渭河流域2008年1月连阴雪天气过程成因分析

针对2008年6月29日下午到夜间，发生在山西省忻州市神池、五寨、原平等县（市）一带的严重局部冰雹天气过程，利用天气环流形势，各种物理量特征，分析其成因。指出：a）500hPa蒙古东部的冷涡东移，冷空气叠加在850hPa暖脊上，产生上冷下暖的位势不稳定能量。b）前期先导槽的滑过，使低层增湿，潜在不稳定度增大。c）降雹区域沙氏指数、K指数等都符合山西降雹标准。d）850hPa-500hPa有较强垂直风切变，使动力不稳定能量加强，为冰雹天气发生发展提供了必要条件。e）特别是山区由于海拔高，山脉阻挡，气流辐合上升，容易产生局地强对流，诱发雹云生成，出现冰雹天气。

Preliminary Study the reason of a Heavy Hail

It was analyzed using the weather circulation and a variety of physical characteristics what caused the occurrence of severe local hail in Shenchi, Wuzhai and Yuanping Shanxi province in June 29, 2007. The result show ： a） It resulted in the instability energy of warm under the cold that 500hpa Mongolia cold vortex shifted east and the cold air superimposed warm ridge at 850hpa. b）It caused low troposphere more humid and more instability that the leader trough passed at earlier stage, c） The SI index and K index were consistent with the standards of Shanxi hail in this region, d） There was a strong vertical wind shear at 850hPa -500hPa so that the instability energy was in the strengthening. It is a necessary condition for hail. e） It is easy for hail to occur in high - altitude mountain area with range block and increased flow convergence.