网格嵌套技术对一次中尺度对流系统降水过程模拟的影响

利用非静力中尺度模式MM5对2002年7月22日12:00~23日12:00(世界时,下同)长江流域的一次梅雨锋暴雨过程进行数值模拟试验,主要讨论了网格嵌套技术对降水和中尺度对流系统的影响。结果表明:三重嵌套在D1,D2域选用积云参数化方案后,模拟的雨区收缩,虚假降水中心相对减少,降水强度及分布更接近观测值。在模式非线性动力、热力及湿物理过程共同驱动下,通过嵌套网格的双向相互作用,使可分辨云尺度的细网格域D3将其信息通过嵌套边界向次细网格域D2传递,然后再通过D2域边界向粗网格域D1域传递。同样,动力、热力反馈也会反向进行。结果将有助于改进各网格域的预报效果。但对D1网格域系统位置及其发展演变过程的影响相对小些;另外,通过双向多重嵌套,可提高模式预报区域的分辨率,特别是提高模式关键预报区域的分辨率,这也就有可能改进预报的中尺度物理场,使其能够较真实地描写大气实况。

Impact of Nested-Grid Skill on a Mesoscale Convective System Rainfall Event

The numerical simulation experiments are conducted using the nonhydrostatic mesoscale model MM5 for a heavy rainstorm event along Meiyu front in the Changjiang basin from 12:00 on 22 to 12:00 on 23 July 2002.The impacts of nested-grid skill on rainfall and mesoscale convective systems are discussed.The results show that the rainfall area shrank reasonably and the spurious rainfall centers comparatively reduced so that the rain intensity and distribution were more approaching to the observational one when the CPS was adopted in the D1 and D2 of triple nesting grid domain.Due to the driving of model nonlinear dynamic,thermodynamic,moist physics process,adopting the two-way interaction multiplenesting mesh technique can make D3 resolve the cloud scale information and pass it to the D2,then to D1 throuth D2.And the dynamic and thermodynamic feedback can do reversely.It can improve the prediction of all nesting grid,but there is a little effect to the position,developing and evolvement of the synoptic system in the D1.On the side,Adopting multiplenesting mesh technique can improve horizontal resolutions of the model forecast area,especially the key forecast area,which can also obtain the improved physical fields.The model can describe what is actually happening about the atmosphere by this way.