HYSPLIT Puff Dispersion Modeling

Single Large Source Impact Assessment

Hypothetical VT Source Modeled Using Two Different Meteorological Data Sets

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This modeling was conducted using the same representative emission rate for a hypothetical source. The purpose of these model runs was to visualize the difference in concentration impacts predicted from the use of two different meteorological data sets representing the same time period. The NOAA archived EDAS (160km horizontal density of data points spatially) was used for one modeling run, while Regional Atmospheric Modeling System (RAMS) wind fields which were calculated by NOAA scientists at 3km horizontal grid spacing, under a cooperative agreement with the Vermont Air Quality Division, was used for the other run. Both runs show hourly average concentration impact isopleths. It is possible to see the more detailed wind flow patterns that result from the RAMS meteorology and the more prominent representation of some north-south valley flows in the RAMS analysis fields as compared to the ETA (EDAS) analysis fields.

Note that the two separate movies do not represent exactly the same length of time, though they start at the same date and hour. The middle movie shows a comparison between three different meteorological model analyses, a very refined RAMS grid of 3 km horizontal spacing, a RAMS grid of 9 km spacing, and an EDAS grid of 160 km spacing.

Movies Developed: 3/7/02       Page Last Updated: 2/26/03