No. of averaging periods (e.g., number of hours in the year)
ITAB = 1 for polar grid; 2 for Cartesian grid; 0 for discrete receptors or
mixed grids
NXTOX = No. of x-coordinates (or distances) in receptor network
NYTOX = No. of y-coordinates (or directions) in receptor network
IDUM1, 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)
D.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
D-7
-------
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) :
-j
o
CO
*
MODELING OPTIONS USED: NonDFAULT CONC FLAT RURAL
*
RANK-FILE OF UP TO 40 TOP 3-HR VALUES FOR 1 SOURCE
GROUPS
*
INCLUDES OVERALL MAXIMUM VALUES WITH DUPLICATE DATA PERIODS REMOVED
*
FORMAT: (IX,I 6,IX,F13.5,IX,I 8.8,2(IX,F13.5),3(IX,F7.2) ,2X,
A8 )
RANK
AVERAGE CONC DATE X Y ZELEV
ZHILL
ZFLAG
GRP
1
329.96009 88030112 433.01270 -250.00000 0.00
1
o
o
o
o
o
o
ALL
2
278.47891 88030115 469.84631 -171.01007 0.00
o
o
o
o
o
o
ALL
3
124.30430 88030118 433.01270 -250.00000 0.00
o
o
o
o
o
o
ALL
D.7 Arc-maximum values for evaluation (EVALFILE 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:
Record 1: Source ID (eight characters)
Date variable (YYMMDDHH)
Arc ID (eight characters)
Arc maximum P/Q
Emission rate for arc maximum (including unit conversions)
Crosswind integrated concentration based on true centerline concentration
Normalized non-dimensional crosswind integrated concentration
Record 2: Downwind distance corresponding to arc maximum (m)
Effective wind speed corresponding to arc maximum (m/s)
Effective Fv corresponding to arc maximum (m/s)
D-8
-------
Effective Fw corresponding to arc maximum (m/s)
Fy corresponding to arc maximum (m)
Effective plume height corresponding to arc maximum (m)
Record 3: Monin-Obukhov length for current hour (m)
Mixing height for current hour (m)
Surface friction velocity for current hour (m/s)
Convective velocity scale for current hour if unstable (m/s), or
Fz for current hour if stable
(Buoyancy flux for current hour
(m4/s3) Momentum flux for
current hour (m4/s2)
Record 4: Bowen ratio for current hour
Plume penetration factor for current hour
Centerline P/Q for direct plume
Centerline P/Q for indirect plume
Centerline P/Q for penetrated plume
Nondimensional downwind distance
Record 5: Plume height/mixing height ratio
Non-dimensional buoyancy flux
Source release height (m)
Arc centerline P/Q
Developmental option settings place holder (string of 10 zeroes)
Flow vector for current hour (degrees)
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),
& OBULEN, 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(IX,A8,IX,18,IX,A8,4(1X,G12.6),
& / , 9X, 6 (IX, G12 . 4 ) , / , 9X, 6 (IX, G12 . 4 ) ,
& /,9X,6(IX,G12.4),/,9X,4(1X,G12.4),IX,'0000000000',
& 1X,G12.4,1X,G12.4)
D-9
-------
D.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 CONC
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 CONC
ZELEV
ZHILL
ZFLAG
GRP
NHRS
SEAS
HOUR
NET ID
30 . 38843
172.34136
34 .14568783
0
00
0.
00
0
. 00
ALL
65
1
1
POL1
60 .77686
344 . 68271
39.19676801
0
00
0.
00
0
. 00
ALL
65
1
1
POL1
86.82409
492 .40388
34 . 59785413
0
00
0.
00
0
. 00
ALL
65
1
1
POL1
173.64818
984 .80775
16.14253303
0
00
0.
00
0
. 00
ALL
65
1
1
POL1
59.85353
164 .44621
32 . 93762092
0
00
0.
00
0
. 00
ALL
65
1
1
POL1
119.70705
328 .89242
41 . 97750583
0
00
0.
00
0
. 00
ALL
65
1
1
POL1
D.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,
D-10
-------
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.
D-ll
-------
*
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,
A.5, 5X,
A8 ,
2X,
3 (F13
5,2X:))
*
X
Y
AVERAGE CONC
ZELEV
ZHILL
Z FLAG
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
4 9757
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
*
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
Z FLAG
AVE
GRP
RANK
NET
ID
CONT STACK1
CONT STACK2
CONT
ALL
200
00000
0.
00000
7 . 91782
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
500
00000
0.
00000
22.53064
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
1000
00000
0.
00000
24.26451
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
3000
00000
0.
00000
8.10584
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
0
00000
-200.
00000
16.96505
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
0
00000
-500.
00000
43.25276
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
14 .
36197
28
8 9079
43.
25276
0
00000
1000.
00000
43.82672
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
10.
92254
32
90417
43.
82672
0
00000
3000.
00000
17.32480
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
-200
00000
-0.
00000
6. 77421
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
-500
00000
-0.
00000
11.56687
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
-1000
00000
-0.
00000
9. 7222 9
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
-3000
00000
-0.
00000
8.03098
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
-0
00000
200.
00000
51.19765
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
51.
19763
0
00002
51.
19765
-0
00000
500.
00000
59. 15581
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
57 .
67153
1
48428
59.
15581
-0
00000
1000.
00000
41.49519
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
18 .
49276
23
00243
41.
49519
-0
00000
3000.
00000
23.24160
0
00
0
.00
0
00
24-HR
ALL
2ND
POL1
0.
00000
0
00000
0.
00000
D-12
-------
D.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.
*
AERMOD
( 15181):
AERMOD OLM/OLMGROUP ALL
Test Case,
with BACKGROUND
07/30/15
*
AERMET
( 13350) :
13
50 : 48
*
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,
13,
2X, 18
.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
35 .00
0
.00
1-HR
ALL
1
~13"
99010113
POL1
300
00000
0
00000
50.00159
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
1000
00000
0
00000
50.20117
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
3000
00000
0
00000
50.12314
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
0
00000
-100
00000
50.00000
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
0
00000
-300
00000
50.00259
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
0
00000
1000
00000
50.22100
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
0
00000
3000
00000
68.29389
35 . 00
35 .00
0
.00
1-HR
ALL
1
7
99010107
POL1
-100
00000
-0
00000
50.00000
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
-300
00000
-0
00000
50.00258
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
-1000
00000
-0
00000
50.2007 9
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
-3000
00000
-0
00000
50.12262
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
-0
00000
100
00000
50 . 00000
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
-0
00000
300
00000
50.00159
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
-0
00000
1000
00000
50.20117
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
-0
00000
3000
00000
50.12314
35 . 00
35 .00
0
.00
1-HR
ALL
1
13
99010113
POL1
100
00000
0
00000
50 . 00000
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
300
00000
0
00000
50 . 00001
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
1000
00000
0
00000
50 . 00008
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
3000
00000
0
00000
50.00280
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
0
00000
-100
00000
50.00000
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
0
00000
-300
00000
50 . 00001
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
0
00000
1000
00000
50.00009
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
0
00000
3000
00000
50.00285
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
-100
00000
-0
00000
50.00000
35 . 00
35 .00
0
.00
1-HR
ALL
2
13
99010213
POL1
D-13
-------
D.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.
D-14
-------
*
AERMOD
( 15181)
: AERMOD OLM/OLMGROUP ALL
Test Case,
with BACKGROUND
07/30/15
*
AERMET
( 13350)
13
50 : 48
*
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,
13,
2X,18.
8,2X,A8)
*
X
Y
AVERAGE CONC
ZELEV
ZHILL
ZFLAG
RANK
GRP
JDAY
HR
DATE
NET ID
100
00000
0
00000
76.74205
35 . 00
35 .00
0
00
4TH
ALL
236
~1~4
99082414
POL1
300
00000
0
00000
174.62886
35 . 00
35 .00
0
00
4TH
ALL
136
14
99051614
POL1
1000
00000
0
00000
146.90191
35 . 00
35 .00
0
00
4TH
ALL
147
14
99052714
POL1
3000
00000
0
00000
91.97719
35 . 00
35 .00
0
00
4TH
ALL
104
13
99041413
POL1
0
00000
-100
00000
99.52361
35 . 00
35 .00
0
00
4TH
ALL
252
15
99090915
POL1
0
00000
-300
00000
171.76063
35 . 00
35 .00
0
00
4TH
ALL
107
11
99041711
POL1
0
00000
-1000
00000
152.93801
35 . 00
35 .00
0
00
4TH
ALL
65
13
99030613
POL1
0
00000
-3000
00000
111.73167
35 . 00
35 .00
0
00
4TH
ALL
293
16
99102016
POL1
-100
00000
-0
00000
91.59388
35 . 00
35 .00
0
00
4TH
ALL
62
14
99030314
POL1
-300
00000
-0
00000
154.65265
35 . 00
35 .00
0
00
4TH
ALL
62
15
99030315
POL1
-1000
00000
-0
00000
131.73020
35 . 00
35 .00
0
00
4TH
ALL
360
13
99122613
POL1
-3000
00000
-0
00000
86.11262
35 . 00
35 .00
0
00
4TH
ALL
312
16
99110816
POL1
-0
00000
100
00000
80.06381
35 . 00
35 .00
0
00
4TH
ALL
203
8
99072208
POL1
-0
00000
300
00000
166.86210
35 . 00
35 .00
0
00
4TH
ALL
139
16
99051916
POL1
-0
00000
1000
00000
156.54681
35 . 00
35 .00
0
00
4TH
ALL
110
15
99042015
POL1
-0
00000
3000
00000
102.04635
35 . 00
35 .00
0
00
4TH
ALL
23
15
99012315
POL1
100
00000
0
00000
65.46639
35 . 00
35 .00
0
00
8TH
ALL
250
17
99090717
POL1
300
00000
0
00000
164.95260
35 . 00
35 .00
0
00
8TH
ALL
147
14
99052714
POL1
1000
00000
0
00000
137.02622
35 . 00
35 .00
0
00
8TH
ALL
145
16
99052516
POL1
3000
00000
0
00000
79.71649
35 . 00
35 .00
0
00
8TH
ALL
102
19
99041219
POL1
0
00000
-100
00000
90 .20572
35 . 00
35 .00
0
00
8TH
ALL
175
9
99062409
POL1
0
00000
-300
00000
167.99537
35 . 00
35 .00
0
00
8TH
ALL
81
14
99032214
POL1
0
00000
-1000
00000
147.76997
35 . 00
35 .00
0
00
8TH
ALL
107
18
99041718
POL1
0
00000
-3000
00000
108.50074
35 . 00
35 .00
0
00
8TH
ALL
272
17
99092917
POL1
-100
00000
-0
00000
86.21569
35 . 00
35 .00
0
00
8TH
ALL
251
12
99090812
POL1
-300
00000
-0
00000
147.43347
35 . 00
35 .00
0
00
8TH
ALL
63
13
99030413
POL1
-1000
00000
-0
00000
113.23071
35 . 00
35 .00
0
00
8TH
ALL
144
8
99052408
POL1
-3000
00000
-0
00000
80.46493
35 . 00
35 .00
0
00
8TH
ALL
251
12
99090812
POL1
-0
00000
100
00000
62.77470
35 . 00
35 .00
0
00
8TH
ALL
213
15
99080115
POL1
-0
00000
300
00000
164.12251
35 . 00
35 .00
0
00
8TH
ALL
212
12
99073112
POL1
-0
00000
1000
00000
147.60345
35 . 00
35 .00
0
00
8TH
ALL
84
15
99032515
POL1
-0
00000
3000
00000
92 .37244
35 . 00
35 .00
0
00
8TH
ALL
264
19
99092119
POL1
100
00000
0
00000
63 . 04954
35 . 00
35 .00
0
00
12TH
ALL
213
15
99080115
POL1
300
00000
0
00000
158.05318
35 . 00
35 .00
0
00
12TH
ALL
182
15
99070115
POL1
1000
00000
0
00000
132.45210
35 . 00
35 .00
0
00
12TH
ALL
123
15
99050315
POL1
3000
00000
0
00000
75.06520
35 . 00
35 .00
0
00
12TH
ALL
56
14
99022514
POL1
0
00000
-100
00000
81.79820
35 . 00
35 .00
0
00
12TH
ALL
230
14
99081814
POL1
0
00000
-300
00000
163.58691
35 . 00
35 .00
0
00
12TH
ALL
150
13
99053013
POL1
0
00000
-1000
00000
143.66477
35 . 00
35 .00
0
00
12TH
ALL
63
11
99030411
POL1
0
00000
-3000
00000
103.84510
35 . 00
35 .00
0
00
12TH
ALL
359
10
99122510
POL1
-100
00000
-0
00000
66.87945
35 . 00
35 .00
0
00
12TH
ALL
210
13
99072913
POL1
-300
00000
-0
00000
134.34226
35 . 00
35 .00
0
00
12TH
ALL
192
11
99071111
POL1
-1000
00000
-0
00000
112.42027
35 . 00
35 .00
0
00
12TH
ALL
90
10
99033110
POL1
-3000
00000
-0
00000
69.14045
35 . 00
35 .00
0
00
12TH
ALL
70
12
99031112
POL1
-0
00000
100
00000
57.29793
35 . 00
35 .00
0
00
12TH
ALL
80
13
99032113
POL1
-0
00000
300
00000
161.46688
35 . 00
35 .00
0
00
12TH
ALL
46
12
99021512
POL1
-0
00000
1000
00000
141.04997
35 . 00
35 .00
0
00
12TH
ALL
165
14
99061414
POL1
-0
00000
3000
00000
89.51271
35 . 00
35 .00
0
00
12TH
ALL
109
19
99041919
POL1
100
00000
0
00000
51.04396
35 . 00
35 .00
0
00
5 0TH
ALL
132
13
99051213
POL1
300
00000
0
00000
126.14782
35 . 00
35 .00
0
00
5 0TH
ALL
175
15
99062415
POL1
1000
00000
0
00000
105.50261
35 . 00
35 .00
0
00
5 0TH
ALL
267
17
99092417
POL1
3000
00000
0
00000
56.90880
35 . 00
35 .00
0
00
5 0TH
ALL
236
14
99082414
POL1
0
00000
-100
00000
56.69467
35 . 00
35 .00
0
00
5 0TH
ALL
287
13
99101413
POL1
0
00000
-300
00000
137.18380
35 . 00
35 .00
0
00
5 0TH
ALL
204
13
99072313
POL1
0
00000
-1000
00000
120.65746
35 . 00
35 .00
0
00
5 0TH
ALL
268
13
99092513
POL1
0
00000
-3000
00000
85.42463
35 . 00
35 .00
0
00
5 0TH
ALL
156
1
99060501
POL1
-100
00000
-0
00000
51.20790
35 . 00
35 .00
0
00
5 0TH
ALL
169
14
99061814
POL1
-300
00000
-0
00000
12. 61516
35 . 00
35 .00
0
00
5 0TH
ALL
32
13
99020113
POL1
-1000
00000
-0
00000
12.1447 6
35 . 00
35 .00
0
00
5 0TH
ALL
270
10
99092710
POL1
-3000
00000
-0
00000
52.15505
35 . 00
35 .00
0
00
5 0TH
ALL
265
13
99092213
POL1
-0
00000
100
00000
50.39602
35 . 00
35 .00
0
00
5 0TH
ALL
180
14
99062914
POL1
-0
00000
300
00000
125.74471
35 . 00
35 .00
0
00
5 0TH
ALL
247
14
99090414
POL1
-0
00000
1000
00000
117.67662
35 . 00
35 .00
0
00
5 0TH
ALL
143
1
99052301
POL1
-0
00000
3000
00000
70 . 84420
35 . 00
35 .00
0
00
5 0TH
ALL
127
2
99050702
POL1
D-15
-------
APPENDIX E. Quick reference for AERMOD
SUMMARY OF CONTROL PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
TITLEONE
Titlel
TITLETWO
Title2
MODELOPT
DFAULT ALPHA BETA CONC AREADPLT FLAT NOSTD NOCHKD NOWARN SCREEN SCIM PVMRM
DEPOS and/or or or OLM
DDEP ELEV WARNCHKD or ARM2
and/or
WDEP
FASTALL DRYDPLT WETDPLT NOURBTRAN VECTORWS
PSDCREDIT
or or or
FASTAREA NODRYDPLT NOWETDPLT
AVERTIME
Timel Time2 . . . TimeN MONTH PERIOD
or
ANNUAL
URBANOPT
UrbanID Urbpop (Urbname) (UrbRoughness)
or
Urbpop (Urbname) (UrbRoughness)
For multiple urban areas]
For single urban areas]
POLLUTID
Pollut (H1H or H2H or INC)
HALFLIFE
Haflif
DCAYCOEF
Decay
GASDEPDF
React F Seas2 F Seas5 (Refpoll)
GASDEPVD
Uservd
GDLANUSE
Seel Sec2 ... Sec36
GDSEASON
Jan Feb ... Dec
LOW WIND
SVmin (WSmin)
or
SVmin WSmin (FRANmax)
AWMADWNW
AWMAUEFF and/or [AWMAUTURB with/without STREAMLINE]
ORD DWNW
ORDUEFF and/or ORDTURB and/or ORDCAV
N02EQUIL
N02Equil
N02STACK
N02Ratio
ARMRAT10
ARM2 Min ARM2 Max
[for ARM2 Option]
03SECT0R
StartSectl StartSect2 . . . StartSectN, where N is < 6
OZONEFIL
03FileName (03Units) (03Format)
or
SECTn 03FileName (03Units) (03Format)
[without 03SECT0Rs]
[with 03SECT0Rs]
OZONEVAL
03Value (03Units )
or
SECTn 03Yalue (03Units)
[without 03SECT0Rs]
[with 03SECT0R]
03VALUES
03Flag 03values(i), i=l,n)
or
SECTn 03Flag 03values(i), i=l,n)
[without 03SECT0Rs]
[with 03SECT0Rs]
E-l
-------
Keyword
Parameters
OZONUNIT
(OzoneUnits)
FLAGPOLE
(Flagdf)
RUNORNOT
RUN or NOT
EVENTFIL
(Evfile) (Evopt)
SAVEFILE
(Savfil) (Dayinc) (Savfl2)
INITFILE
(Inifil)
MULTYEAR
(H6H) Savfil (Inifil)
DEBUGOPT
MODEL (Dbgfil) and/or METEOR (Dbmfil) and/or PRIME (Prmfil) and/or
AWMADW (AwmaDWfil) and/or
DEPOS and/or
[AREA (AreaDbFil) or LINE (LineDbFil)] and/or
[PVMRM (Dbpvfil) or OLM (OLMfil) or ARM2 (ARM2fil)]
ERRORFIL
(Errfil)
E-2
-------
SUMMARY OF SOURCE PATHWAY KEYWORDS AND PARAMETERS
Keyword
ELEVUNIT
Parameters
METERS or FEET
LOCATION
SrcID Srctyp Xs Ys (Zs)
or
(FLAT)
SrcID Srctyp Xsl Ysl Xs2 Ys2 (Zs)
or
(FLAT)
SrcID Srctyp Xsl Ysl Zsl Xs2 Ys2 Zs2 (Zs)
or
(FLAT)
[All except LINE,
BUOYLINE, RLINE, and RLINEXT sources]
[for ^ FLAT & ELEV' option]
[LINE, RLINE, or BUOYLINE source]
[for ^ FLAT & ELEV' option]
[for RLINEXT source]
[for ^ FLAT & ELEV' option]
RLEMCONV
No parameters
SRCPARAM
Ptemis
Stkhgt
Stktmp
Stkvel
Stkdia
[POINT,POINTCAP,
POINTHOR
source]
Vlemis
Relhgt
Syinit
Szinit
[VOLUME
source]
Aremis
Relhgt
Xinit
(Yinit)
(Angle)
(Szinit)
[AREA
source]
Aremis
Relhgt
Nverts
(Szinit)
[AREAPOLY
source]
Aremis
Relhgt
Radius
(Nverts)
( Szinit)
[AREACIRC
source]
Opemis
Relhgt
Xinit
Yinit
Pitvol
(Angle)
[OPENPIT
source]
Lnemis
Relhgt
Width i
; Szinit)
[LINE
or RLINE
source]
BLemis
Relhgt
[BUOYLINE
source]
Qemis
DCL
Szinit
Width
[RLINEXT
source]
BLPINPUT
blavgblen blavgbhgt blavgbwid blavglwid blavgbsep blavgfprm
BUILDHGT
SrcID (or SrcRange) Dsbh(i), i=l,3
BUILDLEN
SrcID (or SrcRange) Dsbl(i
i=l,36
BUILDWID
SrcID (or SrcRange) Dsbw(i
i=l,36
SrcID (or SrcRange) Xbadj (i
i=l,36
SrcID (or SrcRange) Ybadj(i), i=l,3
AREAVERT
SrcID Xv(1) Yv(1) Xv(2) Yv(2)
Xv(i) Yv(i)
RBARRIER
SrcID Htwall DCLwall
RDEPRESS
SrcID Depth Wtop Wbottom
URBANSRC
UrbanID SrcID's and/or SrcRng's
or
SrcID's and/or SrcRng's
[For multiple urban areas]
[For single urban areas]
EMISFACT
SrcID (or SrcRange) Qflag Qfact(i), i=l,n
EMISUNIT
Emifac Emilbl Outlbl
CONCUNIT
Emifac Emilbl Conlbl
DEPOUNIT
Emifac Emilbl Deplbl
PARTDIAM
SrcID (or SrcRange) Pdiam(i), i=l,Npd
MASSFRAX
SrcID (or SrcRange) Phi(i), i=l,Npd
PARTDENS
SrcID (or SrcRange) Pdens(i), i=l,Npd
METHOD 2
SrcID (or SrcRange) FineMassFraction Dmm
GASDEPOS
SrcID (or SrcRange) Da Dw rcl Henry
N02RATI0
SrcID (or SrcRange) N02Ratio
HOUREMIS
Emifil SrcID's SrcRange's
BGSECTOR
StartSectl StartSect2
StartSectN, where N is <
E-3
-------
Keyword
Parameters
BACKGRND
BGflag BGvalue(i), i = l,n
and/or
HOURLY BGfilnam (BGformat)
or
SECTn BGflag BGvalue(i), i=l,n
and/or
SECTn HOURLY BGfilnam (BGformat)
[without BGSECTORs]
[with BGSECTORs]
BACKUNIT
BGunits
INCLUDED
Incfil
OLMGROUP
OLMGrpID SrcID's SrcRange
s
PSDGROUP
PSDGrpID SrcID's SrcRange
s
SRCGROUP
SrcGrpID SrcID's SrcRange
s
SUMMARY OF RECEPTOR PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
ELEVUNIT
METERS
or FEET
GRIDCART
Netid
STA
XYINC
Xinit
Xnum
Xdelta
Yinit
Ynum Ydelta,
or
XPNTS
Gridxl
Gridx2
Gridx3
GridxN, and
YPNTS
Gridyl
Gridy2
Gridy3
GridyN
ELEV
Row
Zelevl
Zelev2
Zelev3
. . . ZelevN
HILL
Row
Zhilll
Zhill2
Zhill3
ZhillN
FLAG
Row
Zflagl
Zflag2
Zflag3
. . . ZflagN
END
GRIDPOLR
Netid
STA
ORIG
Xinit
Yinit,
or
ORIG
Srcid
DIST
Ringl
Ring2
Ring3
RingN
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
DISCCART
Xcoord
Ycoord
( Zelev
Zhill
) (Zflag
)
DISCPOLR
Srcid
Dist Direct
Zelev
Zhill) (
Zflag)
EVALCART
Xcoord
Ycoord
Zelev
Zhill
Zflag Arcid
Mame)
INCLUDED
RecIncFile
E-4
-------
SUMMARY OF METEOROLOGY PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
SURFFILE
Sfcfil
PROFFILE
Profil
SURFDATA
Stanum
Year (Name)
(Xcoord
Ycoord)
UAIRDATA
Stanum
Year (Name)
(Xcoord
Ycoord)
SITEDATA
Stanum
Year (Name)
(Xcoord
Ycoord)
PROFBASE
BaseElev (Units)
STARTEND
Strtyr
Strtmn Strtdy
( Strthr)
Endyr Endmn Enddy (Endhr)
DAYRANGE
Rangel
Range2 Range3 ...
RangeN
SCIMBYHR
NRegStart NReglnt
SfcFilnam PflFilnam)
WDROTATE
Rotang
WINDCATS
Wsl Ws2 Ws3 Ws4 Ws5
SUMMARY OF EVENT PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
EYENTPER
Evname Aveper Grpid Date
EVENTLOC
Evname XR= Xr YR= Yr (Zelev Zhill) (Zflag)
or
RNG= Rng DIR= Dir (Zelev Zhill) (Zflag)
INCLUDED
EventlncFile
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).
E-5
-------
SUMMARY OF OUTPUT PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
RECTABLE
Aveper
Aveper
Aveper
FIRST
1ST
1
SECOND
2ND
2
SIXTH
6TH
6 .
. . TENTH and/or
. . 10TH and/or
10 . . . N ... 999
MAXTABLE
Aveper
Maxnum
DAYTABLE
Avperl
Avper2
Avper3
MAXIFILE
Aveper
GrpID
Thresh
Filnam
(Funit)
POSTFILE
Aveper
GrpID
Format
Filnam
(Funit)
PLOTFILE
Aveper
Aveper
GrpID
GrpID
Hivalu
Filnam
Filnam
(Funit)
(Funit)
[Short-Term values]
[PERIOD or ANNUAL averages]
TOXXFILE
Aveper
Cutoff
Filnam
(Funit
)
RANKFILE
Aveper
Hinum
Filnam
(Funit)
EVALFILE
SrcID
Filnam
(Funit)
SEASONHR
GrpID
FileName
(FileUnit)
MAXDAILY
GrpID
FileName
(FileUnit)
MXDYBYYR
GrpID
FileName
(FileUnit)
MAXDCONT
GrpID
or
GrpID
UpperRank LowerRank FileName
(FileUnit)
UpperRank THRESH ThreshValue
FileName (FileUnit)
SUMMFILE
SummFileName
FILEFORM
EXP or FIX
NOHEADER
FileTypel FileType2
FileType3
FileTypeW
ALL
EVENTOUT
SOCONT
or DETAIL
[EVENT Only]
E-6
-------
APPENDIX F. Evaluation of modified urban option
The urban option in 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 associated
with the urban nighttime heat island effect was ignored once the boundary layer turned
convective. This could result in an unrealistic drop in the mixed layer height during early
morning hours for urban applications, which could contribute to unrealistically high
concentrations for low-level plumes. This effect was observed in the application of AERMOD
for the Risk and Exposure Assessment (REA) in support of the NO2 NAAQS review in
association with mobile source emissions (EPA, 2008). Beginning with version 11059 the urban
option in AERMOD continues application of the urban boundary layer approach for urban
sources until the daytime convective mixing height exceeds the urban nighttime mixing height,
based on the user-specified population (EPA, 2018a)). This revision to AERMOD will generally
reduce concentrations during the early morning transition to convective conditions for low-level
urban sources, but may increase daytime concentrations for elevated urban sources.
The modified implementation of the urban option was evaluated using data from the 1985
Indianapolis SF6 urban field study (Perry, et al, 2005), and model-to-monitor comparisons at four
ambient monitors for 2002 from the Atlanta NO2 REA (EPA, 2008). The Indianapolis study
involved an elevated buoyant release and the Atlanta REA study involved mostly low-level
mobile source emissions. Results from the Indianapolis study are presented in the form of Q-Q
plots of ranked 1-hour modeled vs. observed concentrations, unpaired in time and space. Figure
E-l shows model performance for all stabilities and Figure E-2 shows model performance for
convective conditions only. The revised urban option does not affect results under stable
conditions. Results from the Atlanta NO2 REA are also presented in the form of Q-Q plots of
1-hour ranked modeled vs. observed concentrations, unpaired in time, for each of the four
ambient NO2 monitors, shown in Figures E-3 through E-6. Both of these evaluations show
improved model performance with the modified urban option in AERMOD.
F-l
-------
INDIANAPOLIS SF6 1-HR Q-Q PLOT (CONC) - All Stabilities
10
Q
LU
i—
o
Q
LU
0£
Q.
0.1
0.01
AERMOD v11059
y' f
jjp
r,--''' AERMOD
V09292
0.01
0.1
10
OBSERVED
Figure E-l. 1-hour Q-Q Plot for Indianapolis SF6 Study for All Stabilities
INDIANAPOLIS SF6 1-HR Q-Q CBL (CONC) - Convective Conditions
10
Q
LU
O
G
OL
CL
0.1
0.1 1 10
OBSERVED
1-hour Q-Q Plot for Indianapolis SF6 Study for Convective Conditions
F-2
Figure E-2.
AERMOD v11059
AERMOD
V09292
-------
Atlanta N02 Study - 1-hr QQ Plot for Monitor 0002 - Urban Transition Adjustment
200
O 100
100
Observed Cone (ppb)
~ 0002 - New
¦ 0002 - Old
200
200 n
150
O 100
Figure E-3. 1-hour Q-Q Plot for Atlanta NO2 Study for Monitor 0002
Atlanta N02 Study - 1-hr QQ Plot for Monitor 3001 - Urban Transition Adjustment
/
¦/
*
u
/
f /
¦ ~ /
J ~
¦ * /
50
100
Observed Cone (ppb)
150
~ 3001 - New
¦ 3001 - Old
200
Figure E-4. 1-hour Q-Q Plot for Atlanta NO2 Study for Monitor 3001
F-3
-------
Atlanta N02 Study - 1-hr QQ Plot for Monitor 0048 - Urban Transition Adjustment
/
¦
/
¦ y/
1
/'
~
»~
"""
0 50 100 150 200
Observed Cone (ppb)
Figure E-5. 1-hour Q-Q Plot for Atlanta NO2 Study for Monitor 0048
Atlanta N02 Study - 1-hr QQ Plot for Monitor JST - Urban Transition Adjustment
200
150
~ JST - New
¦ JST - Old
O 100
50
0
0
50
100
150
200
Observed Cone (ppb)
Figure E-6. 1-hour Q-Q Plot for Atlanta NO2 Study for Monitor JST
F-4
-------
APPENDIX G. Overview of AERMOD revisions
1. The first set of revisions, first introduced with version 03273 of AERMOD, includes dry and
wet deposition algorithms for both particulate and gaseous emissions (see Sections 3.2.2.6, 0,
and 3.3.3 for more details), and the OPENPIT source option, originally incorporated in the
ISCST3 model (EPA, 1995a), for modeling particulate emissions from open pit (below grade)
sources, such as surface coal mines and rock quarries;
2. The second set of revisions, first introduced with version 04300 of AERMOD, includes two
non-DFAULT options for modeling conversion of NO to NO2: 1) the Plume Volume Molar
Ratio Method (PVMRM) (Hanrahan, 1999a and 1999b); and 2) the Ozone Limiting Method
(OLM);
3. The third set of revisions, first introduced with version 06341 of AERMOD, includes the
following (additional information is provided in Model Change Bulletin (MCB) # 1 provided
on the SCRAM AERMOD webpage):
a. A new "BETA" option on the CO MODELOPT card to allow for new features to be added
to AERMOD that are still in BETA-test status;
b. A BETA option for incorporating NO/NO2 chemistry for NO2 increment consumption
calculations with PSD credits using the PVMRM option;
c. BETA options for capped and horizontal stack releases;
d. An option to specify an initial default in-stack NO2/NOX ratio for the PVMRM and OLM
options;
e. New options for varying emissions by month, hour-of-day, and day-of-week (MHRDOW
and MHRDOW7);
f. An option to allow multiple urban areas to be defined in a single model run;
g. Updated processing to support modeling demonstrations for the National Ambient Air
Quality Standards (NAAQS) for PM, including the 24-hour average design value for PM-
2.5 impacts; and
h. Use of dynamic array allocation for AREAPOLY sources to allocate array limits for the
maximum number of vertices at model runtime, replacing the previous fixed array limit of
20 vertices.
4. The fourth set of revisions, first introduced with version 09292 of AERMOD, includes the
following (additional information is provided in MCB#3 provided on the SCRAM AERMOD
webpage):
a. New options for varying emissions by hour-of-day and day-of-week (HRDOW and
HRDOW7);
b. Modification of the regulatory default option (DFAULT) on the CO MODELOPT card to
impose a restriction on the urban roughness length parameter to be 1 meter for regulatory
default applications. Any value other than 1 meter for the urban roughness length option
on the CO URBANOPT card will be treated as a non-DFAULT option;
G-l
-------
c. Removal of the TOXICS option from the MODELOPT keyword. Options formerly
associated with the TOXICS option are still considered non-DFAULT options within
AERMOD. The area source optimizations formerly associated with the TOXICS option
are now selected using the new non-DFAULT FASTAREA option on the MODELOPT
keyword;
d. A new non-DFAULT option for optimizing runtime for POINT and VOLUME sources
based on an alternative implementation of the horizontal meander algorithm has been
incorporated through the FASTALL option on the MODELOPT keyword. The FASTALL
option also includes the FASTAREA optimizations if area sources are included in the
model inputs;
e. The option for specifying hourly emissions from a separate file through the HOUREMIS
keyword has been enhanced to allow the use of hourly varying release heights and initial
dispersion coefficients for VOLUME and AREA/AREAPOLY/AREACIRC sources;
f. The OPENPIT source option has been modified to allow for use of the OPENPIT source
for gaseous (non-particulate) emissions and with METHOD2 for particulate emissions;
g. The non-DFAULT option of FLAT terrain can now be specified on a source-by-source
basis, allowing both FLAT and ELEV terrain treatments within the same model run (see
Section 4.1 of the AERMOD Implementation Guide regarding modeling of sources with
terrain-following plumes in sloped terrain);
h. A non-DFAULT option for a user-specified dry deposition velocity for gaseous emissions
has been added under the GASDEPVD keyword on the CO pathway;
i. A new SUMMFILE option has been included on the OU pathway to output the summary
of high ranked values to a separate file;
j. An option to use scientific notation for output result files has been added through the
FILEFORM keyword on the OU pathway. The FILEFORM option is applicable to
PLOTFILEs, plot-formatted POSTFILEs, MAXIFILEs, RANKFILEs, and SEASONHR
files;
k. An option (WARNCHKD) has been added to the MODELOPT keyword to allow issuing
of warning messages rather than fatal errors for non-sequential meteorological data files, in
order to allow use of multi-year meteorological data files that may contain gaps between
years of data under the DFAULT option; and
1. The maximum length of filenames specified in the 'aermod.inp' file has been increased to
200 (controlled by the ILEN FLD parameter in modules.f), and the maximum input string
length to 512 (controlled by the ISTRG parameter in modules.f). Double quotes (") are
also allowed as field delimiters in the 'aermod.inp' file to support filenames with embedded
spaces.
5. The fifth set of revisions, first introduced with version 11059 of AERMOD, includes the
following (additional information is provided in MCB#4 provided on the SCRAM AERMOD
webpage):
a. Revisions to the processing options available for 24-hour averages of PM2.5 to support
implementation of recommendations regarding appropriate modeling procedures for
demonstrating compliance the PM2.5 NAAQS;
G-2
-------
b. Enhancements to support processing for the 1-hour NO2 and SO2 NAAQS, based on the
annual distribution of daily maximum 1-hour values, averaged across the number of years
processed, including three new output file options, MAXDAILY, MXDYBYYR, and
MAXDCONT, and revisions to the RECTABLE keyword to support user-specified ranks
up the 999th highest value to support significant contribution analyses;
c. A new option to specify uniform or temporally-varying background concentrations, using
the BACKGRND keyword on the SO pathway;
d. A new option to specify temporally-varying background ozone concentrations, using the
03VALUES keyword on the CO pathway;
e. Incorporation of the default equilibrium ratio 0.90 for NO2/NOX for the OLM option,
which was previously associated only with the PVMRM option (the CO N02EQUIL
option can also be used to specify a non-default equilibrium ratio for the OLM option);
f. Increasing the maximum length for source IDs from 8 to 12 characters;
g. An option to suppress file headers for formatted output files, using the NOHEADER
keyword on the OU pathway;
h. A modification to the urban option to address issues with the transition from the nighttime
urban boundary layer to the daytime convective boundary layer (a non-DFAULT option
has been included to allow users to revert to the original implementation); and
i. Corrections to several bugs related to the PVMRM algorithm and modifications to the
DEBUGOPT keyword to allow user to specify only PVMRM or deposition (DEPOS)
debug output, without the MODEL debug file, which can be very large.
6. The sixth set of revisions, first introduced with version 11103 of AERMOD, includes the
following (additional information is provided in MCB#5 provided on the SCRAM AERMOD
webpage):
a. Correction to a bug that resulted in all short-term values being 0.0 if only the lst-highest
rank was selected for applications involving the special processing for daily maximum
values (24hr PM25, lhrN02 and lhr S02); and
b. Additional error handling to identify potential problems with the Fortran format specifier
for hourly ozone files and hourly background files specified on the CO OZONEFIL and
SO BACKGRND keywords, respectively. The hourly ozone and/or background
concentrations may have been assigned values of zero (0) in previous versions of
AERMOD if the user-specified Fortran format included an integer (I) format to read the
concentration values. The requirements for user-specified Fortran formats with these
options has been clarified in the appropriate sections below.
7. The seventh set of revisions, first introduced with version 12060 of AERMOD, includes the
following (additional information is provided in MCB#7 provided on the SCRAM AERMOD
webpage):
a. Corrections to bugs associated with the MAXDCONT option for determining source
contributions for the lhr N02, lhr S02 and 24hr PM25 NAAQS based on a distribution
of daily maximum values for applications including a day-of-week component on the
EMISFACT, 03VALUES, or BACKGRND keywords, and for applications using an
G-3
-------
hourly emission file (SO HOUREMIS keyword) for at least one source, but not all
sources, in a particular run;
b. Corrected a bug for applications with the OLM and PVMRM options under the EVENT
processing mode when only the CO OZONEVAL keyword is used to specify a
background ozone value, without an hourly ozone file through the CO OZONEFIL
keyword or varying ozone values through the CO 03VALUES keyword;
c. Replaced subroutine LTOPG for determining PG stability class based on Monin-
Obukhov length and surface roughness used in the FASTAREA option with code from
the CTDMPLUS model that more closely matches the Golder (1972) figure;
d. Incorporated an option for users to indicate that all sources in a particular model run are
to be treated as URBAN sources, by specifying 'ALL' on the SO URBANSRC
keyword. The URBANSRC ALL option is only applicable for applications that include
a single urban area;
e. Included a new option for users to specify the number of years of meteorological data
being processed for multi-year applications of the MAXDCONT option, using the new
NUMYEARS keyword on the ME pathway. This allows users with less than 5 years of
site-specific met data to specify the number of years being processed in order to
minimize memory storage requirements. Consistent with previous versions, the default
number of years absent the NUMYEARS option is five (5); and
f. Includes checks of the range of ranks specified on the OU RECTABLE keyword when
the THRESH option on the MAXDCONT keyword is being used, since the analysis of
contributions for MAXDCONT is limited to the range of ranks specified on the
RECTABLE keyword. A fatal error message will be generated if the range of ranks
specified is less than or equal to the design value rank for the specified pollutant plus 4,
i.e., a fatal error will be generated if the range of ranks is less than or equal to 8 for 1-hr
S02, or less than or equal to 12 for 1-hr N02 or 24-hr PM2.5. A non-fatal warning
message is also generated if the range of ranks is less than or equal to the design value
rank plus 20, i.e., if the range of ranks is less than or equal to 24 for 1-hr S02, or less
than or equal to 28 for 1-hr N02 or 24-hr PM2.5.
8. The eighth set of revisions, first introduced with version 12345 of AERMOD, includes the
following (additional information is provided in MCB#8 provided on the SCRAM AERMOD
webpage):
a. Adjustments to wind speeds based on the assumption that input wind speeds are vector
(or resultant) mean winds (see Eq. 112 on page 79 of the AERMOD Model Formulation
Document (EPA, 2004a)) have been removed. This is considered a formulation bug fix
since current EPA guidance for site-specific meteorological monitoring (EPA, 2000)
recommends that scalar mean wind speeds be used in steady-state Gaussian dispersion
models. Furthermore, all wind speeds derived from NWS or FAA airport data represent
scalar mean wind speeds. An option has also been included on the MODELOPT
keyword on the CO pathway (VECTORWS) that allows users to specify that input wind
speeds are vector means, in which case the previous adjustments will be included. The
new VECTORWS option is not linked with the DFAULT option, but users should be
able to confirm that input speeds are vector means in order to justify use of the option.
However, scalar mean wind speeds, if available, should be used based on the current
guidance.
G-4
-------
b. Modifications to check for large negative hourly emissions (< -90), which may be used
as missing indicators. Since AERMOD allows inputs of negative emissions for use in
emission credit calculations, negative values used as missing indicators in the
HOUREMIS file result in negative hourly concentrations in the previous versions.
Warning messages are generated and the emission rate is set to zero (0) for these cases.
c. Two new BETA (non-Default) options have been included to address concerns regarding
model performance under low wind speed conditions. The LOWWIND1 option
increases the minimum value of sigma-v from 0.2 to 0.5 m/s and "turns off' the
horizontal meander component. The LOWWIND2 option increases the minimum value
of sigma-v from 0.2 to 0.3 m/s, and incorporates the meander component, with some
adjustments to the algorithm, including an upper limit on the meander factor (FRAN) of
0.95. A new LOW_WIND keyword has been added to the CO pathway that allows users
to adjust the minimum sigma-v value (within a range of 0.01 to 1.0 m/s), and the
minimum wind speed value (within a range from 0.01 to 1.0 m/s), with a default value of
0.2828 m/s, consistent with the default applied in previous versions based on
SQRT(2*SVmin*SVmin) with SVmin=0.2. The new LOW_WIND keyword also allows
users to adjust the maximum value for the meander factor (FRAN) within a range of 0.50
to 1.0, inclusive, when the LOWWIND2 option is used. These new LowWind BETA
options can also be used in conjunction with the new option in AERMET (vl2345) to
adjust the surface friction velocity (U*) under low-wind/stable conditions (ADJ_U*),
based on Qian and Venkatram (2011). More details regarding these LowWind BETA
options is provided in Section 3.2.3.
d. A new LINE source type has been included that 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
to account for initial dilution of the emissions. As with the AREA source type, the LINE
source type does not include the horizontal meander component in AERMOD.
e. Additional range checks on hourly stack exit velocities and exit temperatures input
through the SO HOUREMIS option. A fatal error is generated if the hourly exit
temperature is less than 200K (about -100F), unless the hourly emissions are zero (0) for
that hour. This may indicate that incorrect units for exit temperature have been used, or
that the order of exit temperature and exit velocity may have been reversed in the
HOUREMIS file. Also added a new warning message for exit velocities larger than 250
m/s. Comparable changes were incorporated in subroutine PPARM for inputs on the
SRCPARAM keyword.
f. Modified the acceptable AERMET version date from 06341 to 11059. AERMOD will
no longer run with met data based on version 06341 of AERMET. AERMOD will run
using met data based on version 11059. However, a warning message will be generated,
and users are strongly encouraged to update their meteorological data to version 12345
of AERMET due to the scope of changes included in that update.
9. The ninth set of revisions, first introduced with version 13350 of AERMOD, includes the
following (additional information is provided in MCB#9 provided on the SCRAM AERMOD
webpage):
G-5
-------
a. Incorporated new options for modeling N02, including a Default Ambient Ratio Method
(ARM) option and non-Default BETA Ambient Ratio Method - 2 (ARM2);
b. Incorporated options to vary background ozone (03) data by wind sector (new CO
03 SECTOR keyword) for use with the OLM and PVMRM options, and options to vary
background concentrations for the pollutant being modeled by wind sector (new SO
BGSECTOR keyword). Any of the existing options for specifying background data can
be used with the new sector-varying options, and will continue to work as before if no
sectors are defined. The applicable sector is determined by the flow vector (downwind)
based on the wind direction in the surface meteorological data file;
c. Added new "debug" output file options for the OLM option and for the new ARM and
ARM2 options for N02. Also added a new PRIME debug option to separate the debug
information associated with the PRIME downwash algorithm from the non-PRIME
related information provided under the MODEL debug option. Also removed all debug
information from the main 'aermod.out' file.
10. The ninth set of revisions, first introduced with version 14134 of AERMOD, includes the
following (additional information is provided in MCB#10 provided on the SCRAM
AERMOD webpage):
a. Modified subroutine POLLID to allow for an additional user-specified field to disable
the special processing associated with the 1-hr N02, 1-hr S02 and 24-hr PM2.5
NAAQS, which are based on a multi-year average of ranked maximum daily values (1-
hr values in the case of N02 and S02 and 24-hr values in the case of PM2.5). The
optional field allowed after the pollutant ID can be 'H1H', 'H2H', or 'INC' (without the
single quotes), indicating that the results will be processed consistent with a
deterministic standard, such as the original 3-hr and 24-hr S02 standards, which could
be exceeded once per year, and consistent with PSD increments, which can also be
exceeded once per year. These options are intended to provide a mechanism for
modeling to demonstrate compliance with the 24-hr PM2.5 increments, and also to
provide a mechanism to evaluate the various N02 chemistry options incorporated in
AERMOD without the requirement for modeling complete years of meteorological data.
b. Modified subroutine DEBOPT to include a new AREA/LINE debug option, which is
output to a separate file, including an optional user-specified file name. This includes
additional information regarding AREA/LINE (and OPENPIT) calculations as compared
to the AREA-related debug information included under the previous DEBUG option.
Also modified subroutines ACALC and PSIDE to output AREA/LINE debug
information under the new AREA/LINE debug option. Debug information is no longer
included in the main 'aermod.out' file.
c. Modified subroutine MEOPEN to check for flags in the header record of the input
SURFFILE indicating that MMIF-generated meteorological inputs were used, which is
currently treated as non-DFAULT/BETA option, and for use of BULKRN option, which
is treated as a DFAULT option. Subroutine MEOPEN also checks for measurement
heights in the input PROFFILE file and issues a warning if heights exceed 999m, which
could indicate that inputs were based on MMIF or other gridded meteorological data that
were processed in a manner that did not include identifying information in the surface
file header record (e.g., processing MMIF-generated pseudo- surface and upper air data
with user-defined surface characteristics rather than the AERSURF file generate by
MMIF. Subroutine MEOPEN was also modified to include checks for blank/missing
G-6
-------
upper air, surface and/or onsite station IDs in the surface file header record, and issues
warning messages if the respective station IDs specified on the ME pathway in the
aermod input file are not zero (0).
d. Modified subroutine PRTSRC to include a table of SrcIDs for sources identified as
urban sources under the URBANSRC keyword.
e. Modified subroutine PRTDET to include the original GrpVal concentration from the
Non-EVENT run in the header information for the DETAIL output option under EVENT
processing.
f. Modified subroutine PRTOPT to include additional information on the initial input
summary page of the 'aermod.out' file related to the use of N02 options, and to identify
which debug options have been selected on the CO DEBUGOPT keyword.
g. The "acceptable" AERMET version date has been modified to version 12345, and
AERMOD will not run if meteorological data generated by earlier versions of AERMET
are input. AERMOD will run if meteorological data from versions 12345 or later are
used, but a warning message will be issued if meteorological data from other than the
current version of AERMET are used.
11. The tenth set of revisions, first introduced with version 15181 of AERMOD, includes the
following (additional information is provided in MCB#11 provided on the SCRAM
AERMOD webpage):
a. Included a new Plume Volume Molar Ration Method 2 non-DFAULT/BETA option that
uses total dispersion coefficients instead of relative dispersion coefficients for stable
conditions and relative dispersion coefficients for unstable conditions. The new
PVMRM2 option incorporates additional modifications relative to the PVMRM option,
including the use of downwind distance instead of radial distance from source to
receptor to calculate the plume volume and moles ofNOx. See the modified Model
Formulation Document Addendum for additional details.
b. Incorporated a new LOWWIND3 BETA option to address concerns regarding model
performance under low wind speed conditions. The LOWWIND3 option increases the
minimum value of sigma-v from 0.2 to 0.3 m/s, consistent with the LowWind2 option,
but eliminates upwind dispersion, consistent with the LowWindl option. The
LowWind3 option uses an "effective" sigma-y value that replicates the centerline
concentration accounting for meander, but sets concentrations to zero (0) for receptors
that are more than 6* sigma-y off the plume centerline, similar to the FASTALL option.
c. Included a source type option, BUOYLINE, to model buoyant line sources based on the
BLP model.
12. The eleventh set of revisions, first introduced with 16216 of AERMOD, include the following
(additional information is provided in MCB #12 provided on the SCRAM AERMOD
webpage):
a. Replaced PVMRM option with the PVMRM2 option, retaining PVMRM as the option
name and removing PVMRM2 as a valid option name. Refer to the Model Formulation
Document for more details about the implementation of PVMRM in AERMOD.
b. Removed the requirement for specifying the BETA option on the CO pathway for
applications of the ARM2 Tier 1 screening option for NOx-to-N02 conversion, PVMRM
and OLM Tier 2 screening options for NOx-to-N02 conversion, and the POINTCAP and
G-7
-------
POINTHOR source types used to characterize capped and horizontal point sources,
respectively.
c. Removed the requirement for specifying the BETA option on the CO pathway when the
ADJ U* option is applied in AERMET and turbulence measurements (Sigma-Theta
and/or Sigma-W) are not included in the processing of site-specific meteorological data.
Note that the BETA option in AERMOD must still be specified when turbulence
measurements are processed with site-specific data that includes turbulence in
AERMET.
d. Updated subroutines related to the buoyant line source type (BUOYLINE) introduced in
version 15181 of AERMOD. Modifications to BUOYLINE include:
i. Added a receptor exclusion zone in which receptors within the maximum
extents of a buoyant line source are omitted from calculations;
ii. Modified SRCGROUP keyword so than an individual line in a buoyant line
source can be included in a SRCGROUP;
iii. Modified processing hourly emissions file for buoyant lines so that the hourly
emissions fie requires a buoyancy flux parameter for each line of a buoyant
line source; and
iv. Added buoyant line sources to EVENT processing capabilities on the EV
pathway.
13. Summary of 12th revisions, version 18081 of AERMOD:
BUG FIXES
Item
Modification
Pollutants
Source
Types
1
PRIME Downwash Receptor Bug
In the subroutine SZSFCLPR in prime.f, the calculation of the surface layer
dispersion term is different for stable and unstable conditions. For unstable
conditions, in 15181 the term was calculated if the receptor height was less than
1/10 of the mixing height. Otherwise, the surface layer dispersion term was set
to 0.0 in unstable conditions.
In 16216r, the conditional statement was modified to calculate the term if the
release was considered a surface release, regardless of the receptor height.
Thus, the surface layer dispersion term is applied in 16216r under unstable
conditions to all receptors if defined as a surface release which is determined
differently under different conditions.
Code was reverted back to 15181.
All
POINT
2
Urban S02 Half-life for Non-Default Applications
AERMOD includes a decay coefficient for URBAN S02sources. This decay
will automatically apply if the DFAULT option is specified, but was not
applied for Non-DFAULT applications of AERMOD (i.e., when DFAULT
option keyword was omitted). The 4-hour half-life is now applied to S02 urban
sources regardless of whether the DFAULT option is specified or not and a
user-defined value is not specified. The default decay coefficient is 4-hours if a
S02
All
G-8
-------
user-defined value is not specified. Subroutines BL CALC in calcl.f and
DECAY in calc2.f were updated to apply the default (or user-defined) decay
coefficient to urban S02 sources for non-default applications.
3
Annual POSTFILEs
For multi-year runs, when outputting ANNUAL POSTFILEs, AERMOD would
output each year's annual concentration at each receptor with year numbers 1,2,
etc. Following all of the individual years' concentrations, AERMOD would
output the multi-year average at each receptor and labeled the row with the final
year number. Reporting individual year's concentrations was introduced in
15181. Prior to 15181, the POSTFILE would output the multi-year average,
not individual years. In this release, the POSTFILE will have the individual
years, but not the multi-year average. The multi-year average can still be
obtained from a PLOTFILE. In aermod.f, the condition of call to subroutine
PSTANN was modified to avoid writing period average to annual POSTFILE.
All
All
4
Buoyant Line Source Parameters Summary
Summary table of buoyant line source parameters was not included in the
AERMOD.OUT file along with the summaries for other source types.
Summary table was added.
All
BUOYLINE
5
AERMOD Seasonal Assignment
AERMOD was using the wrong seasonal assignment for calculation of cuticle
resistance for ozone (Rcox) for winter and snow precipitation in subroutine
VDP in calcl.f. Conditional statement was corrected to reference seasonal code
4 (winter with snow) rather than 5.
All
All
6
ARM2 Error/Warning Messages for Range Checks
Corrections were made to the range checks for user-defined ARM2 limits and
Error and Warning messages were updated accordingly.
N02
All
7
Background Sectors Output
AERMOD was printing the SECT1 values for both SECT1 and SECT2 for:
SEASON, MONTH, HROFDY, HRDOW, HRDOW7, SHRDOW,
SHRDOW7, MHRDOW, MHRDOW7 (functioning correctly for SEASHR).
SECT2 values were correctly used in the model, but were printed incorrectly in
the output list file Also, AERMOD was not writing any values for WSPEED.
Reporting errors were corrected in this release.
All
All
8
Apply Minimum Wind Speed
The minimum wind speed was applied to vector winds in calcl.f and iblval.f by
taking the max of the calculated effective wind speed and minimum wind set as
a lower limit (either a default value or user-defined value that is entered with
the ALPHA and LOW WIND keywords).
All
All
9
Meteorological Surface File Check
If the surface meteorological file existed, but was empty, AERMOD would
enter an infinite error loop. This cause AERMOD to write to the error file until
the local disk was full, meset.f was modified to check to see if the file was
empty on first read and issue the correct warning if so.
All
All
G-9
-------
ENHANCEMENTS
Item
Modification
Pollutants
Source
Types
1
ARM2 Enabled with Buoyant Line Source
ARM2 was extended for application to buoyant line sources and source groups
that include buoyant line sources.
N02
BUOYLINE
2
Addition of ALPHA Option Flag
Similar to the BETA option flag, an ALPHA option flag was added to
distinguish options that are considered research/experimental options (ALPHA)
from those that have been vetted within the scientific community that are under
consideration for promulgation as regulatory options (BETA).
All
All
3
Command-line Arguments
Capability added for user to specify control filename (.inp) and standard output
filename (.out) on the command-line when AERMOD is executed. User can
include 0, 1, or 2 arguments. If no arguments are included, AERMOD will
assume the default names (aermod.inp and aermod.out). When included, the
first argument must be the control filename, and the second argument must be
the output filename. If only the control filename is provided, AERMOD will
use the path and base of the control filename (excluding extension) as the path
and base filename for the output file and append ".out" to the end of the
filename. Filenames can include the absolute path or relative path from the
working directory.
All
All
4
Removal of LOWWIND1, LOWWIND2, LOWWIND3
Individual BETA options LOWWIND1, LOWWIND2, LOWWIND3 were
removed and replaced with LOW WIND ALPHA option that enables user to
specify different values for minimum wind speed, sigma-v, and maximum
meander factor (see LOW-WIND Alpha Option in the Enhancements section).
All
All
5
ARM Removed
The original Ambient Ratio Method (ARM), which was replaced with ARM2,
was still functional in AERMOD 16216r and could be specified when the
DFAULT keyword was also specified. ARM has been removed from
AERMOD. Equivalent functionality can be obtained by setting the maximum
and minimum ambient ratio to the desired value using the ARM2 options.
N02
All
6
Rename Functions ERF and ERFC
Absoft and gfortran compilers issued warnings that the user-defined functions
ERF and ERFC in prime.f were named the same as two intrinsic functions.
User-defined functions were renamed FNERF and FNERFC to avoid a
potential name conflict. Call statements were updated to reference new function
names.
All
All
7
Uninitialized Variables
Initialized variables identified by gfortran compiler as uninitialized. Exceptions
are the allocated arrays. All variables that were initialized are set = 0.0D0 (all
are double precision). All variables identified were found to be set somewhere
in the code either as the value of another variable or by formula, so
initialization has no effect. Allocatable arrays were already initialized in code at
some point after allocation.
All
All
G-10
-------
FORMULATION UPDATES
Item
Modification
Pollutants
Source
Types
1
LOWWIND ALPHA Option
A new ALPHA option LOW WIND which enables the user to enter user-defined
values for minimum wind speed, sigma-v, and maximum meander factor in lieu of
LOWWIND 1, LOWWIND2, andLOWWIND3.
All
All
14. Summary of 13th revisions, version 19191 of AERMOD:
BUG FIXES
Item
Modification
Pollutants
Source
Types
1
BACKGROUND Concentrations output units
Modified subroutine SUMB ACK to convert background concentrations to the
model output units requested via the EMISUNIT or CONCUNIT keywords.
Background concentrations are converted internally in AERMOD to (ig/m3 but
were not being converted to the requested output units when model outputs were
not (ig/m3. Background concentrations are converted to the requested model output
units by dividing EMIFAC(l) BY l.OxlO6 (the default conversion of grams to mg)
in SUMBACK.
All
All
2
BACKGROUND Concentrations and deposition
Modified subroutine SUMBACK to not include background concentrations with
deposition outputs. Previously, if background concentrations were in an AERMOD
run with deposition outputs, background concentrations were added to deposition
fluxes.
All
All
3
Wet particle deposition and Method_2 particle deposition
Modified subroutine SCAVRAT to calculate the scavenging ratio when using
Method_2 particle deposition based on a parameterization of the washout ratio
from Wesely 2002. Washout ratio is calculated based on the fine mass fraction,
and an assumed diameter of 6 microns for the coarse mode. The washout ratio is
used to calculate the collision efficiency which is then used to calculate the
scavenging ratio. Previously, AERMOD used particle density and settling velocity
for the fine particle to calculate wet deposition parameters when using Method 1 or
2 for particle deposition. These were inconsistent with the Method 2 inputs in that
density is not an input for Method 2 and Method 2 dry deposition assumes a
settling velocity of 0 m/s for the fine particle mode.
Particulates
All
4
Buoyant Line Source Minimum Release Height and Minimum Wind Speed
A minimum release height of 2.0 meters is imposed. A buoyant line source release
height of 0.0 meters caused AERMOD to run very slowly and produce 0.0 ug/m3
for all hours and receptors. A minimum reference height wind speed of 1.0 m/s is
imposed. This value is consistent with the meteorology that was produced with the
CRSTER meteorological processor, the met processor for the Buoyant Line and
Point (BLP) model.
All
Buoyant
Line
5
MODELOPT Number 6
Previously, the AERMOD.out summary file lists two No. 6 user-specified options
when user selects non-DFAULT and URBANOPT. One of the two messages
incorrectly indicates a N02 conversion is applied when non-N02 POLLUTID
used. An if statement was added for N02 processing in inpsum.f to remove the
duplicated message.
ALL
All
6
DFAULT with ADJ Ustar
All
All
G-ll
-------
Previously, a W402 warning message was returned in the AERMOD.out summary
file when the DFAULT MODELOPT was used without use of the AERMET
ADJ U*. The block of code responsible for the incorrect warning message was
eliminated in PFLCNV subroutine of metext.f.
7
ERRMSG(18)
ERRMSG(18) was defined three times in modules.f, using ERRHDL numbers 133,
137, and 138, which resulted in some compilers (g95) not functioning properly.
The modules.f file was reorganized sequentially and ERRMSG(18) usage of
ERRHDL 137 and 138 was removed. ERRHDL 137 and 138 were replaced with
ERRMSG 204 in the coset.f.
All
All
8
LOWWIND Undefined ERROR Message
Previously, an undefined ERROR message and "ELWD" error code was returned
in the AERMOD.out summary file when the LOW WIND MODELOPT was used
without the ALPHA MODELOPT. The ERROR message code was modified to
"E133" in coset.f.
All
All
9
ELEVUNIT
Previously, the optional ELEVUNIT keyword to convert elevation units from feet
to meters was not applied to LINE or BUOYLINE sources. The SOLOCA
subroutine in soset.f was modified to apply the feet to meters conversion used for
other source types to LINE and BUOYLINE sources.
All
Line
and
Buoyant
Line
12
ENHANCEMENTS
Item
Modification
Pollutants
Source
Types
1
ARM2 Enabled with BETA RLINE and ALPHA RLINEXT Source Types
ARM2 was extended for application to sources and source groups that include the
BETA RLINE and ALPHA RLINEXT line sources.
All
Rline
and
Rlinext
2
EVENT Processing Enabled with BETA RLINE and ALPHA RLINEXT
Source Types
EVENT processing was extended for application to sources and source groups that
include RLINE and RLINEXT line sources.
All
Rline
and
Rlinext
3
Urban Stability Enabled with BETA RLINE and ALPHA RLINEXT Source
Types
The URBAN option was extended for application to sources and source groups that
include RLINE and RLINEXT line sources.
All
Rline
and
Rlinext
4
Buoyant Line Source Urban Stability
Previously, AERMOD treated a buoyant line source in an urban environment as a
source in a rural environment, as is done in the Buoyant Line and Point (BLP)
model. The capability to process a buoyant line source in an urban environment
was added as an ALPHA option. The surface roughness (SFCZO), Monin-
Obukhov length (OBULEN), and mixing height (ZI) are adjusted for an urban
environment and a new value of the Pasquill-Gifford (P-G) stability category
(KST) is computed using the subroutine LTOPG.
All
Buoyant
Line
FORMULATION UPDATES - Regulatory
None
G-12
-------
FORMULATION UPDATES - BETA
1
RLINE Source Type
All
Rline
The RLINE source type was added to model roadways, or similar line-type
releases, which uses the dispersion calculations from the R-LINE model (version
1.2) and requires the BETA and FLAT model options. The RLINE source type has
identical inputs to the LINE source type
R-LINE model: current version 1.2, last updated November 2013
dittos ://www.cmasccntcr.orc>/r-linc).
FORMULATION UPDATES - ALPHA
Enhanced Building Downwash Options All Point
Options to examine the effects of enhanced building downwash
algorithms for point sources was added. The user can selectively
apply one or more of these options in the AERMOD input control
file. Two new keywords are added to the CO pathway:
ORD_DWNW and AWMADWNW. Each of these keywords has
several parameters that control downwash processing. For
ORD DWNW, the parameters are: ORDUEFF to control the height
at which an effective wind speed is calculated for main plume
concentrations; ORDTURB to control an adjustment for the non-
dimensional vertical turbulence intensity, wizO, from 0.6 to 0.7; and
ORDCAV to shift the point 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. Parameters
available for the AWMADWNW keyword are: AWMAUEFF to
control the height at which an effective wind speed is calculated for
main plume concentrations; AWMAUTURB to specify new lower
and upper bounds for calculating the effective parameters ueff,
sweff, sveff, and tgeff; and STREAMLINE (or STREAMLINED)
to perform downwash for a streamlined building such as a cooling
tower. Any combination of parameters is allowed EXCEPT
ORDUEFF and AWMAUEFF cannot both be specified in the same
model run. In addition, STREAMLINE (or STREAMLINED)
requires the AWMAUTURB option to also be specified. If any of
these keywords and parameters are used, the ALPHA option must
be specified on the MODELOPT record. An optional debug file is
available for the options associated with the AWMADWNW
keyword by specifying AWMADW on the DEBUGOPT keyword.
If none of these options are applied, the standard AERMOD
building downwash algorithms will be used.
G-13
-------
2
RLINEXT Source Type
The RLINEXT source type was added to model roadways, or
similar line-type releases, using the dispersion calculations from the
R-LINE model (version 1.2) and requires the ALPHA and FLAT
model options. The RLINEXT source has inputs and capabilities
identical to the R-LINE model. The RLINEXT source has
capability to model depressed roadways and roadside barriers; the
RLINE source does not have these capabilities.
R-LINE model: current version 1.2, last updated November 2013
dittos ://www. cmascenter. org/r-line).
All
Rlinext
3
Method 2 particle deposition and gas deposition ALPHA Option
Gas deposition and method 2 particle deposition were switched
from non-DEFAULT to ALPHA options. While the two deposition
options were previously non-DEFAULT, there has been little
evaluation of their use in AERMOD. It was decided to make these
two options ALPHA options while the deposition algorithms
undergo evaluation. Note that METHOD 1 particle deposition is
still allowed with the DFAULT option as it is based on a method
from a previous model, the Acid Deposition and Oxidant model
(ADOM)
Gaseous
and
particulates
using
Method 2
All
G-14
-------
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.
CO — COntrol, the 2-character pathway ID for input control file commands used to specify
overall job control options.
CO Pathway — Collective term for the group of input control file commands used to
specify the overall job control options, including titles, dispersion options, terrain
options, etc.
Directory — A logical subdivision of a disk used to organize files stored on a disk.
Dispersion Model — A group of related mathematical algorithms used to estimate (model) the
dispersion of pollutants in the atmosphere due to transport by the mean (average)
wind and small scale turbulence.
DOS — Disk Operating System. Software that manages applications software and provides
an interface between applications and the system hardware components, such as the
disk drive, terminal, and keyboard.
Echo of inputs — By default, the AERMOD model will echo the input control file commands,
character by character, into the main printed output file. This serves as a record of
the inputs as originally entered by the user, without any rounding of the numerical
values. The echoing can be suppressed with the NO ECHO option.
EOF -- End-of-File.
EPA — U. S. Environmental Protection Agency.
Error message — A message written by the model to the error/message file whenever an error
is encountered that will inhibit data processing.
Error/Message File — A file used for storage of messages written by the model.
EV — EVent, the 2-character pathway ID for input control file commands used to specify event
inputs for the Short-Term EVENT model.
GLOSSARY 1
-------
EV Pathway — Collective term for the group of input control file commands used to specify the
event periods and location for the Short-Term EVENT model.
EVENT Processing — An option in the AERMOD model specifically designed to provide source
contribution (culpability) information for specific events of interest, e.g., design values
or threshold violations.
Extended Memory — Additional memory on 80386 and 80486 PCs that allows programs to
address memory beyond the 640 KB limit of DOS. Special software is required to
utilize this extra memory.
Fatal Error — Any error which inhibits further processing of data by the model. Model
continues to read input images to check for errors during setup, and will continue to read
input meteorological data during calculation phase.
Flow Vector — The direction towards which the wind is
blowing. GMT — Greenwich Mean Time, the time at the 0°
meridian.
Informational Message — Any message written to the error/message file that may be of interest to
the user, but which have no direct bearing on the validity of the results, and do not affect
processing.
Input Image — User supplied input, read through the default input device, controlling the model
options and data input. A single card or record from the input control file. Each input
image consists of a pathway ID (may be blank indicating a continuation of the previous
pathway), a keyword (may also be blank for continuation of a keyword), and possibly
one or more parameter fields.
Input control file — The basic input file to the AERMOD model controlling the modeling options,
source data, receptor locations, meteorological data file specifications, and output
options. Consists of a series of input images grouped into functional pathways.
Julian Day — The number of the day in the year, i.e., Julian Day = 1 for January 1 and 365 (or
366 for leap years) for December 31.
KB — Kilobyte, 1000 bytes, a unit of storage on a disk
Keyword — The 8-character codes that follow immediately after the pathway ID in the input
run stream data.
LST — Local Standard Time.
GLOSSARY 2
-------
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.
Pasquill Stability Categories — A classification of the dispersive capacity of the atmosphere,
GLOSSARY 3
-------
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.
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 CFRPart 51 (as revised).
GLOSSARY 4
-------
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.
Unformatted File — A file written without the use of a FORTRAN FORMAT statement,
sometimes referred to as a binary file.
GLOSSARY 5
-------
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.
GLOSSARY 6
-------
-------
United States Office of Air Quality Planning and Standards Publication No. EPA-454/B-19-027
Environmental Protection Air Quality Assessment Division August 2019
Agency Research Triangle Park, NC
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