一次强降水过程中尺度系统发生发展动力机制的诊断分析

利用1°×1°经纬度NCEP/NCAR再分析资料、地面1h观测降水资料和TRMM卫星产品资料,分析了2009年6月8～9日引发贵州南部的强降水天气过程的中尺度对流系统活动,并进一步研究了大气正压非平衡强迫、湿斜压热动力耦合强迫在强降水天气发生发展与维持过程中的作用。结果表明：8～9日贵州南部的强降水主要是由中尺度系统的发生发展引起的。南海季风不仅给贵州南部强降水区带来充足的水汽,同时也带来足够的能量。正压非平衡强迫在降水的开始阶段与降水落区有较好的对应关系,是强降水的启动机制。斜压热动力耦合强迫在降水的维持阶段,特别是当大气层结转为弱湿中性时,其分布和强度与中尺度对流系统和降水的强度与落区有较好的对应关系,可能是强降水的维持机制。

Diagnostic Analysis on the Dynamic Mechanisms of Occurrence and Maintenance of Mesoscale System in a Heavy Rain

With 1°×1°（longitude×latitude） NCEP/NCAR reanalysis data,surface observed hourly precipitation and TRMM ancillary data products,an analysis is made of mesoscale convective systems triggering heavy rain in southern Guizhou province during 8-9 June 2009 to study the role of barotropic non-equilibrium force and baroclinic coupling forces between dynamic and thermodynamic fields at the stage of occurrence and maintenance of heavy rain.The results show that： the large area rainfall during 8-9 is produced by mesoscale convective system.Moisture transporting to the heavy rain area from the South China Sea is main moisture source supplying severe precipitation,and it also brings enough energy to the south of Guizhou.The barotropic non-equilibrium force＇s negative value region is highly correlated with rainfall at the starting time for precipitation,and it is the dynamic mechanism of heavy rainfall maintenance.The baroclinic coupling forces between dynamic and thermodynamic is well corresponding with rainfall and the mesoscale convective system during the stage of heavy rainfall maintenance,especially when the area atmosphere＇s stratification is neutral or little stability.