热带风暴“菲特”(0114)特大暴雨的诊断研究  

Diagnostic Analysis and Numerical Study of Torrential Rain Associated with the Tropical Storm Fitow (0114)

作　　者：段丽[1] 陈联寿[2] 

机构地区：[1]北京市气象台,北京100089 [2]中国气象科学研究院,北京100081

出　　处：《大气科学》2005年第3期343-353,共11页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金资助项目40175019;科技部社会公益项目2001DIA20026;海南省2002年度自然科学基金资助项目

摘　　要：海南岛破历史记录的两场特大暴雨都是由穿过琼州海峡的台风所造成,热带风暴“菲特”(Fitow)就是其中的一个。由红外卫星云图、雷达和常规地面加密观测资料发现,当“菲特”穿越琼州海峡时,在其西南侧的海南岛五指山西北侧有一个中尺度对流小涡系统(MCS)生成。特大暴雨就出现在MCS所在地区。作者用PSU/NCAR的中尺度模式对这场暴雨和MCS作了模拟研究,发现当“菲特”穿越琼州海峡时,其外围流场和五指山山脉的辐合极有利于MCS的生成。诊断分析的结果表明,山脉地形生成的MCS,具有很强的上层辐散,中低空有大范围辐合和强的正涡度场。在暴雨加强时,正涡度向中层伸展,高层辐散明显加强。同时,暴雨区出现较强的垂直运动。上升运动大值区出现在对流层上层,这可能和上层辐散加强有关。这场暴雨的水汽来自南海北部,经由“菲特”东侧的西南气流卷入涡旋之中,产生较强的水汽辐合。这也是潜热供应的源。诊断分析的结果还表明,MCS所在大气中下层出现了较强的位势不稳定层结,这对这场暴雨提供了对流加强和水汽向上输送的热力条件。The strongest excessive heavy rainfall breaking the fifty\|two\|year historical precipitation records in Hainan Island is caused by the tropical storm passing through Qiongzhou Strait with a southwest turning. Satellite images, radar reflectivities and intensive observations demonstrate that the rain is associated with a mesoscale convective system (MCS) which forms in a convergent area between the Fitow and the mountain range in the middle of Hainan Island. A numerical simulation has been performed with PSU/NCAR mesoscale model MM5V3 to study the relationship between the heavy rain and the MCS. The diagnostic analysis is carried out so as to gain a better understanding of the heavy rain mechanism. The results show that the mountain range in the middle of Hainan Island is favorable for generating a MCS when a tropical cyclone cross the Qiongzhou Strait. The heavy rain does coincide with the MCS on the northwestern side of the mountain. The diagnostic analysis indicates that the convergence and vorticity are concentrative in the lower layer and extend to the middle layer when rain increases while the divergence field is strengthening in the upper level right above the MCS in the heavy rain period. It is also found that the moisture of the rainfall from the South China Sea transported by the southwest flow field around the right cycle of the vortex is drawn into the rainfall area. The study also shows that the vertical motion is quite strong in the MCS and the maximal upward speed appears in the height between middle and upper level due to the strong upper level divergence. The strong unstable stratification at the middle and lower layer of the MCS also offers a positive contribution to the heavy rain associated with the storm Fitow.

关 键 词：热带风暴 特大暴雨 海南岛 中尺度对流小涡系统 MCS 不稳定层结 热力条件 

分 类 号：P458.121.1[天文地球—大气科学及气象学]