Modeling Tips

Peruse or search the air modeling tips that have been part of our newsletters for more than a decade!

April 2026

With our release of AERMOD Wizard 1.10, it would be instructive to review one of the new features found in it. As we mentioned in this newsletter back in December 2024, the upper data format for meteorological data processing changed from Forecast Systems Lab (FSL) to Integrated Global Radiosonde Archive (IGRA). Since one of the features of AERMOD Wizard is that it allows the user to mark and quickly download upper air data, we updated AERMOD Wizard to be able to download data in the IGRA format. It is even easier to do than the former FSL download approach! After launching AERMOD Wizard, turn on the Upper Air / Names display on the left-hand side and go to where your upper air station of interest is. In this example, we’ve identified the Peachtree City, GA station located south of Atlanta, GA.

Next, left-click the upper air station “U” icon to mark the site:

On the drop-down menu, click Met and select Download Upper Air Data:

A check box screen then pop-up, with the name of the station, and a list of years that you can select to download. All you have to do is (1) select the station, (2) select the year(s) you wish to download, and (3) click Download.

If you’ve had to download IGRA data before, you’ll recall that the data are organized by station only, with all years of data for a station found in a single zipped file – which can be quite large. With AERMOD Wizard, it not only finds and downloads the raw, zipped file of all years of data for the station, but it automatically culls out just the year(s) that you requested. However, after downloading the data, you will still need to process that file through our IGRA Files Extractor utility in order to fill in any instances of a missing station elevation:

March 2026

Background concentrations are critical when conducting cumulative NAAQS modeling, or any modeling in which an ambient monitored background value(s) is required. We usually analyze ambient data from the most recent three years of ambient monitoring data and generate a single value or set of values that are assumed to be spatially homogeneous. However, did you know that you can customize your background concentrations by relying on multiple, spatially-varying ambient monitoring data? To be sure, this is a rare occurrence, but AERMOD will allow you to incorporate such data sets. In fact, AERMOD will let you include ambient background data from up to six monitors. In AERMOD, this is referred to as sector-varying background concentrations. Sector-based backgrounds may consist of single values per sector, temporally-varying values per sector (e.g. SEASHR, MONTH, etc), or even hourly background values. These sectors are based upon the flow vector, or direction toward which the wind is blowing; that is, not the wind direction listed in the meteorological data, but that direction plus 180 degrees. In AERMOD, the minimum allowed sector width is 30 degrees but AERMOD will also issue a warning if a sector is less than 60 degrees. Setting up these muti-sector background values is easy to do in BEEST. First, go to Source Options, and click the Groups tab:

From within the Groups tab, go down to the Background Concentrations fields at the bottom:

Here, you can select which Pollutant UserID that you want to associate with one or more sectors. As an example, let’s use the Pollutant UserID of SO2_1hr, with four background sectors.

Then, click the Edit Background button to the right of Number of Sectors to begin filling in your spatial and temporal modes. For this example, we’ll assume only a single “annual” background value for each of the four sectors. You can also tell BEEST where the start of your first sector is. In this case, the sector starts at true north or zero degrees. Input the “annual” background value for sector 1 (20 ppb for this example).

Then, under the Select Sector field, click the drop-down arrow and select Second. In the Sector Limits, put in where you want your Second sector to start, select your temporal mode (assume Annual again), and input the “annual” background value (assumed to be 15 ppb). Note that this also means that your first sector went from zero to 89 degrees in width. The sectors do not have to be exact multiples of 360 degrees divided by the number of sectors. Also, as mentioned earlier, note that the temporal mode can also vary between sectors.

February 2026

One of the nice options in AERMOD Wizard is the ability to display EPA National Emissions Inventory (NEI) sites and data on-screen. Once you have AERMOD Wizard open, go to the selection buttons on the left-hand side and select NEI Sources:

You also have the option to change how the sources’ labels are displayed on-screen. It can be one of six different ways:

• No label (just a marker for the location)
• Just the letters “NEI” for each source
• A pipe (|) for each source
• Each source’s Emissions Inventory System (EIS) ID
• The first ten letters of the source’s name, or
• Display the NEI source’s emissions (in TPY) above a threshold of 0.01 tpy

To access how the source labels are displayed, click the Options button on the left-hand side:

Then, go to the far-right tab, called NEI Sources:

Here, you can select which of the six label display options you want to use. If you opt for the last one (Display the NEI source’s emissions (in TPY) above a threshold of 0.01 tpy), AERMOD Wizard can change the display depending on what pollutant you select on the left-hand side of the screen. Here’s the display for carbon monoxide:

You can click the drop-down arrow on the left to show NOX emissions at the same sites:

And finally, if you want to get a summary of all criteria pollutant emissions at each site, simply hover your cursor over the icon/point and then you’ll see a yellow pop-up appear.

When it appears, right click at the icon, and select NEI Source Data

AERMOD Wizard will then display a summary of all criteria pollutant emissions for that site:

January 2026

To coincide with the release of AerScreen for Windows 5.0, we’ll talk about a couple of the new features in this software. First, there’s the new built-in QA for inputs. That is, if you were to input a non-numeric value into an input field, AerScreen for Windows now shows you before the model is run. For example, if I were to put in a stack height of “35-0” meters, instead of “35.0” meters, here’s what would happen:

I can input 35-0, but as soon as I tab over to another field, AerScreen for Windows outlines the field with the invalid value in red.

I’m now alerted to this issue and can quickly fix it.

After AERSCREEN runs, you can see graphics of the outputs via the Display Line Graph and Display Sector Graph options. With AerScreen for Windows 5.0, you can now customize this display.

In Display Line Graph, you can change the appearance of the concentration and elevation lines, including color, and icon shape. Here’s an example for the concentration line in Display Line Graph:

And you can place your cursor anywhere on the concentration line, and below the x-axis label, AerScreen for Windows will tell you the distance downwind and maximum 1-hour concentration for that distance:

The same options are available for the Elevation display.

The visualization flexibility is also available when using the Display Sector Graph:

December 2025

This month’s tip falls into the category of “always check your inputs after you make a change”. As you know, we use Control Options in BEEST to establish pollutant names, averaging periods, etc. In fact, in the Control Options screen of BEEST, you can input not only the AERMOD-specific pollutant name, e.g. “NO2”, but you can give it a user-defined “Pollutant UserID”, such as “NO2_ST”. The Pollutant UserID is not carried forward or used as part of the AERMOD input file. In Control Options, you define your Pollutant UserID and Pollutant Name here (circled in red):

The Define Pollutant UserIDs field looks like this:

If you set your Pollutant UserID and Pollutant Name here, and start populating your source inputs, all is fine, unless…you decide to change a Pollutant UserID by clicking Define Pollutant UserIDs button again.

For this example, we have rates for all three pollutants as shown here:

However, if you go back into Control Options, click Define Pollutant UserIDs and change “SO2_1hr” (column position 1) to “SO2_ST”, here’s what happens:

BEEST thinks that you entered a new pollutant and, as such, removed the rate associated with column position 1.

So, always make sure you double-check those inputs! However, here’s a workaround that will prevent this from happening. Rather than clicking Define Pollutant UserIDs, double click in the Pollutant UserID field in Control Options:

You can change the Pollutant UserID here, and BEEST won’t delete the emission rate associated with it.

November 2025

We’ve been releasing modeling tips in this newsletter for over 11 years. If you ever wonder if a particular topic has been covered, we’ve got a one-stop location for all of them. Log onto https://www.providenceoris.com/ and browse to Resources | Modeling Tips. You’ll find them all there, going back to August 2014.

This month, we’re going to talk about a utility found in both BEEST and AERMOD Wizard. That tool is the WindRose program. WindRose can read in surface meteorological data in a variety of formats and genrerate a wind rose, which is a plot showing frequency of occurrence of wind directions and wind speed classes. WindRose is found here in BEEST’s Met Options (Display WindRoses):

However, WindRose can only be activated here if you have highlighted/selected a listed meteorological data file. The files that are shown here are from AERMET preprocessed *.SFC files. The displayed wind rose looks like this:

WindRose can also read these data formats:

• Raw Integrated Surface Hourly Database (ISHD) data
• AERMINUTE processed data (“winds” file)
• Raw Solar and Meteorological Surface Observation Network (SAMSON) data
• Raw Hourly US Weather Observations (HUSWO) data
• Raw CD-1440 format data
• Raw EPA SCRAM format data
• Stability Array (STAR) data and
• Raw on-site data

If you want to use WindRose to process raw on-site data, you must first go to the Options tab of WindRose to define the format of your on-site data (Options | On-site Format):

Only after you establish the format will WindRose allow you to select On-site Data under the Met Data tab.

Coming back to the original *.SFC-based wind rose, if you’re interested in the statistics that went into plotting the wind rose, you can click Stats | Frequencies:

Calling WindRose from within AERMOD Wizard is a little different. From within AERMOD Wizard, you hover over a displayed surface station (“S”), and left-click to mark it. The S is then covered by a hatched circle.

Click Met | Download Surface Data | Hourly (Ishd) to have AERMOD Wizard automatically download the raw ISHD data to your computer.

Once it downloads the raw ISHD data, you can place your cursor over the S, and see a yellow pop up with information about the station and its data.

If you then right-click on the S, you’ll see several available options, including WindRose. When you hover over the WindRose row, you’ll see the downloaded years of data that are available for creating wind roses – in this case, we only had 2023.

Click the year you want and AERMOD Wizard automatically calls WindRose and generates your WindRose plot.

For more information about WindRose, click the Help menu to open a WindRose tutorial. This tutorial is also available in BEEST in Help | Tutorials.

October 2025

In BEEST, users can view either a single form at a time or multiple forms at once. If you open a BEEST file, and click File | Preferences | General Setup, you’ll see an option called Main Toolbar Buttons (circled in red):

The default is to Display New Form & Remove Old Form, which means you’d only see only one form at a time on-screen. The displayed form can be any of the icons across the top of the BEEST file or any of the Run drop-downs. However, you can also change the display to show any number of multiple forms on-screen at one time. To do so, click Display Multiple Forms:

Now, you can open/display multiple forms on-screen:

The active form is the one with the darker blue bar. You can move between forms by clicking in an open space on the form you wish to work with next. To close a form, simply click its icon at the top of the BEEST file:

September 2025

This month, we’re going to look at the Split GRF Files utility in BEEST. As you know, when you set up your AERMOD Output Options in BEEST, if you go to the Plot tab, the default is to have the Write Master Graphics File box checked:

In doing so, AERMOD will write a single GRF output file that includes all combinations of source groups, averaging periods, and concentration ranks. It can make for a large file that you may not want to laboriously scroll through to find the information/results that you need. That’s where Split GRF Files comes into play. Split GRF Files will take the Master Graphics File and split it into each of the components – by source groups, by averaging periods, and by ranks. The Split GRF Files icon is circled in red:

Once you’ve opened Split GRF Files, just browse to the directory where your master graphics file is located, and select it:

Then go to the Run tab, click Run and Split GRF Files will write out the split *.grf files and tell you how many individual *.GRF files it generated:

August 2025

Our users have enjoyed having the ability to export objects from BEEST’s Show Current Data Graphically to Google Earth. It’s a very useful way to see how well your sources, fencelines, etc match up with reality. Did you know, though, that you can have your objects exported to Google Earth as either 2-dimensional (2-D) or 3-dimensional (3-D)? If you’re in Show Current Data Graphically, click the Options button on the left-hand side, and go to the Google Earth Options tab:

Something else that’s interesting when exporting to Google Earth is that you can get an idea of how the terrain changes around your site of interest. For example, you can set your Google Earth export option to 3D Export, and then add a tank around your facility/domain. When you add a height to the “tank” and then export to Google Earth, Google Earth shades all area less than the tank height. You could also set the tank height to your stack height to see if you are dealing with complex terrain. Here’s an example from our BEEST Test Case, where a tank was drawn about the source, was given a base elevation equal to the source base elevation, and a tank height of 100 feet.

July 2025

This month’s Modeling Tip is more of a “Hey, this is a nice resource that I didn’t know about.” While EPA endeavors to fix bugs in AERMOD/AERMET/AERMAP, etc., in a timely manner, sometimes a new version release of AERMOD/AERMET/AERMAP may not occur for several months. (as is the case now, with there being no new releases scheduled for 2025) Until a new version is released, EPA has started keeping a log, called AERMOD System Bugs, Errata, and Related Guidance on SCRAM. It not only identifies what the bugs are but also includes work-arounds that can be used until a new version is released.

May 2025

BEEST users know that there are two ways to call/run programs in BEEST: (1) icons:

Or (2) the Run menu

Although you have known the Run menu as another place where you can run AERMOD, AERMET, etc, we’ve recently added some new items that you can access from it.

In order to invoke the Create Line of Receptors or Create Line of Volume Sources, all you have to do first is draw an Other line on-screen (Show Current Data Graphically), and then click the Run menu and click either Create Line of Receptors or Create Line of Volume Sources. You’ll be prompted to select the Other line, and then BEEST pops up either the line of receptors screen or the line of volume sources screen:

Don’t forget, if you’re not sure about how to generate the inputs for the line of volume sources, there’s a Tutorial on it in the BEEST Help menu – Help | Tutorials:

Back at the Run menu, clicking Import KML calls the Import KML utility, which can also be called from the BEEST File | Import | Import | Google Earth Import KML/KMZ menu:

There is also a Tutorial for this tool in BEEST: Help | Tutorials:

Finally, from the Run menu, we can select Unix file to DOS Convert. This utility is helpful when processing raw surface and upper air data through AERMET. Very simply stated, this routine reads in a raw ASCII text file that is in Unix end-of-line format (Line Feed – LF) and converts it to a DOS end-of-line format (Carriage Return Line Feed – CR LF). Selecting Unix file to DOS Convert gives you this easy-to-use pop-up:

Browse to and select the Unix-based end of line file (LF) you want to convert, type in a path/file name for the converted file (CR LF) and then just click Convert.

April 2025

If you look through the AERMOD *.LST output file and scroll toward the bottom, you may see something that looks like this:

Since a model run may be considered unacceptable for regulatory purposes if there’s more than 10% missing hours, it begs the question, how does AERMOD determine if an hour of meteorological data is missing? Does the meteorological data just skip hours, as in going from hour 1 to hour 3 because there’s no hour 2? No, according to section 3.2.2.1 of the AERMOD Users Guide, an hour is considered missing if one or more of the following surface variables have missing value indicators (e.g., -9.000, -999, etc.) for that hour:

surface friction velocity (u*) – 7th field in each *.SFC record
convective velocity scale; (convective hours only) (w*) – 8th field
convective mixing height (convective hours only) (Zic) – 10th field
mechanical mixing height (Zim) – 11th field
Monin-Obukhov length (L) – 12th field
wind speed (Ws) – 16th field
wind direction (Wd) – 17th field
ambient temperature (Ta) – 19th field

In this example, there are missing data flags (-9.000, -999) for w* and Zic but these are early morning/non-convective hours. Therefore, these five hours would all be considered valid/non-missing.

March 2025

This month, we have not one, but two Modeling Tips for you. Both have important ramifications, so without further ado…

In light of the issues associated with BEEST 12.12, we are revisiting the December 2023 Modeling Tip of the Month. We also discussed this in a YouTube video last month (Bugs in BEEST 12.12 and Workarounds). The issue involves using the current version of AERMOD (24142) in an older version of BEEST. The solution is rather simple:

• Uninstall BEEST 12.12 from your computer and download/install the older BEEST 12.11, which is currently found on the Providence/Oris website. (Software Downloads – Providence Oris) BEEST 12.11 comes with the older AERMOD 23132 installed with it.

• Log on to EPA’S Support Center for Regulatory Air Models (SCRAM) website (Support Center for Regulatory Atmospheric Modeling (SCRAM) | US EPA) and browse to Air Quality Dispersion Modeling | Preferred/Recommended Models. Under AERMOD Modeling System | Model Code, you will find AERMOD executables (zipped) for both 32-bit and 64-bit computers. Download the executable to your computer and unzip it. Place the AERMOD executable into a file path other than C:\Program Files (x86)\Providence\Beest\.

• Open BEEST 12.11 and go to File | Preferences. Click the Model Selection tab. In the field for AERMOD, browse to the folder where you placed the AERMOD 24142 executable and select that aermod.exe and click Open.

Now you have the most recent version of AERMOD in BEEST 12.11. Note that in BEEST 12.13, this will not be necessary.

The second tip of the month can be very important if you process raw meteorological data through AERMET. Currently, if you’re processing raw upper air data (In IGRA format), and if your station’s base elevation is greater than 999 meters, then the upper air EXTRACT or QAOUT file can’t read it, and returns the elevation as a series of asterisks. This, in turn, generates an AERMET E05 error (Invalid option for keyword or invalid variable) in the Stage 2 Messages output file. Therefore, no SFC or PFL output files are generated.

In this example, here’s the AERMET input/control file for Stage 1 processing. For this run, the upper air station is Salt Lake City, Utah. Note the upper air station base elevation of 1289m (in red box):

After running Stage 1 of AERMET, here’s what the upper air EXTRACT file looks like. Note that the upper air base elevation is just a series of asterisks in the red box:

And, here’s the upper air QAOUT file. Again, notice that the upper air station’s base elevation is just asterisks:

While EPA will be fixing this error in the next release of AERMET, they do have a suggested workaround that you can use: Run AERMET Stage 1. After it finishes, open the QAOUT file in Notepad and manually correct the elevation on the LOCATION line in the file and then run Stage 2. AERMET should then finish normally and generate your SFC and PFL output files.

February 2025

For this month’s modeling tip, we’re going to look at the ARY Viewer in BEEST. Structurally/visually, it looks similar to the BEEST USF Viewer (see May 2017 Modeling Tip of the Month). However, instead of viewing AERMOD SUM files, it allows the user to view the total number of exceedances created by the ARRAY2 program in BEEST. That is, when preparing to run AERMOD, the user inputs a comparison threshold into the MAXIFILE setup. When AERMOD is running, it compares the calculated concentration for each hour, at each receptor, to that MAXIFILE threshold. When AERMOD finishes, the user can then run ARRAY2, to generate a plot of the number of exceedances at each receptor – over all 8760/8784 hours in the year:

If you click Display Output Graphically, you can then see all exceedances of your MAXIFILE threshold – not only that, but ARRAY2 also saves and displays multiples of the threshold – 1X, 2X, 4X, and 10X.

It may also be useful to view the exceedance data in a tabular format. This is where the ARY Viewer comes in handy.

ARY Viewer gives you a summary of the number of 1X, 2X, 4X, and 10X exceedances for each receptor:

Just like with USF Viewer, you can write the file to the grid shown below:

Also, like USF Viewer, you have the ability to sort and filter the grid values by any of the header columns.

Clicking the header (E.g. East (X), North (Y), Conc, etc) over each column of data will sort that column of data, ascending or descending.

And, of course, you can copy the grid of data to the clipboard and paste into Excel.

January 2025

As you might imagine, any time a new version of a program is released, there may still be some hiccups for users. EPA has recognized this and has released an errata sheet for the recent updates to the AERMOD system: https://gaftp.epa.gov/Air/aqmg/SCRAM/models/preferred/aermod/AERMOD_System_Bugs_and_Related_Guidance.pdf

One such hiccup we’ve heard about lately concerns running the new version of AERSURFACE. Users have downloaded land cover, impervious cover, and tree canopy cover from the Multi-Resolution Land Characteristics (MRLC) web site, and when they try to run AERSURFACE, they get an error message. This is because the MLRC data was recently updated and does not include the Albers Equal Area projection parameters for tree canopy cover data. Although AERSURFACE prompts the user to enter these parameters when missing, AERSURFACE doesn’t recognize them. The AERSURFACE errata information indicates that there are two ways to work around this:

1. Use the 2021 edition of the NLCD files available on the EPA FTP site. The 2021 edition is available for the 2011, 2013, 2016, 2019, and 2021 NLCD years. The files on the FTP site are separated by EPA region and include either the entire region, part of the region, or part of a single state in a few cases (e.g., CA, TX), depending on the geographic size of the region/states. This data works with AERSURFACE as is and is sufficient if you don’t need any data newer than 2021.

2. The second workaround is to use software such as GDAL to rewrite the canopy TIFF file downloaded from the MRLC to add the necessary projection parameters to the file. The EPA has put together a zip file, “GDAL_MRLC_canopy_preprocessor.zip”, containing the GDAL Warp utility (gdalwarp.exe) and associated library and data files required to add the Albers projection parameters to the canopy TIFF files within the CONUS. The zip file can be found here. This would be the approach to take if you need to process 2023 MRLC data.

So, EPA is aware of this “hiccup” and has provided these two workarounds. In addition, EPA is working with the US Geologic Survey (USGS) to come up with a permanent fix. Stay tuned!

December 2024

This month’s tip is good to know with the release of new versions of AERMOD, AERMET, AERMAP, and AERSURFACE. A common reminder that we often get from the agency/permitting authority is to make sure that you are using the most recent version of the model or preprocessor. In BEEST, it’s easy to find out what version you are using. Simply click the Help menu and select About BEEST for Windows.

In the About BEEST for Windows pop-up, we list the versions of each of the EPA component programs that were included with BEEST. We also note that you may need to confirm version numbers by reviewing the output file associated with program of interest.

October 2024

Folks who have to process meteorological data using AERMET or AERMINUTE may be surprised to find out our Graphical User Interfaces (GUIs) for these two programs include an auto-save feature. To enable or modify auto-save in both programs, you can click File -> Preferences on the menu bar and go to the Backup files tab. Click the checkbox to Write backup files and select how often to write the files. You can also change the default folder where the files are saved. Click OK to save the preferences and both programs will write backup files.

In AERMET:

In AERMINUTE, it’s exactly the same way:

September 2024

Time for another AERMOD Wizard modeling tip! When preparing a Prevention of Significant Deterioration (PSD) permit application, one of the items to evaluate is the proposed facility’s impact upon any Class I areas. Under the Federal Clean Air Act, there are 156 mandatory Class I areas -consisting of (1) international parks; (2) national wilderness areas and national memorial parks in excess of 5,000 acres; and (3) national parks in excess of 6,000 acres, that were in existence as of August 7, 1977. Current EPA guidance is to conduct an emissions vs distance evaluation – called Q/D. The object is to sum up all the emissions of light-obscuring pollutants (in tons/year) and divide that by the distance from the proposed facility to the Class I area. If that ratio is less than 10, then it is assumed that the facility will not adversely affect the Class I area. In some cases, the applicant may have to do multiple Q/D analyses, if they are near multiple Class I areas. Regardless of how many Class I areas you have to evaluate, AERMOD Wizard can do this for you with no problem whatsoever.

After opening AERMOD Wizard, place your source on the map:

Populate with your source’s emissions:

You can now show your source and any nearby Class I areas:

To do the Q/D calculation, just place your cursor over the anchor for the Class I area of interest, right-click and select Q/D:

When you select Q/D, a pop-up appears, providing distance from the source to the nearest Class I receptor (in km), the total emission rate (in tpy), and the ratio of Q/D (tpy/km).

In this example, the Q/D is 7.06 tpy/km, which is less than 10, meaning that the source is assumed to not have any adverse impact on this Class I area (Great Smoky Mountains National Park).

By following the same procedure for any other nearby Class I areas, AERMOD Wizard will generate Q/D for those source-to-Class I areas, as well.

July 2024

You know that when you set up an AERMOD run, you have two fields in BEEST | Control Options | CO Options where you can put in a description of what that particular runs entails (Title 1 and Title 2 fields):

These fields can include client/project name, type of analysis, scenario, etc. If that’s not enough room and/or you don’t want to enter in a lot of cryptic information, don’t worry, there is a solution. Another place in BEEST that can be used for providing additional information on the model run(s), etc is the Model Notes option. To access Model Notes, click the Tools drop down in BEEST:

(Or you can just click Ctrl-N from your BEEST screen.) Either way, the Model Notes pop-up appears and you can start entering in your modeling information:

June 2024

This month, you might say we’re taking a step back in time. When the modeled concentration is too high, determining source culpability is a critical exercise. Evaluations of the 24-hour PM2.5, 1-hour SO2, and 1-hour NO2 NAAQS may use the MAXDCONT output option to assess source contributions/culpability. However, if we’re dealing with non-probabilistic pollutants/averaging periods, we can use the AERMOD Event Model. The EVENT Model is a follow-on to a standard AERMOD run. EV is a new pathway that comes from the AERMOD run. Its input file name (EVENTFIL keyword) can be found in the Control Options pathway:

– CO STARTING
– CO TITLEONE Event test case
– CO TITLETWO Max 3-Hr SO2
– CO MODELOPT DFAULT CONC NODRYDPLT NOWETDPLT
– CO AVERTIME 3 24
– CO POLLUTID SO2
– CO RUNORNOT RUN
– CO EVENTFIL “O:\Training classes\AERMOD Event Test w MAXIFILE” DETAIL
– CO FINISHED

The format of the EVENTFIL keyword has the name of the EVENT input file (e.g., “O:\Training classes\AERMOD Event Test w MAXIFILE“) plus the EVOPT secondary keyword (DETAIL or SOCONT).

– SOCONT: gives the average concentration from each source for the averaging period corresponding to each source group

– DETAIL: Same contribution information as SOCONT, but it also gives the hourly concentration for each source for every hour in the averaging period PLUS a summary of the hourly meteorological data for the event period.

Running AERMOD with the EVENTFIL keyword will create an input file for the EVENT model, which must be run as the second step in the process. That is, one of the outputs from the initial AERMOD run will be a new input file for running the EVENT model. If you don’t specify differently, the default EVENT model input file name is EVENTS.INP (however, if you’re using BEEST, you get to specify the input file name). The EVENT model input file will have CO, SO, ME, EV, and OU pathways. (No Receptor path needed)
The EVENT model uses a default nomenclature to describe each Event, defined with the EVENTPER and EVENTLOC keywords:

• EVENTPER – defines the averaging period, data period, and source group. It includes the keywords Evname, Aveper, Grpid and Date

• EVENTLOC –This defines the receptor location for the event. Includes keywords Evname, XR (receptor easting), YR (receptor northing), Zelev, and Zflag. The Zelev and Zflag keywords are optional.

Examples of Event names (Evname) from the EVENT model output:

• H001H24001 – refers to highest first high 24-hour average for source group 1
• H002H03003 – refers to highest second high 3-hour average for source group 3
• TH03000003 – refers to exceedance of 3-hour threshold (from MAXIFILE) for source group 3

Besides source contributions related just to pollutant design values, the user can also determine concentration contributions where a concentration threshold – a MAXIFILE – is input to AERMOD. That is, the EVENT model can also provide culpability for source groups contributing to an Event where a MAXIFILE-defined threshold is exceeded.

With all this talk about the EVENT model, what do these files actually look like? Below is a screenshot of an AERMOD input (DTA) file, but now note the EVENTFIL keyword in the Control Options pathway:

After AERMOD runs, it creates the EVENTFIL, which becomes the input file for the EVENT model run. That input file looks like this:

Notice that the EV pathway lists out the 3 events (and two averaging periods) for which we wish to assess culpability.

To set up and run the EVENT Model in BEEST is very straightforward. In your BEEST file, click on Control Options:

Once there, click the CO Files tab:

If you click the File button for the EVENTFIL Option, you can browse to where you want to generate the EVENTFIL and give it a name. After you do, the Detail and SOCONT buttons are activated. Pick which option you want:

Then, go to Source Options | Source Groups and make sure you’ve set up the groups for which you want to assess contribution/culpability. For example:

Then go to Output Options and make sure you’ve got the correct ranks set (for example, 2nd high for 3-hour and 24-hour SO2 increment):

If you’re evaluating events with a MAXIFILE, go to the Output Options | Maxi tab and set those values (example is 3-hour and 24-hour SO2 increment):

Now, simply run AERMOD like you normally do. After AERMOD finishes running, go to the Run menu at the top of your BEEST screen and select Events.

With the EVENTFIL created in the AERMOD run, clicking Events runs the Event Model and allows you to determine contributions for each event to your target source group (usually ALL). When you click Run | Events, you’ll see this:

Click Run Events, AERMOD runs the Event Model and then you’ll see this:

You can click View Summary and BEEST will open your Event Model list (*.LST) file where you can review the contributions from each source to your target group (ALL) for each event.

May 2024

This month, we’ll be looking at a new feature recently added to BEEST. It seems like every so often, you’ll be modeling a site that happens to have a road or railway that bisects it. In many cases, that road or railway is considered ambient air and you need to place receptors along it. Now, in BEEST 12.10, it’s very simple to do that!

First, in BEEST, go to Show Current Data Graphically and draw an “Other” line where your road or railway is:

Place your cursor on the anchor point of the Other line (here named as “Road”), and when you see the four-sided arrow and yellow pop-up, right-click and select “Create Line of Receptors”.

This pop-up will give you the option to space receptors evenly along the line or have BEEST place a fixed number of receptors along the line, with spacing determined by BEEST.

BEEST tells you how long the Other line is, and you also have the ability to place the first receptor at the beginning of your Other line or to offset the first receptor by ½ of the receptor spacing distance.

After you generate the line of receptors, don’t forget to run AERMAP for them!

April 2024

This month’s tip relates to using the SCREEN3 and AERSCREEN models from within BEEST. If you have those model executables on your computer, you can call/invoke SCREEN3 or AERSCREEN from within your BEEST file.

Note the AERSCREEN icon in BEEST:

And the SCREEN3 icon:

The big advantage to calling these models from within BEEST is that, if you have multiple sources in your BEEST file, you can easily run SCREEN3 or AERSCREEN for any of the BEEST sources. In this example, we have a BEEST file with three sources and two buildings:

If we click the SCREEN3 icon, this form/screen comes up:

Notice that you can select which source you want to run SCREEN3 for AND you can pick which building you want to use (or just enter your values for building height, length, and width). You can then click Run and the process is just like a stand-alone SCREEN3 run.

Similarly, you can click the AERSCREEN icon to see this screen/form:

Selecting the source you want to model with AERSCREEN and clicking OK takes you directly to the AERSCREEN user interface:

February 2024

When running AERSURFACE (either for meteorological data processing or determining site-specific surface roughness length), always make sure that your domain (for land cover, impervious cover, and canopy cover data files) extends at least 5 kilometers in every direction from the coordinate you enter as the site location. The reason for this is the way AERSURFACE calculates Bowen ratio and albedo. Section 2.4.2 of the user’s guide (page 2-20) for AERSURFACE 20060 says:

“Bowen ratio is calculated as the simple geometric mean of the Bowen ratio values of the individual grid cells that make up the 10 km x 10 km area centered on the measurement site.”

Likewise, section 2.4.3 of the AERSURFACE user’s guide says:

Failure to have your location centered within a 10 x 10 km domain will cause AERSURFACE to fail.

January 2024

This month, we are revisiting the Find function in BEEST and we’ll also show how to use the Find function in AERMOD Wizard.

When you open a BEEST file, and go to Show Current Data Graphically, you can right click your mouse and select Find. You then have the option of searching for a Building, Source, Source Group, Tank, or Other.

We’ve updated the Find function in BEEST so that if you just start typing the name of the source of interest, BEEST anticipates and (1) highlights the source it thinks you’re looking for and also (2) begins populating the Search field.

Then, just select your object of interest (a source in this case) and click Find or Find and Zoom. When you’re done, just right-click and select Find → None.

The Find feature in AERMOD Wizard was introduced in version 1.08. It allows the user find on-screen surface meteorological stations, upper air meteorological stations, ambient monitoring stations, and Class I areas. First, in AERMOD Wizard, go to the left-hand side of the screen and select which object(s) you wish to search for (surface met stations, upper air met stations, ambient monitoring sites, and/or Class I areas). If you want to find an ambient monitor location, select the Current Pollutant drop down (yellow arrow) to only display the monitors of your pollutant of interest. The objects you check will display on the screen.

To then find your object, right-click the mouse and select Find, and then the object category.

Once you select your object (Class I Areas, for example), a pop-up appears:

Double-clicking the column header brings up a search field that allows you to type in the site you want to zoom to. Type in the name and click OK.

When you click OK, the Search tool takes you to that object’s entry, where you can then click Find and Zoom and AERMOD Wizard will automatically take you to that object (Yosemite, in this case).

December 2023

Just imagine – you’ve just completed a modeling report and sent it off to the agency. Some time goes by and now you get a comment from the agency that requires you to update the original AERMOD modeling. But wait – the original modeling was done with AERMOD Version 22112 and now you’re using a new version of BEEST that links to AERMOD 23132! How can you run an older version of AERMOD in a newer version of BEEST?

When you download BEEST, it automatically comes with the most recent executable version of EPA’s AERMOD model (AERMOD.EXE). However, did you know that you can run other versions of AERMOD from within BEEST (as far back as AERMOD 19191)? By default, BEEST installs AERMOD.EXE in the path\folder C:\Program Files (x86)\Providence\Beest\. If you have a previous executable version of AERMOD you want to use, you can tell BEEST to use it by going to File | Preferences | Model Selection. There, under AERMOD, you can point BEEST to whatever path/folder your older AERMOD version is in and select it. No matter what version you use, the executable file name is always “AERMOD.EXE”. A few cautions to keep in mind:

BEEST does not display which version of AERMOD you’re pointed toward (unless you look at the File | Preferences | Model Selection menu) while setting up your AERMOD run, although when the model finishes and the version number will be shown in the LST output file.
Also, BEEST does not return to the current version of AERMOD automatically. Once you’re done using the older version of AERMOD you’ll need to go back to the File | Preferences | Model Selection menu to link back to the current version of AERMOD.
The model version link is not specific to a single BEEST file – it will be applied to all AERMOD runs done with any BEEST file on your computer.
If you use the Scheduler utility to execute your model runs rather than using BEEST directly, you’ll also need to link to the desired version of AERMOD in the Scheduler under the File | Preferences menu in Scheduler.

September 2023

If you routinely process meteorological data for use in AERMOD, you know that the AERSURFACE processor must be used to determine spatially- and temporally- varying values of surface roughness length, albedo, and Bowen ratio. EPA last updated AERSURFACE in 2020, and the current version (v20060) can process National Land Cover Database (NLCD) land cover, impervious cover, and tree canopy data for 1992, 2001, 2006, 2011, and 2016 data sets. However, 2 newer years of data sets, 2019 and 2021, are now available from the NLCD (https://www.mrlc.gov/viewer/). If you are processing a meteorological data set that occurred after 2016, you can still process 2019 and 2021 data sets using AERSURFACE. It turns out that the formats of the 2019 and 2021 data sets are exactly the same as the 2016 data sets. In addition, there’s no year check in AERSURFACE, so you can process the more recent data sets in AERSURFACE by just setting the year to 2016.

First, in the AS1 tab in AERMET, click Input Files:

Then, just set the year to 2016 and select your 2019 or 2021 land cover, impervious, and canopy data files and run AERSURFACE like you normally would:

Please note that although the 2019 and 2021 data sets are available through MRLC, they are not yet available on EPA’s land cover website https://gaftp.epa.gov/Air/aqmg/nlcd/.

August 2023

A button that’s very handy when displaying concentration outputs in BEEST is the Options button:

Clicking it and going to the General tab, you’ll see 3 display tools at the bottom: Multiply Values by Scaling Factor, Add Background to display values, and Display values above Threshold. We’re going to look at the second one (Add Background to display values).

Did you know that this tool will also allow you to subtract “background” from values? Consider a case where you ran AERMOD and included a true background value to be included in the run. This is a single “annual” value that gets added to every hour of the year and shows up as part of the ALL source group. If you want to know what your concentration field/display looks like without the true background, click Display Output Graphically, go to Options | General, check Add Background to display values and input the negative of the true background. Your ALL concentrations will then have the true background value subtracted from the ALL concentrations. Here’s an example where the BEEST Test Case was loaded and run for 1-hour SO2. An “annual” background of 22.5 µg/m3 was included. Here’s what ALL output looks like:

Now, if I click Options | General, and input -22.5 in Add Background to display values, it looks like this:

And my concentration display now looks like this:

June 2023

Long-time users of BEEST know about its ability to split or partition an AERMOD run or AERMAP run, but did you also know that the same can be done for building wake effects processing via BPIP-Prime? Within BEEST, this is called BPIP Tool.

BPIP Tool allows you to split a BPIP-Prime run similar to the way BEEST splits or partitions AERMOD runs, except that BPIP Tool splits the number of sources rather than the number of receptors. The process is straightforward.

1. Enter your point sources, buildings and tanks into BEEST.

2. Run BPIP-Prime within BEEST to generate the input (.PRW) file.

3. Click the “Run BPIPTool program” button on the toolbar to open BPIP Tool.

4. Click the Browse button on the Setup tab. Locate the folder with the input file and click the OK button.

5. Select the input (.PRW) file and click the “Add >>” button.

6. Click File → “Save As…” on the menu bar to create a batch file. Enter a name for the batch file and click the Save button.

7. Highlight the file under “Batch file contents” and click the Split button.

8. Enter the number of new input files and click the OK button. In this example, we have a total of 250 sources that will be split among two files (125 point sources per file).

9. Click File → Save on the menu bar.

10. Go to the Schedule tab and run the batch file.

11. Close BPIP Tool.

May 2023

This month, we’ll focus on a feature that’s been in BEEST for a few years now but that hasn’t been discussed here. As all AERMOD modelers know, there’s not a source type in AERMOD for flares, as there is in AERSCREEN (and even SCREEN3 before that). Therefore, in AERMOD, flares must be modeled as a point source, but with special source parameters. What complicates matters somewhat is that different states have slightly different approaches for generating the source inputs for the flare. In general, the approaches use a fixed release temperature and a fixed exit velocity to create an effective flare diameter (and in some cases, an effective flare release height). To help modelers in generating their flare input parameters for AERMOD, BEEST includes the Flare Tool. Flare Tool can be accessed from the Edit Sources screen.

Clicking the Flare Tool button takes you to the Flare Tool screen.

The Flare Tool screen includes a tutorial that takes you through each of the different state flare techniques. After that, it’s as easy as 1-2-3: (1) select the appropriate flare modeling technique, (2) put in the flare inputs required by the selected technique and (3) click the Calculate button. Flare Tool calculates the flare inputs for AERMOD and updates the source when you click the OK button.

We recognize that there is a limited number of state flare modeling techniques that Flare Tool can handle, so if you know of any others, please let us know and we’ll update Flare Tool.

April 2023

Let’s check out some more features of our AERMOD Wizard software. As we told you back in July 2022, AERMOD Wizard has the capability to display the locations of 2017 National Emissions Inventory (NEI) facilities, as well as the criteria pollutant emissions from them. Did you know that you can alter/customize how the sources are displayed? If you open AERMOD Wizard, you can click the “NEI Sources (2017)” checkbox on the left side of the screen.

The default display label for each facility is its EPA Emissions Inventory System (EIS) ID. However, you can change this label if you click the Options button and go to the “NEI Sources” tab.

Notice that you have the option of having no label, showing just the letters “NEI”, showing just an “I” label, showing the EIS ID as a label (default), showing the first 10 characters of the facility name or showing the emissions from that facility. To do the last-named approach, you first decide which pollutant’s emissions you’d like to display. Go to the “Current Pollutant” dropdown to select the pollutant you want.

Click the “X.XX (tpy)” radio button on the “NEI Sources” tab in Options and you’ll see each NEI site labeled with the tons per year emissions for the pollutant you selected.

The NEI sources can be exported to Google Earth along with the other objects in AERMOD Wizard.

March 2023

We do quite a bit of meteorological data processing for AERMOD and wanted to share an interesting tidbit of information related to that. If you process raw meteorological data through AERMET, you know that it can process multiple formats of raw data, including CD-144, SAMSON, HUSWO, and Integrated Surface Hourly Data (ISHD). ISHD is the most recently created format and began in 1995. Unlike predecessor formats, ISHD data are time stamped in Greenwich Mean Time (GMT). This means that there is a difference between the ISHD data time stamp and local standard time. For example, ISHD data for a station located in the US Eastern time zone are 5 hours behind the GMT time stamp. This time offset requires you to not only account for this difference (called Time Adjust in our AerMet GUI) but to also append the first day of the next year’s raw ISHD data to your raw surface data file. This is because AERMET reads the records based on the offset; if you don’t include January 1 of the next year, your last 5, 6, 7, or 8 hours of processed data (based on Eastern, Central, Mountain, or Pacific Standard Time) will show as missing hours.

Bonus tip: for meteorological data processing, everything is based on local standard time. Daylight saving time is never used or accounted for.

January 2023

It is truly amazing what all can be done with our AERMOD Wizard software. Modelers appreciate the ability to identify, download, and process meteorological and ambient data, but it can also perform a task that combines meteorological and ambient data. That task is known as a pollutant rose or pollution rose. Combining ambient data with wind direction data enables a forensic analysis to determine what emission source or sources may be impacting a monitoring station. With AERMOD Wizard, this is very easy to do. First, open AERMOD Wizard and select your pollutant of interest, monitor of interest, and closest surface meteorological station.

Download the surface meteorological data and ambient data – both have to be for the same time period/year. For this example, we are looking at SO₂ for 2018 for a station in east Texas. Click the met station’s icon, which will put a circle around it.

If you right-click the ambient monitoring station, you get a menu with the option to Show Pollutant Rose.

Clicking Show Pollutant Rose will open a form to set up your pollutant rose. For the three dropdowns at the top of the form, make sure that you have the correct year, surface meteorological station, and offset from GMT selected.

You can opt to distribute calms/missing data and define the upper bounds of your pollutant classes, as well as pick either wind direction or flow vector. If you wish to have the rose petals point back toward any culpable sources, you’ll want to select wind direction. Click Calc Frequencies and AERMOD Wizard will calculate the concentration class frequencies based on your inputs. Rather than using the default upper bounds, you may wish to pare these back in order to better display the concentration petals.

Clicking Pollution Rose will then create your pollution rose that pairs the surface meteorological data with the ambient data. After doing so, you can also export the pollution rose to Google Earth.

In this example, the SO₂ pollution rose points back to a large coal-fired power plant.

November 2022

Our AERMOD Wizard software can do many useful tasks, including developing ambient background data for inclusion in AERMOD runs. However, sometimes all you need is just to compare overall monitor design values from available stations. If that applies in your case, have we got something for you! We have created a KMZ file that shows the design values of ambient data from EPA’s AQS database.

Once you open the KMZ file in Google Earth, you can look under Temporary Places on the left side of Google Earth. There, you will see check boxes for the criteria pollutants CO, NO₂, SO₂, PM₁₀, PM_2.5, lead and ozone. Selecting any of those pollutants will cause Google Earth to display all stations that were monitoring that pollutant for the years 2019‑2021 (last three full years). This includes data from the continental US plus Alaska, Hawaii, Puerto Rico and the US Virgin Islands. Clicking one of the station pushpins will display a table identifying the station (both name and EPA AQS ID) and its 3‑year (2019‑2021) design value. Not only that, but by using the dropdowns underneath the pollutant IDs under Temporary Places you can also filter the table display to screen out any monitors that have inadequate data or that are measuring exceptional events.

Interested in trying this out? You can download the KMZ file FOR FREE at https://www.providenceoris.com/epa-aqs-monitors-2019-2021-2/.

October 2022

This month’s tip is related to a change in meteorological data availability. If you’ve processed 1‑minute Automated Surface Observation System (ASOS) data through AerMinute, you downloaded the raw data files from ftp://ftp.ncdc.noaa.gov/pub/data/asos-onemin/. However, starting with the July 2022 1‑minute data set, NOAA has moved the files to a different location and the data are organized differently. The new location is Index of /data/automated-surface-observing-system-one-minute-pg1/access/2022. The files are organized by year (starting with 2022), then by month. Within the subfolder for each month, the files are listed by station (alphabetically). There’s only one file for each station for each month.

We will be updating AerMinute to account for this change.

September 2022

In the air dispersion modeling world, one of the critical inputs is the determination of whether or not a location or source is considered urban or rural. Section 7.2.2.1 of EPA’s Guideline on Air Quality Models prescribes an approach based on the Auer land use analysis. Basically, you draw a 3,000‑meter radius circle around the source or area of interest and determine whether the land use (based on Auer categories I1, I2, C1, R2, and R3) is greater than 50%. If it is, you categorize the source as urban. AERSURFACE offers a way to do this quickly and easily.

1. If you’re using BEEST Suite, open AerMet.

2. On the MP 2 tab, select Annual for the Primary Surface Characteristics Frequency and One for the Primary Wind Sectors. You can also select Seasonal or Monthly frequency and Twelve 30‑degree wind sectors.

3. On the Setup tab, select Run AerSurface under Site Characteristics and go to the AS 1 tab.

4. On the AS 1 tab, click the “Input Files” button and select the (preferably 2016) Land Cover, Impervious and Canopy input files for AERSURFACE.

5. Click the OK button to go back to the AS 1 tab. Enter the path and filename for the output file for AERSURFACE.

6. Under Primary Location, enter the location of your source (longitude is negative in the western hemisphere).

7. For the climatological parameters, you can select the default values: Average for soil moisture, No for Winter Season Snow Cover and No for Arid.

8. Click the “Other Options” button. Under Calculation Method, select Default method and change the surface roughness length radius to 3.0 km. Under Non-Airport Wind Sectors, select None if the source is at or near an airport.

9. Click the OK button to go back to the AS 1 tab and click the “Run AerSurface” button.

10. You will see a dialog box with the message “Import was successful”. Click the OK button to close the dialog box.

11. Open the aersurface.log output file. Scroll down to view a table of land use categories versus wind sectors. Import this table into Excel or another spreadsheet program.

12. Notice that aersurface.log lists the number of pixels associated with each combination of land use category and wind sector.

13. Within the spreadsheet, sum the pixels across all wind sectors for each row to generate a total number of pixels for each land use category. After that, sum the total number of pixels for all land use categories (the grand total) at the bottom of the spreadsheet.

14. Create another column to the right of the totals for each land use category. Divide each land use category’s total pixels by the grand total to calculate a percentage.

15. For urban determination, sum the percentages associated with categories 22 (Developed, Low Intensity), 23 (Developed, Medium Intensity) and 24 (Developed, High Intensity). If this sum is greater than 50%, the entire area is urban. Otherwise, the entire area is rural/non-urban.

July 2022

Our tip this month is related to developing representative ambient background data using a new function in AERMOD Wizard. First, AERMOD Wizard 1.07 allows you to display all National Emissions Inventory (NEI) sources.

We can then add our source to AERMOD Wizard and have AERMOD Wizard draw a 10 km radius circle around our source.

Within our circle, we can place our cursor over our source, right-click and select “Sum NEI 10 km” and AERMOD Wizard will automatically identify all NEI sources within the circle.

AERMOD Wizard also automatically sums the criteria pollutant emissions occurring within the circle. Now, you have an idea of the emissions near your source.

You can center a circle around an ambient monitor and have AERMOD Wizard determine and display the emissions within 10 km of the monitor. Now you have a way to compare whether a particular monitor has the same or greater emissions total compared to the area around your source, bolstering your case for selecting the monitor for background purposes.

For more detail on this, check out our webinar on AERMOD Wizard 1.07.

April 2022

While BEEST has some great importing tools – e.g. generic AERMOD input files, Google Earth KML/KMZ files, etc. – it also has the ability to export emission source data and discrete receptor data. Click File → Export on he menu bar and select either “Sources to a DOS Source File” or “Discrete Receptors to a DOS Receptor File”. BEEST creates a file with sources or discrete receptors extracted from your BEEST file. You can then view the file in a text editor or Excel.

January 2022

Area sources can be tricky to model, but BEEST has you covered. In AERMOD, the emission rate for an area source (whether rectangular, circular or polygon) must be input in terms of mass per unit time per unit area (g/s/m²). However, we generally calculate our emission rates based on a process that is just in terms of mass per unit time (g/s, lb/hr or tpy). If you go to File → Preferences → Misc 1, you can tell BEEST that your inputs are in mass per unit time, and then BEEST will automatically divide that rate by the area of the source and write the rate in g/s/m² to the AERMOD input file.

In addition, if you are curious to know what the actual area of your area source is, you can hover the cursor over the anchor point of the source and BEEST tells you the area.

December 2021

Because it’s the holidays and we’re in such a giving mood, here are *2* Modeling Tips:

Tip #1

SCREEN3 users might remember a series of scalars that were used to convert the SCREEN3-calculated 1-hour concentration into longer time-period averaged concentrations, such as 3-hour, 8-hour, 24-hour, and annual. These were originally listed in EPA’s 1992 document Screening Procedures for Estimating the Air Quality Impact of Stationary Sources, Revised. These scalars actually came with a range:

1-hour to 3-hour, multiply 1-hour concentration by 0.9 (+/- 0.1)
1-hour to 8-hour, multiply 1-hour concentration by 0.7 (+/- 0.2)
1-hour to 24-hour, multiply 1-hour concentration by 0.4 (+/- 0.2)
1-hour to annual, multiply 1-hour concentration by 0.08 (+/- 0.02)

The ranges (e.g. +/- 0.1) were intended for worst case conditions of where the meteorology stayed persistent for multiple hours, or if the plume was impacting in complex terrain. However, AERSCREEN users know that EPA “hard-coded” in the higher ranges into AERSCREEN:

1-hour to 3-hour, multiply 1-hour concentration by 1.0
1-hour to 8-hour, multiply 1-hour concentration by 0.9
1-hour to 24-hour, multiply 1-hour concentration by 0.6
1-hour to annual, multiply 1-hour concentration by 0.10

Although we can’t alter the AERSCREEN Fortran code to use the original SCREEN3 scalars, we *can* change the scalars so that the graphical displays in AERSCREEN for Windows (Line Graph and Flow Sector Graph) show those SCREEN3-based longer term impacts. To do in AERSCREEN for Windows, click on File | Preferences, and enter the SCREEN3 scalars (or whatever scalars you like) into the User Scalars fields:

The shape of the plots remains the same, but the axes are altered based on the scalars entered by the user.

Tip #2

If you use Golden Software’s Surfer graphic plotting program, BEEST has a way to automatically export your inputs and/or outputs to Surfer. From either Show Current Data Graphically or Display Output Graphically in BEEST, click the far left button on the second row from the top (left hand side of either Show Current Data Graphically or Display Output Graphically), which is called Save Surfer Data.

Once you have input what you want to name the DAT, BLN and TXT files, click OK and BEEST not only saves these file names for you, but ALSO opens Surfer using the DAT/BLN/TXT files you created.

All you have to do is customize it by adding a title block, resize the axes (if needed), etc and you now have a report-ready graphical plot!

November 2021

We all enjoy using the BEEST Suite to assist us in setting up and running AERMOD, and then reviewing the results. However, sometimes we might be working with a project that had some previous modeling that was not set up or done with BEEST. Rather than painstakingly retyping all those input data into BEEST, there’s a better solution – importing! Yes, you can import an AERMOD input file into BEEST even if it was created with one of our competitors’ products or with EPA’s “out of the box” version. To do this, open BEEST and go to File | Import. There, you can select “Generic AERMOD dta or inp”. Since the AERMOD input file format is actually the same across all platforms, BEEST reads the input data file and automatically populates the Control Options, Source Options, Receptor Options, and Output Options parts of BEEST. But what about the buildings and tanks for downwash, you may ask? Very simple – within BEEST, again go to File | Import and select “Generic BPIP/BPIP-Prime Input file (Buildings) pip or inp”. BEEST reads in the building information – coordinates, heights, etc, and automatically populates the Buildings and/or Tanks tabs under the Boundary Options tab.

October 2021

So, you’ve loaded in all of your sources, fence lines, tanks, and buildings into BEEST. But before you can go any further, your CAD person comes in and tells you that the plot plan that you’d used to help set up your buildings, fence lines, tanks, and sources is off. Problematic? Not in BEEST! BEEST has a built-in Rotate feature you can access that allows you to quickly and efficiently make changes to one or all of your on-screen objects (buildings, fence lines, tanks, and sources).

First, go into File → Preferences → General Setup and make sure “Allow Rotation” is selected. Then, go to Show Current Data Graphically. Click the Options button on the left hand side array of buttons and then click the Rotate tab.

You now have the ability to select None, All, or a Selected subset of each of your objects. On the right hand side of this form, you can put in an origin point (in UTM coordinates) about which to rotate the selected objects, or X and/or Y values to shift/translate your objects. The nice thing is you can mix and match – some objects might only need to be shifted, some only need to be rotated, some shifted a different distance than others, etc. Very useful!

August 2021

This month, we turn our attention to AERMOD Wizard. One of the nifty little tools in AERMOD Wizard is the ability to generate forward and backward trajectories. Using AERMOD Wizard, you can read nearby meteorological data to calculate a forward trajectory from a source or a backward trajectory ending at a monitoring site. First, for a forward trajectory coming from a source, you’ll need to enter one using the right-click → Place Source command. Then, if you click on the Display Surface stations check box (on the left side of the screen in AERMOD Wizard), you can quickly identify which surface station is closest to your source and then download the year or years of meteorological data you want. You can download the routine Integrated Surface Hourly Database (ISHD) data. After you’ve downloaded the data, simply right-click the icon over the surface station and select Trajectory → Trajectory Set Up and put in the starting and ending time you want to see for your trajectory. In the General tab, select Forward Trajectory, ISHD, and Source (for the starting location). Then go to the ISHD tab to put in the time period you want for your forward trajectory. Once you’ve done that, just click Show and AERMOD Wizard plots the forward trajectory on the screen. You can also export the forward trajectory to Google Earth by clicking the Google Earth menu at the top of the AERMOD Wizard screen.

The process for creating backward trajectories with AERMOD Wizard is similar. You can use the on-screen display to show what ambient monitor you want the backward trajectory to end at and then identify which meteorological station is closest to it. As before, you can then download the ISHD data. Then, you still right click the icon over the surface meteorological station and click Trajectory → Trajectory Set Up. This time, on the General tab, select Backward Trajectory, and put in the coordinates (either Latitude/Longitude or UTM) of the ambient monitoring station. (Hint: if you place your mouse over the monitor’s icon, the lat/lon and UTM coordinates are at the top of the yellow pop-up box.) In the ISHD tab, enter your beginning and ending times as before and then click Show. AERMOD Wizard plots the backward trajectory (ending at the ambient monitor) on-screen, and you can also export it to Google Earth. As we said, quite nifty.

May 2021

Ever since the promulgation of the 1-hour SO2 and 1-hour NO2 NAAQS standards in 2010, and the revised 24-hour PM2.5 NAAQS in 2006, we have found ourselves with much less headspace to work with in conducting NAAQS modeling demonstrations. As we all know, a permit may be granted only if the applicant can demonstrate that the proposed project does not “cause or contribute” to an exceedance of a National Ambient Air Quality Standard. Contribute means that the applicant cannot make a significant impact at a receptor location and time period where the NAAQS is predicted to be exceeded. Because of the probabilistic form of the 1‑hour SO2, 1‑hour NO2, and 24‑hour PM2.5 NAAQS, as well as the low levels of those standards, we need a tool to help us determine whether we contribute to the exceedance. That tool is the MAXDCONT output option in AERMOD. It tracks project contributions to ALL-based exceedances. While it is very useful, it can be a rather large file to review. So, to help in graphically viewing the results in your MAXDCONT file, BEEST Suite includes MaxDCont Viewer.

MaxDCont Viewer shows graphically the depiction of the contributions to ALL from your list of source groups (one of which should include your project-only sources). You can display these contributions for all ranks specified (e.g. beginning with 4^th high for 1‑hour SO2) so that you can quickly determine if your project exceeds the SIL for any of the ranks where an exceedance might be predicted. You can also apply a background map in MaxDCont Viewer; toggle sources, buildings and receptors on and off; and export your MaxDCont Viewer display to Google Earth. As with BEEST’s “Display Output Graphically” mode, you can also filter the MaxDCont Viewer display so that only values above a specified threshold are displayed.

We have a webinar introducing MaxDCont Viewer at Webinars → BEEST Suite. Click the “BEEST 11.05” link and go to the 2:30 mark. There is also a tutorial included in MaxDCont Viewer. Click Help → Tutorial on the menu bar.

March 2021

Partitioning is the most powerful tool we have for running AERMOD faster. Although we tell you about BeestXpress every month (see below), you can also invoke partitioning for AERMOD and AERMAP runs on your computer. That is, you can create as many partitions for AERMOD and AERMAP runs on your computer as you have CPUs / processors / cores. So, if you have a dual quad-core computer, you can have up to eight partitions. If you have 64 cores or processors, you can have up to 64 partitions. Therefore, you can speed up your AERMOD and AERMAP runs dramatically. All you have to do is go to Receptor Options in BEEST; near the bottom of the form, you can select Local Partition Receptors Option, enter the number of cores or processors, and you’re good to go!

It’s also important to note that while our competitors may use a similar approach, the end user is limited in what you can use. Competitor A only allows up to 8 CPUs to be used by default and competitor B has a “parallel” version of their software that allows 2 CPUs to be used by default, although they also have versions available that allow up to 32 CPUs to be used. The difference is that competitor B charges more for the 32 CPU version. With BEEST, there’s just one price, and it’s the same whether you have 2 CPUs or 64 CPUs.

January 2021

When diagnosing problem concentrations, don’t forget to look at what’s going on in the meteorology. Maybe the wind is persistently blowing toward your problem receptor for multiple hours … maybe it’s persistent hours of low wind speeds … maybe there are some missing data. The easiest way to review a day’s worth of meteorological data is by going to “Met Options” → “Select Days” in BEEST. Uncheck “Process Entire Year”, pick the day that you are interested in and click the “View Day” button.

December 2020

Since it is the holiday season, and we’re in a giving mood, we have not one but two modeling tips to share with you.

Tip #1
When you view outputs graphically in BEEST, you can export the results to Excel by clicking the Excel button on the toolbar on the left side of the screen. When you click the Excel button, you will see two options: “Load Values from GRF File” and “Load Values As Displayed”. If you select the second option, the receptors exported to Excel depend on the display options in BEEST. For example, if you only display concentrations above a threshold, only the concentrations above the threshold value will be exported to Excel. If you add a background value to every receptor, the concentrations exported to Excel will include the background value.

Tip #2
BEEST has a pair of useful tools for automatically removing on-screen objects, such as sources, buildings, tanks and receptors. In Show Current Data Graphically, go to the toolbar on the left side of the screen and click one of the rightmost two buttons along the bottom row. These two buttons allow you to select and delete multiple objects by drawing either a rectangle or a polygon. When you draw either a rectangle or a polygon, a pop-up appears and gives you the option to delete any or all categories of objects (sources, buildings, etc.) and delete receptors either inside or outside the rectangle or polygon.

March 2020

Recently, the US Geologic Survey changed the types of elevation data that can be downloaded from the National Map Viewer website (https://viewer.nationalmap.gov/basic/). As you may recall, USGS took down all access to NED data in GeoTIFF format, necessitating users to download NED data in ArcGrid format and then converting it to GeoTIFF using the Terrain Files Converter utility. Then around the first of March, the National Map download site changed so that *only* GeoTIFF formatted NED data was available. Unfortunately, due to a data compression issue, these new GeoTIFF files will not work in AERMAP. However, there is a work-around. If you browse to the USGS Staged Products Directory, you can get the 1 arc-second and 1/3 arc-second elevation files in ArcGrid format. Go to https://prd-tnm.s3.amazonaws.com/index.html?prefix=StagedProducts/ and then navigate as follows:

For 1 arc-second ArcGrid data, go to Elevation → 1 → ArcGrid and then select the zipped file you need. These files are in 1×1 degree tiles.

Similarly, for 1/3 arc-second ArcGrid data, go to Elevation → 13 → ArcGrid and select the zipped file you need. These files are also in 1×1 degree tiles.

Regarding the naming convention of the 1×1 degree files, the numbers listed in the file name alongside “n” and “w” (e.g. USGS_NED_1_n35w082_ArcGrid.zip) refer to the north-most latitude (35 degrees) and west-most longitude (82 degrees) of the tile. After you download the files you need, just follow the instructions for converting ArcGrid to GeoTIFF using Terrain Files Converter.

January 2020

This month, we’ll take a little side trip into building downwash. In fact, we’ve got three little side trips into downwash. First, downwash only applies to point sources, but did you know that you can also limit which point sources you run through BPIP-Prime? When you click the “Run BPIP-Prime” icon, the option to process “All Point Sources” is selected by default. If you deselect this option, you can click the “Select Sources” button and select only the sources you want to run through BPIP-Prime.

Second, something else that’s downwash related that is now in BEEST is the ability to run the new (non-regulatory) version 19191_DRFT of BPIP-Prime. To do this, click File → Preferences on the menu bar and go to the “Model Selection” tab. For the BPIP-Prime executable, click the Browse button and then select the file BpipPrm19191.exe.

Finally, to go even further into downwash, you can test the new EPA ORD and/or AWMA downwash options. To do this, go to Control Options and then go to the “AER Default” tab. Select alpha options and then go to the “AER Non-Default” tab. You’ll now be able to select the EPA ORD and/or AWMA downwash options.

December 2019

We typically model a complete year (or 5 complete years) of meteorological data when conducting regulatory-type modeling for a permit application. However, did you know that there’s a way to model time frames of less than a year in duration? If you open BEEST, and go to Met Options, the “Met Start/End” option on the “Met Options” tab can be used. That is, you can tell AERMOD just run a specific sequence of dates and hours, say, from March 16 hour 15 to April 9 hour 22. Another technique could be to just run a single year of interest out of a 5-year concatenated met data file. For example, if you had a concatenated 5-year data set of 2014-2018, but you only wanted to run 2017, you could tell AERMOD to run from January 1, 2017 hour 1 to December 31, 2017 hour 24.

July 2019

We’re taking a one-month break from our AERMOD Wizard-based modeling tips to talk about our new Terrain Files Converter utility. As you know, the AERMAP processor can only read National Elevation Dataset (NED) data that’s in the GeoTIFF format. However, the USGS has recently removed NED data in GeoTIFF format from several (if not all) of its data download sites. Back in December 2018, EPA released guidance on how to convert the NED data in ArcGrid format to GeoTIFF format. Our new Terrain Files Converter program takes this approach and makes it quick and easy to covert data from ArcGrid to GeoTIFF.

Terrain Files Converter uses the Geospatial Data Abstraction Library (GDAL) to convert downloaded ArcGrid-format data to GeoTIFF-format. So, the first thing you’ll need to do is download the GDAL files to your computer. The download site is https://www.gisinternals.com/query.html?content=filelist&file=release-1900-x64-gdal-2-4-2-mapserver-7-4-0.zip. After you download this zipped file, extract/unzip it to a folder on your computer (e.g. C:\gdal).

Next, you need to access the NED data in ArcGrid format. To do that, visit https://viewer.nationalmap.gov/basic/. On the map shown on the right-hand side of the screen, zoom in to your area of interest – the area for which you want to download elevation data. You can enter an address/location in the Search Location box, too. You can use the Draw Rectangle button found on the left-hand side of the map to draw your area of interest. Once you’ve drawn your area of interest, click Elevation Products (3DEP) and the web site will list all available terrain data for your area of interest. You will probably want to select 1 arc-second DEM or 1/3 arc-second DEM plus the ArcGrid File Format. Click Find Products, then click Download for the data file you wish to download. (Please note that, unlike the former Seamless Server and Landfire NED data, all NED data that is downloaded from the National Map Viewer is in 1‑degree by 1‑degree tiles. Therefore, the file you download will likely be much, much larger than your area of interest.) Once your data has been downloaded, you’ll want to unzip the data.

Now, you can open Terrain Files Converter to start the conversion process. After you open Terrain Files Converter, go to the Files tab. You’ll see two fields to be filled out: the folder containing the downloaded ArcGrid-formatted files and the GeoTIFF-formatted output file. For the first field, browse to the folder where you downloaded the ArcGrid files – you will want to select the subfolder that begins with “grd”. For the second field, just name it what you want the output file to be – Terrain Files Converter automatically appends the “tif” extension. Then go to the Run tab and click the Run button. Once this is done and Terrain Files Converter creates your NED file in GeoTIFF format, you can now run AERMAP just like you did before!

June 2019

AERMOD Wizard is the latest utility from Providence/Oris, and it offers the user many new tools related to air quality modeling. Over the next few months, we’ll be including AERMOD Wizard-based Modeling Tips of the Month. Last month, we looked at ambient monitoring data. This month, we’ll take a look at meteorological data.

Begin by opening AERMOD Wizard. After it opens, you’ll see a map of the US, with several control buttons to the left of the map. Below the word Display on the left, you’ll see checkboxes for several displayable elements, including surface meteorological stations (Surface), upper air met stations (Upper Air), Monitors, Sources, and Class I areas. Check the boxes for Surface and Upper Air, along with the Names checkboxes to the right of each. Along the upper part of the control buttons to the left, you’ll find a Zoom In, Zoom Out, and Zoom to Selected Area buttons. Using any of these, you can zero in to your area of interest and find the surface met station you want to download data for. When you have found it, place your cursor over the S to have a yellow pop-up appear. Left-click and you will see a hatched circle appear over the station, meaning you’ve marked it for download.

Click the Met menu at the top of AERMOD Wizard, left-click Download Surface Data and select the type of data to the right (Hourly ISHD, 5-minute ASOS (6401), or 1-minute ASOS (6405)). Select the years of data you want and AERMOD Wizard will automatically download that data to your computer. With the data downloaded, you will now see that the S has a box drawn around it. Place your cursor over the S again, and the yellow pop-up reappears and tells you the name of the station plus which years were downloaded.

You can then follow the same approach for downloading upper air data. You zoom to the upper air site, which is denoted by a U. The difference is that for upper air, telling AERMOD Wizard to download the upper air data generates a pop-up screen with 4 tabs: the first tab is the actual Radiosonde Database website, while tabs 2-4 provide help for how to create and submit your upper air data request to the Radiosonde Database website. Also notice at the bottom of the first tab, that AERMOD Wizard guides you by instructing you to type the exact type of information needed into the data request fields. After you click Continue Data Access on the second page of the Radiosonde Database request, you will see that the upper air data has been downloaded to your screen. Click Done and AERMOD Wizard saves this data to a file with a .FSL extension.

Once you have the surface and upper air data downloaded, click the Met menu at the top of AERMOD Wizard, click Run AerMet and a dialog box pops up allowing you to select the surface and upper air data (plus years) to process. Click Run AerMet and our AerMet GUI opens, ready to go.

May 2019

AERMOD Wizard is the latest utility from Providence/Oris, and it offers you many new tools related to air quality modeling. Over the next few months, we’ll be including AERMOD Wizard-based Modeling Tips of the Month. For this month, we’ll start with ambient background concentrations. When conducting NAAQS modeling, we always have to account for background concentrations of pollutants, whether characterized by explicitly modeling other sources, or by including ambient monitoring data. AERMOD Wizard makes the development of your monitored ambient background data a snap.

Begin by opening AERMOD Wizard. After it opens, you’ll see a map of the USA, with several control buttons to the left of the map. Above the word Display on the left, you’ll see a dropdown arrow that allows you to select one of the six (6) criteria pollutants: carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), PM2.5, PM10, and sulfur dioxide (SO2). Select NO2 for your pollutant. Under the word Display on the left, check the boxes next to Monitors and Names. When you do that, the letter N shows up at the location of every NO2 monitor all across the US, along with their names/IDs. Along the upper part of the control buttons to the left, you’ll find the Zoom In, Zoom Out, and Zoom to Selected Area buttons. Using any of these, you can zero in to your area of interest and find the NO2 station you want to get ambient data from. When you have found it, place your cursor over the N and you will have a yellow pop-up appear. Left-click, and you will see a hatched circle appear over the station, meaning you’ve marked it for download. Go to the Monitors menu bar at the top of the page, left-click and select Download Monitoring Data and the year(s) of data you want and AERMOD Wizard will automatically download that data to your computer and unzip it.

With the data downloaded, you will now see that the N has a box drawn around it. Place your cursor over the N again, and the yellow pop-up reappears and tells you the name of the station, plus which year(s) was downloaded. Right-click and now you have 3 options to choose from: Summarize Monitoring Data, Process Monitoring Data and Show Pollutant Rose. Select Process Monitoring Data and a popup appears, showing which years you want to select for creating your ambient background data. Click Continue and AERMOD Wizard displays tabular statistics of each of the years of data you wish to process. Click Calculate BG Values and you get a display showing the years to be processed plus a prompt for which temporal mode you want to use (e.g. ANNUAL, SEASON, SEASHR, etc.), plus either the rank (1^st high, 4^th high, etc.) or automatically creating a 98^th percentile. Click Calculate and AERMOD Wizard does the work for you by generating your ambient background data and then pops up a nice array of background values that you can either copy/paste into BEEST or write to a generic AERMOD SO type file.

March 2019

BEEST has several useful features related to building-downwash. The first is BEEST’s ability to display each building’s Good Engineering Practice (GEP) 5*L zone and its direction-specific Structure Influence Zone (SIZ). The SIZ is defined as a rectangle about the building that extends 5*L downwind of the building, 2*L upwind of the building, and ½*L to either side (crosswind of the building). BEEST can create and plot these before you run BPIP-PRIME. To do this, go to Show Current Data Graphically in BEEST.

On the toolbar of buttons to the left, go to the second row down, second button from the right (“Show GEP5L”), and click the button. Then, on your Show Current Data Graphically display, place your cursor over the anchor point of your building of interest, and right-click. Select “Show GEP5L and SIZ” on the pop-up menu. BEEST will then generate that building’s GEP5L area around it (hatched) as well as the SIZ for a wind direction of 10 degrees (solid lines). If you press the left or right arrow keys on the keyboard, BEEST will advance the wind direction 10 degrees counterclockwise or clockwise, respectively. For multiple-tiered buildings, BEEST draws the GEP5L and SIZ for each of the tiers.

A second handy tool within BEEST is the ability to create sloped roof structures, such as gabled roofs or shed-type roofs. To do this, go to Show Current Data Graphically and click the “Add Building” button on the left-hand side (second row from the bottom, second button from the left) and draw in a 4-sided building (it can only be 4-sided, but doesn’t have to be an exact rectangle or square). After the building has been drawn in, the “Add Building” pop-up appears, and you enter a building name and height. Instead of clicking Done, click “Create Sloped Roof”. A pop-up labeled “Create Building Roof” appears. You then tell BEEST to create either a gabled roof or shed-style roof. The height that you initially entered in “Add Building” is the base or lower part of the sloped roof, so you must then tell BEEST how high the apex of the roof is to be. BEEST creates a series of tiers to simulate the gable or shed roof and you may use up to 14 tiers (going from base to apex). You tell BEEST which side(s) of the building are lowest (base of roof) – 2 sides for gable roof, 1 side for shed roof. Then click “Create Roof” and BEEST will generate your gable roof or shed roof for you. You can even click the “3-D View” button to see your new sloped-roof building in 3-D!

December 2018

Analyzing exceedances of threshold concentrations (the MAXIFILE keyword in AERMOD) can be a useful, if not tedious task. If you want to find out when individual exceedances occur, you can open the MAXIFILE that the AERMOD model created in a text editor and copy the data in the file to Excel. However, you should omit the lines at the top of the MAXIFILE that start with an asterisk (*) when copying the data. After that, click the “Text to Columns” button on the Data ribbon in Excel. A wizard for converting the text to columns will appear.

One the first screen, select the Delimited option and click Next. On the second screen, select both Tab and Space as Delimiters and click Next. On the third screen, click Finish. After this is done, you can filter the last column (which displays the concentration) to only display values above whatever threshold you set for the MAXIFILE (or a multiple of that threshold).

August 2018

If you are processing Automated Surface Observation System (ASOS) through the AERMINUTE system, you know that one of the required output files is the HOURFILE, which includes the arithmetic-averaged wind speeds and unit vector-averaged wind directions for each hour. The HOURFILE is then incorporated during Stage 2 of AERMET. If, by chance, you happen to forget the name you assigned to HOURFILE, you can easily find it within your Windows File Explorer/directory by looking for the file that is 242 KB is size (or 243 KB for a leap year).

July 2018

Sometimes we find that we need to model the impacts of two facilities that are separated by more than a kilometer or so. For separations on the order of 10 km or more, you can still have BEEST generate a tiered grid (tight receptors close in, coarser spacing going further out), but it may generate more tightly-spaced receptors than you really need – which increases run times! Here’s a neat workaround you can use:

Copy the coordinates for both property lines to a temporary Excel file.
Remove all receptors and remove property line 2, leaving property line 1 in BEEST.
Generate a receptor grid around property line 1.
Convert the receptors to discrete receptors.
Copy the receptors to a temporary Excel file.
Remove all receptors and remove property line 1.
Add property line 2 to BEEST.
Generate a receptor grid around property line 2.
Convert the receptors to discrete receptors.
Copy the receptors to the same temporary Excel file you used in step 5.
Remove all receptors and add property line 1 to BEEST.
Now, both property lines are in BEEST but all receptors are in Excel.
Use the “Remove Duplicates” button in Excel to remove overlapping receptor coordinates.
Copy all receptors from Excel into BEEST.
If any receptors are inside the property lines, remove them manually.

May 2018

ARM2 and Source Groups – The Ambient Ratio Method 2 (ARM2) is the new Tier 2 approach for modeling NO₂. The science behind it is that the higher the concentration of ambient NOx, the lower the ratio of NO₂ to NOx. ARM2 uses this complex equation to determine the ambient ratio due to the NOX concentration from the ALL source group:

y = -1.1723E-17x⁶ + 4.2795E-14x⁵ – 5.8345E-11x⁴ + 3.4555E-08x³ – 5.6062E-06x²– 2.7383E-03x + 1.2441E+00

where x is the NOx concentration (from ALL) in µg/m³, and y is the calculated ambient ratio.

If you’re using source groups in which they are all concurrent subsets of ALL, everything is fine. However, if you are setting up source groups to determine some optimum worst-case combination of sources – for example, where only 2 out of 3 sources can emit at any given time, then ARM2 will actually yield underpredictions of NO₂ for your non-ALL groups. Again, this is because the originally calculated ratio of NO₂/NOX was based on the total concentration from ALL, which is greater than any of the subset groups. For example, let’s assume we have three engines at a site, but only two can operate at any one time. So, we might start out with these groups:

ALL: Eng1, Eng2, and Eng3 (ALL is required as a source group for ARM2 to work)

SCEN_A group: Eng1 and Eng2

SCEN_B group: Eng2 and Eng3

SCEN_C group: Eng1 and Eng3

If we input total NOx rates for all engines, we might get these Tier 1 NO₂ impacts:

ALL: 415 µg/m³

SCEN_A: 250 “

SCEN_B: 265 “

SCEN_C: 240 “

But if we now remodel using ARM2, AERMOD will calculate the ambient ratio from ALL’s impact and ARM2 equation yields an ambient ratio of 0.35. However, by EPA’s guidance, the minimum ratio is 0.5, so 0.5 will actually be applied to all 4 source groups:

ALL: 415 µg/m³ NOx * 0.5 = 207.5 NO₂

SCEN_A: 250 “ NOx * 0.5 = 125.0 NO₂

SCEN_B: 265 “ NOx * 0.5 = 132.5 NO₂

SCEN_C: 240 “ NOx * 0.5 = 120.0 NO₂

However, this is incorrect because AERMOD based the ratio on ALL and applied it to the non-ALL groups. If you went in and modeled each scenario in a separate AERMOD run, where each of them was considered ALL, you’d get these impacts:

SCEN_A (ALL = Eng1 and Eng2): 250 µg/m³NOx * 0.56 = 140.0 NO₂

Ambient ratio = 0.56

SCEN_B (ALL = Eng2 and Eng3): 265 µg/m³NOx * 0.53 = 140.45 NO₂

Ambient ratio = 0.53

SCEN_C (ALL = Eng1 and Eng3): 240 µg/m³NOx * 0.58 = 139.2 NO₂

Ambient ratio = 0.58

So, as you can see, when doing any kind of a scoping study or when trying to determine what your worst case scenario is, keep in mind that AERMOD bases the ambient ratio on ALL, and you can potentially underestimate NO₂ impacts.

April 2018

This month’s tips have to do with pollutant names or IDs. First, did you know that BEEST allows you to have up to 500 different pollutant names in each BEEST session? Each pollutant name is limited to eight (8) characters, but they can include letters, numbers, underscores, and dashes (and even dots in a couple of special cases). Here’s tip #1: if you’re modeling speciated VOCs, use each compound’s Chemical Abstract Service (CAS) number as its ID. For example, if you’re modeling benzene, its CAS number is “71-43-2”, and you could use an ID of “71-43-2” or “71432”. Both meet the pollutant naming conventions in AERMOD.

Not only that, but within AERMOD, certain pollutant IDs are used to process model outputs in a specific way. For example, if you are modeling SO2, you can have AERMOD provide you output based on the form of the 1-hour SO2 NAAQS. The form of the 1-hour SO2 NAAQS (at any given receptor) is the 99^th percentile of the annual distribution of the daily maximum 1-hour SO2 concentration. To do this, simply call your pollutant “SO2”, select 1-hour averaging period, and an output rank of 4^th-highest. Doing those three things tells AERMOD to produce the NAAQS design value for SO2. A similar pollutant-naming approach can be used for 1-hour NO2 NAAQS, and 24-hour PM2.5 NAAQS:

1-hour NO2 NAAQS: Pollutant ID must be “NO2” (plus 1-hour averaging period and 8^th high rank)
24-hour PM2.5 NAAQS: Pollutant ID can be “PM25”, “PM2.5”, “PM-25”, or “PM-2.5” (plus 24-hour averaging period and 8^th high rank)

February 2018

The right-click options found in BEEST’s Show Current Data Graphically and Display Output Graphically modes are extremely useful tools. In Show Current Data Graphically, right-clicking the mouse provides the user with these options:

Measure Line Length and Angle
Center Screen in Click
Set Anchor Location
Background Map
- Drag Background Map
- Edit and Save Background Map Locations
Find (on-screen)
- None
- Building
- Source
- Source Group
- Tank

Similarly, right-clicking in Display Output Graphically (i.e. when displaying a GRF file) provides these options:

Measure Line Length and Angle
Edit Contours
Background Map
- Drag Background Map
- Edit and Save Background Map Locations
Find (on-screen)
- None
- Building
- Source
- Tank
Radius of Impact Receptors
- Save All Receptors within R-of-I to csv file…
- Save Only Significant Receptors within R-of-I to csv file…

January 2018

Many times, we model an emission source or facility assuming that operations occur 24/7. However, some sources/facility may only operate part of a day (or night). Rather than penalize yourself for emissions occurring when they actually aren’t, AERMOD allows the use of Emission Factors or Scalars to account for hours of operation. In BEEST, go to Source Options | Factors. There, you’ll see several different options for Emission Rate Flags, including HROFDY. HROFDY allows you apply Emission Factors to a source or group of sources on an hour by hour basis that is applied to every day modeled. The HROFDY array includes a field for each of the 24 hours of the day. Into each hourly field, you can place a scalar that is multiplied by the emission rate input in the Sources tab. That is, a user puts in a “1” in the field for a particular hour and the emission rate is multiplied by 1. Likewise, if a source is not operating for a particular hour, a “0” is input to the hour’s field, yielding a modeled emission rate of 0. Within BEEST, you can also create sets of emission sources that have different operating schedules. Simply click Select Sources, highlight and double-click or click Select the sources for a specific operating schedule, give that set a name, and click OK. When you come back to the main Factors tab, highlight that set name, and populate the 1-24 fields with the correct 1 or 0 for each hour.

AERMOD uses a nomenclature of Hour 1, Hour 2, etc. To correspond to actual times, AERMOD interprets Hour 1 as the hour from midnight to 1 am, Hour 2 is 1 am to 2 pm, etc. Also, Daylight Savings Time is not accounted for in the use of Emission Scalars.

December 2017

One of the nifty little tools that’s part of BEEST’s Show Current Data Graphically mode is the 3-D Viewer. 3-D Viewer allows you to get a 3-D view of your sources and buildings. To open 3-D Viewer, go to Show Current Data Graphically and click the button on the first row, fourth column of the toolbar on the left side of the BEEST window.

The controls on the left-hand side of 3-D Viewer allow you to toggle sources and buildings on and off, toggle between solid and wire-frame buildings and rotate your buildings. 3-D Viewer also accounts for the base elevation of a source or building, making it a great QA tool – you can instantly see if you included terrain/ran AERMAP.

September 2017

Many times, we must show what type of land use, structures, or geographic features are within a certain radius of our modeled facility of interest. For example, determining urban/rural might depend on land use within 3,000 meters of modeled facility. Is there an easy way to do that? With BEEST, the answer is YES! In Show Current Data Graphically, simply click Add Tank (centered on your facility or point of interest), and input the *diameter* of the tank, as well as a non-zero height (it can be 1 foot). Next, in BEEST’s Show Current Data Graphically mode, you’ll want to go to Options | Google Earth Options, and select 2-D Export. You can then click Export to Google Earth. After exporting it to Google Earth, you can change the properties of the tank/circle, and then save it as an image.

August 2017

The most commonly used format for raw surface meteorological data is the Integrated Surface Hourly Database (ISHD). Like the twice-daily upper air sounding data, ISHD data is time-stamped in Greenwich Mean Time (GMT), rather than local time. Therefore, when processing ISHD data through AERMET, users need to tell AERMET what the time offset is between local time and GMT. In our AERMET GUI, this is found on the SFC tab | Time Adjust. For local sites in the western hemisphere, the offset is a positive value. For Eastern Standard Time, the Time Adjust value is +5, for Central Standard Time, it is +6, etc. This also means that the user must include the first day of the following year when processing data. Otherwise, because of the Time Adjust, the last set of time adjust hours for the year (e.g. hours 20-24 of December 31 for EST) are interpreted/written as “missing” by AERMET. All you have to do is open the ISHD file for your year of interest (YYYY) in a text editor, open the next year’s ISHD file (YYYY+1) in the text editor and copy all January 1 records of YYYY+1 and append them to the YYYY file. After you finish processing, our AERMET GUI offers to automatically remove the January 1 YYYY+1 processed data records from your finished SFC and PFL files.

Note: If you do not remove the January 1 YYYY+1 records from both of the AERMOD-ready SFC and PFL files prior to concatenating YYYY and YYYY+1, AERMOD will crash.

May 2017

Sometimes, when working with clients or air regulatory agencies, we may be asked “What is the number?”, meaning what’s the maximum concentration from the model run. Fortunately, one of the outputs from AERMOD is its “SUM” file. The SUM file provides a quick listing of the maximum concentration for each combination of source group, averaging period, and rank selected in the model run. BEEST includes the USF Viewer that enables you to view the SUM file (or USF file if ISC is used).

After writing the SUM file to the grid, you can sort and filter data displayed in the grid. To sort any column in the grid, click the name of the column. The data in the column will then be sorted in ascending order. To sort the data in descending order, click the name of the column again. To filter data, move the mouse over the column name and click the triangle that appears to the right of the name. A pop-up will appear and will display options for filtering the data in the column.

You can click the checkboxes next to the items in the pop-up to select items to show, then click the Apply button to save the filter settings. The pop-up will disappear, and the grid will now will hide the deselected items. To remove a filter, make the pop-up appear again and click the Clear button.

One caveat: “SUM” files are also output from the Building Profile Input Program (BPIP), so always make sure you are selecting an AERMOD SUM file and not a BPIP SUM file!

April 2017

Sometimes, when working with clients or air regulatory agencies, we may be asked “What is the number?”, meaning what’s the maximum concentration from the model run. Fortunately, one of the outputs from AERMOD is its “SUM” file. The SUM file provides a quick listing of the maximum concentration for each combination of source group, averaging period, and rank selected in the model run. BEEST includes the USF/SUM Viewer that enables you to view the SUM file (or USF file if ISC).

November 2016

The USF Viewer in BEEST is a great tool for getting a quick look at your modeling results. This handy utility gives you the maximum concentration summary for all source groups and averaging periods in a specific model run. It can read both *.USF (ISC output) and *.SUM (AERMOD output) text files. Part of the real power is that you can write the text file to a grid in the Viewer and then copy that grid of output data into an Excel file (and who doesn’t like working with Excel?).

July 2016

You can use hourly emission rate files to better represent filling/loading emissions from tanks, trucks, rail, and vessels. Filling and loading operations are generally low level fugitive emissions sources whose highest modeled impacts occur during nighttime stable atmospheric conditions. The emission calculations for these sources types contain the inclusion of ambient temperature, and for the usual worst case, a high ambient temperature is used to represent the maximum potential emission rate. However, high temperatures (and the corresponding high emission rates) don’t really occur during the nighttime stable conditions. AERMOD can significantly over-predict impacts by assuming that the high temperature emissions occur during nighttime stable conditions. This over-prediction can be removed by using an hourly emission rate file!

First, calculate an emission rate that corresponds to the temperature of each hour in the meteorological data file and enter it into the hourly emission rate file format:

SO HOUREMIS 2015 01 01 01 TANK1 0.012 283.15 0.001

Year Month Day Hour

Source ID

Emission Rate (based on temperature for this hour from met file) (g/s)

Temperature for this hour from met file (K)

Exit Velocity (m/s)

Then link the hourly emission rate file to the BEEST file using the “File” table under the “Source Options” menu.

March 2016

This month’s tip concerns the use of scaling output concentrations in BEEST. If you open a modeling output file (.GRF file) and click the Options button, one of the options is “Multiply values by Scaling factor.” If you select that option, enter a scaling factor and click OK, the concentrations BEEST displays will be adjusted by the scaling factor. If you then export the concentrations to Surfer or Google Earth, the adjusted concentration values will be exported from BEEST.

February 2016

On a somewhat different tack this month, we thought we’d share with you some of the air quality modeling resources available to you through our websites. BEEST users know that they can access several tutorials from the Help menu, but did you know that those are also available from www.beeline-software.com? Simply browse to Support | Documents and there they are! This site also has links to the same webinars that are found in the BEEST Help menu. (Go to Support | Webinars) The webinars can also be accessed from www.oris-solutions.com. For that web site, go to Demos, and you can see them broken out by category: AERSCREEN, AERMOD, BEEST Suite, and CalPuff. Speaking of www.oris-solutions.com, you can also access links to each US State’s modeling and/or permitting web pages, plus each State’s published modeling guidance. Happy modeling!

January 2016

One of the very useful features within BEEST is its capability to export objects to Google Earth. This includes not only sources, buildings, fence lines, receptors, and concentrations, but also concentration contours. Within Google Earth, you can even alter the contours’ display and it’s very easy. For example, after exporting concentration values and contours from BEEST to Google Earth, you can change the width of the contour lines in Google Earth. In the Places section of the Google Earth sidebar, expand “BEEST to Google Earth” and then expand the Contours folder. Then, right-click a contour value and click Properties on the pop-up menu that appears. The “Google Earth – Edit Folder” window will appear. Go to the “Style, Color” tab within the window. Type a new value for the width of the contour line (for example, 2.5) and click OK. The “Google Earth – Edit Folder” window will be closed and the width of the contour line will be changed.

December 2015

Many BEEST users are aware of its capability in exporting BEEST objects (sources, buildings, fence lines, etc) to Google Earth, but did you know that the converse is also possible? That is, you can bring your shape files into BEEST via Google Earth. So, if you have a shape file with a property line, building outline, or other polygon that you’d like to bring into BEEST or if you want to add these polygons more precisely than simply drawing on top of a background image, you can do that, and here’s how. First, import your shape file into Google Earth PRO (which is now free). Then select the polygons you’d like to bring into the BEEST file and save them as a .kml file on your computer (in Google Earth Pro – File | Save Place As). In BEEST, use the “Import from KML” feature to bring these polygons into an excel-friendly csv file. (in BEEST – File | Import | Google Earth KML) Now you’re ready to copy and paste your polygons into BEEST as fencelines, building corners, area poly vertices, or any “Other” reference boundaries. Not only that, but BEEST’s “Import from KML” feature will even convert the coordinates from NAD83 (in Google Earth) to NAD27, if needed.

April 2015

Speaking of that March 25 webinar, one of the items we showed was the on-screen Find function in BEEST. Do you ever have the case where you’ve got lots of sources or buildings and you’d like to find one quickly? BEEST allows you to do that quickly and easily. It can be done from either the Show Current Data Graphically mode or the Display Output Graphically mode. All you have to do is right-click in your display area, and hover your cursor over “Find”. Doing so gives you a drop down menu with the choices of “None”, “Building”, “Source”, and “Tank”. If you select Source, BEEST pops-up a menu listing each of the sources within your BEEST file. Then, highlight the one you want to find and click either Find or Find and Zoom. “Find” will gray out all other sources, leaving the one you want still on screen and in color. “Find and Zoom” does the same graying, but also zooms in. To get rid of the gray sources, simply right click on screen again, select Find, and click None. The same Find process works for Buildings and Tanks.

February 2015

Our graphic user interface (GUI)-enhanced version of EPA’s AERMINUTE program makes processing meteorological data a piece of cake. One of the nice features of it is its built-in search and select for the meteorological station. With this, all you have to do is open the AERMINUTE GUI, and go to the Station tab. Clicking the Select button gives you a sort-able table with station Call Sign, State, and Station name. Clicking the header atop any of the three columns sorts them alphabetically or reverse alphabetically. From there, you can simply scroll down to where your station is, highlight that row, and click OK. Doing so brings you back to the Station tab, and the station call sign automatically appears in the Station field, along with station’s Ice Free Winds anemometer commission date.

September 2014

This month, we wanted to let you know that you have a substantial amount of “tips” available to you through our website, www.beeline-software.com, as well as through BEEST itself. On the website, if you browse to Support | Webinars, you will find all of our recorded webinars. Over the past 5 years, we’ve covered topics ranging from an overview of BEEST to how to process meteorological data to incorporating background concentrations in AERMOD. Not only that, but we also conduct periodic webinars demonstrating new features of recent BEEST releases. In case there’s a topic there that we haven’t covered in a webinar, your next best option is to go to the BEEST Help | Tutorials menu. There, you’ll find 14 tutorials covering topics ranging from using Google Earth with BEEST to running AERMAP to moving and resizing background maps.

August 2014

As we wade deeper and deeper into modeling for the 1-hour NO2 and 1-hour SO2, we’ve noticed that it’s very difficult to model below each pollutant’s Significant Impact Level (SIL). So, for the cases where you model above the SIL and full NAAQS modeling is required, BEEST can help speed the process of setting that up. First, go to Show Output Graphically to display the results of your SIL run – then if you click Options (on the left hand side of the screen) and go to Display Values above Threshold, and input the SIL, BEEST displays just those receptors/concentrations greater than the SIL. Next, you can identify your radius of significant impact by clicking the Radius of Impact button on the left-hand side, and input the appropriate SIL. BEEST automatically draws a circle about your sources/facility with the radius of Significant Impact. Last, but not least, you can have BEEST automatically create a CSV file with just the significant receptors. To do this, first have BEEST generate your Radius of Impact circle. Then, right-click on the graphical output display – one of your choices will be Radius of Impact Receptors. Two sub-options there are Save all receptors with R-of-I to CSV File or Save Only Significant Receptors within R-of-I to CSV File. Doing this can pare down your full NAAQS modeling analysis substantially!