“海贝思”残留螺旋云带的中尺度暴雨成因分析

Analysis on cause of a mesoscale rainstorm event induced by the residual spiral cloud band from the tropical depression Hagibis(1407)

利用常规观测资料、NCEP 1°×1°再分析资料以及新一代天气雷达和区域自动站资料,对2014年登陆热带气旋(TC)"海贝思"减弱为热带低压(TD)后的残留云带造成的中尺度暴雨的成因进行了分析。结果表明:残余低压环流带来的强降水具有明显的中尺度特征,属于典型的台风螺旋云带中尺度雨团;西南和东南急流的暖式切变、辐合和辐散中心与高低层次级环流的耦合发展,均有利于螺旋云带中的中尺度系统发展。另外,分析利用单雷达反演热带气旋近中心风场的VAP扩展应用方法反演的风场,进一步证实了残余低压的螺旋云带中存在明显的围绕TD中心的中尺度螺旋结构,强降水主要由TD螺旋云带下的中尺度雨团产生。

Using conventional observation data, NCEP reanalysis data with 1°×1° resolution, Doppler weather radar products and intensive observations from automatic weather stations, we study the cause of a mesoscale rainstorm event induced by the residual cloud band from trop-ical depression (TD) after the tropical cyclone (TC) Hagibis (1407) weakened. The results show that the severe precipitation generated by re-sidual circulation of TD is characterized by mesoscale. It belongs to the typical mesoscale rain cluster induced by the outer spiral cloud band of Hagibis. It is found that some key factors have lead to the development of the mesoscale structure of spiral cloud band, including the warm shear between southwesterly jet and southeasterly jet, the coupling of convergence in the low-level and divergence in the upper level and the development of secondary circulation. In addition, an extended VAP (EVAP) method is used to retrieve wind fields in the center of Hagibis to further verify the existence of a significant mesoscale spiral structure around the tropical depression (TD). Consequently, severe precipitation is primarily induced by the mesoscale rain clusters under TD with spiral cloud band.