上海地区PM2.5-O3复合污染特征及气象成因分析

统计分析了上海地区2013~2017年PM_2.5-O₃复合污染事件及与气象条件的关系.结果表明，近5a上海PM_2.5-O₃复合污染天气占O₃总污染天气33.4%，仅出现在3~10月，呈逐年减少的趋势；PM_2.5-O₃复合污染时的O₃峰值浓度和平均浓度较单O₃污染时高，维持时间较单O₃污染时长，主要气象原因是地面辐合和较低的边界层高度；PM_2.5-O₃复合污染的天气形势往往与弱气压场有关，可以分为低压底部和前部、高压顶部和后部、均压场5种天气类型，其中均压场出现次数最多，占比53%；复合污染对气象因子的阈值要求更为严格，并且阈值区间总体向有利于PM_2.5浓度上升的方向偏移；当温度介于27.9~34℃，湿度介于43%~58%，风速介于2.1~3.3m/s，混合层高度介于1122~1599m，并且存在辐合时，最有利于PM_2.5-O₃复合污染发生.

Analysis of characteristics and meteorological causes of PM2.5-O3 compound pollution in Shanghai

Simultaneous pollution events of PM_2.5 and O₃ (PM_2.5-O₃ compound pollution) in Shanghai from 2013 to 2017 and the relationship between PM_2.5-O₃ compound pollution and meteorological conditions were statistically analyzed. In the past five years, PM_2.5-O₃ compound pollution events accounted for 33.4% of total O₃ pollution events in shanghai, which only appeared between March and October and decreased by year. The peak O₃ concentration and average O₃ concentration during PM_2.5-O₃ compound pollution were higher than those during simplex O₃ pollution. The duration of O₃ pollution during PM_2.5-O₃ compound pollution events was longer than that of simplex O₃ pollution. The main meteorological reasons were ground convergence and low boundary layer height. The weather situation of PM_2.5-O₃ compound pollution was related to weak pressure field, which was categorized into 5weather types, namely bottom of low pressure, front of low pressure, top of high pressure, rear of high pressure and equalized pressure. The equalized pressure mostly appeared, which accounted for 53%. The PM_2.5-O₃ compound pollution required strict meteorological threshold ranges, which were more conductive to PM_2.5 concentration increasing than to O₃ concentration increasing. When the temperature was between 27.9~34℃, the humidity was between 43%~58%, the wind speed was between 2.1~3.3m/s, the height of the mixed layer was between 1122~1599m, and when there was convergence, it was the most conductive to the occurrence of PM_2.5-O₃ compound pollution.