The EPA released a new version of AERMOD April 7, 2011 (model version 11059). The new version includes multiple bug fixes, as well as several important enhancements. More specifically, AERMOD is now capable of computing the design concentration for the new 1-hour NO2 and SO2 NAAQS. Additional improvements include the ability to input temporally-varying background concentrations, and several new output options. The new model, as well as a full description of the model changes are available on EPA’s SCRAM website: http://www.epa.gov/ttn/scram/.
As of April 8, 2011 regulatory air dispersion modeling analyses submitted by industries and their consultants must be conducted using the new version of AERMOD (11059), unless prior approval has been granted by the Department to use an older version of AERMOD or a different dispersion model.
The new version of AERMOD will function with the current Iowa DNR meteorological data, but a non-fatal warning will be reported in the model output. This is normal and is acceptable until the DNR is able to processes meteorological data for use with the new version of AERMOD. New meteorological data is anticipated to be available later this year.