秦巴山区东部一次区域性暴雨过程分析

利用常规探空资料、NECP再分析资料、卫星红外云图资料等,通过天气学分析及动力诊断分析对2009年7月10～11日安康、商洛一次大范围暴雨过程进行机理分析。结果表明,此次过程发生在"两槽一脊"的环流背景下,高原上低槽东移,副高维持在长江地区以及低层多低涡活动等是产生暴雨的主要环流形势;低层"人"型切变有利于水汽在暴雨区堆积,水汽通量在700 hPa表现好但聚集程度微弱,850 hPa雨区附近水汽剧烈辐合,弥补了水汽输送较弱的不足;高层辐合较弱,但850 hPa强辐合层产生的上升运动十分有利于将水汽输送到高层;暴雨落区附近K指数维持在36℃以上,大值出现时间比强降水发生时间提前,提前时间与80℃θse高能轴出现时间有关;TBB云图表明雨区上空锋面云系中不断有对流单体生成与消失,配合上有利的水汽和动力条件,从而产生暴雨。

Anylysis of A Regional Torrential Rain in East of Qinling-Bashan Mountainous Area

Based on data of conventional observation,NCEP reanalysis,and infrared satellite images,a regional torrential rain event occurred in Ankang and Shangluo between 10th and 11th of July in 2009 was analyzed through synoptic analysis and dynamic diagnosis method.The results showed that the event occurred under a circulation pattern of two troughs with a ridge.A trough moved eastwards from the Tibet plateau,while the subtropical anticyclone maintained over Yangtze River,accompanied with active low-vortex motions on lower levels and favorable dynamic and thermal condition,which were the pivotal causation of this torrential rain event.On lower levels,wind shear formed a "人"shape which contributed to accumulation of water vapor in rain site.The water influx was good at quantity on 700 hPa level but showed weak accumulation.On 850 hPa level over the rain site,the water vapor converged fiercely,which covered the weak water transfer.Although there was a weak convergence on upper levels,the strong convergence on 850hPa level was favorable for the water vapor transferring to upper levels.The K index maintained above 36 ℃ according with the rain site.The appearance of peak value of K index was earlier than that of the torrential rain,which was correlated to the emergence of the high energy axis of 80 ℃.Meanwhile,the infrared cloud images indicated the consecutive genesis and disappearance of convective cells among frontal cloud system with favorable water vapor and dynamic conditions contributed to the occurrence of the torrential rain.