北京秋季一次先污染后沙尘现象成因分析

Analysis for the Formation of Typical a Phenomenon of Dust Storm after Heavy Polluted during the Autumn in Beijing

利用卫星监测资料、气象站的观测资料和北京市环境保护监测中心的PM10监测资料,通过对天气图进行分析,对发生在2000-11-01—07这一污染天气过程的成因和性质进行了解析。结果表明:在此期间PM10呈现准正态分布。污染过程由2个性质完全不同的阶段构成:第一阶段(11月1—3日)属于雾型污染,污染物是SO2,NO2等经过化学转化而成的硫酸盐和硝酸盐微粒;第二阶段(11月4—7日)属于沙尘型污染,该阶段的污染物是受上游沙尘天气影响而形成的黄土、浮尘。这2个阶段的气象过程及天气形势也完全不同,沙尘暴爆发前(前一阶段)的天气受均压场控制,呈现双层逆温结构,相对湿度较大;沙尘暴期间(后一阶段)的天气受高压前部西北气流控制,相对湿度大幅度下降,空气干燥度从地面到高空基本一致。

According to satellite data,observational meteorology data station and monitoring data of PM\-\{10\} provided by Beijing Municipal Environmental Monitoring Center and through analysis of synoptic chart,the formative causations and the characters of the contaminative synoptic process which lasted from 1\+\{st\} Nov.to 7\+\{th\} Nov. in 2000 have been analyzed.The results showed that PM\-\{10\} has qaasi normal distribution during the research period that was composed of two completely different phases.The first phase (from 1\+\{st\} Nov. to 3rd Nov.) was brume pollution,the pollutants of which were sulfate and nitrate particulate formed by chemical reaction of SO\-2 and NO\-2,etc.The second phase (from 4\+\{th\} Nov. to 7\+\{th\} Nov.)was dust storm pollution,caused by loess,and floating dust produced by the upwind dust storm weather.Corresponding meteorological processes and synoptic forms during the two phases are different.During the first phase and before the sand storm broke out,the weather was controlled by homogeneous pressure field and with inversion structure of double layers and high relative humidity.During the second phase,the weather was dominated by northwest air stream existing foreside of anticyclone,the relative humidity has descended greatly,and the atmospheric drying degree is radically consistent from ground to upper air.