Air pollutant transport within the Mexico City Basin

To better understand the factors that contribute to high ozone and particulate concentrations in Mexico City, a meteorological and aerosol field campaign was conducted over a four-week period in the winter of 1997 that measured vertical profiles of wind, temperature, and humidity at several locations. A coupled mesoscale-chemistry model is employed along with wind profiler and sounding measurements to examine how thermally-driven circulations contribute to the spatial distribution of ozone across the basin. Results from the modeling system demonstrate that recirculation patterns are often formed by the interaction of local thermally-induced flows and regional ambient winds. Layers of ozone and ozone precursors are produced by these recirculation patterns and are subsequently entrained into the growing convective boundary layer. (Author)