2010年秋季一次海南东海岸特大暴雨的中尺度分析  

A MESOSCALE STUDY OF EXTREME RAINFALL ALONG THE EASTERN COAST OF HAINAN ISLAND IN OCTOBER 2010

作　　者：汪汇洁[1,2,3] 孙建华[1,4] 赵思雄[5] 傅慎明[5] 

机构地区：[1]中国科学院大气物理研究所云降水物理与强风暴实验室 [2]中国科学院大学 [3]95968部队气象台 [4]南京信息工程大学气象灾害预报预警与评估协同创新中心 [5]中国科学院大气物理研究所国际气候与环境科学中心

出　　处：《热带气象学报》2014年第3期518-532,共15页Journal of Tropical Meteorology

基　　金：国家重点基础研究规划项目(2012CB417201);国家自然科学基金项目(41075032;41205027)共同资助

摘　　要：综合利用NCEP再分析资料、地面加密观测、多普勒雷达观测和卫星观测等常规和非常规资料,对2010年10月5日海南琼海特大暴雨过程的天气背景、环境场特征以及中尺度云团的活动特征进行分析。这次过程发生时热带辐合带(ITCZ)异常活跃,热带低压在海南岛附近活动,为此次特大暴雨的发生提供了有利的环流背景,偏东气流在海南岛的东岸特殊地形的影响下形成中尺度切变线。切变线上有中尺度对流系统自南向北移近琼海,并发展加强。采用WRF模式的精细模拟结果,进一步研究了造成琼海特大暴雨的中尺度对流系统形成和维持的主要原因。结果表明,在海南岛东岸稳定维持的β中尺度对流带及其上活跃的对流系统是造成特大暴雨的直接影响系统。新的对流系统不断地沿对流带尾部生成,并沿对流带自南向北移动发展可能是造成琼海地区强降水持续的直接原因。该模拟阶段雨强的发展加强,伴随着偏东风急流的发展和北抬。急流的扰动不仅增强垂直风切变,还通过倾斜项的作用将水平涡度转化为垂直涡度,同时,在海南岛中尺度地形的抬升和阻滞下,并有水平平流及热力条件的配合,使对流在迎风坡的上游发展加强,造成此次特大暴雨。The synoptic circulation and mesoscale systems related to extremely heavy rainfall over the eastern coast of Hainan Island on 5 October 2010 are analyzed by using NECP reanalysis data and multiple observational data（surface intensive observation, Doppler radar data and satellite data）. The active ITCZ and tropical depression over South China Sea are the favorite synoptic condition for the record heavy rainfall. A mesoscale convergence line formed as the easterly wind was affected by the topographic distribution in the eastern coast. Mesoscale convective systems moved northward and developed along the convergence line to Qionghai. Based on data analysis, the output of WRF model is used to examine the physical processes that resulted in extremely heavy rainfall over the eastern coast. There was a mesoscale convective zone along the eastern coast, on which active meso-β convective systems（MCS） originating from the rear portion of the convection band developed from south to north. Once the MCS moved close to Qionghai, it developed strongly, accompanied by the intensification of an easterly low-level jet（LLJ）. The calculation of vorticity budget and moist Froude number revealed that the intensification of LLJ resulted in a strong vertical wind shear and a large tilting term. The mesoscale topography in the middle of Hainan Island is favorable for the formation and maintenance of the MCSs when they move close to the northeastern slope, where with a medium value of topographic Fw, the flows around the topography are lifted up, so that the horizontal vorticity is transferred to vertical vorticity through the tilting term, and the topographic blocking effect slows down the MCSs movement, which is beneficial to the formation of the extreme rainfall upstream.

关 键 词：秋季极端降水 观测分析 线状中尺度对流系统 地形 湿Froude数 

分 类 号：P426.62[天文地球—大气科学及气象学]