黄河中游“7·27”暴雨过程的物理量诊断分析

Physical Elements Diagnosis of "July 27" Rainstorm Process in the Middle Yellow River

利用常规气象观测和NCEP/NCAR再分析资料,采取天气学诊断方法,对2012年7月26—27日黄河中游山陕区间的一次暴雨天气过程的物理量特征进行了分析。结果表明:在欧亚中高纬度存在阻塞形势、西北太平洋副热带高压偏北偏强的环流背景下,低层偏南风将孟加拉湾和南海的水汽输送到黄河流域中游地区,提供了此次暴雨产生的水汽条件;高层负涡度、辐散与低层正涡度、辐合相配合的动力结构,以及强垂直上升运动,是触发此次暴雨的动力机制;强降水主要发生在高能轴附近高能中心的左前方和K指数大值区内,热力对流对该次暴雨的形成起了重要作用。

Based on the conventional metrological data and the NCEP/NCAR reanalysis data,the physical elements characteristics of a rainstorm process in the middle Yellow River on July 26-27 of 2012 had been analyzed by using synoptic meteorology diagnosis analysis method.The result indicates that under the background of advantageous circulation of blocking high existing in the Eurasian mid-high latitude region and the northwest Pacific subtropical high more northerly and stronger,water vapor of the middle Yellow River basin mainly comes from the Bay of Bengal and the South Sea by lower-level south wind,which supplies vapor condition for the rainstorm process.The divergence of negative vorticity on higher level matches the convergence of positive vorticity on lower level,and the significant vertical upward movement is the dynamical mechanism to trigger this process.The heavy rainstorm occurs mainly in the front left of the high energy center near the high energy axis and in the maximum of the K index.Thermal convection plays a key role to this rainstorm process.