| The contribution of sophisticated terrain is a key factor of the generation of strong convective weather which is difficult to forecast. In order to improve rainfall simulation of South China in the model, the impact of terrain must be taken into account. In this paper, the rainstorm in warm section occurred in South China during the period from 5-7 June 2008 is investigated by using NCEP/NCAR objective analysis data with resolution of 1°×1°four times a day, the temperature of brightness blackbody on cloud-top(TBB) data for l-hour,and the mesoscale model WRFV3.1.1.It is found that the formation of low-vortex at 850hPa, the divergence in the behind of the jet stream at 200hPa, the southwest airflow from the northwest of subtropical high and the short-wave trough which towards the east provide the large-scale and sub-weather-scale circulation background field of the rainstorm. In addition, the water vapor from the South China Sea provides a good condition for this rainstorm.In this article, in order to realize the influence of this terrain, the rainstorm in warm section occurred in the southeast of Yun Wushan will be investigated for two experiments by one using Gravity Wave Drag by Orography (GWDO) Parameterization which is additional in WRFV3.1. They have been simulated by using the analysis of NCEP (1°×1°) from 5 to 6 June 2008. With an analysis of the comparison of the two experiments, the results are as follows:Sensitivity experiment achieved a success in the simulation of the center and strength of the rainstorm. It succeeds to reappear the large-scale circulation and the evolution of state formed during heavy rain, and successfully duplicates the mesoscale low-voxtes whose temporal evolution characteristics are in accord with the movement of the precipitation center, while the control experiment failed. The using of GWDO Parameterization effectively reduces the zonal wind deviation in the middle troposphere and reasonably simulates the dynamic uplift of airflow caused by terrain. According to experiments, the energy divergence in the middle caused by orography-induced gravity wave is the main cause of rainstorm, which enhances the vertical movement and makes the precipitation strengthen and relatively concentrated.The results of topography experiments show that, the precipitation intensity and its position has much to do with terrain. The intensity of precipitation is much weaker than control experiment, and the rainfall center position appeared more northward whatever the terrain of Yun Wushan is flat or it is reduced in proportion. The rain belt appears Oval-shaped distribution after the terrain increased in proportion, while its precipitation at center is 270mm which is smaller than control experiment, and its area is close to real state. Furthermore, the change of terrain has evident impact on the generation and position of theγmesoscale lee vortex during the period of heavy rain.This paper uses HYSPLITv4.9 three-dimensional air flow trajectory model to track the trajectory of the upper and lower flow at the center of the rainstorm, by employing more reliable high-resolution data sets obtained by WRF model. The results show that the cold air has little or no effect on the rainstorm, and the warm flow is mainly from the South Sea. Upper-level divergence occurs before the low-level convergence, and the upper-level divergence of South Asian High may be one of the induced causes of the heavy rainfall. From the relationship between the vertical component of convective vorticity vector (CW) and rainfall, the vertical component of convective vorticity vector (CW) is highly correlated with rainfall in time and space, and it is a good indicator for tracing the development of rainstorm system.
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