上海“0185”热带低压特大暴雨维持机理研究  

A Research on the Mechanism for the Shanghai Heavy Rainfall Event on 5～6 August 2001 Caused by a Tropical Depression

作　　者：杜小玲[1] 喻自凤[1] 鲁崇明[1] 王元[1] 

机构地区：[1]南京大学大气科学系中尺度灾害性天气教育部重点实验室,南京210093

出　　处：《南京大学学报（自然科学版）》2007年第6期621-632,共12页Journal of Nanjing University（Natural Science）

基　　金：国家重点基础研究发展规划项目(973:2004CB418301);国家自然科学基金(40333025;40175025)

摘　　要：发生在上海地区的2001年8月5～6日热带低压特大暴雨过程(简称"0185"过程)是一次高影响性、灾害性天气.对于此次事件的预报失败,凸现了该过程的动力复杂性,并引起台风研究学者的高度关注.采取天气学诊断、动力学分析和数值模拟相结合的方法,综合应用日本20km高分辨率RSM-RANAL再分析资料、卫星云图资料和中尺度数值模拟产品对于暴雨动力学机理进行了研究.结果表明:引起上海"0185"特大暴雨过程并不是热带低压本体降水;"0185"过程的独特之处在于,在夏季强大的西北太平洋副高控制区域,同样可以维持强盛的中尺度低涡环流中心;而上述两点恰恰是导致预报人员误判并导致预报失败的两个重要原因."0185"过程中北方冷涡南压和热带暖心低压北上产生的强烈冲击导致高压带断裂或减弱,使得中尺度低压环流中心得以发展和维持.冷槽南压和热带暖心低压北上所激发的中尺度对流辐合体(MCC)在卫星云图上清晰可辨.在此分析基础上,引入第二类热成风螺旋度,它能很好地反映温度场水平分布不均匀所导致的水平环境风场垂直切变,而此垂直切变与低涡系统经向移动风矢所构成的水平螺旋度,进一步和上升对流通过涡管倾斜作用相纽结,表征了导致特大暴雨强盛涡旋上升对流的维持机理.事实上,第二类热成风螺旋度确能较好地反映降水落区和降水随时间的演变.The Shanghai heavy rainfall event on 5 - 6 August 2001 （‘0185＇ event, in abbreviation） caused by tropical depression （TD） is a typical high-impact and severe weather. This nature disaster increased by an unsuccessful weather forecast attracts attention by typhoon researchers, since it includes a very unclear dynamic process that puzzles weather forecasters. In this paper, by use of the RSM-RANAL re-analysis data from Japan and the GMS-5 infrared satellite images plus MM5 numerical simulation, the mechanism of the ‘0185＇ event has been studied. The results suggests that the heavy rainfall, very different with other research reports about this event, is not caused by a TD landing itself, instead by southward local cold mesoscale vertex. Another unique characteristics of this event is that such mesoscale vertex maintaining a long time was embedded in a very strong horse high circulation. This two point aforementioned unfortunately misunderstood by local weather forecasters. In fact, the cold mesoscale vertex southward and the warming-core TD northward weakened and even broken the band of horse high, so that the cold vertex and warming-core TD could survive for a longer time. The combination of the two vortices, lead a mesoscale convective complex（MCC） which was significantly appeared on satellite images）. Furthermore, a so-called second kind of thermal helicity was defined in order to describe a possible linkage between an inhomogeneous horizontal temperature distribution and ambient vertical shearing of horizontal wind. It was further found that a strong horizontal helicity was formed under the meridian velocity components of vortices system motion within such ambient vertical shearing（orientated to the south in the ‘0185’ event, i. e. , a strong vorticity tube caused by the ambient vertical shearing plus a vortices system motion along the tube so that a helicity is formed）. Yet the strong horizontal helicity, if combining with an upward triggering of vortices, a tilting effect will

关 键 词：第二类热成风螺旋度 暴雨 热带低压 中尺度对流性云团 

分 类 号：P444[天文地球—大气科学及气象学]