摘要
利用多普勒天气雷达、常规气象观测等资料,从雷达气象学和中小尺度天气学出发,对引发湘东南特大暴雨的两次强热带风暴"碧利斯"与超强台风"圣帕"进行了对比分析。结果表明:两次过程均为东风带系统影响,地形增幅作用显著。螺旋带状、弥合回波阶段是造成强降水的主要时段。均有低质心暖性降水回波特征,降水效率高。"列车效应"是造成特大暴雨的关键,但形成方式不同:"碧利斯"主要由带状回波形成,而"圣帕"主要由回波在同一区域加强形成。"碧利斯"回波强度、回波顶高均大于"圣帕"过程,对流更旺盛,范围小而雨强大,与西风带冷式切变线暴雨回波相似。"圣帕"回波均匀,持续时间长,与西风带暖式切变线暴雨回波特征相似,回波移动缓慢,降水总量大。两次过程都有暖平流上叠加辐合风场的特征,形成了有利于强降水的环境背景。中γ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。谱宽表明,受地面的摩擦作用,低层有强烈的湍流和乱流,有利于低压中心从低层减弱。中层为强而稳定的气流,有利于气旋强度的维持,形成长时间强降水。
Using the Doppler radar data in Shaoguan, Guangdong Province and other conventional meteorological data, the mesoscale system features of torrential rain in southeast of Hunan Province caused by strong tropical cyclone ＂Bills＂ and super-typhoon ＂Sepat＂ were analyzed. Results show that, there are easterly system events with significant topography effect; the helix band echoes and merging echoes are the main stages of heavy rainfall with the warm and low centroid and high efficiency of precipitation features. The ＂train effect＂ is the key of the events, but the ways of formation are different： that of ＂Bilis＂ is caused by the band echo while for ＂Sepat＂ mainly by the locally intensified echo. The echo intensity and echo top of ＂Bilis＂ are higher than those of ＂Sepat＂. The echo of ＂Bills＂ is similar to that of westerly cold shear rainstorm with strong convection, small scope but great intensity of precipitation. The echo of ＂Sepat＂ is homogeneous, long lasting, which is similar to that of westerly warm shear rainstorm with slow speed and high accumulated precipitation. Warm advection superposed on convergence wind fields led the favorable environment for heavy precipitation in two cases. The well organized secondary circulation caused by discontinuous mesoscale jet-core at the medium level of troposphere may be the main reason to form and sustain the train effect. At the low level, the spectral width is quite high and at the medium level it is very homogeneous. This indicates that violent turbulence at low altitude because of the surface friction, which helps the low pressure center weaken from the low level. The stable and strong jet at medium altitude sustained the cyclone and caused the lasting precipitation.
出处
《高原气象》
CSCD
北大核心
2009年第3期626-633,共8页
Plateau Meteorology
基金
湖南省气象局重点项目(022,026,028)资助
