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Support Center for Regulatory Atmospheric Modeling (SCRAM)

  • Model Clearinghouse

    The Model Clearinghouse is a focal point for interpretation of modeling guidance in specific regulatory applications. EPA Regional Offices can use it to resolve implementation issues and non-regulatory applications related to regulatory air quality modeling. 

    Visit the Clearinghouse

This website provides access to air quality models and other mathematical simulation techniques used in assessing control strategies and source impacts. 

  • Air Quality Models

    Air quality models use mathematical and numerical techniques to simulate the physical and chemical processes that affect air pollutants as they disperse and react in the atmosphere.

    Explore air quality models
  • Model Applications and Tools

    EPA conducts modeling analyses to support policy and regulatory decisions using the full range of air quality models and other mathematical simulation techniques used in assessing control strategies and source culpability.

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  • Modeling Guidance and Support

    EPA provides guidance and support to State/local/tribal agencies on the selection and use of models in regulatory settings.

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  • Meteorological Data and Processors

    Air quality models solve for the change in pollutant concentrations over time and space, and thereby require certain meteorological inputs that, in part, determine the formation, transport, and destruction of pollutant material. 

    Use meteorological models
  • Conferences and Workshops

    EPA sponsors a regular series of air quality model/modeling conferences and workshops and also periodically participates in other air quality modeling or related meetings. 

    Review the materials
  • Reports and Journals

    Technical EPA modeling staff conduct modeling analyses to support policy and regulatory decisions and also coordinate with others in the modeling community on the development of new models and techniques. 

    Read the reports

Announcements

04/15/2025 - Save the Dates - July 8 to July 10, 2025 - 2025 Regional, State, and Local Dispersion Modelers' Workshop

03/21/2025 - The final rule revising the Guideline on Air Quality Models (Appendix W to 40 CFR Part 51) became effective on March 21, 2025.

12/10/2025 - The presentation (pdf) (389KB) from the 2024 Revisions to Appendix W / AERMOD Final Rule Webinar is now available.

12/04/2024 - An AERMOD 64-bit Executable Refresh Memorandum (pdf) (236 KB) is now available.

11/20/2024 - An updated version of the AERMOD Modeling System (dated 24142) (pdf) (267 KB), including new versions of AERMOD, AERMET, and AERMAP, and updated versions of AERSUFACE (v24142), AERPLOT (v24142), and MMIF (v4.1.1) are now available.

11/20/2024 - The final Guidance on Developing Background Concentrations for Use in Modeling Demonstrations (pdf) (2.2 MB) is now available.

09/20/2024 - A Model Clearinghouse Concurrence Memorandum to Region 2 regarding the use of a site-specific alternative approach to demonstrate modeled attainment of the 2010 SO2 NAAQS at the Alcoa West Aluminum Smelter in Massena, New York has been added to the MCHISRS database.

08/27/2024 - A Model Clearinghouse Concurrence Memorandum to Region 2 regarding the use of AERCOARE-AERMOD as an alternative model for an Outer Continental Shelf permitting effort (Atlantic Shores P3Co Project) has been added to the MCHISRS database.

07/24/2024 - A Model Clearinghouse Concurrence Memorandum to Region 6 regarding the use of AERMOD-HBP as an alternative model for a 1-hour SO2 attainment demonstration SIP effort (Rusk-Panola Nonattainment Area) has been added to the MCHISRS database.

06/14/2024 - A Model Clearinghouse Concurrence Memorandum to Region 1 regarding the use of AERCOARE-AERMOD as an alternative model for an Outer Continental Shelf permitting effort (Vineyard Wind NE) has been added to the MCHISRS database.

04/30/2024 - Supplement to the Guidance on Significant Impact Levels for Ozone and Fine Particles in the Prevention of Significant Deterioration Permitting Program

04/30/2024 - Effective Permitting Tools for Fine Particulate Matter under the Prevention of Significant Deterioration Permitting Program Fact Sheet

See Historical Announcements

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Last updated on April 15, 2025
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