Abstract:Comparison and analysis on two successive torrential rain events occur red in Beijing on 31 July and 1 August of 2006 were conducted using high spatial temporal resolution data, such as auto weather station (AWS) network data, Do ppler radar data, wind profile data, satellite images and NCEP analysis data. It i s revealed that the two successive torrential rain events are affected by the sa me large scale trough at 500hPa from Hetao area of North China, but in their different temporal phases. Although the two torrential rain events have similar large scale environmental conditions, there are still slight differences in dia g nostic results. For instance, the long distance transfer of moisture from south to north and the confrontment of cold air and warm air over Beijing area in the second event become weaker compared to those in the first one. Investigation usi ng AWS and Weather Radar data shows that the two rainstorms are induced by mesos cale convective systems, developments of which are closely related to the evolut ions of mesoscale convergence lines of surface. However, the features, such as the size, shape, track, radar reflectivity and lifetime of mesoscale convective systems between the two torrential rain events, are quite different. The occurre nce and duration of easterly winds in planetary boundary layer (PBL) in Beijing few hours before the start of rainfall events seem essential to the formation of the torrential rainfalls, although vertical and temporal evolutions of easterly winds in PBL for the two events are different.