云南省大理州“2011.7.14”强降水过程诊断分析

Diagnostic analysis of the heavy precipitation process occurred in Dali prefecture on July 14th,2011

2011年7月14日云南省大理州出现大范围的大雨、暴雨天气过程.本文利用常规气象资料、风廓线雷达资料等,对强降水发生前的天气形势、物理量场特征及风廓线雷达资料特征等进行分析研究.结果表明:季风槽和切变线是这次强降水过程的主要影响系统;深厚的高湿气层的形成,为强降水的发生提供了足够的水汽条件;强降水发生前高层辐散低层辐合形势比较明显;高层的负涡度和强辐散对低层产生抽吸,促使低层辐合上升运动增强,触发对流不稳定能量释放.本州处于中低层不稳定的高能舌内;表征动力热力作用的综合诊断物理量E指数对强降水的落区有较好的指示意义;风廓线雷达资料中负垂直速度对降水出现时间及强度有一定预示作用;信号噪声比与降水强度有很好的对应关系;水平风资料能直观地反映出降水过程中的风场变化特征,强降水出现期间水平风随高度存在明显的不连续现象.

A heavy rainfall process occurred in Dali prefecture on July 14,2011.The routine observed data and the wind- profiling radar data are used to analyze the impact system,the characteristics of physical quantities and so on before and during the rainfall process.The results show that;the mainly impact system of the regional heavy rainfall process was the monsoon trough in 500 hPa and the shear line in 700 hPa;The formation of deep high- humidity layer provided plentiful vapor for the heavy rainfall process.Other characteristics of physical quantity field including lower- level convergence,upper- level divergence,lower level positive velocity and upper- level minus velocity were obvious before the heavy rain.Meanwile,Dali district was located in the area with instability and high energy tongue at the middle low lever.The E index which characterizes dynamical and thermal diagnosis has certain indication to the area of heavy precipitation.The negative vertical velocity of wind profiler radar data showed foretelling effects on the occurrence of the heavy rainfall and its intensity.There was a very close relationship between signal- to — noise and the intensity of heavy rainfall.And the horizontal winds showed obvious discontinuous feature with height changing during the rainfall process.