Analysis of heavy rain causes and distribution caused by the landfall typhoon "Rananim"

Based on the main influenced system,the heavy rain process caused by landfall typhoon Rananim(0414) was divided into two phases.It was showed that the first strong precipitation phase was affected by typhoon itself and for the second precipitation phase,the major casue was the result of interaction between the typhoon circulation and middle latitude weather system.Then focusing on the characteristic of asymmetrical distribution of rainfall at the side of landfall dot,the study was carried out and indicated that this phenomenon associated with asymmetrical structure of typhoon itself,different moisture transportation and meso-scale topography.At the same time,the moist potential vorticity(MPV) was applied to diagnose space-time distribution of rainfall,the results suggested that the corresponding relation between the negative value center of MPV and heavy rain area was better,and its absolute value had positive correlation to the intensity of one hour precipitation.It provided more valuable information for short range weather forecasting,the typhoon torrential rain especially.