Jac Rape Rain-scale System Development Of Numerical Experiments And Mechanism Analysis

The storm rainfall during the Jianghuai MeiYu period is one of China's representative meteorologic disasters. After the disaster caused by continual heavy rainstorm during the Huaihe's MeiYu period since 1991, the abnormal rainstorm weathers during the MeiYu period occur again in June and July, 2003. Currently, many meaningful researches about continual heavy rainstorm during the MeiYu period have been done by domestic and foreign meteorologists and a lot of meaningful results have been achieved. However, due to observation data and complexity of MeiYu weathers itself, the mechanism of MeiYu weathers about its occurrence, development and evolvement has not understood completely by now. What's more, the deeper research about the law of meso-scale and small-scale weather process is needed.Using the new generation mesoscale model of the Weather Research and Forecast (WRF) model, the mesoscale numerical simulation of the heavy storm rainfall of the Jianghuai Mei-yu front during 4 July 2003 was carried out. The simulated results show that the heavy rainfall and the evolution of the mesoscale system's occurrence and development are well described. With the simulated results of the high resolution of space-time, from the aspects of thermodynamic, dynamical, moist available energy and moist potential vorticity, the direct effect mesoscale system was analyzed to this weather process, including mesoscale low level jet, mesoscale vortex etc. Meanwhile, its features and physical mechanism of the formation and development are further discussed to seek for some basis for deeper research and storm rainfall forecast.The results show that mesoscale low level jet, the perturbation in the high level troposphere can enhance and accelarate occurrence and development of mesoscale system; convergence of low level and divergence of higher level are dynamical condition of storm rainfall system. Dynamical and thermodynamic structure of mesoscale low vortex is advantaged to quick development. The accumulation and transportation of moist available potential energy and therelease of the condensation heat offer the material condition for this heavy rainfall. Under the condition of the air's movement through the stiff moist isentropic surfaces, the development of vertical vorticity of mesoscale low vortex system is accelerated due to the slantwise vorticity development, and to form stronger convective system, so as to result in heavy storm rainfall. Mesoscale low vortex's "wandering" at eastern Anhui province and stronger development at the stiff moist isentropic surfaces are very important to this heavy rainfall process. It was pointed out that the horizontal distribution of the moist available energy is helpful for heavy rainfall, and one of the enhanced mechanism of mesoscale low vertox is slantwise vorticity development.