河北省北部中雨后的强沙尘暴成因分析

Analysis on Causes of Strong Sandstorm Following Moderate Rain in Hebei Province

本文利用常规观测资料和数值模拟的方法,对2002年4月6日发生在河北省北部中雨后紧接着出现的强沙尘暴天气过程进行了分析和诊断。结果表明:强冷空气爆发南下、致使斜压能量释放、地面气旋发展是有利于本次沙尘暴天气产生的大尺度背景;高空急流的高度迅速下降代表了动量下传,这是形成大风,产生沙尘暴的动力原因;在高空急流下方,日间湍流加强,湍流涡旋的下沉气流也是沙尘暴形成的动力因子,农谚称它是"刮地风",可见其机制作用;降水结束后,天气转晴,并出现6～7级西北风,在西北大风出现6个多小时的短时间内就能迅速使土表蒸发变干出现沙尘暴。

<Abstrcat> Observed data and numerical simulation method are used to analyze the process of a severe dust storm after a moderate rain on 6 April 2002 in the northern part of Hebei province. The results show the following facts. (1) The strong cold air outbreak, the energy downward transportingandthe cyclone developmentmake for the large-scale background condition of the dust storm; (2) The rapid descending of high jet, the downward transporting of momentum and the strong surface's wind are the important dynamical factors; (3) Under high jet, descending vortex also is the dynamical factors of the dust storm, farmer's proverb calls it 'blowing land wind'; (4) After the rainfall, force 6~7 northwest wind that makes the soil moistures lower and lower in about 6 hours, it is the important cause of the dust storm there.