Case Studies on the Processes of Surface Ozone Pollution in Shanghai

Typical processes of ozone (O3) pollution in the lower atmosphere in Shanghai are studied in the winter, summer, and autumn of 1994. Relationships between O3-NOx (nitrogen oxide) concentrations and meteorological parameters are analyzed in order to find meteorological indices corresponding to high O3 concentration days. Meteorological conditions favorable for high O3 concentrations usually appear when Shanghai is dominated by a high-pressure system in the lower atmosphere, while a northwestern current prevails over this area in the upper atmosphere. High O3 concentrations can occur when the wind speed is relatively high. O3 could increase rapidly on fog days. Temperatures influencing O3 concentrations are not as obvious in summer as in winter. Some possible mechanisms for the measurement results are suggested in this paper.