我国西北地区4.5沙尘暴天气研究

对１９９４年４月５日发生在中国西北地区的一次强沙尘暴天气，从天气事实、天气学成因以及动力诊断等方面进行了探讨分析，揭示了形成东大风沙尘暴天气的物理机制。采用ＮＣＡＲ客观分析方案进行的动力诊断表明，（１）地面热低压与正涡度中心相互对应，涡度随高度迅速减小（ξＺ＜０），有利于中低压的发展加强，沙尘暴产生在正涡度区域内；（２）沙尘暴垂直环流特征是南疆至河西中、东部发展一庞大的垂直环流圈，环流中心在１５０～２００ｈＰａ层，它起到组织低空中尺度系统的重要作用；（３）在南北经向剖面上，蒙古高压是一个非常深厚的大型天气系统，它一直伸展到对流层上部，形成了自南向北的正环流圈，在高压南部的上升气流中激发大风和沙尘暴；（４）４·５沙尘暴后期低层大气层结稳定，不利于浮尘消散，故浮尘持续时间长

STUDY OF SAND AND DUST STORM WEATHER IN NORTHWEST CHINA ON APPIL 5,1994

This paper analyses the strong sand and dust storm weather occurred in the Northwest China on the April 5,1994.It probes into several aspects such as synoptic facts,synoptic causes and dynamic diagnostics etc.Thus,it reveals the physical mechanism of the formation of east gale sand and dust storm weather. Under the favourable high level circulation situation,there were three dominant synoptic systems which induced sand and dust storm weather in the low level,including 1)the development and replace of Nanjiang thermal low;2)the production and development of middle scale low;3)Mongolia high pressure and its cold front went down south,which formed a strong pressure gradient,allobaric gradient and temperature gradient between Hexi middle scale low.It wasthe important mechanism for gale sand and dust storm to transform the potential energy into kinetic energy.