2009年7月17日唐山地区强降水成因分析

摘要

Based on the conventional meteorological data from weather station and NCEP/NCAR reanalysis data,the severe precipitation event in Tangshan on July 17,2009 was analyzed.The results indicate that the severe precipitation event happens because warm and wet air moves to the north and it gathers together with cold air in the low level.Strong vapor convergence in the middle and low levels is necessary prior to precipitation.Cold air invades from the bottom and uplifts the warm and wet current, warm front frontogenesis in the low level increases convective instability, and ascending movement strengthens, so rainfall increases.There exist low level convergence, high level divergence and leaning upward movement mechanism in severe precipitation region.The region of the positive value (MPV1 ＞ 0) of moist potential vorticity is indicative of cold air movement and location of the severe precipitation.%利用常规天气资料和NCEP/NCAR再分析资料,对2009年7月17日唐山地区暴雨天气过程进行分析.结果表明:强降水是暖湿空气向北输送与低层冷空气交汇引起的.降水前期,唐山地区中低层水汽强辐合为强降水提供了水汽条件.冷空气从底层侵入,抬升暖湿气流,低层暖锋锋生使对流不稳定性增大,上升运动加强,降水量增大.强降水区存在低层辐合、高层辐散和斜升运动机制.850 hPa湿位涡正压项MPV1＞0区域较好地反映出冷空气活动特征,强降水出现在MPV1零线附近偏冷空气一侧.