USING NOAA HYSPLIT AND GIS TO INVESTIGATE AIR QUALITY VARIABILITY IN WESTERN PENNYSLVANIA

Airsheds, surface areas that contribute contaminants and/or pollutants to a defined location or the airmass above this location, are often defined statically and are byproducts of forward trajectories from emitters rather than backward trajectories from monitoring locations. We have created a model that specifically uses frequency occurrence of back trajectories in space to delineate airsheds and conduct regional studies of air pollution variability within the resulting airsheds. The program integrates the NOAA HYSPLIT trajectory model with an industry standard GIS platform using several tools that create an easily understood interface. Atmospheric measurements of criteria pollutants, ozone (O₃), carbon monoxide (CO), nitrogen oxides (NO_x), and particulate matter (PM₁₀ and PM_2.5), have been measured for over ten years at seven different sites along the western border of Pennsylvania. We use the NOAA HYSPLIT/GIS interface to investigate the relationship between criteria pollutant concentrations and meteorology. Events with elevated criteria pollutant levels show statistically different airsheds, suggesting that both transport patterns and point source locations play key roles in controlling air quality in western PA. In addition, a seaonal and latitudinal variation in airshed geometry is observed, suggesting widely different regional source emissions impact western PA during different seasons.