The AERMOD air dispersion model features many different settings which provide users the ability to customize how model output is presented. Within the model’s Source Pathway are multiple options for grouping sources, but just what do all these different groups mean? Below is a look at each type.
The Plume Volume Molar Ratio Method (PVMRM) is one of several methods built into AERMOD for assessing the conversion of NOX to NO2. Originally developed by Hanrahan as a post-processor for the ISCST3 model, this conversion method is considered a Tier 3 screening method according to the Guideline on Air Quality Models (Appendix W to 40 CFR Part 51). The conversion rate for NOX to NO2 in this scheme is based on a calculation of NOX moles emitted into the plume and the amount of ozone (O3) moles contained within the volume of the plume between the source and receptor.
Numerous versions of the AERMOD model have been released over the years. These updates include new algorithms, enhancements to existing features, bug fixes, and more. New model versions are published by the US EPA to the Support Center for Regulatory Atmospheric Modeling (SCRAM) website. In the United States, the newly published model officially becomes the preferred version of the model.