【摘要】 对1998 年3 月20 日江淮地区出现的大范围“雷打雪”天气过程(其中浙江中北部地区出现了大范围的寒潮、雷电、冰雹、雪、霰和暴雨等多种天气共存的异常现象)进行了分析,从天气形势特点、物理量场特征、卫星云图等方面着手,对本次过程的成因作了初步探讨. 结果发现:(1)强而势均力敌的冷暖空气在江淮地区交汇是导致本次过程天气异常的主要原因;(2)中低空切变线上温度锋区密集不散,温压场出现强烈斜压不稳定,是本次过程异常天气得以产生的主要触发机制;(3)地形对南下冷锋的强烈变形、高空急流轴上深厚的强风速核区的稳定少动以及散度场和垂直速度场的“Ω”分布有利于强对流天气的加强发展;(4)对流云带发展强烈更多还原

【Abstract】 The abnormal weather phenomenon occurred in March 20th 1998 accompanied with cold wave,thunderstorms,hail,snow and heavy rain is analyzed.In order to investigate its cause of formation,we studied the synoptic situation,physical mechanism and the characteristics of cloud pictures.The results show that a) the confronting of strong cold and warm air over the Yangtse and Huaihe River is the main reason,b) the baroclinic instability along the middle and low level shear line is the major trigger mechanism,c) the orographic deformation of cold fronts,the strong and deep upper level wind,the Ω form of divergence and vertical velocity fields are favorable to the development of severe convection,d) convective cloud developed strongly.更多还原