1. AERSCREEN Hands-on Course #423 Day 4 Morning
Air Pollution Dispersion Models:
Applications with the AERMOD Modeling System
AERSCREEN Hands-on
Course #423
Day 4 Morning

2. Day 4 Morning: AERSCREEN Hands-On

3. Learning Objectives At the end of this session, you will understand:
How to respond to the prompts for an interactive session with AERSCREEN
The output and where to find the results
How to rerun AERSCREEN without responding to all the prompts again

4. Before Running AERSCREEN
AERSCREEN will utilize the programs:
MAKEMET
AERMAP
BPIPPRM
AERMOD
If the executable files are not located in the working directory, you will be prompted to enter the path and filename
“demlist.txt” must be located either in the folder with the AERSCREEN executable or in the working directory
AERSCREEN calls the programs listed as-needed.
MAKEMET is used to generate screening meteorology.
AERMAP extracts terrain elevations for sources and receptor locations and determines receptor hill height scales. AERMAP is not called if terrain is not considered (flat terrain).
BPIPPRM generates building parameters required for building downwash.
AERMOD is called and run in screening mode.
AERSCREEN searches the current working directory for these program executable files. If not found, AERSCREEN will prompt the user to enter their location. Both the path and filename of the executables must be entered.
“demlist.txt” is required if terrain processing is performed. It should be stored either in the folder where the AERSCREEN executable is stored or in the current working directory.
“demlist.txt” names: 1) the location of the NADGRID files required for datum conversion and 2) the path and filenames of the terrain elevation files.

5. Before Running AERSCREEN
demlist.txt
NED NADGRIDS: .\ ..\AERMAP\NED\MC_NED.tif
The contents of “demlist.txt” are displayed here.
The first line specifies the type of terrain elevation data file(s). Here we are using NED files in GeoTIFF format as we did in the AERMAP hands-on.
The NADGRIDS datum conversion files are located in the working directory.
Relative pathing points to the same NED GeoTIFF file used in the AERMAP hands-on.

6. APTI423\Hands-on\AERSCREEN\
Running AERSCREEN
AERSCREEN will be run in interactive mode for this hands-on activity, so there is not a control file
To run AERSCREEN, open a command prompt setting the working directory to AERSCREEN hands-on folder
APTI423\Hands-on\AERSCREEN\
At the command prompt, type: aerscreen
Hit the “Enter” key
We will run AERSCREEN in the prompt-driven interactive mode, so a control file has not been provided for this hands-on activity.
To run AERSCREEN for this activity, open a command prompt and set the working directory to the folder where the AERSCREEN executable file is located. The executable is located in the AERSCREEN hands-on activity folder: APTI423\Hands-on\AERSCREEN\.
Like the other programs we have run, the executable does not have to reside in the working directory. AERSCREEN can be called from the working directory, but the working directory is where the output files will be written.

7. Running AERSCREEN Enter a Title (e.g., AERSCREEN Hands-on)
Next indicate if you are working in English or Metric units – enter ‘M’ (or ‘m’) for Metric
Enter the source type – enter ‘P’ for point source
When AERSCREEN starts, you will be prompted to enter specific information to set up the simulation.
First, enter a Title. Unlike AERMOD which allows two titles, AERSCREEN allows only one.
Next, indicate if you will enter values in English or Metric units. For this activity, enter “M” for metric.
Enter the source type. The valid source types are shown; you only need to enter a single letter, as identified in the parentheses. Enter “P” for point source.
With AERSCREEN, you can model flares (the F). The option to model a flare is not available in AERMOD as a distinct source type.

8. Running AERSCREEN
The screen will clear and prompts for a point source are displayed – we will use physical parameters similar to values for one of the stacks modeled with AERMOD
Enter 1.0 for emission rate (in grams/second)
Enter (meters) for the stack height
Enter 5.3 (meters) for the inside stack diameter
Enter 400 (kelvin) for exit temperature
Enter 1 for the option to enter the exit velocity in meters/second
Enter 11.0 (meters/second) for the exit velocity
Enter R for rural land use
As you are prompted by AERSCREEN, enter the values displayed for the associated parameters .
These should be self-explanatory.

9. Running AERSCREEN Enter 170 (meters) for the distance to ambient air
The next prompt is for NO2 chemistry; since we are not using OLM or PVMRM, enter 1 (no chemistry)
If there is a question as to whether the area is considered rural or urban, you may need to perform an analysis on the surrounding land use. For guidance, see papers such as Auer, 1978 (“Correlation of Land Use and Cover with Meteorological Anomalies”, Journal of Applied Meteorology, 17, ) and Section of Appendix W (Guideline on Air Quality Modeling), Federal Register Notice vol. 70, No. 216, November 9, 2005)
In the diagram that follows, the minimum distance from the source to the fenceline is about 170 meters. This is our distance to ambient air.

10. Running AERSCREEN
Fenceline X
Stack
This slide shows the approximate fenceline (or property line) and receptors at the vertices. The “X” near the center of the property is the approximate location of the stack.

11. Running AERSCREEN - Buildings
The screen will clear and you are prompted on whether or not to include building downwash – enter ‘Y’ or ‘y’ to include downwash
You are given the option to use a pre-existing BPIPPRM input file; for this hands-on, we will not use a pre­ existing file
The screen will clear and you will be prompted for several parameters for one single-tiered building:
Building height: 60 meters
Maximum actual (not projected) horizontal building dimension: 180 meters
Minimum actual horizontal building dimension: 90 meters
We can only represent a single-tiered rectangular building unless we run BPIPPRM outside of AERSCREEN and reference the BPIPPRM output file. Thus, for the purposes of this hands-on, we are only going to represent the bottom tier (Tier 1) as a demonstration of the AERSCREEN inputs. You might want to separately try to figure out these parameters for the smaller, taller tier or re-run AERSCREEN using the BPIPPRM output file generated in the BPIPPRM hands-on.
If you remember, Tier 1 is 180 m X 90 m X 60 m high with the longer side oriented SW- NE. The stack is located on the southwest end of the building. (See next slide.)
Those dimensions are the first three building parameters.

12. Structure Diagram – Bottom TierN
65° C
240° S
Tier 1 N
Tier 2
This slide, similar to the slide shown the BPIPPRM presentation, illustrates the building we are representing in the AERSCREEN hands-on activity.
Two angles that are required as input:
Maximum building dimension angle to true north (65 degrees) and
Direction of the stack from building center (240 degrees).
The red “S” marks the approximate location of the stack, and the blue “C” marks the approximate center of Tier 1. Three dashed arrows originate from the center of the building. One points northward (0 degrees). Going in a clockwise direction, the second arrow is parallel to the building along the maximum dimension showing the longer side of the building is oriented at 65 degrees from North (#1). Continuing in a clockwise direction, the third arrow points toward the stack which is 240 degrees from North (#2).
The distance from the stack to the center of the building is 90 meters.
S = Stack
C = Building Center

13. Running AERSCREEN - Buildings
Maximum building dimension angle to true north: 65 degrees
Direction of the stack from the building center: 240 degrees
Distance between stack and building center: 90 meters
In the next three prompts, enter the values derived on the previous slide for the following:
Maximum building dimension angle to true north: 65 degrees
Direction of the stack from the building center: 240 degrees
Distance between the stack and the center of the building: 90 meters.

14. Running AERSCREEN – Terrain/Receptors/Source
The next prompt is whether or not to include terrain - respond with Y (Yes)
The next set of prompts define receptors and source location
Maximum distance (in meters) to probe: the default value will depend on the application - we will use 5000 meters
Include up to 10 optional discrete receptors: N (No)
Flagpole receptors: N (No)
Source elevation: press the ‘Enter’ key to let AERMAP derive the elevation
FLAT terrain is a non-default option in AERMOD (and therefore AERSCREEN). Unless the FLAT option can be justified, the effects of terrain should be included.
The maximum distance to probe matches the distance from the facility to the edge of our receptor boundary in the AERMOD example.
We will not model:
Optional discrete receptors, but could if we know the locations of sensitive populations, or
Flagpole receptors.
The source elevation can be entered directly or derived from AERMAP (which AERSCREEN will run). We will let AERSCREEN derive the elevation.

15. Running AERSCREEN – Terrain/Receptors/Source
Coordinate type: UTM coordinates
Easting: meters
Northing: meters
Zone: 18
UTM datum: 4
For our example, we will not enter any discrete receptors. If you answer ‘Yes’ to the prompt, you will be asked to provide the name of the file with the locations of the discrete receptors.
Nor will we use flagpole receptors.
Unless you know the elevation of your source, it is easiest to let AERMAP determine the source elevation. Although we have the elevation from our AERMOD modeling run, we will allow AERMAP to recompute it.
Since we are working in UTM coordinates, respond with UTM coordinates, entered in meters, and the corresponding UTM zone. The zone is important since there are 60 zones around the world (6 degrees latitude for each) and the coordinates do repeat across the zones for a given longitude.
There are only two choices for the datum: 1 (for the 1927 North American Datum) and 4 (for the 1983 North American Datum)

16. Running AERSCREEN – Terrain/Receptors/Source
This slide is a screenshot of the terrain related input parameters entered into AERSCREEN as prompted.

17. Running AERSCREEN - Meteorology
The next set of prompts is for meteorological input
Minimum and maximum ambient temperature: accept the default values ( kelvin) by pressing ENTER
Minimum wind speed: accept the default value of 0.5 m/s
Anemometer height: accept the default value of 10 meters
There are three options for the surface characteristics – select option 1 to enter a single set of values that apply to all hours and wind directions:
Albedo: 0.18
Bowen ratio: 0.55
Roughness Length: 0.1 (meters)
AERSCREEN runs a program called MAKEMET to develop the screening meteorology. Based on user responses it will generate the files of hourly meteorology (SFC and PFL) needed by AERMOD.
Default minimum and maximum ambient temperatures are 250 kelvin (-10 °F) to 310 kelvin (98 °F). Minimum wind speed is 0.5 meters/second. Accept the default values.
The lowest level in the site-specific data is 10 meters, also the default value for MAKEMET.FOR the surface characteristics.
For the three surface characteristics, we use an approximate average of the characteristics found in the AERMET stage 3 run.

18. Running AERSCREEN - Meteorology
This is a screenshot of the meteorological parameters input into AERSCREEN as the prompts are displayed.

19. Running AERSCREEN - Output Filename
AERSCREEN prompts for the output file name
Use any name or use the default aerscreen.out – for this exercise, use the default name
AERSCREEN prompts for the name of the output file or you can forego entering a name and press the “Enter” key to accept the default name “aerscreen.out”

20. Running AERSCREEN - Validation
After entering the filename or accepting the default name, a screen of validation information is presented
At the bottom, you can make changes or accept it and press enter to run AERSCREEN (next slide)

21. Running AERSCREEN - Validation
Review the input on the screen. You have the option of changing one or most of the input parameters or simply pressing the ENTER key and starting the AERSCREEN run.

22. Running AERSCREEN – Executable Files
Next, we will need to tell AERSCREEN the locations and names of the program executables when prompted:
AERMOD: ..\AERMOD\aermod.exe
MAKEMET: ..\MAKEMET\makemet.exe
BPIPPRM: ..\BPIPPRM\bpipprm.exe
AERMAP: ..\AERMAP\aermap.exe
If the executable files for the programs AERSCREEN calls are not found in the working directory, AERSCREEN will prompt for the location (path) and filename separately for each one not find.
For our hands-on activity, we will specify the path and filename of the executable files used for the previous hands-on activities to ensure we are using the same versions. The path and filename are listed based on the directory structure set-up for the hands- on activities.
Be sure to include the filename of the executable! If you do not, the prompt will repeat.
As you enter the path and filename for each executable file, AERSCREEN will verify it exists, and copy the executable file to the current working directory. If you should decide to rerun AERSCREEN from the same working directory, there should then already be a copy of each executable from the first AERSCREEN run. In that case you will not be prompted to enter this information.

23. Running AERSCREEN - Validation
This is a screenshot of the prompts and entries for the locations and filenames of each of the executable files listed on the previous slide. You can see that each executable file was copied.

24. AERSCREEN - Output
Based on the responses to the prompts, AERSCREEN generated 195 receptors along 36 radials for a total of 7,020 receptors
The screening meteorology generated by the MAKEMET program consisted of 678 ‘hours’
AERSCREEN writes information to the computer monitor and then displays the progress such as wind flow sectors and receptors
It will take AERSCREEN about 20 minutes to complete depending on the speed of your computer.
Since the distance to the ambient boundary is 170 meters, AERSCREEN adjusts the receptor array to start at the next multiple of 25 (i.e., 175 meters) with 25 meter spacing out to 5000 meters which is our probe distance. So, the number of receptors along a single radial is 195:
1 receptor at the probe distance
194 along the radial spaced 25 meters apart ( ( ) + 1) ).
Given there are 36 radials (1 every 10 degrees), there is a total of 7,020 receptors.
Except when it begins actual calculations, information is displayed on the screen too fast to read and could not be captured for this presentation.

25. AERSCREEN.LOG
Start date and time 01/27/14 22:50:43
AERSCREEN 11126
AERSCREEN Hands-on
DATA ENTRY VALIDATION
METRIC ENGLISH
** STACKDATA **
Emission Rate: g/s lb/hr
Stack Height: meters feet
Stack Diameter: meters inches
Stack Temperature: K Deg F
Exit Velocity: m/s ft/s
Stack Flow Rate: ACFM
Model Mode: RURAL
Dist to Ambient Air: meters feet .
**********************************************
AERSCREEN Finished Successfully
But with Warnings
0 receptors skipped for FLOWSECTOR
0 receptors skipped for REFINE
Check log file for details
***********************************************
Ending date and time 01/27/14 23:14:02
Shown here are the first 20 or so lines and last 10 lines of the log file.
The log file consists of (not all shown here)
The data validation that was displayed prior to AERSCREEN performing the calculations (shown above)
Summary of the surface characteristics
Summary of the AERMAP run
AERMOD processing for each flow sector
Running AERMAP and AERMOD for the REFINEd run for those receptors in the direction of the maximum concentration (a more refined receptor spacing)
The number of receptors skipped (shown above)
The date and time the run ended (shown above)

26. AERSCREEN.OUT
AERSCREEN / AERMOD /27/14
23:14:00
TITLE: AERSCREEN Hands-on
***************************** STACK PARAMETERS ****************************
SOURCE EMISSION RATE: g/s lb/hr
STACK HEIGHT: meters feet
STACK INNER DIAMETER: meters inches
PLUME EXIT TEMPERATURE: K Deg F
PLUME EXIT VELOCITY: m/s ft/s
STACK AIR FLOW RATE: ACFM
STACK BASE LONGITUDE: deg Easting
STACK BASE LATITUDE: deg Northing
STACK BASE UTM ZONE:
REFERENCE DATUM (NADA):
STACK BASE ELEVATION: meters feet
RURAL OR URBAN: RURAL
DIGITAL ELEVATION MAP(S) \AERMAP\NED\MC_NED.tif
INITIAL PROBE DISTANCE = meters feet
The file AERSCREEN .OUT (recall we opted to use the default file name) contains the concentration estimates.
The file consists of
Stack parameters (since we modeled a point source)
(Continued on the next slide)

27. AERSCREEN.OUT The file AERSCREEN .OUT, continued
*********************** BUILDING DOWNWASH PARAMETERS **********************
BUILDING HEIGHT: meters feet
MAX BUILDING DIMENSION: meters feet
MIN BUILDING DIMENSION: meters feet
BUILDING ORIENTATION TO NORTH: degrees
STACK DIRECTION FROM CENTER: degrees
STACK DISTANCE FROM CENTER: meters feet
The file AERSCREEN .OUT, continued
Building downwash parameters.
(Continued on the next slide)

28. AERSCREEN.OUT AERSCREEN.OUT – continued
************************** FLOW SECTOR ANALYSIS ***************************
25 meter receptor spacing: 170. meters meters
MAXIMUM IMPACT RECEPTOR
FLOW BUILD BUILD HR CONC DIST HEIGHT TEMPORAL
SECTOR WIDTH LENGTH XBADJ YBADJ (ug/m3) (m) (m) PERIOD
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
140* ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
ANN
* = worst case flow sector
AERSCREEN.OUT – continued
Flow sector analysis showing building and downwash parameters, max 1-hr concentration, and distance to concentration from the source for every 10 degrees of direction starting at 10 degrees through 360 degrees. The receptor height is the height relative to the ground elevation of the source.
(Continued on the next slide)

29. AERSCREEN.OUT AERSCREEN.OUT, continued
********************** MAKEMET METEOROLOGY PARAMETERS *********************
MIN/MAX TEMPERATURE: / (K)
MINIMUM WIND SPEED: m/s
ANEMOMETER HEIGHT: meters
SURFACE CHARACTERISTICS INPUT: USER ENTERED
ALBEDO:
BOWEN RATIO:
ROUGHNESS LENGTH: (meters)
METEOROLOGY CONDITIONS USED TO PREDICT OVERALL MAXIMUM IMPACT
YR MO DY JDY HR
H0 U* W* DT/DZ ZICNV ZIMCH M-O LEN Z0 BOWEN ALBEDO REF WS
HT REF TA HT
ESTIMATED FINAL PLUME HEIGHT (non-downwash): meters Continued on next slide
AERSCREEN.OUT, continued
Meteorological parameters used by MAKEMET and the conditions associated with the overall maximum impact.
(Continued on the next slide)

30. AERSCREEN.OUT AERSCREEN.OUT, continued
METEOROLOGY CONDITIONS USED TO PREDICT AMBIENT BOUNDARY IMPACT
YR MO DY JDY HR
H0 U* W* DT/DZ ZICNV ZIMCH M-O LEN Z0 BOWEN ALBEDO REF WS
HT REF TA HT
ESTIMATED FINAL PLUME HEIGHT (non-downwash): meters
AERSCREEN.OUT, continued
Meteorological parameters – continued
(Continued on the next slide)

31. AERSCREEN.OUT AERSCREEN.OUT, continued
************************ 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)
AERSCREEN.OUT, continued
Overall maximum concentration by (automated) distance :
AERSCREEN sets the first receptor at the distance to the ambient boundary (based on our response of 170 meters to one of the prompts), then finds the next distance that is a multiple of 25, in this case 175 meters and continues every 25 meters to 5000 meters
Note that the results are in two set of columns. Due to space limitations, the columns on left side in our example only extend to 750 meters, but the distances in the output file extend to 2575 meters; the columns on the right side extend to 5000 meters, but are only shown to 3200 meters
(Continued on the next slide)

32. AERSCREEN.OUT AERSCREEN.OUT, concluded
********************** AERSCREEN MAXIMUM IMPACT SUMMARY *********************
MAXIMUM SCALED SCALED SCALED SCALED
1-HOUR HOUR HOUR HOUR ANNUAL
CALCULATION CONC CONC CONC CONC CONC
PROCEDURE (ug/m3) (ug/m3) (ug/m3) (ug/m3) (ug/m3)
ELEVATED TERRAIN
DISTANCE FROM SOURCE meters directed toward 140 degrees
RECEPTOR HEIGHT meters
IMPACT AT THE
AMBIENT BOUNDARY E-01
DISTANCE FROM SOURCE meters directed toward 80 degrees
RECEPTOR HEIGHT meters
AERSCREEN.OUT, concluded
AERSCREEN concludes with the maximum impact summary.
Here we see that the 1-hr maximum impact, based on 1 g/s emission rate, is just over 4 micrograms per cubic meter. The scaled 3-hr, 8-hr, 224-hr and annual concentrations are also shown. These impacts are at a distance of 3000 meters from the source. The impact at the boundary was more than an order of magnitude smaller at 0.26.
How does this compare to AERMOD results? We cannot make a direct comparison to the results we already have since we modeled 3 point sources with an hourly emission rate file with variable emissions and used surface characteristics created by AERSURFACE.
To make such a comparison we re-ran AERMET (stage 3 with site-specific data and the surface characteristics as input to AERSCREEN) and AERMOD with the same inputs as for AERSCREEN - single source, constant stack parameters, and 1 gram/second emission rate. These files are included in “APTI423/Hands-on/AERSCREEN/AERMOD_Comparison.”
The comparison is shown on the next page.

33. AERSCREEN to AERMOD Comparison
Averaging
Time
AERSCREEN
(µg/m3)
AERMOD
AERSCREEN/
1-hr
4.03
2.18
1.85
3-hr
1.03
3.91
8-hr
3.63
0.68
5.34
24-hr
2.42
0.27
8.96
Annual
0.40
0.018
22.2
AERMET and AERMOD were rerun using the same values that were input to AERSCREEN, e.g., the surface characteristics and the single point source parameters. The table shows the high 1st high for AERMOD concentration estimates. As we can see in the last column, AERSCREEN’s results are from a factor of 2 to 22 higher for our example.
If AERSCREEN modeling demonstrates that the screening results show compliance with ambient air quality standards, can you stop and skip refined modeling with AERMOD? Possibly, but it will depend on the application and what the regulatory agency requires.

34. AERSCREEN - Restart AERSCREEN looks for the file aerscreen.inp
If you accepted the default AERSCREEN output filename (aerscreen.out), AERSCREEN created the file aerscreen.inp for you
This file is used as a ‘restart’ file
If the file exists in the working folder, AERSCREEN asks if you want to use the restart file
Enter ‘Y’ or ‘y’ if you want to use the file (otherwise press ENTER to start a new set of prompts)
You are given the option of changing the input parameters
You can restart (or re-run) AERMOD without having to walk through each of the prompts by using the restart file, aerscreen.inp. The restart only works with a filename of aerscreen.inp. If you entered something other than accepting the default, for example MyTest.out, then AERSCREEN will not ask if you want to use the restart file, unless …
You can, however, copy or rename the filename to aerscreen.inp and run AERSCREEN to use the restart option.
This option can be useful if you only want to change one or two parameters to see the effect on the output. If you are doing this, be careful not to overwrite output from previous runs you intended to keep.
The first part of AERSCREEN.INP is shown next, followed by the prompt to use the restart option. If you use the restart option, the validation screen is displayed, allowing you to make changes to one or more parameters. The options to change a stack parameter are shown after the restart prompt.

35. AERSCREEN.INP - Restart
** STACK DATA Rate Height Temp. Velocity Diam. Flow
** E
** BUILDING DATA BPIP Height Max dim. Min dim. Orient. Direct. Offset
** Y
** MAKEMET DATA MinT MaxT Speed AnemHt Surf Clim Albedo Bowen Length SC FILE
** "NA"
** TERRAIN DATA Terrain UTM East UTM North Zone Nada Probe PROFBASE Use AERMAP elev
** Y Y
** DISCRETE RECEPTORS Discflag Receptor file
** N "NA"
** UNITS/POPULATION Units R/U Population Amb. dist. Flagpole Flagpole height
** M R N
** OUTPUT FILE "AERSCREEN.OUT"
** Temporal sector: Annual, flow vector: 140 degrees, spatial sector: 1
CO STARTING
TITLEONE AERSCREEN Hands-on
** REFINE STAGE 3
MODELOPT CONC SCREEN
AVERTIME 1
POLLUTID OTHER
RUNORNOT RUN
CO FINISHED
SO STARTING
LOCATION SOURCE POINT
SRCPARAM SOURCE E
The lines from ** STACK DATA through ** Temporal Sector are used as the restart information. For example, to rerun AERSCREEN with different stack parameters, the changes to the stack parameters should be made in this section and NOT in the SO pathway below this section. You will have to experiment with the aerscreen.inp file to see which parameters can be safely turned off/on/modified without causing AERSCREEN to fail.
Following those lines are the pathway/keywords for an AERMOD run based on the responses to the prompts. Only the CO pathway and a portion of the SO pathway are shown. In this example, the entire file is 170 records, most of which are the discrete receptor locations.

36. Running AERSCREEN - Restart
The screen prompt asking if you would like to use the RESTART file.

37. Running AERSCREEN - Validation
On this screen, you can change the source parameters, one at a time, or optionally all of them (item 12).
Once you have made the changes to the source information, pressing Enter will return you to the validation page, at which point you can make your next AERSCREEN run.