中文摘要：

选取2004年6月23日一次梅雨锋MCS暴雨过程，在天气分析的基础上，利用非静力中尺度模式MM5（V3．6）进行了数值模拟。对于可分辨尺度的降水，采用Reisner霰显式方案，对云内微物理过程特别是对各种水成物的源项进行了详细分析。结果表明：冷云过程是此次降水的主要云物理过程。云中以霰和雪为主要的降水元，尤其霰的作用最大。在强降水时段，雨水的主要源项都与霰有关，霰的生长过程中冰相粒子与过冷水的碰并以及霰的凝华过程最为重要。零度层上方存在着丰富的过冷水，最大的云水含量中心也在过冷层中。在过冷层中冰相粒子主要通过凝华过程和碰并过程增长，MCS发展强盛期冰晶与过冷水的碰并增长要大于液水的蒸凝过程的增长。最后给出了本次梅雨锋上MCS降水云系的三层云结构及微物理过程模型。

英文摘要：

A rainstorm process occurred on 23 June 2004 is selected to get further comprehension of the cloud physical processes and precipitation mechanisms of the mesoscale convective system （MCS） in Meiyu front. Numerical simulation of this weather process is carried out using the nonhydrostatic mesoseale model MM5 （V3.6） on the basis of synoptic analysis. The nonconvective precipitations are calculated by using the Reisner graupel explicit scheme. Cloud microphysical processes, especially the source terms of hydrometeors, are analyzed in detail. It is demonstrated that the cold cloud process is the primary cloud physical process, and the graupel and snow are the primary precipitation elements in the clouds. During the heavy rainfall hours, the leading source terms of rain water are all related to the graupel. The most important factors in the course of the growing of graupel are the coalescence of the ice phase particles and supercooled water and the condensation of the graupel. It is shown that plenty of supercooled water exists over the 0 ℃ level and the biggest cloud water center is also at this supercooling level. Ice phase particles grow by means of the Bergeron and coalescence process at the supercooling level . The coalescence of the ice crystal and supercooled water during the intensive developing of MCS is much more important than that of the evaporation and deposition process of liquid water. The three-level cloud structure and the microphysieal process model of the MCS precipitation system in the Meiyu front is presented finally.