| Summary: | Southern California experiences the worst ozone air quality in the United States. A case study of the air pollution episode of 3-7 October 1996 is presented. Rapid subsidence and depression of the marine inversion begin 2 October. Wind data from two 915 MHz radar wind profilers suggest the development of a mesoscale eddy off the California coast by 4 October. The conceptual model for the episode explains high ozone concentrations in the Los Angeles basin and Ventura County, over the California bight and in mountainous San Diego County, while coastal San Diego concentrations remain low until the late stages of the episode. The deepening marine layer and cyclonic wind patterns associated with the eddy carry ozone and precursors more than 100 km offshore, to San Clemente Island (SCI). Some of these pollutants may be carried back into San Diego on southerly winds through Mexico.
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