台风强暴雨的中尺度分析

Mesoscale analysis of heavy typhoon rainfall

利用严重影响浙江东南地区的2005年05号台风的雷达和地面加密风场资料,分析对比台风中尺度暴雨过程中雷达回波与实况降水、中尺度地面流场与暴雨之间的关系,结果得到:多普勒雷达近地面强回波带或中心往往达到50 dbz时,与一小时的强降水区有很好的对应关系,暴雨中心区也与地面加密的中尺度流场中出现的中尺度气旋性环流和汇合气流有关,强暴雨区落在同时刻中尺度涡旋或汇合线附近.当台风移近大陆时,靠近沿海地区的地面流场中尺度涡旋特征并不明显,主要表现在台风近地面偏东南气流出现分支,形成偏东与偏东南气流,有利于在沿海地区形成局部气流汇合并引起或增强对流.利用中尺度数值模式(WRF)的高分辨输出结果,分析了近地面流场特征及演变,证实了暴雨带近地面流场中存在气流汇合,它在沿海地区台风暴雨过程中起到十分重要的作用.

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 ap- proaching 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.