AERSCREEN User‟s Guide 

EPA-454/B-11-001

March 2011

AERSCREEN User’s Guide

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Air Quality Assessment Division

Air Quality Modeling Group

Research Triangle Park, North Carolina
ii

Preface

This document provides a description of AERSCREEN, the screening version of AERMOD. 

Included in the document are descriptions of inputs, processing methodology in AERSCREEN, 

and outputs.
iii

Acknowledgements

AERSCREEN and the AERSCREEN User‟s guide The AERSURFACE User‟s Guide has been 

developed by the Air Quality Modeling Group within EPA‟s Office of Air Quality Planning and 

Standards and AERSCREEN Workgroup, with input from the AERMOD Implementation 

Workgroup. The AERSCREEN code was initially developed by James Haywood, Michigan 

Department of Environmental Quality.
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Contents

Preface............................................................................................................................................. ii

Acknowledgements........................................................................................................................iii

Figures............................................................................................................................................ vi

Tables........................................................................................................................................... viii

1. Overview of AERSCREEN....................................................................................................... 1

1.1 Description of AERSCREEN .............................................................................................................2

1.2 Description of MAKEMET ................................................................................................................3

1.3 Differences with SCREEN3................................................................................................................6

2. AERSCREEN features................................................................................................................ 8

2.1 Source inputs.......................................................................................................................................8

2.1.1 Point, capped stacks and horizontal stack sources......................................................................9

2.1.2 Flares.........................................................................................................................................12

2.1.3 Volume sources..........................................................................................................................13

2.1.4 Rectangular area sources..........................................................................................................14

2.1.5 Circular area sources................................................................................................................15

2.1.6 NOx to NO2 conversion ..............................................................................................................16

2.1.7 Other inputs ...............................................................................................................................17

2.2 Downwash.........................................................................................................................................17

2.3 Meteorology and surface characteristics...........................................................................................20

2.4 Terrain...............................................................................................................................................24

2.6 Inclusion of discrete distances ..........................................................................................................28

2.7 Other inputs.......................................................................................................................................30

2.8 Non-default name for output file ......................................................................................................31

2.9 Error checking...................................................................................................................................32

3. AERSCREEN Program Execution .......................................................................................... 34

3.1 Data input and validation ..................................................................................................................35

3.2 Meteorological data files...................................................................................................................41

3.3 BPIPPRM execution .........................................................................................................................43
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3.4 Source elevation calculation .............................................................................................................43

3.4 Receptor network..............................................................................................................................43

3.5 PROBE..............................................................................................................................................44

3.6 FLOWSECTOR................................................................................................................................45

3.6.1 Rectangular area sources..........................................................................................................46

3.6.2 Non-rectangular area sources...................................................................................................49

3.7 REFINE.............................................................................................................................................52

3.8 Output ...............................................................................................................................................53

4. Example run............................................................................................................................. 55

4.1 Processing and log file ......................................................................................................................58

4.2 AERSCREEN output........................................................................................................................76

5. References................................................................................................................................ 86

Appendix A. Input parameters and invalid responses ............................................................... A-1
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Figures

Figure 1. User prompts for MAKEMET........................................................................................ 4

Figure 2. AERSCREEN.INP and prompts inputs for point sources............................................ 10

Figure 3. AERSCREEN.INP and prompts inputs for capped stack sources. .............................. 11

Figure 4. AERSCREEN.INP and prompts inputs for horizontal stack sources........................... 12

Figure 5. AERSCREEN.INP and prompts inputs for flare sources............................................. 13

Figure 6. AERSCREEN.INP and prompts inputs for volume sources. ....................................... 14

Figure 7. AERSCREEN.INP and prompts inputs for rectangular area sources. ......................... 15

Figure 8. AERSCREEN.INP and prompts inputs for circular area sources. ............................... 15

Figure 9. AERSCREEN.INP and prompts inputs for NOx to NO2 conversion. ......................... 17

Figure 10. AERSCREEN.INP and prompts inputs for building inputs....................................... 19

Figure 11. Stack and building orientation for a building oriented 90 degrees to north and stack 

oriented 45 degrees to north.......................................................................................................... 20

Figure 12. AERSCREEN.INP and prompts inputs for meteorological and surface characteristics 

data................................................................................................................................................ 22

Figure 13. AERSCREEN.INP and prompts inputs for terrain data............................................. 25

Figure 14. Example formats of demlist.txt. ................................................................................. 28

Figure 15. AERSCREEN.INP and prompts inputs for including discrete distances................... 29

Figure 16. Sample distances in a discrete distances text file. ...................................................... 29

Figure 17. AERSCREEN.INP and prompts inputs for other inputs. ........................................... 30

Figure 18. AERSCREEN.INP and prompts inputs for output filename...................................... 32

Figure 19. AERSCREEN processing and stages. ........................................................................ 34

Figure 20. AERSCREEN start screen.......................................................................................... 35

Figure 21. AERSCREEN validation page. .................................................................................. 37

Figure 22. Submenus for changing source parameters for a) point, capped or horizontal stack, b) 

volume, c) rectangular area, d) circular area, and e) flare sources. .............................................. 38

Figure 23. Building downwash submenus for a) building downwash included and b) building 

downwash not included................................................................................................................. 39

Figure 24. Terrain submenus for a) terrain heights included, b) terrain heights not included and 

c) rectangular area sources............................................................................................................ 40

Figure 25. Meteorological data submenu..................................................................................... 40

Figure 26. Meteorological file creation for monthly 12 sector AERSURFACE output.............. 41

Figure 27. Sequence of AERMOD runs in PROBE for different surface characteristics 

combinations................................................................................................................................. 44

Figure 28. Receptor radials for rectangular area sources............................................................. 46

Figure 29. ME pathway in the AERMOD runstream with WRDOTATE keyword and values for 

various angles................................................................................................................................ 47

Figure 30. AERMOD run sequences for rectangular area source for seasonal 12 sector surface 

characteristics................................................................................................................................ 48

Figure 31. Receptor placement for point (including capped and horizontal stacks), flare, volume, 

or circular area sources in FLOWSECTOR.................................................................................. 49

Figure 32. AERMOD sequence for seasonal 12 sector surface characteristics when processing 

terrain and/or building downwash. ............................................................................................... 50
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Figure 33. Flow vector (solid arrow) of 10 degrees and associated upwind surface roughness 

sector for three surface roughness sectors (0 to 90, 90 to 225, 225 to 0). .................................... 51

Figure 34. Receptor skipping notification during FLOWSECTOR run, with notification of 

missing elevations in AERMAP, and total number of receptors skipped for FLOWSECTOR and 

REFINE......................................................................................................................................... 52

Figure 35. Plane view of building and stack orientation for example AERSCREEN run........... 56

Figure 36. a) landuse pattern and sectors used for surface characteristics and b) terrain. The 

circle represents the 1 km radius from the source......................................................................... 57

Figure 37. Contents of demlist.txt for terrain processing. ........................................................... 57

Figure 38. Contents of discrete_receptors.txt. ............................................................................. 58

Figure 39. Initial AERSCREEN title, units, and source type prompts........................................ 58

Figure 40. Source parameter inputs. ............................................................................................ 59

Figure 41. Initial building downwash prompts. ........................................................................... 60

Figure 42. Building parameter inputs. ......................................................................................... 60

Figure 43. Terrain parameter prompts. ........................................................................................ 61

Figure 44. Meteorological parameter prompts and inputs........................................................... 62

Figure 45. Output filename prompt and response........................................................................ 62

Figure 46. Data validation page. .................................................................................................. 64

Figure 47. Input data in AERSCREEN.LOG. ............................................................................. 65

Figure 48. Surface characteristics processing and meteorological files creation. ....................... 66

Figure 49. AERMAP processing and elevation of source. .......................................................... 67

Figure 50. AERSCREEN.LOG records for AERMAP processing for FLOWSECTOR............ 67

Figure 51. Status of AERMAP processing for FLOWSECTOR................................................. 68

Figure 52. AERSCREEN.LOG summary of AERMAP.OUT warning and error messages....... 68

Figure 53. Partial AERMAP output for FLOWSECTOR. ......................................................... 69

Figure 54. AERSCREEN processing during FLOWSECTOR.................................................... 70

Figure 55. Partial AERMOD.INP file used in FLOWSECTOR for 20 degree flow vector........ 71

Figure 56. AERSCREEN.LOG partial output of AERMOD.OUT checks for FLOWSECTOR.72

Figure 57. Status of AERMAP processing for REFINE.............................................................. 73

Figure 58. Partial AERMOD.INP file for REFINE processing................................................... 74

Figure 59. REFINE and final AERSCREEN.LOG messages. .................................................... 75

Figure 60. Overall maximum and maximum ambient boundary concentration statistics. ......... 76

Figure 61. AERSCREEN_EXAMPLE.OUT section with source and building information...... 77

Figure 62. FLOWSECTOR results in AERSCREEN_EXAMPLE.OUT. .................................. 78

Figure 63. Meteorological data associated with maximum FLOWSECTOR concentration and 

ambient boundary concentration................................................................................................... 80

Figure 64. Summary of maximum concentrations by distance in 

AERSCREEN_EXAMPLE.OUT. ................................................................................................ 81

Figure 65. Maximum concentration impact and ambient boundary summaries in 

AERSCREEN_EXAMPLE.OUT. ................................................................................................ 82

Figure 66. Output of aerscreen_example_max_conc_distance.txt. ............................................. 83

Figure 67. Header portion of new AERSCREEN.INP file.......................................................... 85
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Tables

Table 1. MAKEMET prompts and example values for the first month and surface roughness 

sector and last month and surface roughness sector for monthly 12 sector AERSURFACE output.

....................................................................................................................................................... 42

Table 2. Variables listed in max_conc_distance.txt..................................................................... 54

Table 3. Inputs for example AERSCREEN run.......................................................................... 55

Table 4. Seasonal surface characteristics by sector. .................................................................... 56
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1. Overview of AERSCREEN

AERSCREEN is a screening-level air quality model based on AERMOD (U.S. EPA, 2004a). 

The AERSCREEN model consists of two main components: 1) the MAKEMET program which 

generates a site-specific matrix of meteorological conditions for input to the AERMOD model; 

and 2) the AERSCREEN command-prompt interface program. AERSCREEN interfaces with

MAKEMET for generating the meteorological matrix, but also interfaces with AERMAP (U.S. 

EPA, 2004b) and BPIPPRM (Schulman et al. 2000; U.S. EPA, 2004d) to automate the 

processing of terrain and building information respectively, and interfaces with the AERMOD

model utilizing the SCREEN option to perform the modeling runs. AERSCREEN interfaces 

with version 09292 and later versions of AERMOD and will not work with earlier versions of 

AERMOD. The AERSCREEN program also includes averaging time factors for worst-case 3-

hr, 8-hr, 24-hr and annual averages. 

The screening mode of the current version of AERMOD, which is controlled by the 

SCREEN option on the CO 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 in a screening mode to estimate 

worst-case impacts. Since the screening option in AERMOD is designed to be used with a nonsequential meteorological data file representing a matrix of conditions, currently generated by 

the MAKEMET program, the SCREEN option also forces the use of the NOCHKD option even 

if NOCHKD is not included on the MODELOPT card. The NOCHKD option suspends the 

checks made within AERMOD for proper date sequences in the surface and profile 

meteorological input data files. The SCREEN option also restricts the averaging period options 

to 1-hour averages only on the CO AVERTIME card.

Given these two basic components of AERSCREEN, the AERMOD model can be run in a 

screening mode by either: 1) using the AERSCREEN command-prompt interface; or 2) using the 

stand-alone MAKEMET program to generate the matrix of meteorological conditions and 

running AERMOD directly with the SCREEN option. The first approach automates much of the 

processing for the user, including building and terrain processing, while the second approach 

gives the user more flexibility for defining the receptor network to be used in the screening 

analysis and may be more appropriate in certain situations, especially in very complex terrain 

settings. These two options for running AERMOD in a screening mode will not necessarily 

produce the same results. This is because the results for the stand-alone application of 

AERMOD with MAKEMET-generated meteorology will be determined by the user-specified 

receptor network, whereas the AERSCREEN program performs a more precise search to isolate 

the receptor distance with the highest impact, similar to the automated distance option in 

SCREEN3 (U.S. EPA, 1995). In general, the AERSCREEN program should produce slightly

more conservative results than stand-alone AERMOD with MAKEMET data, depending on the 

receptor resolution used for the latter.
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Before running AERSCREEN, users should consult and become familiar the following:

AERMOD User‟s Guide and addenda (U.S. EPA, 2004a)

AERMAP User‟s Guide and addenda (U.S. EPA, 2004b)

AERMET User‟s Guide [for surface characteristics tables] (U.S. EPA, 2004c)

BPIPPRM User‟s Guide (U.S. EPA, 2004d)

Guideline on Air Quality Models (Appendix W) (U.S. EPA, 2005)

AERSURFACE User‟s Guide (U.S. EPA, 2008)

AERMOD Implementation Guide (U.S., EPA, 2009)

Screening Procedures for Estimating the Air Quality Impact of Stationary Sources (U.S. 

EPA, 1992)

The above documents and other support documents can be found at the AERMOD modeling 

page of the Support Center for Regulatory Atmospheric Modeling (SCRAM) page at: 

http://www.epa.gov/scram001/dispersion_prefrec.htm#aermod and the Guideline on Air Quality 

Models (hereafter referred to as Appendix W) can be found at: 

http://www.epa.gov/scram001/guidance/guide/appw_05.pdf

1.1 Description of AERSCREEN

As stated above, AERSCREEN is an interactive command-prompt application that interfaces 

with MAKEMET for generating the meteorological matrix, but also interfaces with AERMAP 

and BPIPPRM to automate the processing of terrain and building information, and interfaces 

with the AERMOD model utilizing the SCREEN option to perform the modeling runs. The 

AERSCREEN program also includes averaging time factors for worst-case 3-hr, 8-hr, 24-hr and 

annual averages. The AERSCREEN program is currently limited to modeling a single point

(vertical uncapped stack), capped stack, horizontal stack, rectangular area, circular area, flare, or 

volume source. 

Inputs or options to AERSCREEN are:

Source parameters for point, rectangular area, circular area, volume, capped stack, 

horizontal stack or flare sources

Building downwash information for point, capped stack, horizontal stack, and flare 

sources

Ability to model NOx to NO2 conversion

o Plume Volume Molar Ratio (PVMRM) (Hanrahan, 1999a and 1999b) or

o Ozone Limiting Method (OLM)

o Input of representative ozone background concentration

Ability to use terrain heights for source and receptors via AERMAP

Specify ambient minimum and maximum temperatures for MAKEMET

Specify minimum wind speed and anemometer height for MAKEMET

Specify surface characteristics for input to MAKEMET by the following methods:
3

o user-defined single values for albedo, Bowen ratio, and surface roughness (no 

temporal or spatial variation in surface characteristics)

o AERMET seasonal tables (temporal variation only)

o Values listed in an external file, either an AERSURFACE (U.S. EPA, 2008)

output file or surface characteristics listed in an AERMET stage 3 input file

Probe distance (maximum downwind distance) of receptors 

Use of flagpole receptors and define flagpole height

Specify urban or rural source and urban population if urban source

Minimum ambient distance for ambient air receptors

Up to ten discrete receptor distances in a user supplied text file

Performs error checks on AERSCREEN inputs, AERMOD output and/or AERMAP 

output

Calculate maximum concentration by distance

Search routine to find overall worst case scenario (maximum 1-hour concentration)

AERSCREEN automatically provides impacts for other averaging periods using scaling 

ratios. The averaging period ratios currently implemented in AERSCREEN are as follows 

(SCREEN3 factors are shown for comparison):

3-hour fixed ratio of 1.00 0.90

8-hour fixed ratio of 0.90 0.70

24-hour fixed ratio of 0.60 0.40

Annual fixed ratio of 0.10 0.08

For area sources (rectangular and circular), the averaging factors are based on guidance in 

Section 4.5.4 of the EPA screening guidance document (U.S. EPA, 1992). For area sources, the 

3, 8, and 24-hour average concentrations are equal to the 1-hour average calculated by 

AERMOD in screening mode. No annual average concentration is calculated.

1.2 Description of MAKEMET

The MAKEMET program generates a matrix of meteorological conditions, in the form of 

AERMET-ready surface (AERSCREEN.sfc) and profile (AERSCREEN.pfl) files, based on userspecified surface characteristics, ambient temperatures, minimum wind speed, and anemometer 

height. See the AERMET User‟s Guide (U.S. EPA, 2004c) for file formats. The current version 

of MAKEMET also allows the user to specify the minimum wind speed to include in the matrix 

and the anemometer height as well. These options have been included to facilitate comparisons 

of AERSCREEN estimates to estimates from AERMOD in a refined mode to eliminate 

differences that may be due to either the minimum wind speed in the refined data or the 

anemometer height. The suggested default values for routine application of MAKEMET are 0.5 

m/s for the minimum wind speed and 10 meters for the anemometer height.
4

MAKEMET allows the user to specify more than one set of surface characteristics and 

ambient temperatures, such as for seasonal or monthly variations, and will concatenate the 

resulting meteorological matrices into single surface and profile files. For AERSCREEN, this 

option is not used and separate files are created for seasonal or monthly variations in surface 

characteristics. No variation in minimum and maximum temperature is done in MAKEMET. 

MAKEMET also allows the user to specify a single wind direction or a range of wind directions 

for the meteorological matrix. This option may be useful for applications involving building 

downwash to ensure that building dimensions for all sectors are included in the screening 

analysis (the treatment of building downwash in the AERSCREEN program is described in 

Section 3.2.2). However, in AERSCREEN processing, the wind direction is set to a single 

direction of 270 degrees.

MAKEMET can be run from the command-prompt, with the prompts in Figure 1 for user input.

ENTER SFC MET FILE NAME

ENTER PFL MET FILE NAME

ENTER MIN. WS (M/S) 

ENTER ANEM HT (M) 

ENTER NUMBER OF WIND DIRECTIONS 

If the user enters one for the number of wind directions 

ENTER WIND DIRECTION 

Otherwise

ENTER STARTING WIND DIRECTION 

ENTER CLOCKWISE WIND DIRECTION INCREMENT 

ENTER MIN AND MAX AMBIENT TEMPS IN KELVIN 

ENTER ALBEDO

ENTER BOWEN RATIO 

ENTER SURFACE ROUGHNESS LENGTH IN METERS 

DO YOU WANT TO GENERATE ANOTHER MET SET THAT WILL BE

APPENDED TO CURRENT FILE?

[TYPE EITHER "Y" OR "y" FOR YES; OR HIT "ENTER" TO EXIT

If ("Y" or "y") then the program loops through prompts 7 through 10 for each additional data set (e.g. seasonal).

Figure 1. User prompts for MAKEMET.

The MAKEMET program has a long complex history, dating back over 10 years. Suffice it 

to say that the version of MAKEMET supplied with AERSCREEN operates in the following 
5

manner. As mentioned earlier, MAKEMET generates a matrix of meteorological conditions for 

application of AERMOD in a screening mode and output the results in the form of AERMODready surface and profile meteorological data files. The matrix is generated based on looping 

through a range of wind speeds, cloud covers, ambient temperatures, solar elevation angles, and 

convective velocity scales (w* for convective conditions only) for user-specified surface 

characteristics (Zo, Bo, r). For stable cases, the mechanical mixing height (Zim) is calculated 

based on the friction velocity, u*. A loop through Zim factors (multiplied times the initial value 

calculated form u*) is also included to account for smoothing of Zim that occurs with refined 

AERMET data. Stable transition cases with solar angle greater than zero but less than the 

critical solar angle (ACRIT) are also included in the matrix.

The program calculates u*, Monin-Obukhov length (L), and Zim for each combination in the 

matrix, and also calculates the convective mixing height (Zic) based on w* for convective cases. 

The program uses subroutines from AERMET (U.S. EPA, 2004c) to calculate boundary layer 

parameters for each combination in the matrix. The program generates a log file, called 

MAKEMET.LOG, which summarizes the inputs selected for that run, and the number of “hours” 

in the final screening matrix for each set of surface characteristics. An effort has been made to 

optimize the MAKEMET program for AERMOD screening applications by eliminating 

combinations that are unnecessary in terms of identifying worst-case impacts, based on a wide 

range of tests comparing screening to refined AERMOD estimates (which are briefly 

summarized below). The number of “hours” per set of surface characteristics will typically be 

around 300-400, but will vary depending on the user inputs. The number will tend to be larger 

for applications with lower surface roughness due to the internal checks made to eliminate 

unnecessary combinations. 

MAKEMET uses the following scheme to assign dates for each of the “hours” in the 

meteorological matrix. The default starting year for the data is 10, and the year is incremented 

by 10 for each additional data set generated. Thus, for seasonal data files, the first season date 

will start with a '1', second season will start with a '2', etc. The hour is used to distinguish 

between stable and convective conditions, with hours 01 through 11 indicating stable hours, and 

hours 12 through 24 indicating convective hours. Note that for monthly data sets and/or for large 

numbers of wind directions (greater than 36), duplicate dates may be generated. A warning 

message is written to the log file in these cases. AERMOD will still run since the NOCHKD 

option is invoked, but determining which conditions produced the worst-case results could 

become problematic. In addition to the required variables for input to AERMOD, the surface file 

generated by MAKEMET also includes five columns of integer variables that provide the loop 

indices for each of the loops in the met matrix corresponding to each "hour" of screening 

meteorology. These indices can be used to analyze the frequency of occurrence for various 

combinations within the meteorological matrix resulting in the controlling (highest) 

concentration.

AERSCREEN provides three options for surface characteristics inputs for generating the 

screening meteorology. One option allows for user-specified surface characteristics – albedo, 

Bowen ratio, and surface roughness (no spatial or temporal variation), the second option is to use 

seasonally varying surface characteristics for generic land use classifications based on Tables 4-
6

1, 4-2, and 4-3 of the AERMET User‟s Guide (U.S. EPA 2004c). The third option is to input the 

name of an external file such as an AERSURFACE (U.S. EPA, 2008) output file or AERMET 

stage 3 input file that contains surface characteristics. Monthly, seasonal, and annual output for 

one sector or multiple sectors is allowed with the third option. AERSCREEN will setup and run 

the MAKEMET program to generate the screening meteorological data for input to AERMOD. 

AERSCREEN will run MAKEMET for each combination of temporal period and spatial sector

of the surface characteristics. If AERSURFACE output is used, AERSCREEN does not call

AERSURFACE, so the user must run AERSURFACE prior to running AERSCREEN.

1.3 Differences with SCREEN3

The three areas where AERSCREEN deviates significantly from SCREEN3 and will, thus, 

be the most difficult for first time users are:

1) Building wake effects – AERSCREEN utilizes all the advantages of PRIME (Schulman 

et al., 2000) including stacks detached from the building. This requires three additional 

pieces of information from the user beyond the normal building height and dimensions. 

The additional information is orientation of the maximum dimension relative to north, 

angle relative to north of the stack and, distance between the stack and building center.

AERSCREEN will use this information to setup and run the BPIPPRM program and 

extract the information needed for the AERMOD model. More downwash details can be 

found in Section 2.2.

2) Meteorology – AERSCREEN provides three options for generating the screening 

meteorology. One option allows for user-specified surface characteristics – albedo, 

Bowen ratio, and surface roughness (no temporal or spatial variation) – the second option 

is to use seasonally varying surface characteristics for generic land use classifications 

based on Tables 4-1, 4-2, and 4-3 of the AERMET User‟s Guide. The third option is to 

use surface characteristics listed in an external file such as an AERSURFACE output file 

or AERMET stage 3 input file. The user enters the name of the file. The user also 

specifies the overall minimum and maximum ambient temperatures. AERSCREEN will 

setup and run the MAKEMET program to generate the screening meteorological data for 

input to AERMOD. More details about meteorology can be found in Section 2.3.

3) Terrain – AERSCREEN provides the option for incorporating terrain impacts on the 

screening analysis. The user must create a file called demlist.txt. The first line of this 

file describes the type of terrain file being used. The file type must be DEM or NED. 

DEM refers to any DEM file type and NED refers to National Elevation Dataset. The 

third line of the file lists the location of the NAD conversion files and the fourth line

begins the list of terrain files with each file on a separate line. When AERSCREEN is 

run, the user will be prompted to provide the source coordinates and associated NAD

datum. AERSCREEN will then setup the necessary input file for AERMAP, run 

AERMAP, and extract the information needed for the AERMOD model. More terrain 

processing details can be found in Section 2.4
7

Given the use of surface characteristics and terrain, it is important that the user know the 

exact coordinates of the source, i.e., stack or center location of volume or area source. 
8

2. AERSCREEN features

As noted in Section 1.1, AERSCREEN has many features and options available to the user. 

In this section, the features and inputs to the restart file, AERSCREEN.INP, are described. 

When running AERSCREEN from a restart file, the file must be named AERSCREEN.INP or 

AERSCREEN will automatically begin prompting the user for data. The prompts used to enter 

the data interactively are described in each relevant section as well. Prompts are not necessarily 

shown in the order in which they appear but in the order for the parameters shown in

AERSCREEN.INP for each data section. The prompts described are based on metric units. 

When processing data from the input file, all units are assumed to be metric. Some variables 

listed below are not requested when using the prompts to enter data, but are automatically 

defaulted, such as when processing a rectangular area source, volume source, or circular area 

source. In the case of a rectangular area source, terrain use and downwash are automatically set 

to “no” and the user is not prompted for the choice of terrain processing and source coordinates. 

For all three source types, downwash is automatically set to “no” and downwash information is 

not requested. When reading data from the input file, if one of the data sections (source, 

building, terrain, meteorology, etc.) is missing, AERSCREEN will notify the user and stop 

processing. Also, if the source data is listed after the building, terrain, or miscellaneous data, 

AERSCREEN will alert the user and stop processing. This is done because the source type is 

needed to determine if parameters must be reset in the building or terrain sections, such as 

resetting building downwash to “no” if an area or volume source is being processed. Also, if 

data is missing or invalid (such as negative emission rate) when reading AERSCREEN.INP, 

AERSCREEN alerts the user and stops processing.

2.1 Source inputs

AERSCREEN can be used for a single point, flare, capped stack, horizontal stack, volume, 

rectangular area source, or circular area source. Below are listed the source types with required 

input variables and example values from the first line of the AERSCREEN.INP file. Building 

downwash is allowed for the point, capped stack, horizontal stack, and flare sources but not for 

volume or area (rectangular or circular) sources. Terrain processing is allowed for all sources 

except rectangular area sources. For all source types, emission rates are in g/s or lb/hr. For area 

source types, AERSCREEN calculates the emission rate per unit area, the required input for 

AERMOD.
9

2.1.1 Point, capped stacks and horizontal stack sources

Stack parameters for point (vertical stacks with no caps), capped stacks, and horizontal stacks 

are the same. Point sources are denoted by the term “** STACK DATA “in the input file in the 

line above the source parameters. Capped stacks are denoted by the term “** POINTCAP 

DATA” in the input file and horizontal stacks are denoted by the term “** POINTHOR DATA” 

in the input file. Source inputs for these three source types are, with English and metric units in 

parentheses:

emission rate (lb/hr or g/s)

stack height (feet or meters)

stack diameter (inches or meters)

stack temperature (degrees Fahrenheit or Kelvin)

and stack velocity (ft/s or m/s) or flow rate (ACFM)

Note that stack velocity can be input as ft/s or m/s, regardless of using English or metric units 

for other parameters. AERSCREEN.INP and prompt inputs (shown in italics) are shown in 

Figures 2 through 4 for point, capped stack and horizontal stacks, respectively. If a stack 

temperature of zero (Fahrenheit or Kelvin) or negative stack temperature is entered, the entered 

temperature will be used as a difference between the stack and ambient temperature. A negative 

number, such as -10, implies that the stack is 10 degrees warmer than the ambient temperature. 

For capped and horizontal stacks, AERMOD uses the BETA option on the MODELOPT 

keyword in the AERMOD runstream file, AERMOD.INP, to invoke the algorithms for those 

source types.
10

AERSCREEN.INP point source inputs

** STACK DATA Rate Height Temp. Velocity Diam. Flow

** 0.1896E+01 5.0902 353.7056 13.2662 0.6096 8204.

Point source prompts inputs

If the user enters “P” or “p” for point source:

Enter Emission Rate (g/s):

Enter Stack Height (meters):

Enter Stack Diameter (meters):

Enter Stack Temperature (K)

Enter 0 for ambient temperature

or a negative number for temperature difference ((K))

between stack temperature and ambient temperature:

Option (1) - Exit Velocity (m/s)

Option (2) - Exit Velocity (ft/s)

Option (3) - Flow Rate (ACFM)

Enter Option for Flow Rate or Exit Velocity:

If the user chooses option 1, the prompt is:

Enter Exit Velocity (m/s):

If the user chooses option 2, the prompt is:

Enter Exit Velocity (ft/s):

If the user chooses option 3, the prompt is:

Enter Flow Rate (ACFM):

Figure 2. AERSCREEN.INP and prompts inputs for point sources.
11

AERSCREEN.INP capped stack source inputs

** POINTCAP DATA Rate Height Temp. Velocity Diam. Flow

** 0.1896E+01 5.0902 353.7056 13.2662 0.6096 8204.

Capped stack source prompts inputs

If the user enters “S” or “s” for capped stack source:

Enter Emission Rate (g/s):

Enter Stack Height (meters):

Enter Stack Diameter (meters):

Enter Stack Temperature (K)

Enter 0 for ambient temperature

or a negative number for temperature difference ((K))

between stack temperature and ambient temperature:

Option (1) - Exit Velocity (m/s)

Option (2) - Exit Velocity (ft/s)

Option (3) - Flow Rate (ACFM)

Enter Option for Flow Rate or Exit Velocity:

If the user chooses option 1, the prompt is:

Enter Exit Velocity (m/s):

If the user chooses option 2, the prompt is:

Enter Exit Velocity (ft/s):

If the user chooses option 3, the prompt is:

Enter Flow Rate (ACFM):

Figure 3. AERSCREEN.INP and prompts inputs for capped stack sources.
12

AERSCREEN.INP horizontal stack source inputs

** POINTHOR DATA Rate Height Temp. Velocity Diam. Flow

** 0.1896E+01 5.0902 353.7056 13.2662 0.6096 8204.

Horizontal stack source prompts inputs

If the user enters “H” or “h” for horizontal stack source:

Enter Emission Rate (g/s):

Enter Stack Height (meters):

Enter Stack Diameter (meters):

Enter Stack Temperature (K)

Enter 0 for ambient temperature

or a negative number for temperature difference ((K))

between stack temperature and ambient temperature:

Option (1) - Exit Velocity (m/s)

Option (2) - Exit Velocity (ft/s)

Option (3) - Flow Rate (ACFM)

Enter Option for Flow Rate or Exit Velocity:

If the user chooses option 1, the prompt is:

Enter Exit Velocity (m/s):

If the user chooses option 2, the prompt is:

Enter Exit Velocity (ft/s):

If the user chooses option 3, the prompt is:

Enter Flow Rate (ACFM):

Figure 4. AERSCREEN.INP and prompts inputs for horizontal stack sources.

2.1.2 Flares

Flare sources are denoted by the term “** FLARE DATA” in the input file in the line above 

the source parameters. Flare source inputs are, with English and metric units:

emission rate (lb/hr or g/s)

stack height (feet or meters)

total heat release rate (cal/sec)

radiative heat loss fraction 

The heat loss fraction can be user selected or the SCREEN3 default value of 0.55. For 

information about heat loss fractions, see Leahey and Davies (1984). AERSCREEN will process 
13

the flare in AERMOD as a POINT source type. For the exit velocity and exit temperature, 

AERSCREEN defaults these values to 20 m/s and 1,273 K, respectively as done in SCREEN3 

(U.S. EPA, 1995). The stack diameter and effective stack height used in AERMOD are 

calculated from the inputs as:

D 9.88 10 HR 1 HL 4

 (1)

3 0.478 Heff Hs 4.56 10 HR

(2)

Where D is effective stack diameter, HR is the heat release rate, HL is the heat loss fraction, 

Heff is effective stack height and Hs is the stack height entered by the user.

AERSCREEN.INP and prompt inputs (in italics) are shown in Figure 5.

AERSCREEN.INP flare source inputs

** FLARE DATA Rate Height Heat HeatLoss

** 0.1000E+03 35.0000 0.1000E+08 0.550

Flare source prompts inputs

If the user enters “F” or “f” for flare source:

Enter Emission Rate (g/s):

Enter Flare Stack Height (meters):

Enter Total Heat Release Rate (cal/sec):

Enter Radiative Heat Loss Fraction –

<Enter> for default value of 0.55:

Figure 5. AERSCREEN.INP and prompts inputs for flare sources.

2.1.3 Volume sources

Volume sources are denoted by the term “** VOLUME DATA” in the input file in the line 

above the source parameters. Volume source inputs are, with English and metric units:

emission rate (lb/hr or g/s)

release height, i.e. center of volume (feet or meters)

initial lateral dimension of the volume (feet or meters)

initial vertical dimension of the volume (feet or meters)

AERSCREEN.INP and prompt inputs (in italics) are shown in Figure 6.
14

AERSCREEN.INP volume source inputs

** VOLUME DATA Rate Height Syinit Szinit

** 0.1000E+03 2.0000 1.5000 3.0000

Volume source prompts inputs

If the user enters “V” or “v” for volume source:

Enter Emission Rate (g/s):

Enter Center of Volume Height (meters):

Enter Initial Lateral Dimension (meters):

Enter initial Vertical Dimension (meters):

Figure 6. AERSCREEN.INP and prompts inputs for volume sources.

2.1.4 Rectangular area sources

Rectangular area sources are denoted by the term “** AREA DATA” in the input file in the 

line above the source parameters. Rectangular area source inputs are, with English and metric 

units:

emission rate (lb/hr or g/s)

release height above ground (feet or meters)

long and short dimensions of area (feet or meters)

initial vertical dimension of plume (feet or meters)

As previously noted, the emission rate is in g/s or lb/hour, not emission rate per unit area as 

entered in AERMOD input files. AERSCREEN automatically calculates the emission rate per 

unit area to input into AERMOD. The angle of the source relative to north is automatically set to 

0 degrees. Note that the long dimension of the area source is in the x-direction and short 

dimension in the y-direction. AERSCREEN.INP and prompt inputs (in italics) are shown in 

Figure 7. For rectangular area sources, AERMOD uses the non-default FASTAREA keyword on 

the MODELOPT keyword in the CO pathway of the AERMOD.INP file.
15

AERSCREEN.INP rectangular area inputs

** AREA DATA Rate Height Length Width Angle Szinit

** 0.1000E+03 2.0000 500.0000 200.0000 0.0 1.50

Rectangular area source prompts inputs

If the user enters “A” or “a” for rectangular area source:

Enter Emission Rate (g/s):

Enter Release Height Above Ground (meters):

Enter Long Side of Area Source (meters):

Enter Short Side of Area Source (meters):

Enter Initial Vertical Dimension (meters):

Figure 7. AERSCREEN.INP and prompts inputs for rectangular area sources.

2.1.5 Circular area sources

Circular area sources are denoted by the term “** AREACIRC DATA” in the input file in the 

line above the source parameters. Circular area source inputs are, with English and metric units:

emission rate (lb/hr or g/s)

release height above ground (feet or meters)

radius of circle (feet or meters)

initial vertical dimension of plume (feet or meters)

As with rectangular area sources, the emission rate is in g/s or lb/hour, not emission rate per 

unit area. AERSCREEN.INP and prompt inputs (in italics) are shown in Figure 8. For circular 

area sources, AERMOD uses the non-default FASTAREA keyword on the MODELOPT 

keyword in the CO pathway of the AERMOD.INP file.

AERSCREEN.INP circular area source inputs

** AREACIRC DATA Rate Height Radius NVerts Szinit

** 0.1000E+03 2.0000 250.0000 20 1.50

Circular area source prompts inputs

If the user enters “C” or “c” for circular area source:

Enter Emission Rate (g/s):

Enter Release Height Above Ground (meters):

Enter Radius of AREACIRC Source (meters):

Enter Initial Vertical Dimension (meters):

Figure 8. AERSCREEN.INP and prompts inputs for circular area sources.
16

2.1.6 NOx to NO2 conversion

Beginning with version 11060, AERSCREEN allows the option to include NOx to NO2

conversion either by using the Plume Volume Molar Ratio Method (PVMRM) or the Ozone 

Limiting Method (OLM). See Section 2.4 of the AERMOD User‟s Guide Addendum for more 

information about PVMRM and OLM and Hanrahan (1999a and 1999b) for background on 

PVMRM. 

When entering data via the prompts, the user is asked to enter an option for modeling NOx to 

NO2 conversion:

1. No chemistry or pollutant is not NO2

2. Use Ozone Limiting Method (OLM)

3. Use Plume Volume Molar Ratio Method (PVMRM)

If option two or three is chosen, the user is prompted for the NO2/NOx in-stack ratio

(AERMOD card CO NOSTACK) and a representative ozone background concentration

(AERMOD card CO OZONEVAL). The NO2/NOX in-stack ratio can range from zero to one 

and units of the background concentration can be parts per million (ppm), parts per billion (ppb) 

or micrograms per cubic meter ( g/m3). For PVMRM the NO2EQUIL ratio is set at the default 

value of 0.9. For OLM use, since only one source is being modeled, the OLMGROUP keyword 

is not needed. 

When entering data via AERSCREEN.INP, the user can specify NOx to NO2 conversion by 

setting the appropriate keywords in the CO pathway of the AERMOD runstream file portion of 

AERSCREEN.INP. PVMRM or OLM must be included on the MODELOPT keyword string, 

POLLUTID must be NO2, NO2STACK must be specified with a ratio, and the background 

ozone concentration and units must be specified using OZONEVAL. Figure 9 shows the inputs 

using AERSCREEN.INP or interactive prompts.
17

AERSCREEN.INP NOx to NO2 chemistry inputs

 MODELOPT CONC SCREEN OLM

 POLLUTID NO2

 NO2STACK 0.9000

 OZONEVAL 0.4000 UG/M3

 MODELOPT CONC SCREEN PVMRM

 POLLUTID NO2

 NO2STACK 0.9000

 OZONEVAL 0.4000 UG/M3

NOx to NO2 chemistry prompts inputs

Enter an option for modeling NO2 chemistry

1) No chemistry or pollutant is not NO2

2) Use Ozone Limiting Method (OLM)

3) Use Plume Volume Molar Ratio Method (PVMRM)

If the user enters “2” or “3”

Enter in-stack NO2/NOx ratio ( 0 to 1.0):

Enter concentration units for representative ozone concentration

1) Micrograms per cubic meter (ugm/m^3)

2) Parts per million (ppm)

3) Parts per billion (ppb)

Enter ozone concentration:

Figure 9. AERSCREEN.INP and prompts inputs for NOx to NO2 conversion.

2.1.7 Other inputs

Other inputs in the source input prompts are urban/rural classification and minimum ambient

distance. These are discussed in more detail in Section 2.7.

2.2 Downwash

Several parameters are needed by AERSCREEN for input into BPIPPRM. These are:

Include downwash (Y=use building downwash, N=no downwash)

Option to use an existing BPIPPRM input file or,

Building height (feet or meters)

Maximum building horizontal dimension (feet or meters)

Minimum building horizontal dimension (feet or meters)

Degrees from North of maximum building horizontal dimension (0-179 degrees)

Degrees from North of stack location relative to building center (0-360 degrees)

Distance between stack and building center (feet or meters) 
18

Building parameter data are denoted by the term “** BUILDING DATA” in the input file in 

the line above the building dimensions. These inputs are listed in the second block of data of 

AERSCREEN.INP (Figure 10) and must be entered in the AERSCREEN.INP file after the 

emissions data or AERSCREEN will stop processing. The order of variables is as listed above. 

Prompts for building downwash are also shown in Figure 10. When entering data via the 

prompts, building prompts will only appear when processing point, capped stack, horizontal 

stacks, or flare sources. Building dimensions are in feet or meters. Angles are in degrees 

relative to North (0 to 360 degrees). An example building/stack configuration is shown in Figure 

11. When entering building parameters, either through the building data line or prompts shown 

in Figure 10, the parameters are for a single tier rectangular or square shaped building. If the 

user wishes to use downwash for multiple buildings, tiers, or more complicated geometries, the 

user can enter a BPIPPRM input filename at the prompts (“Use pre-existing BPIPPRM input 

file”) or in the CO pathway of the AERSCREEN input file using the TITLETWO keyword. If a 

BPIPPRM input filename is entered, AERSCREEN will use the parameters from the file but will 

not overwrite parameters from the building data block. If a pre-existing BPIPPRM input file is 

used, the process, line 2 of the BPIPPRM input file, must be set to „P‟ or „p‟ for PRIME 

downwash and only one stack located within the file or AERSCREEN will abort.
19

AERSCREEN.INP building inputs on BUILDING DATA line

** BUILDING DATA BPIP Height Max dim. Min dim. Orient. Direct. Offset

** Y 34.0000 120.0000 60.0000 90.0000 26.6000 45.0000

AERSCREEN.INP building BPIPPRM input filename line

CO STARTING

 TITLEONE flare 

 TITLETWO BUILDING.INP 

** REFINE STAGE 3

 MODELOPT CONC SCREEN 

 AVERTIME 1

 POLLUTID OTHER

 RUNORNOT RUN

CO FINISHED

Building prompts inputs

Include Building Downwash? (y/n):

If user enters “y” or “Y”:

Use pre-existing BPIPPRM input file? (y/n):

If user enters “y” or “Y” for pre-existing BPIPPRM input file:

Enter user created BPIPPRM input file:

If user enters “n” or “N” for pre-existing BPIPPRM input file:

Enter Building Height (meters):

Enter Maximum Horizontal Building Dimension (meters):

Enter Minimum Horizontal Building Dimension (meters):

Enter Maximum Building Dimension Angle to True North (0 - 179 degees):

Enter Direction of Stack from Building Center (0 - 360 degrees):

Enter Distance Between Stack and Building Center (meters):

If user enters “n” or “N” for building downwash use then no prompts are processed.

Figure 10. AERSCREEN.INP and prompts inputs for building inputs.
20

Figure 11. Stack and building orientation for a building oriented 90 degrees to north and 

stack oriented 45 degrees to north.

2.3 Meteorology and surface characteristics

For inputs to MAKEMET, the user enters the following:

Minimum and maximum ambient air temperatures (Fahrenheit or Kelvin)

Minimum wind speed (m/s)

Anemometer height (m)

Surface characteristics type (user-entered, AERMET tables, or surface characteristics 

listed in an external file)

When entering data via the prompts, the user can choose to enter default values for 

temperatures, wind speed, and anemometer height (see Figure 12). If using non-default values 

for temperatures, the record minimum and maximum temperatures for the area containing the 

source should be entered. If using a non-default value for the minimum wind speed, a wind 

speed less than 0.5 m/s is allowed. When entering surface characteristics, if the user chooses to 
21

utilize user-entered single value surface characteristics, the user will be prompted for those 

values. If the user chooses to use AERMET seasonal tables, the user will be prompted for land 

use type and surface moisture (average, dry, or wet). If the user chooses to use an external file, 

i.e. AERSURFACE output or AERMET stage 3 input file, the user will be prompted to enter the 

name of the file. If the filename contains spaces or the pathname contains spaces, the pathname 

should be entered in quotations. If the surface characteristics are in a file that is not an 

AERSURFACE file or AERMET stage 3 input file, the format should follow that as outlined in 

the AERMET User‟s Guide, Section 4.7.7 (U.S. EPA, 2004c). After entering the filename, 

AERSCREEN will check for its existence and if it does not exist, the user will be re-prompted 

for the filename. AERSCREEN will also check the file for format and valid values for surface 

characteristics and if the format is incorrect or surface characteristics are not valid, the user will 

be re-prompted for the surface characteristics type (user, AERMET tables, or external file) when 

entering data from the prompts. If the data is entered from AERSCREEN.INP and the file is 

missing, the format is incorrect or surface characteristics are not valid, AERSCREEN will alert 

the user and stop processing.

 

AERSCREEN will also alert the user if the ambient temperatures exceed current world 

record temperatures (183 K and 331 K), Bowen ratio is less than -10 or greater than 10, and if 

the surface roughness is less than 0.001 (but positive) or greater than two meters. If surface 

roughness is less than 0.001 and not negative, AERSCREEN automatically resets the value to 

0.001 and notifies the user. In the case of these warnings, AERSCREEN will use the entered 

values but warns the user that they may exceed reasonable values.

If the user uses the AERSCREEN input file to enter the meteorological parameters, the 

inputs are as follows in the third block of data of the input file and the data section is denoted by 

“** MAKEMET DATA” in the input file. The order of the MAKEMET data line relative to the 

other data sections is unimportant. In the AERSCREEN.INP file, temperatures are in degrees 

Kelvin. For prompts based input, temperatures are in degrees Fahrenheit or Kelvin. Regardless 

of the units convention, wind speeds are in m/s and anemometer height is in meters. The 

AERSCREEN.INP and prompts inputs are shown in Figure 12.
22

AERSCREEN.INP meteorological inputs

** MAKEMET DATA MinT MaxT Speed AnemHt Surf Clim Albedo Bowen Length SC FILE 

** 250.00 310.00 0.5 10.000 0 0 0.1600 0.8700 0.0440 “aersurface_12.out”

Prompts inputs

Enter Min & Max Ambient Temperatures (K) or 

<Enter> to default to 250 310 K...

Enter Minimum Temperature (K):

If user enters a number for minimum temperature:

Enter Maximum Temperature (K):

Enter Minimum Wind Speed or <Enter> to default to 0.5 m/s...

Enter Anemometer Height or <Enter> to default to 10.0 meters...

--------------------------------

1) Single user specified values

2) AERMET seasonal tables

3) External file

--------------------------------

 Enter surface characteristics option:

If the user enters 1

Enter Albedo:

Enter Bowen Ratio:

Enter Surface Roughness Length (m):

If the user enters 2

1) Water

2) Deciduous Forest 

3) Coniferous Forest

4) Swamp 

5) Cultivated Land 

6) Grassland 

7) Urban 

8) Desert Shrubland 

Enter Dominant Surface Profile:

1) Average Moisture 

2) Wet Conditions 

3) Dry Conditions 

Enter Dominant Climate Profile:

If user enters 3

Enter filename containing surface characteristics.

Enclose filename with quotes if path or filename includes spaces...

Figure 12. AERSCREEN.INP and prompts inputs for meteorological and surface 

characteristics data. 
23

The parameters in the input file are:

Minimum temperature

Maximum temperature

Minimum wind speed

Anemometer height

Land use type for surface characteristics

o 0 = user-entered surface characteristics

o 1 = water

o 2 = deciduous forest

o 3 = coniferous forest

o 4 = swamp

o 5 = cultivated land

o 6 = grassland

o 7 = urban

o 8 = desert shrub land

o 9 = use external file of surface characteristics

Climatology type ( for land use of 1 through 8)

o 1 = average moisture

o 2 = wet conditions

o 3 = dry conditions

User defined albedo (not used/requested if land use type is 1 through 9)

User defined Bowen ratio (not used/requested if land use type is 1 through 9)

User defined surface roughness (not used/requested if land use type is 1 through 9)

External surface characteristics filename (not used/requested if land use type is 0 through 

8 )

When determining surface characteristics, the user should consider the location of the source 

(stack or center of volume or area source). Often in emission inventories, the location given for 

a source is not the actual location of the source, but an average of sources in a facility or location 

of an address. The user should verify coordinates of a stack, volume, or area source. The exact 

location of the source is important in determining surface characteristics, especially when using a 

tool such as AERSURFACE. Inaccurate source locations can lead to inaccurate surface 

characteristics estimations, especially surface roughness. When determining surface 

characteristics for the source, regardless of method (user-entered, AERMET tables, or 

AERSURFACE), the user is highly encouraged to review Section 3.1 of the AERMOD 

Implementation Guide (U.S. EPA, 2009) and if using AERSURFACE, to review the 

AERSURFACE User‟s Guide (U.S. EPA, 2008).
24

2.4 Terrain

For terrain processing in AERMAP, the user enters the following:

Include terrain processing (yes=include terrain, no=do not include terrain effects)

Probe distance (meters)

Include discrete receptor distances (discussed in Section 2.6) (beginning with version 

11060)

Flagpole receptors (discussed in Section 2.7)

Source elevation or use AERMAP to determine source elevation

Source coordinates (geographic or UTM)

NAD datum (NAD 27 or 83)

UTM zone (if UTM coordinates entered)

If the user is processing a rectangular area source, the only inputs the user enters via the 

prompts are probe distance, use of discrete receptor distances (version 11060), flagpole 

receptors, and source elevation. The user will not have the choice of using AERMAP for source 

elevation determination. If flat terrain is being processed for any source type, the user cannot use 

AERMAP for source elevation determination. When entering data via the prompts and 

processing terrain, the user has the choice of inputting geographic coordinates (latitude and 

longitude) or UTM coordinates, as well as the NAD datum of the coordinates , North American 

Datum of 1927 (NAD 27) or North American Datum of 1983 (NAD 83). If the user enters 

geographic or UTM coordinates with NAD 27 datum, AERSCREEN converts the coordinates to 

UTM coordinates with NAD 83 datum. If the user enters geographic coordinates with NAD 83, 

AERSCREEN converts the coordinates to UTM coordinates with NAD 83 datum and writes 

those to the AERSCREEN.INP file. If the terrain files read in AERMAP are NAD datum 27 and 

not datum 83, AERMAP will do the necessary conversions to NAD 27 for terrain processing in 

AERMAP. For more information about the NAD conversion process see the AERMAP User‟s 

Guide (U.S. EPA, 2004b).

If geographic to UTM conversion is performed, AERSCREEN will write the converted NAD 

83 UTM coordinates to the new AERSCREEN.INP file with a message that the latitude and 

longitude coordinates were converted to UTM coordinates. AERSCREEN will also write a 

message to the input file if coordinates were switched from NAD 1927 to NAD 1983. When 

entering data using the AERSCREEN.INP file, coordinates must be in UTM coordinates. If the 

coordinates are indicated to be in NAD 1927, AERSCREEN will convert to NAD 1983 UTM 

coordinates and notify the user. Coordinates should only be in NAD 1927 if the user manually 

changed the coordinates and NAD in AERSCREEN.INP. The variables are as follows in the

fourth line of the AERSCREEN input file (Figure 13). Terrain data is denoted by the term “** 

TERRAIN DATA” in the input file. Prompts are also shown in Figure 13.
25

AERSCREEN.INP inputs

** TERRAIN DATA Terrain UTM East UTM North Zone Nada Probe PROFBASE Use AERMAP elev

** N 406672.0 3698970.8 12 1 5.0 18.30 N

Prompts inputs

Include Terrain Heights? (y/n):

If user enters “y” or “Y”:

Enter Maximum Distance (m) to probe

<Enter> for default (10000 m):

If user enters “n” or “N”:

Enter Maximum Distance (m) to probe

<Enter> for default (5000 m):

Enter stack elevation (m) or

<Enter> for AERMAP derived elevation:

If the user enters “n” or “N” for terrain or source is a rectangular area source:

Enter source elevation (m) or

<Enter> for default 0 m:

If user enters “y” or “Y” for terrain:

Enter coordinate type: 

LATLON for latitutde & longitude or

UTM for UTM coordinates

If the user enters LATLON:

Enter Source Latitude (North positive) (xx.xxxx):

Enter Source Longitude (West negaitive) (xxx.xxxx):

If the user enters UTM:

Enter Source UTM Easting (xxxxxx.x):

Enter Source UTM Northing (xxxxxxx.x):

The following prompt is shown for UTM coordinates:

Enter Source UTM Zone (xx):

------------------------------------------------------------------------------

Option (1) - North American Datum of 1927

Option (4) - North American Datum of 1983

-----------------------------------------------------------------------------

Enter Option for Applicable UTM Nada:

Figure 13. AERSCREEN.INP and prompts inputs for terrain data.
26

Input parameters in AERSCREEN.INP are:

Terrain flag (Y=use terrain, N=do not use terrain)

UTM X coordinate

UTM Y coordinate

UTM zone

NAD datum of source location

Probe distance in meters

Source elevation (feet or meters)

Override source elevation with AERMAP value (Y=yes, N=no)

When the probe distance is entered, AERSCREEN checks to see if the probe distance is a 

multiple of 25 meters. If the distance is not a multiple of 25, the probe distance is reset to the 

next distance that is greater than the entered probe distance and is a multiple of 25. 

AERSCREEN alerts the user of the change. For example, if the entered probe distance is 1,031 

m, AERSCREEN will reset the distance to 1,050 m. This is done because the receptor spacing

between zero and 5 km is 25 m and a multiple of 100 between 5 km and the probe distance. The 

reset makes it easier to perform the calculations.

If the user enters the source coordinates as latitude and longitude, the UTM zone will not be 

requested and is determined by AERSCREEN. If not processing terrain, the user can enter the 

actual elevation for the source or choose a default of zero. The user will not be prompted for 

AERMAP override of user-entered source elevation. 

When entering data via the prompts, the prompt for terrain processing and overriding of 

source elevation with AERMAP will appear for all source types except rectangular area sources. 

The other prompts will appear for all sources.

The name(s) of the terrain input file(s) that AERMAP reads are input into AERSCREEN by 

a file called demlist.txt, which is to be located in the same directory as the AERSCREEN 

executable or local folder in which the user is working. The demlist.txt file is not created by 

AERSCREEN but the user must create the file prior to running AERSCREEN. If terrain is to be 

processed, AERSCREEN will check for the existence of this file and if it is not present, 

AERSCREEN will stop processing. The general format of the file and three examples are shown 

in Figure 14. The general format is that the first line contains either “NED” or “DEM” (the case 

can be lower or upper case) as the first three characters to denote the file type. The rest of the 

line is for informational purposes and not read by AERSCREEN. The second line is a delineator 

between the file type and the file list, usually a series of dashes. The third line is to specify the 

location of the grid files (conus.las, conus.los, etc.) that will be used for NAD conversion (from 

27 to 83 or vice versa). The location is specified by starting the line with “NADGRIDS” 

followed by the pathname of the files. If the pathname contains spaces, the entire pathname 

should be enclosed in quotations. Beginning with AERSCREEN version 11060, a trailing “\” is 

no longer necessary at the end of the pathname. In Figure 14a, AERSCREEN will accept 
27

“c:\grid files\” or “c:\grid files”. If the files are in the current working directory1, the rest of the 

line after “NADGRIDS” can be the full path of the current working directory, blank, or .\,.

However, if the files are not in the working directory, AERSCREEN will stop processing. 

Regardless of the NAD datum of the coordinates, the field will be read by AERSCREEN and 

input into AERMAP. If the line beginning with NADGRIDS is not in the demlist.txt file, 

AERSCREEN will notify the user and stop processing.

Finally beginning with the fourth line, is the list of the files to be read into AERMAP, each 

file on a separate line. If the filename or pathname of the file contains spaces, the filename or 

pathname must be enclosed in quotations. For NED files only, the units of the terrain data can be 

included. The units are:

FEET for units of feet

DECI-FEET or DECIFEET for units of decifeet

DECA-FEET or DECAFEET for units of decafeet

METERS for meters

DECI-METERS or DECIMETERS for units of decimeters

DECA-METERS or DECAMETERS for units of decameters

Note that the units are not case sensitive, so lower-case text is allowed. If no units are 

entered, i.e. blank after the filename, the units are understood to be meters and AERMAP will 

give a non-fatal warning to the user when AERMAP is executed. If units are included, when 

AERSCREEN creates the AERMAP.INP file, the TIFFDEBUG keyword will be added to the 

DATAFILE line in the AERMAP.INP file.

In Figure 14a, a single National Elevation Data (NED) file called ned_file.tif is to be read 

into AERMAP with units of meters by default. Also, the NADGRIDS files are located in a 

folder with spaces in the pathname so the filename is in quotations. Figure 14b gives an example 

of a NED file whose pathname contains spaces, so the name is enclosed in quotations. The units 

of the terrain are specified to be meters. Figure 14b also shows that the location of the grid files 

used for NAD conversion. Figure 14c shows a list of DEM files that will be processed in 

AERMAP with NAD grid files located in the current working directory. Note that units cannot 

be included with DEM files.

Users are encouraged to use NED data as DEM data is static and no longer updated. NED 

data is more up to date and is regularly updated.

 

1 Current working directory refers to the directory or folder that a DOS prompt is working in when using a DOS 

window or to the folder that the AERSCREEN executable is in when double clicking the AERSCREEN executable 

icon.
28

Figure 14. Example formats of demlist.txt.

If terrain is to be included, users should consult the AERMOD Implementation Guide, 

specifically sections 4.3, 4.4, and 4.5 (U.S. EPA, 2009) as well as the AERMAP User‟s Guide 

and addendum (U.S. EPA, 2004b). 

2.6 Inclusion of discrete distances

Beginning with version 11060, AERSCREEN allows for the input of up to ten discrete 

receptor distances that are not part of the regularly spaced receptor network created by 

AERSCREEN (See Section 3.4) . These could include distances to specific locations near a 

source such as a monitor, school, residential area, etc. AERSCREEN will read all of the 

locations input by the user but will only process receptors that are between the ambient distance 

and probe distance. Discrete receptor use is entered in AERSCREEN.INP via the 6th data line in 

AERSCREEN.INP (Figure 15) or during the terrain processing prompts when entering via the 

prompts. If the user wishes to include discrete distances, the distances should be entered into a 

simple text file. The user will also be prompted for the filename of distances. The distances 
29

listed in the file can be in several units: meters, feet, kilometers, or miles and is independent of 

whether other data (source inputs, meteorology, etc.) are in metric or English units. To define 

the units, the first line of the text file should be the line “units: “followed by the units of the 

distances. An example file is shown in Figure 16 with distances listed in meters. The format of 

the units line is not case sensitive but it must be the first line of the file. Distances can be entered 

as:

FEET or FT for feet

METERS for meters

KILOMETERS, KILO-METERS, or KM for kilometers

MILES for miles

If the units line is present but no distance units are entered, i.e. the line is just “units: “, then 

AERSCREEN will assume distance units of meters. When entering the filename from 

AERSCREEN.INP, if the file does not exist, or the number of receptors exceeds ten, or no units 

line is listed, AERSCREEN will alert the user and stop processing. If entering the filename 

using prompts and one of the conditions above is met, AERSCREEN will alert the user and reprompt for a filename.

If the discrete receptor data line is not in AERSCREEN.INP, AERSCREEN will assume no 

discrete receptor distances will be used in modeling. The user can then include discrete receptor 

use in the data validation phase of AERSCREEN. 

AERSCREEN.INP inputs

** DISCRETE RECEPTORS Discflag Receptor file

** Y "discrete_rec.txt"

Prompts inputs

Include up to 10 discrete receptors (y/n)?

If user enters “y” or “Y”:

Enter name of file with discrete receptors.

Enclose filename with quotes if path or filename includes spaces...

Figure 15. AERSCREEN.INP and prompts inputs for including discrete distances.

units: meters

26.0

35.1

111.5

427.35

535.0

Figure 16. Sample distances in a discrete distances text file.
30

2.7 Other inputs

Other inputs or options used by AERSCREEN are:

units of inputs (metric or English), 

urban/rural classification

urban population if urban

minimum ambient distance (feet or meters)

use of flagpole receptors

flagpole receptor height (feet or meters) 

These variables in the sixth line of the AERSCREEN input file are shown in Figure 15 and 

are denoted by the term “** UNITS/POPULATION.” This line must be listed after the source 

input line. While entering data via prompts, the English or metrics unit prompt is before any 

other prompts, while the urban/rural and ambient distance prompts occur during the source input 

processing. The flagpole receptor prompts occur in the terrain inputs processing.

AERSCREEN.INP inputs

** UNITS/POPULATION Units R/U Population Amb. dist. Flagpole Flagpole height

** M R 0. 50.000 N 0.00

Prompts inputs

English or Metric Units? (E or M):

Rural or Urban? (R or U):

Enter Population of Urban Area:

Enter Minimum Distance (meters) to Ambient Air –

<Enter> for default (1 m):

Use Flagpole receptors? (y or n):

If user enters “y” or “Y”:

Enter Flagpole receptor height (meters)

Figure 17. AERSCREEN.INP and prompts inputs for other inputs.

Inputs in AERSCREEN.INP are:

Units of data (M=metric, E=English)

Urban/rural flag (U=urban, R=Rural)

Population for urban source

Minimum ambient distance

Use Flagpole receptors

Flagpole receptor height (ignored if flagpole receptors = no)
31

If the units flag in AERSCREEN.INP is set to “E” AERSCREEN will stop processing and 

notify the user that the flag is not set to “M.” for metric. The user can enter the data in English 

units when entering data from the prompts but AERSCREEN will change the units flag to metric 

and convert the variables from English to metric units during processing. When AERSCREEN

creates the AERSCREEN.INP file from prompt-entered data, there will be a comment in the new 

input file that units were converted from English to metric.

For minimum ambient air distances for non-volume sources, when entering data with English 

units, the default value listed will be 3.3 feet, or 1 meter. For volume sources, the ambient

distance must be greater than or equal to 2.15 times the initial lateral dimension, 2.15σy plus one 

meter. In AERMOD, receptors with source-receptor distances less than 2.15σy plus one meter 

are not included in concentration calculations. When entering data via the prompts, the default 

value that is listed will be 2.15σy plus 1 m (or equivalent in feet). If the user chooses the default 

value by hitting <Enter>, that will be the ambient distance. If the user enters a different value 

from the listed default value, it must be greater than or equal to the default value listed. 

Otherwise, the user will receive a message that the value reset to 2.15σy plus 1 m. When 

obtaining the ambient distance from AERSCREEN.INP, AERSCREEN will compare that value 

against 2.15σy plus 1 m and if the entered value is less than 2.15σy plus 1m, it is reset to 2.15σy

plus 1 m. If the user does not wish to use the reset value, it change be changed at the validation 

page but must be greater than or equal to 2.15σy plus 1m. 

When the source is a non-volume source and the ambient distance is less than 1 meter in the 

AERSCREEN.INP, the distance will be reset to 1 meter and AERSCREEN will alert the user. If 

the user enters a distance less than 1 meter using the prompts, the distance will be reset to 1 m 

and the user will be alerted.

2.8 Non-default name for output file

The default output files for AERSCREEN are AERSCREEN.OUT and 

max_conc_distance.txt. AERSCREEN.OUT lists the inputs and various outputs of the 

AERSCREEN run. The file max_conc_distance.txt, lists the maximum concentration by 

distance. Beginning with AERSCREEN version 11060, the user can choose different names 

other than the defaults. The filename must have an “.out” extension. The user can specify a 

filename within the current working folder or a complete path. If a complete pathname is 

entered, AERSCREEN will check to make sure that the target folder or directory exists. If the 

folder does not exist, the user must re-enter the filename. The filename that is used for output 

file is also used to construct the maximum concentration by distance file. The prefix (including 

folder name) of the new output file is used for the maximum concentration file. The prefix 

(including folder name) is also used to copy the final AERSCREEN.INP file and 

AERSCREEN.LOG files to new files that have the same prefix as the output file. The user can 

change the filename using prompts or by the seventh data line beginning with “** OUTPUT 

FILE” followed by the output filename. Figure 18 shows the AERSCREEN.INP inputs and 

prompts inputs. If the output file option is not listed in AERSCREEN.INP, AERSCREEN will 
32

assume the default AERSCREEN.OUT for the filename and the user can change the filename 

during the data validation phase of AERSCREEN.

AERSCREEN.INP inputs

** OUTPUT FILE "AERSCREEN.OUT"

Prompts inputs

Enter name of AERSCREEN output file

Enter <Enter> to use default name AERSCREEN.OUT

Filename should include .out or .OUT extension

If filename contains spaces, enter entire filename in quotations

Figure 18. AERSCREEN.INP and prompts inputs for output filename.

2.9 Error checking

When entering data via the AERSCREEN.INP file or via prompts, AERSCREEN will check 

for invalid responses for flags (use downwash, terrain, urban/rural, etc.) and numeric values 

(stack height, building height, etc.). When processing input from the AERSCREEN.INP file, 

any flags or parameters found to be invalid or outside a realistic data range (minimum ambient 

temperature is greater than maximum ambient temperature), AERSCREEN lists error messages 

for the parameters to the AERSCREEN.LOG file and stops AERSCREEN processing to allow 

the user to correct the values in the AERSCREEN.INP file. Examples would be a character 

other than “Y”, “y”, “N”, or “n” for the building downwash flag or a negative building height for 

downwash. If processing input data from the prompts, AERSCREEN will re-prompt the user for 

a valid response. For the two examples listed above, AERSCREEN would re-prompt the user 

for responses. Appendix A lists the input parameters, reasons for invalid values, and actions 

taken by AERSCREEN. 

When entering data from AERSCREEN.INP, AERSCREEN checks to make sure that the 

emissions data is listed before the building, terrain, and miscellaneous data lines. If the 

emissions data line is listed after one of the other three lines, AERSCREEN notifies the user and 

stops processing.

AERSCREEN also checks for the presence of several files, if applicable:

Demlist.txt (when processing terrain)

BPIPPRM input file (if processing downwash and filename is entered)

External surface characteristics file (if isurf equals 9)

Discrete receptor file (if processing discrete receptors)

If these files are not found, AERSCREEN issues a message and stops processing. Note that 

if demlist.txt does not exist, AERSCREEN stops processing, regardless of whether data is being 

entered via prompts or AERSCREEN.INP. AERSCREEN will also check if the pathname of the 

output file is valid. If the folder or directory does not exist, AERSCREEN issues a message and 
33

stops processing. AERSCREEN also checks for the presence of the AERMOD and MAKEMET 

executables in the current working folder. If one of those executables is not present, 

AERSCREEN issues a warning and prompts the user for the location of the executable.

AERSCREEN will copy the executable from the entered locations to the current working folder. 

If processing downwash, AERSCREEN will check for the presence of the BPIPPRM executable 

and the AERMAP executable if processing terrain. If those are not present, AERSCREEN will 

issue a warning, prompt the user for the locations of the executables, and copy them to the 

current working folder.
34

3. AERSCREEN Program Execution

The AERSCREEN program can be run from the command-prompt or by double-clicking on 

the AERSCREEN.EXE from Windows Explorer. The user should make sure that demlist.txt, the 

AERMOD, MAKEMET, and if necessary the AERMAP and BPIPPRM executables are in the 

current working directory. General AERSCREEN processing is shown in Figure 19. If a restart 

file generated from a previous run (called „AERSCREEN.INP‟) is present in the folder, then the 

user will be asked to continue with the restart file or enter data via the prompts (Figure 20a). If 

there is no restart file, the prompts will begin automatically (Figure 20b). 

Figure 19. AERSCREEN processing and stages.
35

Figure 20. AERSCREEN start screen.

3.1 Data input and validation

If the user chooses the restart file, AERSCREEN goes directly into the user validation page. 

The user should carefully review the data to ensure accurate inputs. If processing terrain,

particular attention should be paid to the coordinates to ensure that any NAD conversions were 

successful. Also on the validation page, the user will have the option of rerunning the same 

inputs or selectively modifying specific components, such as building or terrain information 

(Figure 21). For example, if changes are to be made to building parameters, the user chooses 

option 2 and a list of further options will appear (Figure 23). The user can change individual 

parameters without having to re-enter all the parameters. The option to re-enter all parameters is 

a choice as well. Changes to individual parameters are available for source, meteorological, and 

terrain parameters as well. Some options cannot be changed without changing another parameter 

first. These include changing urban population for a rural source or surface characteristics (i.e. 

user defined values when AERMET tables are chosen). Figure 22 shows the list of choices for 

various source types, Figure 23 shows the choices for building parameters, Figure 24 lists the 

choices for terrain processing, and Figure 25 lists the choices for meteorological processing. For 

each submenu, once the desired changes are made, the user can hit <Enter> to return to the 

validation page. Some changes will automatically return the user to the validation page, such as 

choosing option 1 in Figure 23a for building downwash. 
36

Note, that if the user chooses to change source data, the source type cannot be changed; only 

parameters for the source type from the AERSCREEN.INP file or from the prompts. For 

example, the user cannot change the source from point to rectangular area. For building data, if 

the user is running AERSCREEN for an area source, rectangular or circular, or a volume source 

(which do not use building downwash) and chooses option 2 from the validation page, 

AERSCREEN will give the message that building parameters cannot be changed due to source 

type and return to the validation page. The same is true for changing terrain data when running a 

rectangular area source. The user may also change parameters in the AERSCREEN.INP file 

before running AERSCREEN, instead of modifying the data using the prompts.
37

 AERSCREEN 11060

 ----------------- DATA ENTRY VALIDATION -----------------

 METRIC ENGLISH

** STACKDATA ** --------------- ----------------

Emission Rate: 1.0000 g/s 7.937 lb/hr

Stack Height: 61.00 meters 200.13 feet

Stack Diameter: 5.000 meters 196.85 inches

Stack Temperature: 415.0 K 287.3 Deg F

Exit Velocity: 11.000 m/s 36.09 ft/s

Stack Flow Rate: 457646 ACFM

Model Mode: RURAL

Dist to Ambient Air: 50.0 meters 164. feet

** BUILDING DATA **

User defined BPIPPRM input file: 

BUILDING.INP

** TERRAIN DATA **

No Terrain Elevations

Source Base Elevation: 25.0 meters 82.0 feet

Probe distance: 10000. meters 32808. feet

No flagpole receptors

Using discrete receptors in

discrete_rec.txt

Only receptors between the ambient and probe distances will be included

Input distance units are: METERS

** METEOROLOGY DATA **

Min/Max Temperature: 270.0 / 310.0 K 26.3 / 98.3 Deg F

Minimum Wind Speed: 0.5 m/s

Anemometer Height: 10.000 meters

Using surface characteristics in file: season_3.out

AERSCREEN output file: 

POINT_FLAT_DW.OUT

*** AERSCREEN Run is Ready to Begin - Choose Option to Proceed ***

 1 - Change Source Data;

 2 - Change Building Data;

 3 - Change Terrain Data;

 4 - Change Meteorology Data;

 5 - Change Title;

 6 - Change Output Filename;

 7 - Stop AERSCREEN;

 - or -

 Hit <Enter> to Start Run

Figure 21. AERSCREEN validation page.
38

Figure 22. Submenus for changing source parameters for a) point, capped or horizontal 

stack, b) volume, c) rectangular area, d) circular area, and e) flare sources. 
39

Figure 23. Building downwash submenus for a) building downwash included and b) 

building downwash not included.
40

Figure 24. Terrain submenus for a) terrain heights included, b) terrain heights not 

included and c) rectangular area sources.

-----------------------------------------------------

Enter number of parameter to change or

<Enter> to return to validation page

1) Use default min and max temperatures

2) Minimum temperature

3) Maximum temperature

4) Minimum wind speed

5) Anemometer height

6) Input surface characteristics

7) User albedo

8) User Bowen ratio

9) User surface roughness length

10) landuse

11) Moisture

12) AERSURFACE output file

13) Update all parameters

----------------------------------------------------

Figure 25. Meteorological data submenu.
41

If the user chooses to run from the restart file, while reading the file, AERSCREEN may 

automatically change some of the options in the file, depending on other options. If the source 

being modeled is a rectangular area source and the terrain flag is set to “y” or “Y” then the 

terrain flag is reset to “N.” For rectangular area sources, circular area sources, or volume 

sources, if the BPIP flag is set to “Y” or “y” in the input file then the BPIP flag is set to “N” and 

no downwash is calculated. If the user enters data using prompts instead of the 

AERSCREEN.INP file, the validation page will appear after all prompts have been processed for 

the source, building, terrain, and meteorological data. 

3.2 Meteorological data files

After reading the input file or prompt inputs, and prompting the user for any changes, 

AERSCREEN processes the surface characteristics and runs MAKEMET to create the 

AERMOD meteorological input files (.sfc, and .pfl files). MAKEMET is run for each temporal

period /spatial sector combination of surface characteristics. Depending on the temporal 

resolution and number of spatial sectors of the surface characteristics, one surface and one 

profile file (annual, 1 sector) to a maximum of 144 (monthly, 12 sector) surface files and 144 

profile files are created, one for each temporal period/spatial sector combination (Figure 26). In 

the meteorological files naming convention, the first set of 2-digit numbers refers to the temporal 

period of the surface characteristics, which ranges from 1 to 12. If processing annual surface 

characteristics, the number would be “01” and if processing seasonal or monthly surface 

characteristics, the number would be range from “01” to “04” for seasonal output and “01” to 

“12” for monthly output. The second set of numbers in the filenames is the number of spatial 

sectors for surface roughness. This can range from “01” to “12” for one sector to 12 sectors.

In Figure 26, aerscreen_01_01.sfc and aerscreen_01_01.pfl use surface characteristics for 

January, sector 1; aerscreen_01_02.sfc and aerscreen_01_02.pfl use surface characteristics for 

January, sector 2 and so on with aerscreen_12_12.sfc and aerscreen_12_12.pfl using surface 

characteristics for December, and sector 12. 

Creating met files aerscreen_01_01.sfc & aerscreen_01_01.pfl

Creating met files aerscreen_01_02.sfc & aerscreen_01_02.pfl

Creating met files aerscreen_01_03.sfc & aerscreen_01_03.pfl

Creating met files aerscreen_01_04.sfc & aerscreen_01_04.pfl

Creating met files aerscreen_01_05.sfc & aerscreen_01_05.pfl

.

.

.

Creating met files aerscreen_12_12.sfc & aerscreen_12_12.pfl

Figure 26. Meteorological file creation for monthly 12 sector AERSURFACE output.
42

The input parameters to MAKEMET, which are normally entered using prompts, are written 

to a text file called prompts.inp by AERSCREEN and then “piped” to the MAKEMET call by 

AERSCREEN with the call system command, “makemet < prompts.inp.” Using the 

MAKEMET prompts shown in Figure 1 as a guide, AERSCREEN assigns the names for the 

surface and upper air meteorological files requested in the first two prompts shown in Figure 1

based on the file naming convention described above. The minimum wind speed and 

anemometer height are assigned the values entered by the user. The number of wind directions 

is automatically set to 1 by AERSCREEN and the wind direction is set to 270 degrees. The 

minimum and maximum temperatures are assigned the values entered by the user. The albedo,

Bowen ratio and surface roughness length are assigned the values for the particular 

temporal/spatial combination being processed. The final prompt, “DO YOU WANT TO 

GENERATE ANOTHER MET SET THAT WILL BE APPENDED TO CURRENT FILE? 

[TYPE EITHER "Y" OR "y" FOR YES; OR HIT "ENTER" TO EXIT]” is set not to generate 

another file. An example for monthly, 12 sector AERSURFACE output is shown in Table 1.

Table 1. MAKEMET prompts and example values for the first month and surface 

roughness sector and last month and surface roughness sector for monthly 12 sector 

AERSURFACE output.

MAKEMET prompt Value (month 1, sector 1) Value (month 12, sector 12)

ENTER SFC MET FILE NAME aerscreen_01_01.sfc aerscreen_12_12.sfc

ENTER PFL MET FILE NAME aerscreen_01_01.pfl aerscreen_12_12.pfl

ENTER MIN. WS (M/S) User input minimum wind 

speed

User input minimum wind 

speed

ENTER ANEM HT (M) User input anemometer 

height

User input anemometer 

height

ENTER NUMBER OF WIND DIRECTIONS 1 1

ENTER WIND DIRECTION 270 270

ENTER MIN AND MAX AMBIENT TEMPS IN 

KELVIN

User entered temperatures User entered temperatures

ENTER ALBEDO Albedo for month 1, sector 

1

Albedo for month 12, sector 

12

ENTER BOWEN RATIO Bowen ratio for month 1, 

sector 1

Bowen ratio for month 12, 

sector 12

ENTER SURFACE ROUGHNESS LENGTH IN 

METERS

Surface roughness for 

month 1, sector 1

Surface roughness for month 

12, sector 12

DO YOU WANT TO GENERATE ANOTHER MET 

SET THAT WILL BE

APPENDED TO CURRENT FILE?

[TYPE EITHER "Y" OR "y" FOR YES; OR HIT 

"ENTER" EXIT]

N N
43

3.3 BPIPPRM execution

If downwash is to be considered, BPIPPRM inputs are calculated and written to a BPIPPRM

input file or the user entered input file is used. For either method, BPIPPRM is executed to 

create the projected building dimensions for input into AERMOD. If a user-entered file is used 

and the processing flag (line 2) of the BPIPPRM input file is not a “P” or “p” then BPIPPRM 

will abort and AERSCREEN will notify the user and stop processing. Beginning with 

AERSCREEN version 11060, AERSCREEN also checks to make sure only one stack is listed in 

the BPIPPRM input file. If more than one stack is listed, AERSCREEN will stop processing and 

notify the user.

3.4 Source elevation calculation

If terrain is being used, AERSCREEN calls AERMAP to get the source location‟s elevation. 

The source elevation, user-entered or AERMAP calculated, can be used as the source elevation 

in the SO pathway of the AERMOD runstream file, AERMOD.INP, and as the station elevation, 

keyword PROFBASE in the ME pathway of the AERMOD input file. If the user has chosen to 

replace the input source elevation, either from the restart file or via prompts, AERSCREEN will 

use the AERMAP elevation as the source location‟s elevation. If the user chose to keep the input 

elevation, AERSCREEN will calculate a percent difference between the user-entered elevation 

and the AERMAP calculated elevation and write the difference to the AERSCREEN log file.

3.4 Receptor network

An array of receptor distances is also created including the minimum ambient distance, 

automatically calculated distances (as described in steps 1 and 2 below), and any discrete 

receptor distances. The probe distance is set to the user-specified probe distance, or reset probe 

distance (as described in Section 2.4). Depending on the probe distance, there may be two 

receptor spacing values:

1. 25 meters from zero to 5 km

2. From 5 km to the final probe distance, the spacing is the greater of 25 m or a spacing 

calculated by: (probe distance – 5,000 m)/100 where 100 represents 100 receptors

For example, if the user enters a probe distance of 12, 500 m, the receptor spacing from zero 

to 5,000 m is 25 m and the spacing from 5,000 to 12,500 is 75 m (7,500 m/100).

Receptors located at distances less than the minimum ambient distance, either discrete or 

automatically calculated, are not included in the set of receptors. Also, any discrete receptor 

distances that exceed the probe distance are not included. Discrete receptors that are also equal 

to any distance in the automatic array are not included to avoid duplicate receptors. Receptor 

distances are relative to x=0 and y=0. For point, capped stacks, horizontal stacks, and flare 
44

sources, x=0 and y=0 represent the stack or flare location. For volume and circular area sources, 

x=0 and y=0 represent the center of the source.

There are three main routines in AERSCREEN: PROBE, FLOWSECTOR and REFINE as 

shown in Figure 19. PROBE is executed when there is no source-receptor direction dependency 

(no terrain, no building downwash, and the source is not a rectangular area source). 

FLOWSECTOR is executed when there is a source-receptor direction dependency (terrain and/or

building downwash, or source is a rectangular area source). REFINE is executed after PROBE

or FLOWSECTOR. Details about each section and the final output of AERSCREEN are 

described in each of the following sections.

3.5 PROBE

PROBE executes AERMOD for each combination of temporal periods and spatial sectors. For 

example, if user defined surface characteristics are used (annual, 1 spatial sector), AERMOD is 

executed once (Figure 27a). If monthly, 12 spatial sector AERSURFACE output is used, then 

AERMOD is executed 144 times, 12 months x 12 sectors (Figure 27b). 

Figure 27. Sequence of AERMOD runs in PROBE for different surface characteristics 

combinations.

AERSCREEN reads the output from AERMOD for each run and the highest concentration

and its distance from the source are stored in arrays that will be used to find the highest overall 
45

concentration in REFINE. AERSCREEN also retains the high first high (H1H) 1-hour 

concentration for each receptor. These concentrations are later used in determining the 

maximum concentration by downwind distance.

3.6 FLOWSECTOR

FLOWSECTOR is executed when there is a source-receptor direction dependency (terrain and/or 

building downwash, or rectangular area source). 

If terrain is to be used, AERSCREEN checks for the presence of output from a previous 

AERMAP run. If there is output available, AERSCREEN checks the following against the same 

parameters in the current AERSCREEN run:

source location

probe distance

minimum ambient distance

receptor spacing

number of receptors

NAD datum

UTM zone

Type (DEM or NED files), number and names of terrain input files 

If all of the above parameters match between the existing AERMAP output and the 

current AERSCREEN run, AERSCREEN then checks the receptor coordinates in the 

previous AERMAP run to ensure the distances and directions match the receptor spacing

of the current run and that all 36 radial directions are included. This step is done in case 

the file was changed or corrupted without the user‟s knowledge or if different discrete 

receptors are used, but the number of receptors has not changed.

If any of the above parameters differ, AERMAP will be executed to create new receptor 

elevations. If all parameters match, the user is prompted to decide to use the elevations from the 

previous output, or to run AERMAP to create new elevations. If the older AERMAP output is 

for a source type different than the one being processed in the current run, the user may want to 

consider re-running AERMAP. AERSCREEN sets the ANCHORXY, x=0 and y=0 to the source 

location and receptor locations are relative to this location. For volume and circular area 

sources, this represents the center of the source. For point and flare sources, this is the stack

location. 

If AERMAP is run in FLOWSECTOR, AERSCREEN will calculate a domain for the 

receptor grid to include with the DOMAINXY keyword in the AERMAP.INP file that 

AERSCREEN generates to run AERMAP. This will speed up processing, especially if large 

terrain files are used. For FLOWSECTOR, the domain is 1.1 times the probe distance. 
46

After running AERMAP for the receptor elevations, AERSCREEN checks the 

AERMAP.OUT file for any warnings or errors. If any are found, they are written to the 

AERSCREEN log file and AERSCREEN stops processing.

3.6.1 Rectangular area sources

For rectangular area sources, the angle of the diagonal is calculated from the center to the 

corner of the rectangle. Next, radials are calculated every five degrees, beginning with 0 degrees

up to the nearest 5 degrees past the diagonal. For example, if the diagonal of the source was 

found to be 26 degrees, radials are calculated for 0, 5, 10, 15, 20, 25, and 30 degrees, as shown in 

Figure 28.

Figure 28. Receptor radials for rectangular area sources.

For each one of these radials, receptors are placed out to the probe distance at the calculated 

spacing(s). For each radial, the WDROTATE keyword is used in the ME pathway of the 

AERMOD runstream input file with the value set to the angle of the radial (0, 5, 10, etc.). See 

Figure 29 for examples.
47

Figure 29. ME pathway in the AERMOD runstream with WRDOTATE keyword and 

values for various angles.

The WDROTATE keyword rotates the wind to be along the radial being processed in 

AERMOD because the wind direction in the meteorological files is 270 degrees. Receptor x and 

y coordinates are also calculated based on the angle of the radial, i.e. for the 10 degree radial at 

50 m x=49.24 m, y=8.68 m. AERMOD is run for each of the radials for each surface 

characteristic temporal/spatial sector combination. In the example in Figure 28, for annual 

surface characteristics for the whole 360 degree sector, AERMOD is executed seven times, once 

for each radial. For seasonal surface characteristics for 2 spatial sectors, AERMOD is executed

56 times, once for each radial for each season and sector. For monthly surface characteristics 

with the maximum 12 sectors for surface roughness, AERMOD is executed 1,008 times, once for 

each radial, month, and surface roughness sector. Figure 30 shows sample AERMOD run 

sequences for seasonal, 12 sector surface characteristics for a rectangular area source with six 

radials. First, winter surface characteristics for sector 1 are used for each of the six radials. 

Next, winter surface characteristics for sector 2 are used for each of the six radials. This process 

is followed for each season and surface characteristic sector finishing with autumn sector 12 

surface characteristics. For each temporal/sector combination, AERSCREEN then determines 

the worst case concentration, associated radial, and meteorology to be used later in the REFINE

stage.
48

Processing Winter 

Processing surface roughness sector 1

Processing wind flow sector 1

Processing wind flow sector 2

Processing wind flow sector 3

Processing wind flow sector 4

Processing wind flow sector 5

Processing wind flow sector 6

Processing surface roughness sector 2

Processing wind flow sector 1

Processing wind flow sector 2

Processing wind flow sector 3

Processing wind flow sector 4

Processing wind flow sector 5

Processing wind flow sector 6

.

.

Processing surface roughness sector 12

Processing wind flow sector 1

Processing wind flow sector 2

Processing wind flow sector 3

Processing wind flow sector 4

Processing wind flow sector 5

Processing wind flow sector 6

.

.

Processing Autumn 

Processing surface roughness sector 12

Processing wind flow sector 1

Processing wind flow sector 2

Processing wind flow sector 3

Processing wind flow sector 4

Processing wind flow sector 5

Processing wind flow sector 6

Figure 30. AERMOD run sequences for rectangular area source for seasonal 12 sector 

surface characteristics.
49

3.6.2 Non-rectangular area sources

For non-rectangular area sources, FLOWSECTOR arranges receptors along 36 radials from 

the source, every 10 degrees, shown below in Figure 31. AERMOD is executed for each 

temporal period (annual, seasonal, or monthly) of the surface characteristics (Figure 32). 

However, it is not executed for each surface roughness sector. Instead, for each radial, 

AERSCREEN determines the upwind surface roughness sector of the radial being processed. 

That is, AERSCREEN determines the sector that contains the direction 180 degrees from the 

radial being processed. That is done because the radial is considered in the direction of the flow 

while surface characteristics are for the sector from which the wind is blowing, i.e. upwind. 

Figure 33 shows which sector is used for the 10 degree flow vector (solid black arrow) for three 

sectors from AERSURFACE output. In this case, the upwind direction of 10 degrees, 190 

degrees (dashed black arrow), is contained in the 90 to 225 surface roughness sector.

Figure 31. Receptor placement for point (including capped and horizontal stacks), flare, 

volume, or circular area sources in FLOWSECTOR.
50

Processing Winter 

Processing wind flow sector 10

Processing wind flow sector 20

Processing wind flow sector 30

Processing wind flow sector 40

.

.

Processing wind flow sector 360

.

.

Processing Spring

Processing wind flow sector 10

.

.

Processing Autumn

Processing wind flow sector 10

Processing wind flow sector 20

Processing wind flow sector 30

Processing wind flow sector 40

.

.

Processing wind flow sector 360

Figure 32. AERMOD sequence for seasonal 12 sector surface characteristics when 

processing terrain and/or building downwash.
51

Figure 33. Flow vector (solid arrow) of 10 degrees and associated upwind surface 

roughness sector for three surface roughness sectors (0 to 90, 90 to 225, 225 to 0). 

If building downwash is considered, projected building dimensions calculated by BPIPPRM 

for the flow direction being modeled are included in the AERMOD run. If terrain is processed, 

AERSCREEN will find the appropriate receptors (based on distance and direction) from the 

AERMAP output and include the appropriate terrain data in the AERMOD input file. 

AERSCREEN also checks to ensure the receptor coordinates match the specified distance and 

direction. If they do not, AERSCREEN will issue an error and stop processing. Since 

AERSCREEN generates the receptor elevations via AERMAP, this should not happen, unless 

the AERMAP output file became corrupted during processing. When extracting the appropriate 

receptors, if any receptors have a missing elevation, i.e. -9999.0, AERSCREEN will skip those 

receptors and they will not be included in the AERMOD run for that particular direction. 

AERSCREEN will notify the user of how many receptors were skipped for the particular 

AERMOD run (Figure 34a). If any receptors did have missing elevations, the warning messages 

for those receptors will appear in the AERSCREEN.LOG file for the AERMAP quality 

assurance check (Figure 34b). AERSCREEN will notify the user of the total number of 

receptors skipped for FLOWSECTOR at the end of the AERSCREEN run (Figure 34c). If the 

user finds that receptors have been skipped due to missing elevations, the user may want to 

check the input terrain files for gaps or other irregularities or reconsider the probe distance, as 

this can affect the final maximum 1-hour concentration from AERSCREEN.
52

Figure 34. Receptor skipping notification during FLOWSECTOR run, with notification of 

missing elevations in AERMAP, and total number of receptors skipped for 

FLOWSECTOR and REFINE.

For each AERMOD run in FLOWSECTOR, the maximum concentration, downwind 

distance, and terrain (if applicable) are stored for later use in REFINE. The stored 

concentrations are concentrations for each radial and temporal period of the surface 

characteristics.

3.7 REFINE

REFINE finds the maximum concentration and associated distance and date output from 

PROBE or FLOWSECTOR. If output is from PROBE or a rectangular area source from 
53

FLOWSECTOR, REFINE uses the meteorological files for the temporal period and surface 

roughness sector of the maximum concentration. If output is from FLOWSECTOR for nonrectangular area sources, REFINE finds the upwind surface characteristic sector of the flow 

direction of maximum concentration as in Figure 33. REFINE then uses the meteorological files 

for the appropriate temporal and surface characteristics sector. Receptor spacing becomes one, 

two, or five meters, depending on maximum concentration distance, to refine the output. For 

rectangular area sources, the receptors are placed along the radial associated with the maximum 

concentration. Any discrete receptors supplied by the user are not included in the REFINE 

AERMOD run. If building downwash is used, building dimensions based on the flow direction 

of maximum concentration are used. If terrain is used, REFINE will rerun AERMAP with the 

new receptors in the flow direction of the maximum concentration output from FLOWSECTOR. 

As in FLOWSECTOR, REFINE will create a domain to be used with the DOMAINXY keyword 

in AERMAP. After running AERMAP, REFINE then runs AERMOD using the new receptors 

and appropriate meteorological, building and terrain data. As with FLOWSECTOR, if any 

receptors have a missing elevation, they will be skipped, and the user will be notified of how 

many were skipped (Figure 34c).

3.8 Output

AERSCREEN creates the file AERSCREEN.OUT or user-supplied output filename which

contains source information, output from either PROBE or FLOWSECTOR, meteorology 

associated with the maximum concentration output from PROBE or FLOWSECTOR, maximum

concentrations by distance, and REFINE output: final maximum concentration and maximum

concentration at the minimum ambient distance. See Section 4 for example output. 

AERSCREEN also outputs a file called max_conc_distance.txt, or name based on the usersupplied output filename, that contains the highest concentration by distance, independent of 

worst case meteorology and flow direction, with associated meteorology for the concentrations. 

These concentrations were calculated in PROBE or FLOWSECTOR. Also included in the file is 

the overall maximum concentration output from REFINE. This concentration is denoted by an 

asterisk in the file. The format of this file is shown in Table 1. AERSCREEN also copies the 

AERMOD.INP file from the REFINE AERMOD run to the file AERSCREEN.INP, containing 

the inputs to AERSCREEN entered via prompts or a previous AERSCREEN.INP file with any 

changes that were made during AERSCREEN processing2. AERSCREEN also copies the 

AERSCREEN.INP and AERSCREEN.LOG files to new files with names based on the usersupplied filename. 

 

2

If at any time, AERSCREEN aborts during PROBE, FLOWSECTOR, or REFINE, the user may be able to copy 

the current AERMOD.INP file to AERSCREEN.INP to avoid re-entering data.
54

Table 2. Variables listed in max_conc_distance.txt.

Variable Description

Concentration Maximum 1-hour screening concentration (μg/m3). A concentration with a 

preceding asterisk is the overall maximum concentration.

Distance Distance (m) from source of maximum 1-hour concentration

Elevation Elevation (m) of maximum 1-hour concentration

Flow Flow vector (degrees) associated with maximum 1-hour concentration

Season/Month Season/Month of maximum 1-hour concentration (can be annual, season, or 

month)

Zo sector Surface roughness sector number of maximum 1-hour concentration

Date Date of maximum 1-hour concentration

H0 Heat flux (W/m2)of hour of maximum 1-hour concentration

U* Friction velocity (m/s) of hour of maximum 1-hour concentration

W* Convective velocity (m/s) of hour of maximum 1-hour concentration

DT/DZ Lapse rate (K/m) of hour of maximum 1-hour concentration

ZICNV Convective mixing height (m) of hour of maximum 1-hour concentration

ZIMCH Mechanical mixing height (m) of hour of maximum 1-hour concentration

M-O LEN Monin-Obukhov length (m) of hour of maximum 1-hour concentration

Z0 Surface roughness length (m) of hour of maximum 1-hour concentration

Bowen Bowen ratio of hour of maximum 1-hour concentration

Albedo Albedo of hour of maximum 1-hour concentration

REF WS Wind speed (m/s) of hour of maximum 1-hour concentration

HT Anemometer height (m) of hour of maximum 1-hour concentration

REF TA Temperature (K) of hour of maximum 1-hour concentration

HT Height of Temperature (m) of hour of maximum 1-hour concentration
55

4. Example run

This section will show an example AERSCREEN run for a point source with building 

downwash and terrain. Table 3 gives a summary of the AERSCREEN inputs and Figure 35

shows the building/stack orientation. Table 4 lists the seasonal surface characteristics and Figure 

36 shows the land use and terrain for the example. Figure 37 lists the inputs for demlist.txt and 

Figure 38 lists the discrete receptor file contents. 

Table 3. Inputs for example AERSCREEN run.

Parameters Inputs Input values

Source Source type POINT

Stack height 10 m

Emission rate 1 g/s

Stack diameter 0.5 m

Stack exit temperature 300 K

Stack exit velocity 15 m/s

Building Include building downwash Yes

Building height 34 m

Maximum horizontal dimension 120 m

Orientation of maximum building dimension to North 90°

Minimum horizontal dimension 60 m

Direction of stack from North 26.6°

Distance from stack to building center 67 m

Meteorology Minimum temperature 261.4

Maximum temperature 313.1

Minimum wind speed 1.5 m/s

Anemometer height 10 m

Source of surface characteristics AERSURFACE (aersurface_12.out)

Terrain Include terrain Yes

Coordinate type Latitude and longitude (LATLON)

Source latitude 35.891400° N

Source longitude 78.781940° W

NAD 83

Probe distance 1 km

Source elevation 126.8

Override input elevation with AERMAP derived value No

Discrete 

receptors

Use five discrete receptors, units in meters discrete_receptors.txt

Other inputs Input units Metric

Rural/urban Urban

Input population 2400000

Minimum ambient distance 30 m

Use flagpole receptors No

Output file Use non-default name aerscreen_example.out
56

Figure 35. Plane view of building and stack orientation for example AERSCREEN run.

Table 4. Seasonal surface characteristics by sector.

Variable Season Sector

1 2 3 4 5 6 7 8 9 10 11 12

Albedo Winter 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15

Spring 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14

Summer 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15

Autumn 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15

Bowen 

ratio

Winter 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85

Spring 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63

Summer 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36

Autumn 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84

Surface 

roughness

Winter 0.089 0.011 0.025 0.029 0.032 0.034 0.031 0.013 0.115 0.244 0.391 0.305

Spring 0.118 0.016 0.032 0.036 0.04 0.042 0.038 0.019 0.141 0.289 0.458 0.379

Summer 0.143 0.022 0.038 0.043 0.048 0.049 0.045 0.025 0.163 0.335 0.509 0.435

Autumn 0.123 0.016 0.032 0.036 0.041 0.042 0.038 0.019 0.142 0.311 0.478 0.405
57

Figure 36. a) landuse pattern and sectors used for surface characteristics and b) terrain. 

The circle represents the 1 km radius from the source.

NED : 

 ----------------------------------------------------

NADGRIDS .\

NED_22944813\NED_22944813.tif

Figure 37. Contents of demlist.txt for terrain processing.
58

Figure 38. Contents of discrete_receptors.txt.

4.1 Processing and log file

Below in Figures 39 through 34 are the prompts and inputs for the source, building 

information, terrain data and meteorological data. In Figure 39, the initial prompts are shown. 

Since there is no existing AERSCREEN.INP file, AERSCREEN alerts the user that 

AERSCREEN.INP does not exist and the user must enter the data. The user enters a title, 

whether the inputs are in English or metric units, and the source type (point, volume, etc.).

Figure 39. Initial AERSCREEN title, units, and source type prompts.

After the initial prompts, the user then enters source parameters (Figure 40). The stack 

parameters, stack height, inner stack diameter, stack exit temperature, stack velocity units, and 

stack velocity. The user also enters if the source is urban or rural, and the urban population if an 

urban source. The user then enters the minimum distance to ambient air, i.e. ambient boundary. 

Values entered are as described in Table 3.

units: METERS

53

105

201

503

702
59

Figure 40. Source parameter inputs.

After source parameters have been entered, the user enters the building parameters for 

building downwash effects (Figures 41 and 42). In Figure 41, the initial prompts are shown. 

The user is prompted to include downwash if desired and if so, the user is prompted if an 

existing BPIPPRM input file is to be used. If the answer is yes to downwash but no to an 

existing BPIPPRM file, the user is then prompted for the building dimensions, building 

orientation, and stack orientation relative to the building (Figure 42). The inputs are building 

height, maximum horizontal dimension, minimum horizontal dimension, angle of maximum 

horizontal dimension to North, angle of stack from North, and distance between stack and 

building center. Building dimensions are shown in Table 3 and Figure 35.
60

Figure 41. Initial building downwash prompts.

Figure 42. Building parameter inputs.

The next set of inputs is for terrain (Figure 43). The user is prompted if terrain is to be used. 

The user is then prompted for the probe distance with a default of 10 km available. Note, that 

the terrain input file or files (NED or DEM), must encompass the probe distance. Following the 

probe distance, the user is prompted for the use of discrete receptors and then the user is 

prompted for the use of flagpole receptors and if so, the flagpole height. After the flagpole 

information, the source elevation is input by the user. This can be an elevation or the user can hit 

<Enter> to use AERMAP to calculate elevation. In this case, the user has entered 126.8 m. Note 

if terrain is not used, this is the last prompt in the terrain section of inputs. If terrain is to be 

used, the user enters the coordinate type and coordinates. The NAD datum is also entered by the 

user. If coordinates are UTM coordinates, the user will be prompted for the UTM zone. Since 

geographic coordinates are used in this example, the UTM zone is determined by AERMAP.
61

Figure 43. Terrain parameter prompts.

The meteorological parameters are the next inputs by the user (Figure 44). The user enters 

the minimum and maximum air temperatures for the AERSCREEN run or accepts defaults of 

250 and 310 K. The user then enters the minimum wind speed and anemometer height. For this 

example, a minimum of 1.5 m/s was selected for the wind speed and the default 10 m 

anemometer height was entered. After the anemometer height, the surface characteristics type, 

user-entered single values (option 1), AERMET seasonal tables (option 2), or use of an external 

file (option 3) is chosen. Option 3, an external file, is chosen by the user and the user then enters 

the filename. The file is in the same folder as the current working directory so no pathnames are 

necessary.
62

Figure 44. Meteorological parameter prompts and inputs.

After processing the meteorological data, the user is prompted for the name of the output file 

(Figure 45).

Figure 45. Output filename prompt and response.
63

Finally after the meteorological inputs, the validation page is displayed to the user listing all 

input parameters for the source, building downwash, terrain, and meteorological data (Figure 

46). The source and building parameters are listed in both metric and English units as well as the 

minimum and maximum temperatures, source elevation and probe distance. AERSCREEN also 

displays the UTM and geographic coordinates for the source with the message that coordinates 

were converted from geographic to UTM coordinates. Coordinates are displayed in NAD datum 

of 1983. If coordinates were initially entered in NAD 1927 datum, those coordinates would be 

listed as well with the message that coordinates were switched from NAD 27 to NAD 83 with 

the NAD 27 geographic and UTM coordinates listed as well. The options listed below the 

meteorological data can be used to change parameters for the source, building, terrain, or 

meteorological data. If options 1 through 4 are chosen, the user then sees a sub-menu of 

parameters to choose (See Section 3). If the user is ready to proceed, option 6 is chosen and 

AERSCREEN begins processing the data. After choosing option 6, the same data as seen on the 

validation page is written to the AERSCREEN.LOG file (Figure 47).
64

Figure 46. Data validation page.
65

Start date and time 03/08/11 15:11:23

 AERSCREEN 11060

Example stack 

 Example stack 

 

 ----------------- DATA ENTRY VALIDATION -----------------

 METRIC ENGLISH

** STACKDATA ** --------------- ----------------

Emission Rate: 1.0000 g/s 7.937 lb/hr

Stack Height: 10.00 meters 32.81 feet

Stack Diameter: 0.500 meters 19.69 inches

Stack Temperature: 300.0 K 80.3 Deg F

Exit Velocity: 15.000 m/s 49.21 ft/s

Stack Flow Rate: 6240 ACFM

Model Mode: URBAN

Population: 2400000

Dist to Ambient Air: 30.0 meters 98. feet

** BUILDING DATA **

Building Height: 34.0 meters 111.5 feet

Max Building Dimension: 120.0 meters 393.7 feet

Min Building Dimension: 60.0 meters 196.9 feet

Building Orientation: 90.0 degrees

Stack Direction: 26.6 degrees

Stack Distance: 67.0 meters 219.8 feet

** TERRAIN DATA **

Input coordinates switched from geographic to UTM

Source Longitude: -78.78194 deg 700198. Easting

Source Latitude: 35.89140 deg 3974176. Northing

UTM Zone: 17 Reference Datum: 4 (NAD 83)

Source Base Elevation: 126.8 meters 416.0 feet

Probe distance: 1000. meters 3281. feet

No flagpole receptors

Using discrete receptors in 

discrete_receptors.txt

Only receptors between the ambient and probe distances will be included

Input distance units are: METERS

** METEOROLOGY DATA **

Min/Max Temperature: 261.4 / 313.1 K 10.9 / 103.9 Deg F

Minimum Wind Speed: 1.5 m/s

Anemometer Height: 10.000 meters

Using surface characteristics in file: 

aersurface_12.out

*** AERSCREEN Run is Ready to Begin 

Terrain to be used,AERMAP will be run 

**************************************************

Figure 47. Input data in AERSCREEN.LOG.
66

After data validation, AERSCREEN reads the AERSURFACE output file and lists the 

surface characteristics (Figure 48).

SURFACE CHARACTERISTICS & MAKEMET

Obtaining surface characteristics...

Using seasonal surface characteristics for 12 spatial sector(s)

Sector Start End

 1 0 30

 2 30 60

 3 60 90

 4 90 120

 5 120 150

 6 150 180

 7 180 210

 8 210 240

 9 240 270

 10 270 300

 11 300 330

 12 330 0

Season Sector Albedo Bo zo

Winter 1 0.15 0.85 0.089

Winter 2 0.15 0.85 0.011

Winter 3 0.15 0.85 0.025

Winter 4 0.15 0.85 0.029

Winter 5 0.15 0.85 0.032

Winter 6 0.15 0.85 0.034

Winter 7 0.15 0.85 0.031

Winter 8 0.15 0.85 0.013

Winter 9 0.15 0.85 0.115

Winter 10 0.15 0.85 0.244

Winter 11 0.15 0.85 0.391

Winter 12 0.15 0.85 0.305

Spring 1 0.14 0.63 0.118

Spring 2 0.14 0.63 0.016

.

.

.

Autumn 11 0.15 0.84 0.478

Autumn 12 0.15 0.84 0.405

Creating met files aerscreen_01_01.sfc & aerscreen_01_01.pfl

Creating met files aerscreen_01_02.sfc & aerscreen_01_02.pfl

.

.

.

Creating met files aerscreen_04_11.sfc & aerscreen_04_11.pfl

Creating met files aerscreen_04_12.sfc & aerscreen_04_12.pfl

***************************************************

Figure 48. Surface characteristics processing and meteorological files creation.
67

AERSCREEN then runs AERMAP for the source and determines the percent difference 

between the user-entered source elevation and the AERMAP derived elevation (Figure 49). The 

AERMAP elevation will not be used by AERSCREEN. AERSCREEN also lists any fatal error 

or warning messages from AERMAP. In this case warning messages about the use of default 

elevation units of meters for the NED file are displayed. For the example case, the difference 

between the AERMAP elevation, 120.98 m, and the user-entered elevation, 126.8 m, differ by 

4.59%.

Running AERMAP for stage 0

 *** AERMAP Finishes Successfully *** for source

 ******** WARNING MESSAGES ******** 

OU W473 26 NEDCHK:Default elevation units of METERS used; NED file: 1 

AERMAP elevation, 120.98 differs from user entered elevation, 126.80 by 4.59%

Figure 49. AERMAP processing and elevation of source.

Once AERMAP has been run for the source, AERSCREEN then begins the FLOWSECTOR 

stage and executes AERMAP for the receptors (Figure 50). While processing the receptors, 

AERMAP writes the processing status to the screen (Figure 51). Once AERMAP is completed

for all receptors for all thirty-six directions, AERSCREEN checks the AERMAP.OUT file for 

any warnings or errors (Figure 52). 

Buildings and/or terrain present or rectangular area source, skipping probe

FLOWSECTOR started 03/08/11 15:15:30

***************************************************

Running AERMAP for FLOWSECTOR

Figure 50. AERSCREEN.LOG records for AERMAP processing for FLOWSECTOR.
68

Figure 51. Status of AERMAP processing for FLOWSECTOR.

 *** AERMAP Finishes Successfully *** for FLOWSECTOR

 ******** WARNING MESSAGES ******** 

OU W473 1461 NEDCHK:Default elevation units of METERS used; NED file: 

1 

********************************************

Figure 52. AERSCREEN.LOG summary of AERMAP.OUT warning and error messages.
69

Figure 53 shows partial AERMAP output for FLOWSECTOR. It is from this output that 

AERSCREEN will extract the receptor elevations for AERMOD processing in FLOWSECTOR. 

Receptor spacing for this example was 25 m since the probe distance was less than 5 km. 

Summing across all 36 radials, excluding receptors less than the minimum ambient distance, 

including the ambient distance, discrete receptors, and the source location, results in 1,621 total 

receptors. Also listed in the output is information that will be used for later AERSCREEN runs 

to determine if AERMAP needs to be rerun for FLOWSECTOR. This includes the UTM 

coordinates, probe distance (meters), receptor spacing, UTM zone, NAD datum, number of NED 

files and number of receptors. Coordinates, probe distance, receptor spacing, UTM zone, and 

NAD datum are listed in the line after “** Example stack.”

** AERMAP - VERSION 09040 03/08/11

** 15:15:31

** Example stack

** 700198.4 3974175.8 1000.0 25.0 25.0 17 4

** A total of 1 NED files were used

** A total of 1621 receptors were processed

** DOMAINXY 699098.4 3973075.8 17 701298.4 3975275.8 17

** ANCHORXY 0.0 0.0 700198.4 3974175.8 17 4

** Terrain heights were extracted by default

 

RE ELEVUNIT METERS

 DISCCART 0.00 0.00 120.98 120.98

 DISCCART 5.21 29.54 119.75 119.75

 DISCCART 8.68 49.24 119.60 119.60

 DISCCART 9.20 52.19 119.84 119.84

 DISCCART 13.02 73.86 120.82 120.82

 DISCCART 17.36 98.48 120.82 120.82

 DISCCART 18.23 103.40 120.81 120.81

 DISCCART 21.71 123.10 120.73 120.73

 DISCCART 26.05 147.72 120.36 120.36

 DISCCART 30.39 172.34 119.77 120.36

 DISCCART 34.73 196.96 117.76 120.49

 DISCCART 34.90 197.95 117.69 120.49

 DISCCART 39.07 221.58 117.96 117.96

Figure 53. Partial AERMAP output for FLOWSECTOR.

Once AERMAP has been run for all receptors, AERSCREEN processes each flow vector 

every 10 degrees from 10 degrees to 360 degrees. The appropriate building dimensions and 

meteorological files are used for each flow vector. During processing, AERSCREEN notifies 

the user what season or month and flow vector is being processed (Figure 54). A sample 

AERMOD.INP file is shown in Figure 55 with projected building dimensions and receptors for a 

particular flow vector. Note that the y-coordinate for each receptor is reset to 0. After 

AERMOD is executed for each flow vector, AERSCREEN checks the AERMOD.OUT file and 

notifies the user of any warning or error messages for that flow vector (Figure 56). 
70

Figure 54. AERSCREEN processing during FLOWSECTOR.
71

SO STARTING

 LOCATION SOURCE POINT 0.0 0.0 126.80

 SRCPARAM SOURCE 0.1000E+01 10.000 300.000 15.000 0.500

 BUILDHGT SOURCE 36*34.00

 BUILDWID SOURCE 36*133.28

 BUILDLEN SOURCE 36*97.42

 XBADJ SOURCE 36*-115.27

 YBADJ SOURCE 36*7.70

 URBANSRC SOURCE

 SRCGROUP ALL

SO FINISHED

RE STARTING

** Fence line receptor

 DISCCART 30.0 0.0 120.90 120.90

** Automatic receptors

 DISCCART 50.0 0.0 120.84 120.84

 DISCCART 53.0 0.0 120.88 120.88

 DISCCART 75.0 0.0 121.31 121.31

.

.

.

RE FINISHED

Figure 55. Partial AERMOD.INP file used in FLOWSECTOR for 20 degree flow vector.
72

Running AERMOD

Processing Winter

*****************************************************

Processing wind flow sector 10

AERMOD Finishes Successfully for FLOWSECTOR stage 2 Winter sector 10

 0 receptors skipped due to missing elevations

 ******** WARNING MESSAGES ******** 

 *** NONE *** 

*****************************************************

.

.

*****************************************************

Processing wind flow sector 360

AERMOD Finishes Successfully for FLOWSECTOR stage 2 Autumn sector 360

 0 receptors skipped due to missing elevations

 ******** WARNING MESSAGES ******** 

 *** NONE *** 

FLOWSECTOR ended 03/08/11 15:18:02

Figure 56. AERSCREEN.LOG partial output of AERMOD.OUT checks for 

FLOWSECTOR.

After FLOWSECTOR, AERSCREEN enters the REFINE subroutine and calculates the 

overall maximum concentration and its associated distance, flow vector, projected building 

dimensions, terrain and meteorology. AERSCREEN then reruns AERMAP (Figure 57) and 

AERMOD with refined receptor spacing using the terrain, projected building dimensions, and 

meteorology of the maximum concentration‟s flow vector. The receptors include the minimum 

ambient receptor and receptors near the maximum concentration with 1 to 5 m spacing. See 

Figure 58 for the partial AERMOD.INP file used in REFINE. Messages from 

AERSCREEN.LOG for REFINE and final processing are shown in Figure 59. The maximum 

concentration is along the 270 degree flow vector. AERSCREEN ends and notifies the user that 

AERSCREEN ended successfully with warnings and gives the end time. AERSCREEN also 

outputs the overall maximum 1-hour concentration and maximum 1-hour ambient boundary

concentration, with scaled 3, 8, 24-hour, and annual average concentrations (Figure 60). Also 

listed are the distances, flow vectors direction, and receptor elevations relative to the source 

elevation. For the example case, the overall maximum 1-hour concentration was 378 μg/m3at 

117 m toward 270° and the receptor‟s elevation was 21.07 m below the source or 105.73 m. The 

maximum ambient boundary concentration was 301.3 μg/m3north of the source at an elevation 

of about 118.93 m or 7.87 m below the source elevation.
73

Figure 57. Status of AERMAP processing for REFINE.
74

SO STARTING

 LOCATION SOURCE POINT 0.0 0.0 126.80

 SRCPARAM SOURCE 0.1000E+01 10.000 300.000 15.000 0.500

 BUILDHGT SOURCE 36*.00

 BUILDWID SOURCE 36*.00

 BUILDLEN SOURCE 36*.00

 XBADJ SOURCE 36*.00

 YBADJ SOURCE 36*.00

 URBANSRC SOURCE

 SRCGROUP ALL

SO FINISHED

RE STARTING

** Fence line receptor

 DISCCART 30.00 0.00 117.88 121.12

** Refined receptors

 DISCCART 75.00 0.00 108.82 122.03

 DISCCART 76.00 0.00 108.69 122.03

 DISCCART 77.00 0.00 108.57 122.03

 DISCCART 78.00 0.00 108.45 122.03

.

.

.

RE FINISHED

Figure 58. Partial AERMOD.INP file for REFINE processing.
75

REFINE started 03/08/11 15:18:02

***************************************************

Running AERMAP for REFINE

 *** AERMAP Finishes Successfully *** for stage 3

 ******** WARNING MESSAGES ******** 

OU W473 123 NEDCHK:Default elevation units of METERS used; NED file: 1 

AERMOD Finishes Successfully for REFINE stage 3 Winter sector 290

 0 receptors skipped due to missing elevations

 ******** WARNING MESSAGES ******** 

 *** NONE *** 

REFINE ended 03/08/11 15:18:04

**********************************************

AERSCREEN Finished Successfully

But with Warnings

Source coordinates switched from lat/lon to UTM

 0 receptors skipped for FLOWSECTOR

 0 receptors skipped for REFINE

Check log file for details

***********************************************

Ending date and time 03/08/11 15:18:05

Figure 59. REFINE and final AERSCREEN.LOG messages.
76

Figure 60. Overall maximum and maximum ambient boundary concentration statistics.

4.2 AERSCREEN output

Output from AERSCREEN is written to AERSCREEN_EXAMPLE.OUT. Following are 

sections with explanations.
77

The first section shown lists information also shown in the log file, emissions inputs, terrain 

information (input terrain file and probe distance), and building inputs in both metric and English 

units (Figure 61).

AERSCREEN 11060 / AERMOD 09292 03/08/11

 15:18:04

TITLE: Example stack 

-----------------------------------------------------------------------------

***************************** STACK PARAMETERS ****************************

-----------------------------------------------------------------------------

SOURCE EMISSION RATE: 1.0000 g/s 7.937 lb/hr

STACK HEIGHT: 10.00 meters 32.81 feet

STACK INNER DIAMETER: 0.500 meters 19.69 inches

PLUME EXIT TEMPERATURE: 300.0 K 80.3 Deg F

PLUME EXIT VELOCITY: 15.000 m/s 49.21 ft/s

STACK AIR FLOW RATE: 6241 ACFM

STACK BASE LONGITUDE: -78.7819 deg 700198. Easting

STACK BASE LATITUDE: 35.8914 deg 3974176. Northing

STACK BASE UTM ZONE: 17

REFERENCE DATUM (NADA): 4

STACK BASE ELEVATION: 126.80 meters 416.01 feet

RURAL OR URBAN: URBAN

POPULATION: 2400000

DIGITAL ELEVATION MAP(S) NED_22944813\NED_22944813.tif 

INITIAL PROBE DISTANCE = 1000. meters 3281. feet

-----------------------------------------------------------------------------

*********************** BUILDING DOWNWASH PARAMETERS **********************

-----------------------------------------------------------------------------

BUILDING HEIGHT: 34.0 meters 111.5 feet

MAX BUILDING DIMENSION: 120.0 meters 393.7 feet

MIN BUILDING DIMENSION: 60.0 meters 196.9 feet

BUILDING ORIENTATION TO NORTH: 90. degrees

STACK DIRECTION FROM CENTER: 27. degrees

STACK DISTANCE FROM CENTER: 67.0 meters 219.8 feet

Figure 61. AERSCREEN_EXAMPLE.OUT section with source and building information.

The next section gives information about the results of FLOWSECTOR (Figure 62). The 

header for the section gives the receptor spacing, 25 m. Next, follows the flow sectors from 10 

to 360 degrees. Included for each sector are the projected building width and length output from 

BPIPPRM, the x and y building adjustments from BPIPPRM, the maximum 1-hour 
78

concentration ( g/m3), the downwind distance from the source, and the elevation of the receptor 

relative to the source (receptor – source). Concentrations are written in with the “G” FORTRAN 

descriptor with 4 significant digits. The sector followed by an “*” indicates that this is the 

highest concentration sector or “worst case sector.” In this case it is flow sector 270 degrees 

with a concentration of approximately 376.2 g/m3at 125 m from the source. The relative

receptor elevation is -21.38 m, meaning the receptor is at an elevation of approximately 105 m. 

The temporal period associated with the maximum concentration is winter.

-----------------------------------------------------------------------------

************************** FLOW SECTOR ANALYSIS *************************** 

 25 meter receptor spacing: 30. meters - 1000. meters

-----------------------------------------------------------------------------

 MAXIMUM IMPACT RECEPTOR

 FLOW BUILD BUILD 1-HR CONC DIST HEIGHT TEMPORAL

 SECTOR WIDTH LENGTH XBADJ YBADJ (ug/m3) (m) (m) PERIOD

 ----------------------------------------------------------------------------------

 10 128.60 79.93 -104.17 19.14 269.7 53.0 -6.96 SPR

 20 133.28 97.42 -115.27 7.70 219.6 30.0 -6.26 SPR

 30 133.92 111.96 -122.86 -3.97 164.6 30.0 -5.90 WIN

 40 130.49 123.10 -126.73 -15.53 89.78 475.0 -3.69 SUM

 50 123.10 130.49 -126.74 -26.61 79.97 100.0 -4.85 SPR

 60 111.96 133.92 -122.90 -36.88 116.5 75.0 -4.81 WIN

 70 97.42 133.28 -115.32 -46.04 132.7 75.0 -4.63 WIN

 80 79.93 128.60 -104.25 -53.79 256.9 75.0 -4.51 WIN

 90 0.00 0.00 0.00 0.00 308.2 100.0 -4.41 WIN

 100 0.00 0.00 0.00 0.00 307.2 100.0 -4.58 WIN

 110 0.00 0.00 0.00 0.00 305.4 100.0 -4.90 WIN

 120 111.96 133.92 -62.99 -66.88 256.8 53.0 -4.72 WIN

 130 123.10 130.49 -49.72 -65.18 217.6 100.0 -5.31 WIN

 140 130.49 123.10 -34.94 -61.49 216.2 125.0 -6.09 WIN

 150 133.92 111.96 -19.10 -55.94 230.7 150.0 -6.31 WIN

 160 133.28 97.42 -2.68 -48.68 232.8 175.0 -5.95 WIN

 170 128.60 79.93 13.83 -39.95 246.5 175.0 -6.76 WIN

 180 120.00 60.00 29.91 -30.00 233.4 100.0 -5.13 WIN

 190 128.60 79.93 24.25 -19.14 246.2 105.0 -5.17 WIN

 200 133.28 97.42 17.85 -7.70 243.4 125.0 -5.34 WIN

 210 133.92 111.96 10.90 3.97 259.0 125.0 -5.69 WIN

 220 130.49 123.10 3.63 15.53 250.1 150.0 -6.42 WIN

 230 123.10 130.49 -3.76 26.61 220.0 125.0 -7.83 WIN

 240 111.96 133.92 -11.03 36.88 182.9 200.0 -13.09 WIN

 250 97.42 133.28 -17.96 46.04 208.2 150.0 -19.38 WIN

 260 79.93 128.60 -24.35 53.79 258.3 53.0 -11.47 WIN

 270* 0.00 0.00 0.00 0.00 376.2 125.0 -21.38 WIN

 280 0.00 0.00 0.00 0.00 376.2 125.0 -19.18 WIN

 290 0.00 0.00 0.00 0.00 376.2 125.0 -16.65 WIN

 300 111.96 133.92 -70.94 66.88 231.0 53.0 -14.84 WIN

 310 123.10 130.49 -80.77 65.18 167.6 100.0 -12.94 WIN

 320 130.49 123.10 -88.16 61.49 186.4 105.0 -11.18 AUT

 330 133.92 111.96 -92.86 55.94 159.2 100.0 -11.05 SPR

 340 133.28 97.42 -94.75 48.68 100.5 75.0 -10.81 WIN

 350 128.60 79.93 -93.75 39.95 213.4 30.0 -8.59 SUM

 360 120.00 60.00 -89.91 30.00 301.3 30.0 -7.87 WIN

* = worst case flow sector

Figure 62. FLOWSECTOR results in AERSCREEN_EXAMPLE.OUT.
79

Next, follows meteorological inputs and meteorology used to calculate the overall worst case 

scenario (Figure 63). Listed first are the inputs: minimum and maximum temperatures (K), 

minimum wind speed and anemometer height. Also listed is the dominant season and surface 

roughness sector associated with the worst case concentration. For this case it is winter and 

roughness sector 4 with beginning direction 90 degrees and ending with 120 degrees. Note that 

this is the sector of the upwind direction of the worst case scenario. Shown below the season 

and sector are the surface characteristics for that season and sector.

Next, follows the meteorological parameters used to predict the worst case concentration at 

the ambient boundary (Figure 63): year, month, day, Julian date, hour, heat flux, u*, w*, lapse 

rate, convective mixing height, mechanical mixing height, Monin-Obukhov length, surface 

roughness, Bowen ratio, albedo reference wind speed, anemometer height, temperature, and 

temperature measurement height (2 meters). The surface characteristics listed should match 

those listed in association with the dominant season and sector in the AERSURFACE output file 

or AERSCREEN.LOG file. After the meteorological parameters, the final plume rise is also 

shown. After that are listed the meteorological parameters and plume height of the maximum 

concentration at the ambient boundary. Plume heights do not include downwash effects.
80

-----------------------------------------------------------------------------

********************** MAKEMET METEOROLOGY PARAMETERS *********************

-----------------------------------------------------------------------------

MIN/MAX TEMPERATURE: 261.4 / 313.1 (K)

MINIMUM WIND SPEED: 1.5 m/s

ANEMOMETER HEIGHT: 10.000 meters

SURFACE CHARACTERISTICS INPUT: aersurface_12.out

DOMINANT SECTOR: 4 ( 90 120)

DOMINANT SEASON: Winter

ALBEDO: 0.15

BOWEN RATIO: 0.85

ROUGHNESS LENGTH: 0.029 (meters)

 METEOROLOGY CONDITIONS USED TO PREDICT OVERALL MAXIMUM IMPACT

 -------------------------------------------------------------

 YR MO DY JDY HR

 -- -- -- --- --

 10 01 09 9 01

 H0 U* W* DT/DZ ZICNV ZIMCH M-O LEN Z0 BOWEN ALBEDO REF WS

 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 -2.90 0.051 -9.000 0.020 -999. 27. 4.5 0.029 0.85 0.15 1.50

 HT REF TA HT

- - - - - - - - - - -

 10.0 313.1 2.0

ESTIMATED FINAL PLUME HEIGHT (non-downwash): 22.7 meters

 METEOROLOGY CONDITIONS USED TO PREDICT AMBIENT BOUNDARY IMPACT

 --------------------------------------------------------------

 YR MO DY JDY HR

 -- -- -- --- --

 10 01 09 9 01

 H0 U* W* DT/DZ ZICNV ZIMCH M-O LEN Z0 BOWEN ALBEDO REF WS

 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50

 HT REF TA HT

- - - - - - - - - - -

 10.0 313.1 2.0

ESTIMATED FINAL PLUME HEIGHT (non-downwash): 22.6 meters

Figure 63. Meteorological data associated with maximum FLOWSECTOR concentration 

and ambient boundary concentration.
81

After the meteorological parameters, follows a summary of maximum concentrations by 

distance (Figure 64). The concentrations shown are not necessarily in the same direction as the 

overall maximum concentration shown in the flow sector analysis, i.e., the maximum 30 m 

concentration may not be directed toward 180. Details about the concentrations‟ meteorology

can be found in the file aerscreen_example_max_conc_distance.txt, whose format is listed in 

Table 1. The maximum concentration and its distance, 125 m (shown in red in Figure 64) found 

from FLOWSECTOR should be listed in the table and in 

aerscreen_example_max_conc_distances.txt.

-----------------------------------------------------------------------------

************************ AERSCREEN AUTOMATED DISTANCES **********************

 OVERALL MAXIMUM CONCENTRATIONS BY DISTANCE

-----------------------------------------------------------------------------

 MAXIMUM RECEPTOR MAXIMUM RECEPTOR

 DIST 1-HR CONC HEIGHT DIST 1-HR CONC HEIGHT

 (m) (ug/m3) (m) (m) (ug/m3) (m)

 ---------------------------- -----------------------------

 30.00 301.3 -7.87 503.00 214.7 -6.90

 50.00 292.9 -9.01 525.00 210.9 -7.24

 53.00 294.5 -8.78 550.00 205.4 -7.95

 75.00 282.3 -4.49 575.00 200.0 -8.66

 100.00 367.7 -20.23 600.00 196.4 -8.92

 105.00 373.3 -20.49 625.00 187.4 -10.78

 125.00 376.2 -21.38 650.00 186.2 -10.38

 150.00 356.3 -22.38 675.00 188.7 -8.86

 175.00 328.0 -23.26 700.00 190.4 -7.54

 200.00 299.2 -16.13 702.00 190.2 -7.54

 201.00 298.1 -15.96 725.00 187.4 -7.64

 225.00 272.2 -16.55 750.00 182.0 -8.44

 250.00 247.8 -18.24 775.00 176.4 -9.29

 275.00 226.2 -17.91 800.00 171.5 -9.91

 300.00 213.5 -14.10 825.00 167.1 -10.43

 325.00 209.0 -15.04 850.00 162.4 -11.04

 350.00 208.5 -13.90 875.00 157.8 -11.65

 375.00 202.8 -15.03 900.00 150.6 -13.42

 400.00 201.4 -14.07 925.00 142.3 -16.06

 425.00 204.4 -11.77 950.00 136.9 -17.60

 450.00 210.0 -9.52 975.00 134.6 -17.23

 475.00 216.2 -7.32 1000.00 132.2 -16.96

 500.00 215.0 -6.93

Figure 64. Summary of maximum concentrations by distance in 

AERSCREEN_EXAMPLE.OUT. 

The final section of the output file lists the results of REFINE (Figure 65). This is the overall 

maximum concentration in the direction of the worst case scenario found in FLOWSECTOR, 

using the same surface characteristics (winter, 90 to 120 degrees sector). In addition to the 1-

hour concentration calculated by AERMOD, the scaled 3-hr, 8-hr, 24-hr, and annual 

concentrations are calculated by AERSCREEN and output. Also output is the distance of the 

maximum concentration and its direction. Similar output is listed for the maximum 

concentration at the minimum ambient distance. 
82

-----------------------------------------------------------------------------

********************** AERSCREEN MAXIMUM IMPACT SUMMARY *********************

-----------------------------------------------------------------------------

 MAXIMUM SCALED SCALED SCALED SCALED

 1-HOUR 3-HOUR 8-HOUR 24-HOUR ANNUAL

 CALCULATION CONC CONC CONC CONC CONC

 PROCEDURE (ug/m3) (ug/m3) (ug/m3) (ug/m3) (ug/m3)

--------------- ---------- ---------- ---------- ---------- ----------

ELEVATED TERRAIN 378.0 378.0 340.2 226.8 37.80 

DISTANCE FROM SOURCE 117.0 meters directed toward 270 degrees

RECEPTOR HEIGHT -21.07 meters

IMPACT AT THE

AMBIENT BOUNDARY 301.3 301.3 271.2 180.8 31.13 

DISTANCE FROM SOURCE 30.0 meters directed toward 360 degrees

RECEPTOR HEIGHT -7.87 meters

Figure 65. Maximum concentration impact and ambient boundary summaries in 

AERSCREEN_EXAMPLE.OUT.

Figure 66 shows partial output for aerscreen_example_max_conc_distances.txt. Note that 

the overall maximum concentration 378.0 g/m3is denoted by the asterisk. See Table 2 for 

format.
83

Concentration Distance Elevation Flow Season/Month Zo sector Date H0 U* W* DT/DZ ZICNV ZIMCH M-O LEN Z0 BOWEN ALBEDO REF WS HT REF TA HT

 0.30135E+03 30.00 -7.87 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.29286E+03 50.00 -9.01 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.29450E+03 53.00 -8.78 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.28229E+03 75.00 -4.49 90 Winter 270-300 10010601 -5.73 0.081 -9.000 0.020 -999. 53. 8.9 0.244 0.85 0.15 1.50 10.0 313.1 2.0

 0.36774E+03 100.00 -20.23 270 Winter 90-120 10010901 -2.90 0.051 -9.000 0.020 -999. 27. 4.5 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.37332E+03 105.00 -20.49 270 Winter 90-120 10010901 -2.90 0.051 -9.000 0.020 -999. 27. 4.5 0.029 0.85 0.15 1.50 10.0 313.1 2.0

* 0.37804E+03 117.00 -21.07 270 Winter 90-120 10010901 -2.90 0.051 -9.000 0.020 -999. 27. 4.5 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.37619E+03 125.00 -21.38 270 Winter 90-120 10010901 -2.90 0.051 -9.000 0.020 -999. 27. 4.5 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.35634E+03 150.00 -22.38 270 Winter 90-120 10010901 -2.90 0.051 -9.000 0.020 -999. 27. 4.5 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.32799E+03 175.00 -23.26 270 Winter 90-120 10012501 -2.06 0.051 -9.000 0.020 -999. 27. 6.3 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.29923E+03 200.00 -16.13 290 Winter 90-120 10012501 -2.06 0.051 -9.000 0.020 -999. 27. 6.3 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.29811E+03 201.00 -15.96 290 Winter 90-120 10012501 -2.06 0.051 -9.000 0.020 -999. 27. 6.3 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.27219E+03 225.00 -16.55 280 Winter 90-120 10012501 -2.06 0.051 -9.000 0.020 -999. 27. 6.3 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.24776E+03 250.00 -18.24 270 Winter 90-120 10012501 -2.06 0.051 -9.000 0.020 -999. 27. 6.3 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.22623E+03 275.00 -17.91 270 Winter 90-120 10012501 -2.06 0.051 -9.000 0.020 -999. 27. 6.3 0.029 0.85 0.15 1.50 10.0 313.1 2.0

 0.21350E+03 300.00 -14.10 360 Winter 180-210 10011501 -0.99 0.094 -9.000 0.020 -999. 66. 80.4 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.20904E+03 325.00 -15.04 360 Winter 180-210 10011501 -0.99 0.094 -9.000 0.020 -999. 66. 80.4 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.20853E+03 350.00 -13.90 360 Winter 180-210 10011501 -0.99 0.094 -9.000 0.020 -999. 66. 80.4 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.20283E+03 375.00 -15.03 360 Winter 180-210 10011501 -0.99 0.094 -9.000 0.020 -999. 66. 80.4 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.20142E+03 400.00 -14.07 360 Winter 180-210 10011501 -0.99 0.094 -9.000 0.020 -999. 66. 80.4 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.20437E+03 425.00 -11.77 360 Winter 180-210 10011501 -0.99 0.094 -9.000 0.020 -999. 66. 80.4 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.20999E+03 450.00 -9.52 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.21620E+03 475.00 -7.32 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.21496E+03 500.00 -6.93 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.21475E+03 503.00 -6.90 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.21093E+03 525.00 -7.24 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.20542E+03 550.00 -7.95 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.20003E+03 575.00 -8.66 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.19640E+03 600.00 -8.92 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.18740E+03 625.00 -10.78 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.18620E+03 650.00 -10.38 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.18871E+03 675.00 -8.86 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.19044E+03 700.00 -7.54 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.19022E+03 702.00 -7.54 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.18737E+03 725.00 -7.64 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.18205E+03 750.00 -8.44 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.17640E+03 775.00 -9.29 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.17155E+03 800.00 -9.91 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.16706E+03 825.00 -10.43 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.16240E+03 850.00 -11.04 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.15782E+03 875.00 -11.65 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.15059E+03 900.00 -13.42 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.14228E+03 925.00 -16.06 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.13686E+03 950.00 -17.60 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.13463E+03 975.00 -17.23 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

 0.13223E+03 1000.00 -16.96 360 Winter 180-210 10010901 -2.95 0.052 -9.000 0.020 -999. 27. 4.6 0.031 0.85 0.15 1.50 10.0 313.1 2.0

Figure 66. Output of aerscreen_example_max_conc_distance.txt.
84

After processing, AERSCREEN creates a new AERSCREEN.INP file, with any user input 

changes added (Figure 67). Note that any options are that are alphabetic have been set to 

uppercase. AERSCREEN sets all flags to uppercase internally for program efficiency.

AERSCREEN will also output the surface characteristics for the maximum concentration as the 

user-entered values in the MAKEMET DATA section and lists the time, flow vector, and surface 

roughness sector of the overall maximum concentration. AERSCREEN also copies the new 

AERSCREEN.INP file to AERSCREEN_EXAMPLE.INP and AERSCREEN.LOG to 

AERSCREEN_EXAMPLE.LOG.
85

** Coordinates switched from geographic to UTM

** STACK DATA Rate Height Temp. Velocity Diam. Flow

** 0.1000E+01 10.0000 300.0000 15.0000 0.5000 6241.

** BUILDING DATA BPIP Height Max dim. Min dim. Orient. Direct. Offset

** Y 34.0000 120.0000 60.0000 90.0000 26.6000 67.0000

** MAKEMET DATA MinT MaxT Speed AnemHt Surf Clim Albedo Bowen Length SC FILE 

** 261.40 313.10 1.5 10.000 9 0 0.1500 0.8500 0.0290 "aersurface_12.out"

** TERRAIN DATA Terrain UTM East UTM North Zone Nada Probe PROFBASE Use AERMAP elev

** Y 700198.4 3974175.8 17 4 1000.0 126.80 N

** DISCRETE RECEPTORS Discflag Receptor file

** Y "discrete_receptors.txt"

** UNITS/POPULATION Units R/U Population Amb. dist. Flagpole Flagpole height

** M U 2400000. 30.000 N 0.00

** OUTPUT FILE "aerscreen_example.out"

** Temporal sector: Winter, flow vector: 270 degrees, spatial sector: 4

Figure 67. Header portion of new AERSCREEN.INP file.
86

5. References

Hanrahan, P.L., 1999a. "The plume volume molar ratio method for determining NO2/NOx ratios 

in modeling. Part I: Methodology," Journal of the Air & Waste

Management Association, 49, 1324-1331. 

Hanrahan, P.L., 1999b. "The plume volume molar ratio method for determining NO2/NOx ratios 

in modeling. Part II: Evaluation Studies," Journal of the Air & Waste

Management Association, 49, 1332-1338.

Leahey, D.M., and M. J. E. Davies, 1984: Observations of Plume Rise From Sour Gas Flares. 

Atmospheric Environment, Vol. 18, pp. 917-922.

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.

U.S. EPA, 1992: Screening Procedures for Estimating the Air Quality Impact of Stationary 

Sources. EPA-454/R-92-019. U.S. Environmental Protection Agency, Research Triangle 

Park, NC 27711.

U.S. EPA, 1995: SCREEN3 Model User‟s Guide. EPA-454/B-95-004. U.S. Environmental 

Protection Agency, Research Triangle Park, NC 27711.

U.S. EPA, 2004a: User's Guide for the AMS/EPA Regulatory Model – AERMOD. EPA-454/B03-001. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711.

U.S. EPA, 2004b: User's Guide for the AERMOD Terrain Preprocessor

(AERMAP). EPA-454/B-03-003. U.S. Environmental Protection Agency, Research

Triangle Park, North Carolina 27711.

U.S. EPA, 2004c: User's Guide for the AERMOD Meteorological

Preprocessor (AERMET). EPA-454/B-03-002. U.S. Environmental Protection Agency,

Research Triangle Park, North Carolina 27711.

U.S. EPA, 2004d: User's Guide to the Building Profile Input Program. EPA-454/R-93-038. U.S. 

Environmental Protection Agency, Research Triangle Park, North Carolina 27711.

U.S. EPA, 2005. Guideline on Air Quality Models. 40 CFR Part 51 Appendix W.

U.S. EPA, 2008: AERSURFACE User‟s Guide. EPA-454/B-08-001. U.S. Environmental 

Protection Agency, Research Triangle Park, North Carolina 27711.
87

U.S. EPA, 2009: AERMOD Implementation Guide. U.S. Environmental Protection Agency, 

Research Triangle Park, North Carolina 27711. 
A-1

Appendix A. Input parameters and invalid responses

Below, AERSCREEN input parameters are listed with invalid responses and actions taken by 

AERSCREEN when reading the data from the AERSCREEN.INP file or prompts. Some 

variables are only checked if the appropriate flags are set. Building dimensions are not checked 

if downwash is not included in AERSCREEN processing. Other variables such as urban 

population or flagpole heights are not checked if the source is not urban or flagpole receptors are 

not used.

As previously noted, when reading data from AERSCREEN.INP, if any of the data sections, 

emissions, building information, terrain information, meteorological information, and other 

parameters, is missing, AERSCREEN will alert the user and stop processing. If the emissions 

data is listed after the building, terrain, or other parameter data sections, AERSCREEN will alert 

the user and stop processing.
A-2

Source parameters and invalid values.

Parameter Source type Invalid response AERSCREEN.INP Prompts

Units flag All If prompts, response is not upper or lower case E or M. If input file, 

response is not upper or lowercase M.

Issue message and stop Re-prompt

Source type All Response is not upper or lower-case: P, F, H, A, C, S, or V Issue message and stop Re-prompt

Emission rate All Negative or non-numeric Issue message and stop Re-prompt

Stack height Point, capped stack, 

horizontal stack

Negative or non-numeric Issue message and stop Re-prompt

Stack diameter Point, capped stack, 

horizontal stack

Negative or non-numeric Issue message and stop Re-prompt

Negative exit velocity Point, capped stack, 

horizontal stack

Non-numeric Issue message and reset to 1x10-5 m/s

if negative

Issue message and reset to 

1x10-5 m/s if negative

Flare height Flare Negative or non-numeric Issue message and stop Re-prompt

Heat release rate Flare Negative or non-numeric Issue message and stop Re-prompt

Heat loss fraction Flare Non-numeric Issue message and reset to 0 if 

negative

Issue message and reset to 

0 if negative

Release height Area, volume, circular 

area

Negative or non-numeric Issue message and stop Re-prompt

Initial vertical 

dimension

Area, volume, circular 

area

Negative or non-numeric Issue message and stop Re-prompt

Initial lateral dimension Volume Negative or non-numeric Issue message and stop Re-prompt

Circular radius Circular area Negative or non-numeric Issue message and stop Re-prompt

Rectangular area source 

horizontal dimensions

Area Negative or non-numeric Issue message and stop Re-prompt

Orientation angle Area Non-numeric or non-zero Issue message and stop N/A

Number of vertices Circular area Non-numeric or not equal to 20 Issue message and stop N/A

Urban/rural flag All Response is not upper or lower-case Y or N Issue message and stop Re-prompt

Urban population All Non-numeric, negative or less than 100 people Issue message and stop (if source is 

urban)

Re-prompt

Minimum ambient

distance

All Non-numeric, negative or if volume source, inside the volume. Issue message and reset to minimum 

distance based on source type if 

negative. If non-numeric issue 

message and stop

Re-prompt if non-numeric

NO2 conversion method All “PVMRM” and “OLM” are both on MODELOPT card or 

POLLUTID is NO2 and neither PVMRM or OLM is on 

MODELOPT card

Issue message and stop N/A

NO2/NOX in-stack ratio All Non-numeric, negative, or exceeds 1.0 Issue message and stop Re-prompt

Ozone background 

concentration

All Non-numeric, negative, or exceeds 1.0 Issue message and stop Re-prompt

Ozone background 

concentration units

All Not upper or lower-case “PPB”, “PPM”, or “UG/M3” Issue message and stop Re-prompt

Pollutant ID All Not set to NO2 but MODELOPT includes PVMRM or OLM Issue message and stop N/A
A-3

Invalid building parameter inputs.

Parameter Invalid response AERSCREEN.INP Prompts

Downwash flag Response is not upper or 

lower-case Y or N

Issue message and stop Re-prompt

Building height Negative or non-numeric Issue message and stop Re-prompt

Maximum building 

horizontal dimension

Negative or non-numeric Issue message and stop Re-prompt

Minimum building 

horizontal dimension

Non-numeric, negative or 

exceeds maximum 

horizontal dimension

Issue message and stop Re-prompt

Angle of maximum 

horizontal dimension 

relative to North

Non-numeric, less than 

zero or exceeds 179 

degrees

Issue message and stop Re-prompt

Angle of stack location 

relative to North

Non-numeric, less than 

zero or exceeds 360 

degrees

Issue message and stop Re-prompt

Distance from stack to 

building center

Negative or non-numeric Issue message and stop Re-prompt

Use pre-existing 

BPIPPRM input file

File does not exist Issue message and stop Re-prompt

Processing flag in file 

incorrectly set for 

AERMOD or more than 

one stack listed in file.

Issue message and stop Issue message and stop
A-4

Invalid meteorological data inputs.

Parameter Invalid response AERSCREEN.INP Prompts

Minimum Temperature Non-numeric, negative (if 

Kelvin), or minimum 

temperature is equal to or 

exceeds maximum 

temperature

Issue message and stop Re-prompt for 

Maximum Temperature temperatures

Minimum wind speed Negative or non-numeric Issue message and stop Re-prompt

Anemometer height Negative or non-numeric Issue message and stop Re-prompt

Surface code Non-numeric, negative or 

greater than 9

Issue message and stop Re-prompt

Climatology code Non-numeric, less than 1or 

exceeds 4 if surface code 

between 1 and 8 inclusive

Issue message and stop Re-prompt

User albedo Non-numeric, negative, or 

exceeds 1.0

Issue message and stop if 

non-numeric. 

Issue message and stop if 

negative or exceeds 1.0 

and surface code is 0

Re-prompt

User Bowen Ratio Non-numeric Issue message and stop if 

non-numeric. 

Re-prompt

User surface roughness Negative or non-numeric Issue message and stop if 

non-numeric. 

Issue message and stop if 

negative and surface code 

is 0

Re-prompt

AERSURFACE output file Does not exist (if surface 

code = 9)

Issue message and stop Re-prompt for surface 

characteristics type

Surface characteristics 

non-numeric, albedo is 

negative or exceeds 1.0 or 

surface roughness is 

negative

Issue message and stop if 

surface code is 9

Issue message and reprompt for surface 

characteristics type
A-5

Invalid terrain data inputs.

Parameter Invalid response AERSCREEN.INP Prompts

Terrain flag Response is not upper or lowercase Y or NIssue message and stop Re-prompt

Latitude Absolute value exceeds 90 

degrees

N/A Re-prompt

Longitude Absolute value exceeds 180 

degrees

N/A Re-prompt

UTM Easting N/A N/A N/A

UTM Northing N/A N/A N/A

UTM zone Negative Issue message and stop Re-prompt

NAD code Not equal to 1 or 4 Issue message and stop Re-prompt

Probe distance Negative or less than minimum 

ambient distance

Issue message and stop Re-prompt for probe 

distance and minimum 

ambient distance

Discrete receptor 

flag

Response is not upper or lowercase Y or NIssue message and stop Re-prompt

Discrete receptor file File does not exist Issue message and stop Re-prompt

The number of distances exceeds 

ten or negative distances found

Issue message and stop Re-prompt

Units line not included in file Issue message and stop Re-prompt

Flagpole receptor 

use flag

Response is not upper or lowercase Y or NIssue message and stop Re-prompt

Flagpole height Negative or non-numeric Issue message and stop (if 

flagpole receptors used)

Re-prompt

Source elevation N/A N/A N/A

AERMAP use flag Response is not upper or lowercase Y or NIssue message and stop Re-prompt

Demlist.txt File is not in current folder Issue message and stop Issue message and stop

NADGRIDS 

directory or folder

No grid files are in directory or 

folder or NADGRIDS keyword 

not listed in demlist.txt

Issue message and stop Issue message and stop

United States

Environmental Protection

Agency

Office of Air Quality Planning and Standards

Air Quality Assessment Division

Research Triangle Park, NC

Publication No. EPA-454/B-11-001

March 2011