平流计算方案对一次江淮梅雨暴雨模拟的影响

为对比MM5模式中原中央差平流方案和新型半拉格朗日插值计算方案CIP的模拟差别,针对2006年7月5~6日的江淮流域梅雨暴雨过程进行了模拟,证实了CIP方案对这次暴雨过程具有较好的模拟效果,它更加真实地再现了梅雨锋降水的中尺度结构,改进了模式的模拟结果,特别是对梅雨锋内对流运动结构的模拟,显示了CIP对刻画大梯度分布和强对流运动计算的良好性能。平流的高精度计算对提高这类系统的模拟精度非常重要。

The Influence of Advection on the Meiyu Rainstorm Simulation in Yangtze River and Huanhe Damins

By comparing the semi-Lagrangian scheme CIP with the central finite differencing scheme(CFD) in the mesoscale model MM5,a Meiyu heavy rainfall case during 5~6 July 2006 has been studied in this paper.Additional variables of the spatial gradient are used and predicted in the CIP scheme to increase the accuracy of interpolation with little increase of computational cost.The result shows that the simulated mesoscale structure of the meiyu front by the CIP scheme is better than by the CFD one,even thougy both the schemes show the simulated large-scale wind and moisture distributions very well.The CIP scheme improves both the rain amount and rainfall region in the simulaton,because of the location of the discontinuous zone of the front being effectively simulated.The numerical diffusion in CFD makes it not so efficient to describe a frontal interface as the CIP scheme.The results display that it is very important to improve the transport computation for the simulation of this kind of frontal systems,where sharp variations of water vapor and temperature exist across the front.