强沙尘暴天气形成机制个例分析

从气候背景、天气形势、地形作用、沙尘形成热力和动力学机制等方面,分别对2005年4月19、20日两天发生在冀南地区的扬沙、沙尘暴天气进行分析。结果表明:对流层低层横切变线和华北地形槽的存在使冀南地区沙尘天气加剧;沙尘发生前冀南弱辐合上升运动和上冷下暖的不稳定垂直结构可以迫使当地沙尘向空中扬起,上游地区较强的上升运动将当地的沙尘垂直输送到空中,在高空强西北气流的引导下将沙尘水平输送到下游地区;沙尘天气发生在上游地区对流层螺旋度最大正值区的下游,对流层螺旋度大小对沙尘暴预报有一定的指示意义。

Dynamical and Thermodynamic Mechanisms of a Severe Dust Storm

A case study is made of the dust storm occurred on 19,20 April 2005 in the southern Hebei Province from the aspects of the climatic background,synoptic features,orographic effect and dynamical and thermodynamic mechanisms.The results indicate that before the occurrence of the storm,the local weak convergence,upward motion and unstable vertical structure drew local dusts up;the upstream strong upward motion drew dusts up and then the upper-air strong northwesterly transported the dusts to the downstream area horizontally;the dust storm occurred at the downstream area of the maximum positive helicity zone in the troposphere.The magnitude of the helicity in the troposphere is useful for the prediction of dust storms.