Revision to the AERMOD Modeling System v19191

An updated version of the AERMOD Modeling System (dated 19191) has now been posted to the SCRAM website and replaces the previous version (dated 18081). Specifically, the AERMET and AERMOD executables, source code, documentation, and test cases have been revised. The respective link to the updated version of the AERMOD Modeling System is

With this update, the EPA is releasing the AERMOD Modeling System Development and Update Plan discussed at the 2018 & 2019 Regional, State, and Local Modelers’ Workshop. The EPA is also announcing the AERMOD development website, which contains the Development Plan and the AERMOD development white papers (

The v19191 release of the AERMOD Modeling System includes a number of bug fixes and model enhancements. The following list provides a few highlights, but it is strongly encouraged that everyone review the appropriate Model Change Bulletins (MCBs) and related documentation for the respective model system components:

  • The addition of the BETA RLINE and ALPHA RLINEXT source types, which utilize the dispersion parameters from EPA’s ORD R-LINE model. A guidance document that clarifies the possible regulatory applications of the BETA RLINE source in AERMOD will also be provided on SCRAM.
  • The ALPHA  RLINEXT source also has options for modeling solid noise barriers and depressed roadways.  The ALPHA version is not intended for regulatory purposes at this point.
  • The URBAN option has been added as an ALPHA option for the RLINE, RLINEXT, and BOUYLINE sources.
  • Several new ALPHA downwash options have been added to explore improvements to the treatment of downwash for POINT sources.
  • Several bug fixes have been made to the Method_2 approach for calculating deposition. Based on these changes Method_2 is now an ALPHA option.
  • Gas deposition has been made an ALPHA option as it undergoes evaluation
  • Several bug fixes have been completed that correct the calculation and conversion of background concentrations when requesting model output in units other than micrograms per cubic meter.
  • Several bug fixes for error and informational messages in AERMOD.
  • Several miscellaneous bug fixes in AERMET.

Questions, clarifications, and/or feedback can be sent to Chris Owen, EPA ([email protected]).

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