“98.5”华南前汛期暴雨的非静力数值模拟和中尺度系统分析

Nonhydrostatic Numerical Simulation and Analyses on the Mesoscale Systems of “98.5” Heavy Rain in the South China Preflood Season

为了对华南暴雨进行深入的数值模拟研究,在对1998年5月23～24日(简称'98.5')华南暴雨进行天气分析的基础上,利用非静力中尺度数值模式MM5对该次暴雨过程进行了数值模拟.数值模拟结果和客观分析结果的比较表明,模拟结果可以再现造成暴雨的大、中尺度环流条件.造成此次暴雨的中尺度系统具有暖心高湿结构,高空辐散,低空辐合及对应的强上升运动和气旋性涡柱是造成这次暴雨的动力学机制,低空偏南气流对这次暴雨的产生和发展起着重要的作用.模拟的降水中心与观测的较接近,位置略偏南、偏西,雨量略小,但降水时段和雨区模拟较好.降水发生在喇叭口等有利地形;高低分辨率的地形资料对本次降水的模拟结果影响不大.

In order to study in detail the heavy rain event of South China, the simulation for !98.5' heavy rain using the nonhydrostatic mesoscale numerical model was conducted on the basis of synoptic analysis of heavy rain on 23~24 May 1998 (!98.5'). The comparions between the simulated results and objective analysis have shown that the simulated results reappeared the large- and meso-scale circulations. The mesoscale system producing this heavy rain has the warm and wet core. Divergence on upper levels, convergence on low levels,and ascending motion as well as the cyclonic vorticity column are the dynamic mechanisms causing the heavy rain. The southwest jet over low levels is importantfor this heavy rainfall. The centre of the simulated precipitation is close to that of the observed, but its location is southward and westward, rainfall is light. Their simulated precipitation is smaller than the observed. Rainfall usually occur in favorable terrain in where is the bell-mouthed. Simulated results using differentterrain data of high or low resolutions were similar.