Atmospheric Modeling

REGIONAL SCALE AIR QUALITY SOURCE DISPERSION MODELING

The Air Planning Section employs two modeling tools which use source emissions as the focus for the analysis. The Section utilizes the CALPUFF dispersion modeling system for doing analyses of Vermont sources and large sources within several hundred kilometers of Vermont. A model called HYSPLIT, configured as a forward dispersion model, is used for longer distance transport studies of very large sources that are believed to have the potential to affect Vermont's air quality.

REGIONAL SCALE AIR QUALITY RECEPTOR MODELING

Another tool which is useful for identifying general source regions that contribute to levels of air pollutants measured in Vermont's air is the HYSPLIT model configured as a back-trajectory model. This modeling approach identifies where air came from by calculating backward in time from a receptor location (for instance the monitors where air quality is measured).

Using these tools the Section has conducted modeling studies for both criteria pollutants and hazardous air contaminants to try to identify the amount of transported air pollution reaching Vermont from sources outside the state.

REGIONAL & LOCAL SCALE METEOROLOGICAL MODELING

Meteorological modeling tools such as MESOPAC, CALMET, RAMS, and MM5 are employed to create the upper level wind fields that are needed for doing regional scale modeling. The Division's activities in this area include utilizing RAMS and MM5 output fields produced by other agencies as well as creating meteorological wind fields in-house with models such as MESOPAC and CALMET. These activities are critical to being able to quantify impacts of sources located at distances greater than 30 to 50 kilometers from sensitive receptor areas.