Numerical Experiment of Terrain Effect of a Vortex Rainstorm Process on East Side of Qinghai-Xizang Plateau

Because of different degree of deviations between model terrain and real terrain, and important effect of the terrain on precipitations, using WRFV3.1 model, the influence of topography on the numerical model forecast was analyzed as to an heavy precipitation in Sichuan basin on 20-22 July 2008 through the meteorological station elevation changing the model grid point terrain height method and introduction of the more realistic model terrain. The results show that more real terrain in the model is introduce to increase the intensity of precipitation, the location and occurring time of severe precipitation center are improved; the ascending motion and cyclonic shear in middle and lower troposphere increase significantly, the vortex position is improved, which result in more severe precipitation occurrence and the improvements of the location and occurring time. The changing of terrain height at single point cause meteorological elements changes around the point. The variation of meteorological element is more remarkable with the increasing of terrain height change in the model. The more real terrain makes the characteristics of the humidity ascending, height decreasing and temperature increasing more significant. Variations of meteorological elements are in favor of low value system strengthening and precipitation intensity increasing after the topography change. The change of terrain height at single point cause a slight deviation of initial local meteorological elements, and the deviation further increases with integration time. How to construct terrain model in complex terrain area, how to consider the influence of topography is particularly important and needs to be treated with caution. So, if a terrain processing method of a regional model can be considered that real terrain height is introduced into the model through some key points to improve the prediction effect，especially improve precipitation prediction effect under the precondition of ensuring the integral stability of the model.