中文摘要：

利用2013年“华南季风强降水外场试验与研究”的外场试验数据、美国NCEP FNL资料和卫星云顶黑体辐射温度资料，对2013年5月7—17日华南地区出现的两次强降水过程（7—12日和14—17日）中的高低空环流以及相关气象要素场的变化进行了对比分析。中国南海夏季风于5月第3候建立，两次过程分处于夏季风爆发前后。通过对比影响两次强降水过程的主要环流系统如南亚高压、高空副热带西风急流、500 hPa环流型、水汽来源等，指出影响两次强降水过程大尺度环流场之间的显著区别，说明南海季风爆发前后大尺度环流场对暴雨影响的典型差异。7—12日过程主要受北方锋面影响和南方暖湿气流辐合作用，导致华南地区出现南北两条雨带。14—17日过程则由于季风爆发后强的暖湿空气活动致使华南地区对流活跃，从而形成一条位于广东北部的雨带，此次过程强降水比第1次过程集中且对流性更强。两次降水过程的内在物理机制是一个准平衡态的热力适应过程，由于第2次过程降水更强，导致热源作用明显增强，动力向热力的适应过程也更显著。利用探空资料揭示出两次过程暖区暴雨大气热力和动力条件存在显著区别，7—12日南海季风爆发前的暖区暴雨主要受低层强垂直风切变导致的大气斜压不稳定影响；14—17日南海季风爆发后的暖区暴雨主要受高低空急流的强耦合作用影响。

英文摘要：

Based on the field observation of the South China Monsoon Rainfall Experiment （SCMREX）,the National Centers for Environment Prediction （NCEP）final （FNL）operational global analysis data and the equivalent temperature of the black-body at the top of the cloud （TBB）data,a comparative analysis of the circulation and related meteorological elements between two severe rainfall events （7-12 and 14-17 May）in South China in 2013 was conducted.The South China Sea （SCS）sum-mer monsoon established in the third pentad of May 2013,just in between two severe rainy stages.There exist significant differences between two events in the major circulation systems,e.g.the South Asia High （SAH）and the subtropical high westerly jet at the higher levels,the circulation pattern at 500 hPa,the water vapor transportation,etc.It indicates typical va-riances of the effects of the large scale circulation on severe rainfalls before and after the onset of SCS monsoon.During 7-12 May,influenced mainly by both the southward invasion of cold front and the convergence of warm moist airflow from the tropi-cal region,the two rain-bands appeared in northern and southern South China.Differently,due to the vigorous convective ac-tivity over South China caused by the strong warm and moist air after the onset of monsoon,the rain-band was formed in the north of Guangdong Province during 14-17 May,with more concentrated and convective precipitation than the former event. The underlying physical mechanisms for the two severe rainfall events are quasi-balanced thermal adjustment process,which is better reflected during the second event because of heavier precipitation.The sounding data in Guangdong are also applied to re-veal differences of the atmosphere dynamic and thermodynamic effects between the two warm sector rainstorms.The warm sec-tor rainstorm during 7-12 May occurred under the condition of the atmospheric baroclinic instability induced by the strong low-levels vertical wind shear.However,the strong coupling between the hi