A sensitivity experiment to the orographic effect on the Bengal storm of Mala during its landing

The Bay of Bengal is among the eight areas where tropic cyclones appear frequently. When a Bengal storm moves northward or eastward, it will affect weather over the Qinghai-Tibet Plateaun and the westnorthern part of China, and also the large-scale topography of the QinghaiTibet Plateanu and the YunnanGuizhou Plateau will affect the moving path of the Bengal storm. To analyze the effect of the this topography on the path, the structure and the precipitation for the Bengal storm. The Bengal storm of Mala landfall process from 29 to 30 April in 2006 is simulated by the Weather Research and Forecast meso-scale numerical model (WRF).The results show that although there are certain errors between the simulated track and intensity for the storm and the observation, both the general moving tend and the intensity are properly simulated with small errors. The WRF can well simulate the track and precipitation of Mala occurring in Yunnan province. The sensitivity experiment results from the respective schemes with the full height, half height and zero height effect on changes in the storm track are discussed, and the circulation, the dynamical structure and the precipitation over Yunnan are analyzed as well. The results show that before the storm landfall, the topography affects the storm structure in an indirect way, with its structure in higher levels becoming slant. During its landfall, the topographic countercheck and friction are able to significantly affect the moving track and velocity of the storm. After its landfall, the topography caused the storm intensity to weaken and its moving velocity to quicken. On the other hand, its structure goes through the course from a basic symmetric storm to an asymmetric one with evident baroclinicity. The topographic effects on the precipitation are embodies in the two aspects, one is to make the precipitation increase and another is to cause the storm intensity to weaken and thus the precipitation to decrease.