北京秋季一次重污染天气过程的成因分析

Impacting factors of a heavy air pollution process in autumn over Beijing

近年来,北京的大气环境问题日益受到关注。以2002年10月8—13日北京地区一次重污染过程为例,采用中国气象局的M ICAPS系统和美国的HYSPLT模式,分别从污染过程产生的天气条件、污染物输送轨迹等方面分析此次空气污染的形成原因。结果表明:造成此次重污染过程的不利因素主要包括三个方面,一是较强的海平面高压、均压场控制导致北京地区垂直大气层结稳定,不利于污染物垂直扩散;二是北京地区三面环山,导致近地面为弱的偏南气流控制,不利于污染物水平扩散;三是近地面弱的偏南气流从江苏、山东、河北、天津等地携带了大量的污染物向北京地区输送。

Air pollution has been one of the main urban environmental problems in Beijing recently.A heavy air pollution process happens on October 8-13,2002 in Beijing.Weather conditions and pollutant transport trajectory of this process were analyzed by MICAPS system and HYSPLT model.The results indicate that three disadvantageous conditions lead to this heavy air pollution.One is the weather conditions,namely,the strong high pressure and equal pressure at sea level make vertical atmospheric stratification stable over Beijing,which is not benefit to horizontal diffusion of air pollutants.Another is the terrain,namely,Beijing region is surrounded by mountains in the west and the north as well as the northeast,which becomes barrier to horizontal diffusion of air pollutants when the breeze comes from the south.The last is transport pathway,namely,lots of air pollutants are taken from Jiangsu province,Shandong province,Hebei province and Tianjin region by the southward breeze into Beijing region.