Mesoscale analysis of heavy typhoon rainfall

Observation of radar and intensive surface wind of 0505 typhoon Haitang is used to analyze the relationship between radar reflectivity and observed precipitation and the relationship between mesoscale surface stream field and heavy rainfall.The analysis shows that when the Doppler radar reflectivity reaches 50 dbz,it has a good correspondence to the heavy one hour precipitation.Besides,heavy precipitation is also related to the mesoscale cyclonical current and confluent currents,it occurs near the mesoscale cyclonical or confluent current appearing at the same time.The mesoscale cyclonical feature in the surface stream near the coastal areas is not apparent while the typhoon approaching the main land.The surface southeast current of typhoon is divided into an east current and a southeast current,making for confluence of local currents and convection.Output with high resolution from mesoscale numerical simulation model WRF is used to analyze the features and evolvement of surface stream filed.The results confirm the important reason for current confluence in the surface stream field in heavy rainfall area,which plays a very important role in typhoon heavy rainfall in costal areas.