12/06/2019 - A Model Clearinghouse Concurrence Memorandum to Region 6 regarding the use of AERCOARE-AERMOD as an alternative model in the Gulf of Mexico (SPOT DWP) has been added to the MCHISRS database.

11/13/2019 - The MERPs VIEW Qlik applications are now available.

11/08/2019 - SMAT-CE Version 1.6 is now available and is being released as a replacement for the MATS tool.

10/31/2019 - The Evaluating Reduced-Form Tools for Estimating Air Quality Benefits final report is now available.

10/25/2019 - The presentations, transcripts, and audio recordings from the Twelfth Conference on Air Quality Modeling are now available.

08/28/2019 - The AERMOD Implementation Guide has been updated to include a new section that provides information on known model implementation issues, including two issues pertaining to the BUOYLINE source and processing site-specific data in AERMET.

08/21/2019 - An updated version of AERMOD Modeling System (dated 19191) is now available. Specifically, the AERMET and AERMOD executables, source code, documentation, and test cases have been revised.

08/21/2019 - A draft BPIPPRM (version 19191_DRFT) is now available for review and comment. This draft version is being released simultaneously with AERMOD version 19191 to facilitate testing and evaluation of the APHA options in AERMOD related to building downwash.

06/13/2019 - The final MERPs Guidance webinar presentation from June 13th is now available.

06/11/2010 - MMIF has been updated to version 3.4.1 to support a new choice for cloud cover data, as well as to correct a bug for CALPUFF and SCICHEM modes when a user is providing MM5 output.

05/30/2019 - The final version of the Fine Particulate Matter (PM_2.5) Precursor Demonstration Guidance is now available.

04/30/2019 - The final Guidance on the Development of Modeled Emission Rates for Precursors (MERPs) as a Tier 1 Demonstration Tool for Ozone and PM2.5 under the PSD Permitting Program (PDF) is now available.

04/04/2019 - A Clarification Memo on additional Methods, Determinations, and Analyses to Modify Air Quality Beyond Exceptional Events is now available.

03/20/2019 – A Model Clearinghouse Concurrence Memorandum to Region 5 regarding the use of a BLP/AERMOD hybrid alternative model approach for modeling buoyant fugitive emissions from coke oven batteries in complex terrain at the AK Steel – Mountain State Carbon – Follansbee Plant has been added to the MCHISRS database.

11/08/2018 – The Technical Guidance for Demonstration of Inter-Precursor Trading (IPT) for Ozone in the Nonattainment New Source Review Program is now available.

10/30/2018 – A Model Clearinghouse Concurrence Memorandum to Region 3 regarding the use of a BLP/AERMOD hybrid alternative model approach for modeling buoyant fugitive emissions from coke oven batteries in complex terrain at the AK Steel – Mountain State Carbon – Follansbee Plant has been added to the MCHISRS database.

08/23/2018 – A Model Clearinghouse Concurrence Memorandum to Region 3 regarding the use of a BLP/AERMOD hybrid alternative model approach for modeling buoyant fugitive emissions from coke oven batteries in complex terrain at the U.S. Steel Mon Valley Works - Clairton Plant has been added to the MCHISRS database.

04/17/2018 - The EPA has finalized the Guidance on Significant Impact Levels for Ozone and Fine Particles that may be used in the PSD permitting program.

03/28/2018 – A Model Clearinghouse Concurrence Memorandum to Region 9 regarding the use of a BLP/AERMOD hybrid alternative model approach for modeling buoyant roofline sources has been added to the MCHISRS database.

03/13/2018 – A Model Clearinghouse Concurrence Memorandum to Region 4 regarding the use of an alternative model technique to address two issues with modeling buoyant line sources in AERMOD has been added to the MCHISRS database.

10/19/2017 - The preliminary 2028 visibility modeling data and results are now available through a transmittal memorandum and accompanying technical support document (TSD).

09/19/2017 - A compilation of AERMOD Development White Papers are now available for review.

08/04/2017 - A Clarification Memorandum providing an alternative model demonstration for specific photochemical transports models establishing their fit for purpose in PSD compliance demonstrations for Ozone and PM_2.5 and in NAAQS attainment demonstrations for Ozone, PM_2.5 and Regional Haze is now available.

07/11/2017 – An Informational Webinar regarding the establishment of appropriate Modeling Domain, Source Data, and Background Concentrations under Section 8 of the revised Guideline on Air Quality Models is available for reference.

07/11/2017 – The Informational Webinar regarding O₃ and Secondary PM_2.5 assessments under Section 5 of the revised Guideline of Air Quality Models is available for reference.

06/05/2017 – A revised version of the AERMOD Model Formulation and Evaluation Document is available. The revision includes an appendix evaluating low wind model performance.

05/26/2017 – A Compilation of Comments document regarding the Draft PM_2.5 Precursor Demonstration Guidance is now available.

05/22/2017 – The final revisions to the Guideline on Air Quality Models, as published in the Federal Register on January 17, 2017, are now effective. An Informational Webinar presentation, presented on February 16, is also available for reference.

03/21/2017 – The Informational Webinar regarding the use of prognostic met data for NSR permit modeling and specifically the EPA’s Mesoscale Model InterFace (MMIF) is available for reference.

03/08/2017 – Clarification Memorandum on the AERMOD Modeling System version for use in SO₂ implementation efforts and other regulatory actions.

08/04/2016 – The draft SO₂ Modeling Technical Assistance Document (PDF) has been updated to clarify receptor placement and the minimum number of years to model.

07/26/2016 – Updated regulatory versions of CALPUFF and CALMET (version 5.8.5, dated 151214) are now available. The links to the updated CALPUFF Modeling System files, the associated Model Change Bulletin (MCB-H) can be found on the CALPUFF webpage.

12/10/2015 – A Clarification on the Approval Process for Regulatory Application of the AERMOD Modeling System Beta Options memorandum is now available. This memo discusses the appropriate process for the approval of the AERMOD Modeling System with the use of various beta options for regulatory applications.

12/04/2014 – The Draft Modeling Guidance for Demonstrating Attainment of Air Quality Goals for Ozone, PM_2.5, and Regional Haze is now available for consideration, review, and comment. This document is a revision to the previous modeling guidance which was released in April 2007.

04/08/2014 – Interim guidance for the treatment of condensable particulate matter test results in the PSD and NSR permitting programs is now available.

01/14/2014 – The draft SO₂Monitoring and Modeling Technical Assistance Documents have been updated based on public comments and are available on the Sulfur Dioxide Implementation web page.

08/26/2013 – The NO₂/NO_x In-Stack Ratio (ISR) Database has been updated based on the first database submission from the State of Oklahoma and the second database submission from the State of Alaska.