天津局地暴雨特征及落区预报分析

利用常规观测资料分析2009-2011年天津地区33次局地暴雨天气过程的影响系统。对局地暴雨天气发生前的大气环境物理参数进行统计，对比不同影响系统下预报着眼点的差异。结果表明：天津局地暴雨主要发生在蒙古冷涡、东北冷涡、高空槽前以及高空槽后四种天气系统的影响下。蒙古冷涡系统下应以整层良好的水汽和涡旋系统东南象限深厚的辐合上升运动为着眼点；而东北冷涡系统下则需关注低层水汽条件充沛和中层强烈的辐合抬升；高空槽系统下在动力、水汽以及能量条件配合较为均衡；而槽后型系统影响下若发生局地暴雨,各种强对流参数特征则最为显著。在此基础上，通过典型局地暴雨过程对强降水落区进行诊断表明，天津构造加密探空由于充分考虑了近地面的温湿风特征，计算所得的可降水量、对流有效位能以及地面至3km高度的垂直风切变对局地暴雨落区具有良好的指示性。同时，个例研究也表明TJ-WRF对局地暴雨天气过程有较好的预报能力，综合应用模式物理量结果能较好地预报局地暴雨落区。

Characteristics of local rainstorm and its falling area forecast in Tianjin

Based on conventional observed data from 2009 to 2011 in Tianjin, weather systems of 33 local rainstorm processes were analyzed. Atmospheric physical parameters were analyzed statistically before local rainstorm happened, and key points of forecasting under different weather systems were compared. The results show that local rainstorms often occur under four weather systems, namely, Mongolia cold vertex, northeast cold vertex, before or after upper trough. Plenty of water vapor throughout the atmosphere and deep convergence ascending motion on the southeast quadrant of vortex system are main factors of forecasting under Mongolia cold vertex, while low-level moisture conditions and middle-level strong convergence uplift are emphasis of forecasting under northeast cold vortex systems. Dynamic, water vapor and energy conditions under upper trough system are more balanced. However, all kinds of strong convective characteristics are very significant if the local rainstorm happens after upper trough. Diagnosis of falling areas of typical local rainstorms suggests that precipitable water, convection effective potential energy and vertical wind shear between ground to 3 km height are of indicative to falling area of rainstorm, because these three parameters are calculated based on data in Tianjin radiosonde station where temperature, humidity and wind are considered fully. At the same time, the case analysis shows that a TJ-WRF numerical model has a good ability for predicting local rainstorms, and physical parameters calculated by the model can be used to well forecast the local rainfall area.