“碧利斯”引发湘东南特大暴雨的多普勒雷达回波特征分析

Analysis of the Torrential Rain in Southeastern Hunan Caused by the Severe Tropical Storm Bilis Using Doppler Radar Data

利用广东韶关多普勒天气雷达资料分析了2006年7月14—17日因受强热带风暴"碧利斯"影响湘东南发生的特大暴雨过程的回波特征及中小尺度系统。结果表明,"碧利斯"回波经历了初始发展、螺旋带状、弥合、减弱消失阶段,其路径经历了自东北向西南进入、绕雷达站旋转、由西南向东北方向移出三个阶段。"列车效应"是造成该特大暴雨的主要回波特征。多普勒速度图上,"逆风区"存在时间较短,对流层中层不连续中小尺度"大风核"造成有组织的次级环流可能是"列车效应"形成和维持的主要原因之一。谱宽图上,"碧利斯"在低层具有较大的谱宽值;在强回波带上,中层十分均匀,表明"碧利斯"过程低层由于受地形磨擦作用湍流活动很强,中层平稳的大风急流也是过程长时间维持的主要原因之一。

The echoes and meso-scale system features of the torrential rain in southeastern Hunan caused by the severe tropical storm Bilis between July 14 and 17,2006 was analyzed by using the Doppler radar data in Shaoguan, Guangdong province. The results show that the echoes of Bilis experienced the stages of initial genesis,helix band, merging, decreasing and extinction. The movement of Bilis could be divided into three phases：moving in from northeast to southwest, rotating around the radar station and moving out from southwest to northeast. The ＂train effect＂ was the major character that caused this torrential rain. Although the adverse wind regions in the imagery of velocity existed for only a short period of time,the well organized secondary circulation caused by discontinuous micro- and meso-scale jetcore at the medium level of troposphere could be one of the main reasons for the formation and maintaining of the ＂train effect＂. The spectral width was quite large at the low level and it was very homoge- neous at the medium level, which indicated that the turbulence caused by surface friction was very strong and the stable jet at medium level was also one of the major reasons for the long duration of the torrential rain.