黄土高原低值对流有效位能区中β尺度大暴雨综合分析

Comprehensive Analysis for Meso-β-Scale Heavy Rainstorm Occurred in the Area of Low Convective Available Potential Energy on Loess Plateau

为了提高对黄土高原中β尺度暴雨的预报和预警能力,利用中国气象局气象资料综合处理MICAPS系统提供的资料及多普勒雷达资料,对2007年8月28日黄土高原在低值对流有效位能区发生的一次中β尺度暴雨天气过程进行了大尺度环境场和物理量的诊断分析以及三维流场结构分析。结果表明:这次黄土高原中β尺度大暴雨主要是由3次中β尺度强对流单体活动造成的;地面风速脉动、地面能量比高值舌配合上下游能量比大梯度区的生成,是中β尺度暴雨触发机制之一;对流层低层倾斜涡度的发展、纬向双次级环流圈的形成,为暴雨的发生、发展和维持提供了动力机制;列车效应是形成降水时间长、累积雨量大的重要因素;在多普勒雷达径向速度场上看到,暴雨区上游从对流层中层到对流层高层气旋性环流的发展和暴雨区对流层中高层西南急流的发展和稳定,也是形成暴雨的动力机制之一。

In order to improve the capability of forecast and warning of rainstorm in Loess Plateau, the process of a meso-β-scale heavy rainstorm is analyzed using the normal observation data, Doppler radar data and others, which occurred at the Loess Plateau on 28 Augast 2007. The results show that the three meso-β-scale strong covective cells were acting on the rainstorm; both the surface wind speed pulsing and the generation of high tongue of the surface energy ratio and the bigger gradient area of the surface energy ratio that lie on the two sides of the high tongue of the surface energy ratio provide the triggering mechanisms for the generation of the meso-β-scale heavy rainstorm. The development of slantwise vorticity and the couple sencond circulation system along the latitude provide the dynamical mechanism for the genera- tion and development and maintenance of the rainstorm. The train-effect is an important factor that the rainfall last and increase accumulation rainfall. At the field of Doppler radar speed, the development o{ the cyclonic circulation on the rainstorm area upstream from the tropospheric low level to the tropospheric high level and the development and maintenance of the southwest jet from the middle level to the high level provide the dynamical mechanisms for the generation of the heavy rainstorm too.