广东2008年罕见“龙舟水”特点及成因诊断分析  

Causality Analysis of the Infrequent Dragon-Boat Precipitation in Guangdong Province in 2008

作　　者：林良勋[1] 吴乃庚[1,2] 黄忠[1] 蔡安安[1] 

机构地区：[1]广州中心气象台,广州510080 [2]中山大学季风与环境研究中心/大气科学系

出　　处：《气象》2009年第4期43-50,共8页Meteorological Monthly

基　　金：广东省应急管理研究课题(广东省气象灾害特征与应急管理工作机制研究);广州市科技局项目(亚运会气象预报服务系统研究)共同资助

摘　　要：2008年5月下旬末至6月中旬,广东出现了历史罕见的持续时间长、范围大、强度强、灾害重的暴雨到大暴雨降水过程,并有4个明显降水期。诊断分析发现:过程是在亚洲中纬度两槽一弱脊,东槽明显的平均背景场产生的,副高较弱位置较东,南支槽活跃,每一强降水期与一次西风槽的影响相联系,高空急流和低层切变线的南压过程配合一次强降水的发生;低空急流的最大风速变化与暴雨的发生同步,降水的减弱期伴随低空急流的向上抬升;过程的水汽源于孟加拉湾和南海,而以前者为主,水汽的辐合主要发生在华南沿海;龙舟水期间存在两个明显的局地经向环流,低层的两股气流在20～25°N区辐合抬升为持续性强龙舟水的产生提供了稳定的上升运动背景;4个主降水期有3个是在层结不稳定的条件下出现暴雨。Guangdong suffered the heaviest rainfall during late May to mid June 2008 （so-called ＂dragon-boat＂ precipitation）, according to records since 1951. Result of diagnostic analysis shows that in this case the circulation situations of the middle and high levels in Asia and Europe are two trough and one ridge circulation pattern and the western Pacific subtropical high is weaker than normal and expands eastward. Four main heavy rain periods in this case are associated with the influence of westerly trough and southward movement of low level shear line. The variance of low-level jet has a close relationship with the occurrence of the rainstorm. The cold air moving down from the mid-latitude areas and joining up against moist southerly from the Bay of Bengal and the South China Sea produces the vapor convergence at southern China coastal areas and the anomalous local meridional circulation, which causes the continuous heavy rainfall. Three of four heavy rainfall periods are associated with the instable stratification.

关 键 词：龙舟水 低空急流 经向环流 不稳定层结 

分 类 号：P458.121[天文地球—大气科学及气象学] P458.121.1