SWAN系统在一次暴雨天气过程分析中的应用

对2011年7月25-26日镇江市暴雨天气过程的天气背景、稳定指数和垂直风切变进行分析,利用SWAN系统研究CAPPI回波和液态水含量的相关演变特征,并检验SWAN系统下TITAN风暴识别和追踪技术的精度和水平,得出结论:7月25-26日镇江市暴雨天气过程有着较好的动力、水汽、层结不稳定以及垂直风切变条件,构成了产生大风暴雨天气的有利环境场.两个降水集中时段风暴特征有所不同,第1阶段为飑线影响,第2阶段为风暴群影响,二者均包含了普通单体和强降水超级单体,此两种单体均具有中心强度大、回波顶高度高的特征.液态水含量的演变与风暴强度吻合较好.TITAN系统对风暴未来1h内位置和轮廓预报没有30 min内预报精确度高,对处在发展、成熟阶段的风暴,30 min跟踪和预报与实况接近,对处在减弱阶段的风暴,较实况则略有滞后.

Application of SWAN System in Analysis of a Heavy Rain

The synoptic background, stability index, and vertical shear of horizontal winds in a heavy rain happened on 25 and 26 July 2011 in Zhenjiang are analyzed. By using the SWAN system, the evolution characteristics of CAPPI radar echo images and VIL are studied. The TITAN storm identification and tracing techniques in SWAN are tested. The results show that the adequate dynamic condition, vapor condition, unsteady stratified atmosphere, and strong vertical shear of horizontal winds provided a favorable environment for the heavy rain process and resulted in the strong wind weather in Zhenjiang on 25 and 26 July. The characteristics of heavy rainfall in the two time periods were different: there was a squall weather process in the first period, and a group of rainstorms in the second period; both squall line and rainstorms contain common cells and high precipitation super cells, both of which have the characteristics of strong centers and high echo tops. A good corresponding relation between the evolution of VIL and the strength of storm is obtained. For the position and outline of a storm, the one hour forecast is less accurate than 30 minute forecast. For a developing or a well developed storm, the 30 minute tracking and forecasting are close to the real case, and for a weakening storm, there is a lag.