||MESOMET, Inc., Chicago, IL. ;R-Scan Corp., Minneapolis, MN. ;Cape Town Univ. (South Africa).;Environmental Protection Agency, Research Triangle Park, NC. Atmospheric Sciences Research Lab.
Atmospheric pollutants can be transported over large distances, with sources impacting on receptors more than 1000 km downwind. The redistribution and removal of various pollutant species may be significantly controlled by mesoscale phenomena, such as mesoscale convective systems (MCS). A case study (1-2 August 1980), using data from PEPE/NEROS-80, reveals the dramatic impact of several types of MCS (MCC, squall line, air-mass shower cluster) on regional ozone and visibility. In the air mass traversed by the MCS, afternoon ozone was significantly depleted (less than 20-40 ppb vs 100-120 ppb in the polluted regional air mass.) Visibilities, which prior to the wind shift/rain had typically been 4-13 km rose in a matter of a few hours to 27-56 km at many locations. This CARE (convective aerosol removal event) covered Virginia, northern North Carolina, Delmarva, and extended more than 500 km into the Atlantic, as clearly shown by GOES satellite imagery on the morning of 1 August 1980. (Copyright (c) 1986 American Meteorological Society.)