北京2002年3月20～21日尘暴过程的降尘量与降尘粒度特征

本文对2002年3月20～21日发生在北京地区的一次尘暴过程进行了降尘量和降尘粒度的研究。通过对分时段监测取得的13组降尘样品进行降尘量和粒度测定,结合风速变化情况,可将本次尘暴分为尘暴前期和尘暴后期两个过程。降尘量和粒度参数值在尘暴前期和后期都呈现不同特征。结论认为,风速是降尘量变化的重要因素。当风速进一步增大时,降尘量反而有所下降。说明北京地区尘暴降尘量除受本地风速影响外,还与粉尘浓度等特征有关。尘暴降尘的粒度基本呈双峰态分布。本次尘暴初始降尘主要为细粒径颗粒,尘暴前期降尘粒径随风速而变化,尘暴后期降尘粒径基本维持在5～6之间

DUST FLUX AND PARTICLE SIZE OF DUSTFALL OF THE DUSTSTORM ON MARCH 20～21,2002 IN BEIJING

A heavy dust storm occurred in Beijing on March 20～21, 2002. We collected samples of the dust derived from the dust storm with an interval of 4 hours and obtained 13 groups of sample which had been dried and weighted in lab. Grain size of the sample had been measured. According to the weather condition and dust influx data gained by weight, this heavy dust storm in Beijing could by divided into tow phases: 1) prophase with more dust accumulated under higher wind speed; 2) anaphase with less dust accumulation under lower wind speed. Our result demonstrated that dust fall flux fluctuated mainly with the wind speed during the dust storm but not synchronously, which was maybe influenced by particle concentration of blown dust. The grain size distribution was bimodal as a whole. In prophase of the dust storm, mean grain size of dust was relatively fine and varied with wind speed. In anaphase mean grain size remained basically around 5～6.