Support Center for Regulatory Atmospheric Modeling (SCRAM)
SCRAM Frequently Asked Questions
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Administrative and Other Structures
Models and Modeling
Unique Questions by Model
Support Center for Regulatory Atmospheric Modeling (SCRAM)
Model Clearinghouse (MCH)
Licensing and cost
Use of the Command Prompt
UnZIP 'ing Files
Land Use and Terrain Data
Model Version for later and other Operating Systems (OSes)
Tips for Students and others
Problems with running models
OCD – Offshore and Coastal Dispersion Model
Administrative Structure [Back to Top]
Support Center for Regulatory Atmospheric Modeling (SCRAM) [Back to Top]
Model Clearinghouse (MCH) [Back to Top]
- Regional Office makes a determination that the issue is a precedent-setting decision or may have national implications.
- Regional Office submits a formal memorandum (on RO letterhead) detailing issue and proposed solution for concurrence to MC Director (via email), along with supporting technical and related documentation.
- MC facilitates review across the Regional Office and EPA Headquarters to determine appropriateness of proposed solution.
- After review, MC generates a formal memorandum of findings (on EPA letterhead) and submits to Regional Office.
- MC Director sends formal MC memo via email to all ROs and archives in MCHISRS for public access and reference.
Models and Modeling [Back to Top]
Q1: What is the copyright status of our models, programs and data?
A: All of our models **on** SCRAM are a ”work of the United States government..”. A non-legal explanation can be found here: http://en.wikipedia.org/wiki/Copyright_status_of_work_by_the_U.S._government. Therefore, you can copy the programs, manuals, data, models, etc. without penalty. This is not to be confused with links to other models that are not in the public domain for which you have to “Exit” SCRAM to obtain access to those models. We have links to other models and data that are not EPA models, programs, and data but are owned by others. You will have to make contact with the proper person to determine the copyright status of their material. For instance, CALPUFF was developed by Sigma Research Corporation, a private company, and the model’s ownership may have been transferred via a business transaction. The United States government does not own or have copyright to this model and its documentation. However, through agreements with the owners of CALPUFF, we have secured public access to certain versions with the right for the public to use this model. Further clarifications are on SCRAM and are subject to copyright laws.
Q2: What does it cost to purchase your models, programs and/or data?
A: Everything on our SCRAM web site is free for the download. We have links to other models and data that are not EPA models and data but are owned by others. You will have to make contact with the proper person to determine the cost of their materials.
Q3: How do the commercial versions of EPA models differ from the EPA models on SCRAM?
A: You will have to contact the vendor to obtain an answer from the respective vendor. Any change to our executable programs or data by a vendor null and voids that model or data as being an EPA model or data. Any use of that model is treated as an “Alternative Model” per Appendix W. Our understanding of these commercial packages is that the vendor maintains the integrity of our executables and “wraps” a Graphic User Interface (GUI) around the model. The GUI provides a convenient method for creating data input files, accessing associated files such as meteorological data, and providing a way of saving and viewing output. EPA has generally created the executables but has left GUI development up to the private sector. We do have a few models with GUIs but our practice has been to husband our resources and create GUIs only when necessary or where an acquired model already came with a GUI.
Q4: Does EPA test, approve, or certify third party versions of our models (e.g. Lakes Environmental, Breeze, Beest, etc.)?
A: EPA does not have the resources to test, approve, nor certify models claiming to perform as one of our models. It is up to the user to determine whether or not these vendor created programs perform as advertised.
Q1: Does the EPA offer training?
A: EPA sponsors the APTI Learning Management System where courses are offered on various aspects of air pollution modeling, guidance, monitoring, and enforcement at various locations nationwide. Further information is available from their web site.
Q2: Who else offers training?
A: There are a number of schools, universities, and commercial companies that offer various courses on air pollution and air quality dispersion modeling. We can not and do not endorse any non-EPA training. However, a search on the internet can reveal a number of such teaching entities
Q3: Is the Air Quality Modeling Group able to offer ad hoc training?
A: The Air Quality Modeling Group does not have the time nor the resources to do training per se.
- ) we are involved in updating material for the Air Pollution Training Institute,
- ) we do make time to answer questions, and
- ) we have to stop if the questions appear to be more like training than resolving an air quality modeling issue or confusion about a set of instructions or procedures.
Q4: Where can I find the meaning of various acronyms used by EPA?
A: EPA had created a “Slang Dictionary”. It was replaced by this list of AQSAcronyms.pdfAcronyms and Definitions PDF: https://www.epa.gov/ttn/airs/airsaqs/manuals/AQSAcronyms.pdf.
Various groups have added acronyms definitions to their various documents.
Here are a couple of examples:
- https://www.epa.gov/superfund/sites/rods/fulltext/r0298053.pdf - Chapter VI
These lists are nowhere near complete. If you come across an acronym without a nearby or earlier definition, please email the acronym along with a link and/or name of the document where you found the acronym via the SCRAM Contact Us page.
Q1: What formats are your SCRAM documents stored in?
A: In the distant past, our documents were typed and placed in folders. Over time, many of these older documents have disappeared. Efforts have been made to find and scan these older documents and to place them into Adobe PDF format. The documents for the most part, have not been run through an Optical Character Recognition (OCR) process. We find that an OCR process is very good but not perfect. Since we have not had the time and priority to review documents that have gone through an OCR process, we have left these earlier documents in a graphics only form under the PDF format standard. In other words, when an area of a PDF is highlighted and cut, the pasted object is a picture of the text and not the text itself.
We have also generated files using DOS based versions of WordPerfect, Lotus 1-2-3, Freelance, and other programs that were popular during the Windows DOS, Windows for Workgroups, and Windows 98 eras. Most, but not all of the documents generated under these older programs have been scanned to an Adobe PDF format or were converted to new formats such as Word and Excel. The documents that were created with programs such as Word and Excel have been processed through Adobe Acrobat to generate PDF formatted files. Word documents under this process have retained their text. Therefore, when a graphical image in a PDF file is selected, the underlying text represented by that graphical image can be copied and pasted to other documents. The result is actual text that a Spell Checker can recognize. We have used other software packages such as Golden Software’s Surfer and Grapher to generate figures for our documents. The extensions for these formats are srf and grf. Both programs work with the Excel format xls. Often the output is cut and pasted into our documents and you are not likely to see this format on SCRAM. File extensions of dat, inp, out, met, txt, rme, etc. are ASCII text formats. The bin file extension indicates a binary file format. Binary file formats tend to be compact but not easy to read. You have to know the program write statements that were used to generate the file in order to easily decode its contents. If you have problems with a file format, please email us through our SCRAM Contact Us page.
Q2: I can’t read or find a manual. Where can I get a readable/working copy?
A: Many of our documents are stored on a server at the National Service Center for Environmental Publications (NSCEP) and can be downloaded in PDF, Multipage TIFF, or Unformatted Text formats. Online access to this service is through this link: https://www.epa.gov/nscep/ As an alternative, you might also want to try to find the document through one of the internet search engine (e.g. Google). Sometimes it is faster finding a NSCEP stored document this way. If you still cannot find the document, please email us through our SCRAM Contact Us page.
Q3: What is a WP, WPF, or WPD format?
A: A long time ago, WordPerfect was our Agency’s defacto word processor. WPF and WPD are the file extensions often seen on our older documents. The newer version of Word and Libre Office are not able to read these formats. However, many of these documents reside at the National Service Center for Environmental Publications (NSCEP) and can be downloaded in PDF, Multipage TIFF, or Unformatted Text formats.
Q4: I need help in downloading documents. Can you help?
A: In some very rare circumstances, a person may not be able to download a document from an EPA web site. We do not know why this happens but when it does, please email us through our SCRAM Contact Us page. We have been able to help in the past.
Q5: Where can I find the Current Memos and the Generic/Recurring Issue memos?
A: Many of these memos reside on MCHISRS but are not currently identified as such. We are in the process of reviewing each memo for relevancy.
Q6: I see the AERMOD Addendums but where are the original documents?
A: The original User Guide is part of the Addendum package. You may want to reread the README file that accompanies the ZIP file package. Pertinent passages and sections in the Under Revision User’s Guide are being reviewed and transferred to a newer User’s Guide. The Addendum has the latest and corrected Keyword input formats, etc.
Q1: How do I go about getting my business permitted by the EPA?
A: We suggest contacting your State or local Modeling Contact. We provide contact information at: /ttn/scram/guidance_cont_states.htm . Some States have local governmental organizations and they are listed there.
Q2: Can I do the modeling myself?
A: If you know or want to learn how to do it yourself, there is no law stopping you from doing so. However, there are a number of consultants who are likely familiar with what you want to do and who know the permitting process. They likely have an internet presence. A State or local Agency may be able to help.
Q3: What if modeling shows that my industry is over some standard?
A: A consultant may be able to suggest ways for you industry to reduce its emissions.
Q4: What model(s) should I use?
A: We would suggest you read Appendix W. Models are listed and their purposes are described.
Q1: What is a SIP?
A: is a United States state plan for complying with the Federal Clean Air Act, administered by the Environmental Protection Agency.
Q2: How is a SIP constructed?
A: The SIP consists of narrative, rules, technical documentation, and agreements that an individual state will use to clean up polluted areas.
Q3: Who approves a SIP?
A: A States’ SIP is approved within EPA.
Q4: What happens if my business is affected by a SIP?
A: That business will be required to reduce emissions. This may mean the use of scrubbers, cleaner fuel, taller stacks, and other methods for cleaning up emissions
Q5: How can I appeal?
A: Appeal generally take the form of a lawsuit against the EPA.
Q1: How come EPA models have to be run from the Command Prompt instead of Windows Explorer?
A: The EPA models are compiled with standard compilers that have an underlying DOS foundation. It would add another layer of complexity if we were to design our models to run from a Window.
Q2: What is DOS and what are DOS commands?
A: DOS is an acronym that stands for Disk Operating System. It was created before the Windows Operating Systems were created. To do anything, DOS commands had to be invoked. Programs had to be executed at the DOS prompt (now the command prompt in the Command Prompt window). More information can be found at: http://en.wikipedia.org/wiki/DOS
DOS commands were executed to perform various routine functions such as moving and copying files, formatting drives, checking the integrity of data on disk systems. A list of DOS commands can be found at: http://en.wikipedia.org/wiki/List_of_MS-DOS_commands along with an explanation of each command and various attributes for tailoring the command for sub-functions such a verifying that copied files exist verbatim in another subdirectory. We still use DOS commands when moving and moving files from one subdirectory to another or using the FC command to verify that a user’s run of a test “matches” the output of the original test case.
Some people do all their subdirectory creation and file moving in Windows Explorer and then bring up the Command Prompt to run their execution.
Q1: Where can I find a copy of pkunzip or a similarly good unzipping program?
A: Pkunzip can be downloaded from: https://www.epa.gov/ttn/tools.html. This same URL provides a link to the WINZIP web site.
WINZIP is a commercially created product. In the past, they have provided a free trial version.
Other unzipping programs and products are available from the internet. Some may require a purchase of that product.
Q2: How come pkunzip does not run completely from Windows Explorer?
A: Pkunzip is DOS based and pkunzip is available from: https://www.epa.gov/ttn/pkunzip.exe. When it runs from Windows Explorer, the program opens immediately in a Command Prompt (DOS) window displaying its Help screen. The unzipping part of the program cannot be executed from this window. Pkunzip has to exit from this help screen Command Prompt window and the program has to be re-executed from different Command Prompt window.
Q3: I unzipped one of your ZIP files and found more ZIP files. What happened?
A: In some cases, documentation for one model may apply to another similar model. Such is the case with CAL3QHC and CAL3QHCR. This occurs where the models are very similar and the documentation for one model complements or supports the model and or documentation of the other model. Both the user’s guides for CAL3QHC and CAL3QHCR are compressed by using PKZIP or WinZip and then zipped again to from one zip file. The content of one User’s Guide is useful in understanding the underlying physics of the other model. Both share similar input file structures where the input from one file can be slightly modified to create the input for the other model. Therefore, it is convenient to store both users’ guides together. We did the same for the source code.
In the case of CAL3QHC and CAL3QHCR User’s Guides, unzip the main package and then unzip each guide.
Q4: I am having problems unzipping a file. What is going wrong?
A: Pkunzip is DOS based and does not run well from Windows Explorer and ** should only be run from a Command Prompt**. WinZip does run well from Windows Explorer and will open up a separate Windows GUI for unzipping and extracting files to user selected subdirectory.
In the past, we have had reported problems with third party unzipping programs. Therefore, we have recommended use of pkunzip and WinZip. These are two programs that have not given us any reported problems. However, we do not want to discourage the use of third party unzipping programs. The software writers, through the evidence of newer versions, are fixing their codes and/or enhancing features. It has been awhile since we have heard of a third party unzipping program causing problems.
There are very rare instances where the transmission of the download becomes corrupted. The solution is to redownload the file.
Q5) Can I use pkunzip on a “gz” or “tar” file? ?
A: The simple answer is: ”no”. PKUNZIP is purely a Windows program and gz and tar are Unix file compression formats.
Q1: Where can I obtain emissions data?
A: There are two general sources of emissions: natural and man-made. The natural sources can be from vegetation such as Oak trees, entrainment of dust from strong winds, sulphur compounds from volcanos, methane from warming permafrost bogs, etc. Some of these emissions have been quantified and are available with the CMAQ model. It would be best to go to the CMAS site at: http://www.cmascenter.org/ to obtain information and data.
Man-made emissions can be from industrial sources, vehicles, etc. When a company wants to build a plant and that plant will emit pollutants in significant quantities that company has to secure a Permit from the EPA. In that Permit, the company has to quantify the maximum emissions it will generate. That Permit is a source of emissions data. Plant and source parameters should also be available from the Permit.
Vehicle emissions, commonly called mobile source emissions, need to be modeled under certain circumstances. Information and vehicle emissions models and inventories are available from or through: https://www.epa.gov/otaq/models/moves/index.htm
Additional information on emission inventories, Factors, modeling, and an Emissions Monitoring Knowledge Base are available from the CHIEF web site at: https://www.epa.gov/ttn/chief/.
Q2: How can I get Speciate data to run with CMB?
A: This is tricky and not very straight forward. Please email us through our SCRAM Contact Us page.
Q3: Where can I go to find emissions for generic type industries?
A: On the CHIEF web site mentioned above, there is a section of the web site that provides ways and means of determining emission factors. The main page is located at: https://www.epa.gov/ttn/chief/efpac/index.html.
Q4: Does AERMOD allow for **negative** emissions to account for offsets or credits?
A: AERMOD currently does not allow the use of negative emissions to explicitly account for emission offsets or credits with the PVMRM or OLM options for NO2. This is due to the fact that these non-default options have not been sufficiently evaluated to be considered as refined options, and are considered to be screening options under current guidance. Screening options are presumed to include some level of conservatism, and therefore such options may overestimate the credit associated with the negative emissions.
Q1: Where can I obtain land use data?
A: The AERSURFACE User’s Guide mentions obtaining land use data from the USGS Land Cover Institute (LCI) website: http://landcover.usgs.gov/natllandcover.php. There are additional links and information in the AERSURFACE User’s Guide.
Q2: Where can I obtain terrain data?
A: One degree Digital Elevation Model (DEM) terrain data is available from the USGS at: http://ned.usgs.gov/. The 7.5-minute DEM data may be purchased from the USGS or one of the internet sites noted above. Users should check the USGS website for the current availability status of these data. More details are available from the AERMAP User’s Guide(s).
Q1: What meteorological data do I need in order to run EPA Gaussian air dispersion models such as AERMOD, CALPUFF, etc.?
A: Anyone who wants to run any of our models will generally need, in part, surface and upper air meteorological data. Surface data is derived from hourly observations made at fixed locations throughout the world. Collected data that are needed to run these models consists mainly of air temperature, cloud cover, wind direction and speed. Additional data such as humidity, precipitation amount, intensity, and type are needed for a few select models and/or situations.
The upper air data is derived from radiosonde balloon launches where instrumented packages transmit back data that are comprised mainly of air temperature, humidity, wind direction and speed.
The AERMOD modeling system requires land use data be processed through AERSURFACE and the output is used as input to AERMET, the AERMOD meteorological preprocessing program.
The types of data collected will vary along with the quality and completeness of the records.
Q2: Where can I obtain the latest 5 years of hourly surface data for a particular station?
A: The latest surface data standard is called the Integrated Surface Data (ISD). ISD (pronounced: ish-D) is a world-wide standard. Data is available from the National Climatological Data Center at: ISD Data CD
The ISD TD-3505 format is read by our latest models such as AERMET and CALMET. The ‘abbreviated’ format for ISD data is not supported.
Q3: Where can I obtain older surface and upper air data?
A: For convenience, this is a copy of a table in the AERMET Addendum User’s Guide indicating the periods when several types of meteorological data format standards were active. That table is reproduced here:
|NWS Surface Format||Start Date||End Date|
- The Earth System Research Laboratory (ESRL) has an online Radiosonde Database for immediate data download and also has media data sets of radiosonde data available for purchase.
- a) The online interactive program for downloading worldwide sets of radiosonde data is located at http://esrl.noaa.gov/raobs/.. Data in this inventory is from the year 2000 and is “model-ready”. The original FSL (Forecast System Laboratory) format should be selected.
- b) Non online products are available for purchase on CDs or DVD via this site at: http://esrl.noaa.gov/raobs/General_Information.html ESRL is offering to sell The North American Radiosonde Archive (1946-1996) on 4 CDs and the Global Archive (1994-2010) on DVD. These sets are no longer available through the National Climatic Data Center.