鄂西南地区地面中-β尺度环流系统与暴雨

THE RELATIONSHIP BETWEEN THE NEAR-SURFACE MESO-β SCALE CIRCULATION SYSTEMS AND THE HEAVY RAINFALL EVENTS IN THE SANXIA GORGE REGION OF THE CHANGJIANG RIVER

分析长江三峡—湖北西南部地区五年夏季的暴雨过程,发现80%的过程中都有中-β尺度的气旋(平均直径97km)和反气旋(平均直径114km)环流系统活动,它们各有其集中出现的区域,基本不相混杂。这些区域和该地区夏季地面平均流场图上的中-β尺度气旋及反气旋中心位置一致。在平均雨量及暴雨月数分布上也有反映。其中,气旋环流中心对暴雨的作用可能主要是触发机制。从它们经常出现的区域及位置集中的事实,并配合地形图来看,表明地形对它们的生成有决定性影响。

In this paper,the heavy rainfall events in the Sanxia Gorge region of the Changjiang Riverand the southwestern region of Hubei province during the summers 1983—1987 are analyzed.Itis found that about 80% of the events are associated with meso-β scale cyclones and anticycloneswith mean diameters of 97 and 114km respectively.These meso-β scale cyclones and anticyclonesare respectively concentrated in different areas essentially without overlapping.The areas are co-incided with the meso-β scale cyclone or anticyclone systems on the mean surface streamline chartand with the climatological distribution of the rainfall and heavy rainy day in the region.Com-pared the areas of high frequency of occurrence of the meso-β cyclones and anticyclones with thetopographical features,it is demonstrated that the terrain plays a crucial role in producing themeso-β cyclones or anticyclones.