一次暴雨过程数值模拟与诊断分析

利用NCEP/NCAR分辨率为1°×1°再分析资料和气象台实测降水资料及TRMM 3 h降水资料，采用WRF中尺度数值模式，对2010年7月22日发生在黄河流域中游南部的一次暴雨过程进行了数值模拟及诊断分析。结果表明：WRF模式能较为成功的模拟出本次暴雨过程。此次暴雨在大尺度环流形势上，是由于西太平洋副热带高压与河套低压槽的共同影响产生的；来自印度洋、中国南海的大量水汽输送为暴雨提供了充足的水汽来源。处于200 hPa的高空急流，由于地转调整激发出了中尺度重力波，使用散度场、云水分布，能够确定中尺度重力波的存在和移动方向。在利用模拟资料分析重力波对甘肃省东部地区暴雨产生的原因时得出：高空急流中产生的中尺度重力波与低层大气对中尺度重力波的吸收作用，共同导致了该地暴雨的发生。由高空急流风向和非线性平衡方程的数值分布情况，可以提前判断中尺度重力波发生的区域和移动方向，从而能够提前对暴雨可能发生的区域和时间作出预报。

Numerical simulation and diagnostic analysis of a rainstorm process

Based on the NCEP/NCAR reanalysis data with the resolution of 1° × 1°and the observational precipita- tion as well as the 3 h interval TRMM precipitation data,a heavy rain process on July 22,2010 in the south of the middle of the Yellow River was analyzed using a mesoscale Weather Research and Forecasting model（WRF）. The results indicate that this rainstorm is simulated successfully by the WRF model. This rainstorm is generated together by a subtropical high over the West Pacific and a low trough in the Hetao area under a situation of large scale cir- culation. The abundant water vapor source is from the Indian Ocean and the Southern China Sea. The mesoscale gravity wave is excited by the upper level jet stream on 200 hPa. According to the divergence field and cloud water distribution, the existence and moving direction of the mesoscale gravity wave could be determined. The reasons that effect of gravity wave on rainstorm generation in the east area of Gansu province are analyzed based on the simulation data. It shows that the mesoscale gravity wave in upper level jet and its absorption in lower atmosphere cause the formation of the rainstorm. According to the wind direction in upper jet and values distributions of the nonlinear balance equation（ NBE）, the area and moving direction of the mesoscale gravity wave could be deter- mined in advance, so the falling area and time of rainstorm could be forecasted.