Eastern US Transport Climatology During High and Low Ozone Conditions: Source Regions of Influence To be submitted to section 123: Source/receptor relationships for ozone, PM, and regional haze. Bret Schichtel and Rudolf Husar, Washington University Campus Box 1124 One Brookings Drive St. Louis MO, 63143-4899 (314) 935-6099 (Voice) (314) 935-6145 (Fax) [email protected] [email protected] Abstract The source region of influence (SRI) is the area around a source that it is most likely to impact over a given period of time. It is a measure of the regional scale transport from a source. The SRI is dependent upon a pollutant's transport direction and speed from the source as well as its lifetime. A transport wind vector is derived from the SRI, which is similar to an average wind vector over time, height, and along the transport pathway from the source. Using the SRIs and transport wind vectors, the regional scale transport climatology for average, high, and low ozone condition were established for the Eastern US during the five summers, June – August, 1991 95. The high and low ozone was defined as the 90th and 10th percentile of daily maximum ozone. These condition were defined for local and regional scales, with regional being the averaged over Eastern US. At any given time, the transport can be in any direction over the Eastern US. However, on average the transport was eastward, with the slowest speeds and regions of influence in the south. The highest local ozone days in the Central east and Southeast were associated with slow stagnant transport conditions, while in the North they were associated with stronger more persistent winds from the west-southwest. Transport winds during low local ozone days, were associated with swift transport from Canada, Atlantic, and Gulf of Mexico. During the highest regional ozone days there is clockwise circulation around the Central east, Southern Ohio, West Virginia, Tennessee, and Kentucky. The lowest regional ozone days have higher speed transport from the Gulf of Mexico and Canada in a general eastward direction.