山东“99·8”大暴雨维持机制的数值模拟

A Numerical Simulation of the Heavy Rainfall MaintainingMechanisms in Shandong Area

利用中尺度大气非静力模式 MM5对山东 1 999年 8月 1 1～ 1 2日的大暴雨过程进行了数值模拟。将模拟的气压场、风场、相对湿度场、降水与实况进行对比检验 ,在模拟效果比较合理的情况下 ,着重对大暴雨的维持机制进行了研究。结果表明 :位于我国东北、渤海和山东上空的东北西南向的锋面系统、位于锋面西南端山东江苏上空的苏鲁中 -α涡旋及其诱发出的位于其北部的中 -β涡旋是影响山东大暴雨的天气尺度系统和中尺度对流系统 ;中 -α涡旋的东支气流—东南风为中 -β涡旋输送水汽 ;锋面系统抬升了中 -β涡旋北部的东南暖湿气流 ,形成垂直上升运动 ,并形成雷暴云团 ,同时激发出新的对流单体 ;雷暴云团在西移的过程中 ,受到泰沂山区的抬升作用 ,在山前也形成强烈的垂直上升运动 ;因此 。

A case of heavy rainfall in Shandong in 11～12 August, 1999 is simulated by using the meso scale nonhydrostatic model MM5. Compared the simulated results of pressure field, wind vectors, relative humidity and precipitation with the real results, in the condition of relatively right, the maintaining mechanisms of the heavy rainfall is analysed emphasisly. The results show that the front of northeast southwest orientation in Baohai Sea and Shandong area, the meso α vortex of the southwest end of the front in Shandong and Jiangsu areas, as well as the meso β vortex in north of the meso α vortex are synoptic system and meso scale convective systems affecting the heavy rainfall in Shandong; the southeasterly wind of the meso α vortex in its easterly flow transports the water vapor to the meso β vortex; the front lifts the southeasterly warm moist inflow of the meso β vortex, generating the vertical motion upward and the storm cloud in the meso β vortex, and arousing a new convective cell; the storm cloud moving slightly westward is lifted by TaiYi mountain area, generating strong vertical motion upward; therefore rainfall is maintained.