重庆城区浓雾的基本特征

Characteristics of Fog in Chongqing Urban Area

统计分析沙坪坝 195 1～ 2 0 0 2年间发生的浓雾事件 ,结合 2 0 0 1年 12月重庆市雾的外场试验资料 ,探索重庆市主城区浓雾的基本特征。重庆主城区浓雾随年代演变有减缓趋势 ;主城区浓雾是自然雾与烟尘等的混合物 ,河谷及城市效应使雾更浓 ;城市中出现浓雾的大气边界层特征是在近地面层有逆温及增湿降温现象 ;高浓度气溶胶的净辐射效应阻碍白天混合层发展 ,使大气边界层趋于稳定 ,它是重庆连续几天有雾的原因之一 ;浓雾具有一定的湿沉降作用 ,能有限地清洁空气 ;有浓雾的天气条件下 ,建议降低污染物的排放总量 ,以避免严重大气污染事件发生。

Fog field observation data during December 2002 and historic data from 1951 to 2002 in the Shapingba district of Chongqing were analyzed, and major characteristics of fog were described. The occurrence frequency of heavy fogs has a decreasing trend. Heavy fogs in the downtown area are the mixture of natural fog, smoke and dust, and the river valley and urban effects densify fogs. The PBL characteristics associated with heavy fogs are the temperature inversion, humidity increase and temperature decrease in the near-surface layer. The net radiation effect of high-concentration aerosol prevents the daytime mixing layer from developing, leading to the stabilization of PBL. It is the main reason for heavy fogs to last several days in the Chongqing downtown area. Heavy fogs play a role of wet deposition, cleaning the air to a certain degree. It is suggested that the total emission of pollutants should be controlled during heavy fog days to avoid the occurrence of heavy pollution events.