一次湖南暴雨过程β中尺度系统分析与模拟

Numerical Simulation and Analysis of Meso- β Scale Systems of a Heavy Rain Process in Hunan

利用常规观测资料、卫星观测的高时空分辨率TBB资料和NCEP 1°×1°再分析资料,对2010年6月19-20日湖南一次大范围暴雨过程β中尺度系统活动特征进行了分析,并利用中尺度模式WRF对暴雨过程进行了数值模拟研究。结果表明:(1)在有利的大尺度环境条件下,存在多个β中尺度系统,主要强降雨团与地面中尺度辐合线活动相联系。(2)卫星资料分析显示,该β中尺度系统首先在α中尺度对流云团前部生成,新的β中尺度系统总是在母体对流云团前被激发出来。(3)模拟输出的高分辨率资料分析结果与观测实况相一致,β中尺度系统首先在天气尺度低涡的前部生成,并有多个β中尺度系统同时活动;在中尺度系统活动过程中,β中尺度系统向下游传播,并存在合并现象。(4)强烈发展的β中尺度系统具有从地面延伸到200 hPa以上的正涡度柱,并配合中低层辐合和高层辐散的散度结构。

Using the routine observational data,high spatial-temporal data on temperature of black bold observed by satellite and NCEP 1°×1° grid data,the evolution of the meso-β scale systems of a heavy rain process in Hunan during 19 —20 June 2010 was analyzed.Using the high-resolution output from WRF model,the structure and evolution of the meso-β scale systems was analysed.The results show that:(1) There are multiple meso-βscale systems in the large scale favorable weather situations,and the heavy rainfall groups are associated with the development of the ground mesoscale convergence lines.(2) The analysis of TBB indicates that the meso-βscale system first generated from the meso-α scale convective cloud cluster front,and new meso-β scale systems are always triggered for the rainstorm.(3) WRF model are successfully simulated.Model outputs also indicates that there are several active meso-β scale systems in the front of the synoptic scale vortex,it is a phenomenon that meso-β scale systems are combined and propagated to downstream during actively.(4) The strong development of the meso-β scale systems are supported by the favorable mesoscale dynamic configuration,namely,a positive vorticity column extending from surface to 200 hPa is coupled with strong lower-level convergence and upper-level divergence.