长江三角洲地区大气污染物水平输送场特征分析

以长江三角洲地区为研究对象,探讨城市群环境污染规律.利用区域中尺度大气数值预报模式MM5模拟2004年1,4,7和10月长江三角洲地区的气象场.结果表明:冬季,长江三角洲地区近地面及500 m高度层主要为西北风控制,输送气流主要来自西部内陆地区;春季,盛行东南风和偏东风,存在明显的东南向西北方向的输送气流;夏季,则以偏南输送气流为主,杭州湾地区海面向内陆方向以及太湖湖面风速较大,输送扩散能力较强;秋季则转为东北风,近地面杭州湾以北盛行北风,以南主要受海面东北风的影响.结合HYSPLIT-4三维轨迹模式计算分析该地区典型污染过程时污染物的输送气流轨迹,证实了污染过程伴随500 m高度处东北主频气流的"外源"输入现象.

Analysis on the Characteristics of Horizontal Transport of the Atmospheric Pollutant over the Yangtze Delta

The Yangtze Delta was studied to explore the rule of environmental pollution over urban agglomerations. Mesoseale model MM5 was used to simulate the meteorological field of January, April, July and October in 2004. The results showed that the ground level and 500 m level were mainly controlled by northwest wind in winter in the Yangtze Delta. Transport currents arriving Yangtze Delta mainly came from the inland region in the west. In spring, east wind and southeast wind were prevailing in Yangtie Delta. There was a significant transport current from southeast to northwest. In summer, south wind dominated in this area. The wind from sea to inland in Hangzhou Bay and Taihu Lake surface wind were speedy and the transport and dispersion capability was strong. In autumn, Yangtze Delta was under the influence of northeast wind. The subaerial north wind prevailed to the north of Hangzhou Bay, while the northeast wind from the sea dominated. Combined with 3-D trajectory model HYSPLIT-4, the backward trajectories in a typical pollution episode was calculated. The backward trajectories confirmed that problem of pollutant input from Yangtze Delta did exist in 500 m level.