“7.21”北京特大暴雨个例分析Ⅱ:动力条件分析

Analysis of a Torrential Rain Occurring in Beijing on 21 July 2012 Ⅱ: Dynamics Analysis

利用FNL资料、卫星TBB资料以及北京站点探空资料，对2012年北京“7．21”特大暴雨过程的垂直运动条件、不稳定条件和TBB图像特征进行了诊断分析。结果表明，7月21日北京地区整个对流层盛行上升运动，上升运动经历了一个由弱到强的过程，18：00～21：00垂直速度强度最强，最大达－3 Pa／s，该阶段对应的北京降水强度最强；大暴雨发生前，CAPE值、地面抬升指数等多个对流环境参数均达到暴雨指标，对暴雨预报有较好的指示意义；利用TBB资料分析中尺度系统表明，此次暴雨过程中中尺度对流系统起始是镶嵌在低槽云团中发展起来的，TBB演变趋势与降水有很好的对应关系，对此次暴雨预报有良好的指示作用。

FNL （Final the Operational Global Analysis） data, TBB （Black Body Temperature） data, and sounding data in Beijing station were used to analyze the vertical movement condition, unstable condition and TBB image feature of a torrential rain occurring in Beijing on 21 July 2012.The results showed that upward movement prevailed in the whole troposphere.The vertical velocity increased on July 21 in Beijing area. The vertical velocity was the strongest from 18：00 to 21：00 when the precipitation intensity was the greatest .The biggest vertical velocity was -3 Pa/s.Before torrential rain occurred, many convective environment parameters including CAPE value and surface uplift index all reached the index of torrential rain, and had relatively good indicative significance for heavy rain forecast.TBB data were used to analyze the mesoscale sys-tem, indicating that the developing mesoscale convective system was set in the cloud of trough in the beginning .TBB evolutional trend had very good corresponding relationship with precipitation, so TBB was the good indicator of the rainstorm.