On December 20, 2016, the EPA finalized updates to the Guideline on Air Quality Models (Appendix W) as well as updated versions (v16216) of AERMOD, AERSCREEN and AERMET. The updated Appendix W guidance and aforementioned modeling programs can be found on the SCRAM website here:
https://www.epa.gov/scram
AERMET version 16216 includes bug fixes to subroutines enabled during Stage 3 of the meteorological pre-processor as well as minor changes to documentation throughout (refer to the AERMET user guide for details, which is also available on the SCRAM website).
Due to the AERMET modifications, the DNR has reprocessed the meteorological data available on the DNR’s website (Version C).
The sensitivity of AERMOD to the changes being introduced by the reprocessed meteorological data was tested. On average, users can expect a negligible amount of change to predicted concentrations for both the change to the latest version of the meteorological data and the new version of AERMOD.
Applicants should begin using the latest version of AERMOD (v16216) and meteorological data (Version C) immediately. The previous version of the meteorological data (Version B) can be used in cases where it has been approved in a dispersion modeling protocol.
The revised surface and upper air meteorological data files are available under the Dispersion Modeling page on the Department’s website.
Please contact Brad Ashton at Brad.Ashton@dnr.iowa.gov or by phone at (515) 725-9527, with any questions or comments on this update.