青藏高原东部地区的大气电特征

COLD-FRONT ACTIVITIES AND ITSINFLUENCE ON AIR POLLUTION ATURBAN DISTRICTS OF LANZHOUIN COLD HALF YEAR

对青藏高原东部地区大气电特征的分析发现：晴天大气电场的日变化呈单峰单谷型，峰值出现在０４：００～０５：００左右，谷值出现在１７：００～１８：００左右；雷暴电荷结构主要为偶极性，雷暴持续时间短，大约有７３．３％的雷暴持续时间小于０．５ｈ，闪电较少。不同降水过程的雷暴，地面电场特性不同。负地闪比正地闪多，正负地闪的比例约为１：８。７７．８％的负地闪为单次回击，正地闪均为单次回击。正地闪比负地闪的强度要大。

It has been analysed that the data of 500hPa historical synoptic maps and the data of air pollutant concentrations were monitored by automatic monitoring system in Environmental Monitoring Station of Lanzhou in the period of 1988～1991. The analysed results are as follows:under the control of two-trough and one-ridge synoptic circulation pattern the frequency of cold-front activities at Lanzhou is the highest with 54.8%. It is higher with 35.5% under the control of one -ridge and one-trough synoptic circulation pattern. In cold half year the activest stages of the strongest and stronger cold fronts are in March. The other activer stages of cold fronts are in October. The activest stages of weak cold fronts is in January. Influence of cold-front passage on SO2 concentrations at Lanzhou is the most remarkable. The average decreasing rate of SO2 concentration is about 30% to 50% and the maximum decreasing rate is about 70% to 80%. The decreasing rate of NOx concentration is also more remarkable.In the process of cold front weather, the correlation between inversion depth and air pollutant concentration is the most remarkable. The correlations between temperature, mixing depth and air pollutant concentrations respectively are reducing in proper order. Influences of above mentioned three meteorological factors on the changes of air pollutant concentrations are different in the processes of the strongest, stronger and weak cold front weather.