The AERMOD atmospheric dispersion modeling system is an integrated system that includes three modules:
A steady-state dispersion model designed for short-range (up to 50 kilometers) dispersion of air pollutant emissions from stationary industrial sources.A meteorological data preprocessor (AERMET) that accepts surface meteorological data, upper air soundings, and optionally, data from on-site instrument towers. It then calculates atmospheric parameters needed by the dispersion model, such as atmospheric turbulence characteristics, mixing heights, friction velocity, Monin-Obukov length and surface heat flux.A terrain preprocessor (AERMAP) whose main purpose is to provide a physical relationship between terrain features and the behavior of air pollution plumes. It generates location and height data for each receptor location. It also provides information that allows the dispersion model to simulate the effects of air flowing over hills or splitting to flow around hills.AERMOD also includes PRIME (Plume Rise Model Enhancements) which is an algorithm for modeling the effects of downwash created by the pollution plume flowing over nearby buildings.
AERMOD was developed by the AERMIC (American Meteorological Society (AMS)/United States Environmental Protection Agency (EPA) Regulatory Model Improvement Committee), a collaborative working group of scientists from the AMS and the EPA. The AERMIC was initially formed in 1991.
The AERMIC developed AERMOD in seven steps:
Initial model formulationDevelopmental evaluationInternal peer review and beta testingRevised model formulationPerformance evaluation and sensitivity testingExternal peer reviewSubmission to the EPA for consideration as a regulatory model.On April 21 of 2000, the EPA proposed that AERMOD be adopted as the EPA's preferred regulatory model for both simple and complex terrain. On November 9 of 2005, AERMOD was adopted by the EPA and promulgated as their preferred regulatory model, effective as of December 9 of 2005. The entire developmental and adoption process took 14 years (from 1991 to 2005).
Features and capabilities of AERMOD
Some of the primary features and capabilities of AERMOD are:
Source types: Multiple point, area and volume sourcesSource releases: Surface, near surface and elevated sourcesSource locations: Urban or rural locations. Urban effects are scaled by population.Plume types: Continuous, buoyant plumesPlume deposition: Dry or wet deposition of particulates and/or gasesPlume dispersion treatment: Gaussian model treatment in horizontal and in vertical for stable atmospheres. Non-Gaussian treatment in vertical for unstable atmospheresTerrain types: Simple or complex terrainBuilding effects: Handled by PRIME downwash algorithmsMeteorology data height levels: Accepts meteorology data from multiple heightsMeteorological data profiles: Vertical profiles of wind, turbulence and temperature are created