“7·30”大暴雨的数值模拟及贺兰山地形影响分析

The Contribution of Helan Mountain to the Formation of a Heavy Rainstorm Occurred over Yinchuan Plain by Numerical Simulation

对2012年7月30日大暴雨过程应用常规资料、中尺度数值模拟进行分析。结果表明:此次大暴雨是在大环流形势背景下,贺兰山地形对底层风场的辐合触发了中低层不稳定层结;700 hPa偏南暖湿气流、850 hPa切变及地面中β尺度切变线,给短时强降水的产生与维持提供了有利的水汽和动力条件;经对贺兰山地形影响的强降水强度数值模拟,得出贺兰山地形对银川大暴雨的形成有明显的正贡献。

A heavy rainstorm occurred over north Ningxia on July 29 th 2012. In this paper, this heavy rainstorm event was analyzed by using the upper-air observation data, ground automatic weather station data and products of WRF model. The result shows: this heavy rainstorm occurred at the backdrop of beneficial large-scale circulation; and topography of Helan Mountain caused the lower wind convergence and detonated the heavy rainfall; the main influencing weather systems are southerly warm-wet air at 700 hPa, shear line at 850 hPa and meso-β shear line at ground; These weather systems stored and detonated unstable energy, and provided plentiful vapor and dynamic for the occurrence and maintain of short-term heavy rainfall. The results of numerical simulation show The windward side of Helan Mountain on the east side can make their easterly wind speed increases, develop middle vertical movement, and increase rainstorm center precipitation by 42.3%.The Helan Mountain terrain have obvious positive contribution to the formation of a heavy rainstorm over Yinchuan Plain.