一次区域性暴雨的数值模拟和诊断分析

Numerical simulation and diagnostic analysis of a regional rainstorm

利用1次/6 h的NCEP-NCAR再分析资料,对2013年7月21-22日发生在陕西中部的一次大暴雨过程进行了数值模拟和诊断分析.结果表明副热带高压的加强西伸,低层大量暖湿气流输送和中高层冷空气交汇,是造成此次降水的主要原因.分析数值模拟结果发现WRF模式能很好地模拟降水区域、降水中心和降水强度.暴雨期间,低层辐合、高层辐散的耦合结构和整层强上升运动以及正涡度的变化均与暴雨中的垂直螺旋度分布特征紧密联系,与暴雨大值时段对应.垂直螺旋度随时间的变化与强降水发生的时间和强度具有明显的相关关系.

Based on the NCEP/NCAR reanalyzed data,a mesoscale model WRF was used to simulate a heavy rain process that occurred on July 21-22,2013 in Shaanxi Province.The result showed that the main reasons accounting for the rainfall were the western streching of the subtropical high,as well the warm and humid air from low-levels meeting the cold air from high-levels.Analysis of the numerical simulation results indicated that the WRF model could precisely simulate the area,center and intensity of the precipitation.The coupled structure of the low-level convergence,upper-level divergence,the strong upward movement,and the change of positive vorticity were all closely related to the vertical helicity distribution characteristics,corresponding to the crest value time.The change of vertical helicity was in a significant correlation with the time and intensity of the heavy precipitation.