Case studies on the processes of surface ozone pollution in Shanghai

Typical processes of ozone (O-3) pollution in the lower atmosphere in Shanghai are studied in the winter, summer, and autumn of 1994. Relationships between O-3-NOx (nitrogen oxide) concentrations and meteorological parameters are analyzed in order to find meteorological indices corresponding to high O-3 concentration days. Meteorological conditions favorable for high O-3 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 O-3 concentrations can occur when the wind speed is relatively high. O-3 could increase rapidly on fog days. Temperatures influencing O-3 concentrations are not as obvious in summer as in winter. Some possible mechanisms for the measurement results are suggested in this paper.