Source Regions of Influence: Eastern US Transport Climatology

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]
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.