水汽输送对云南夏季风爆发及初夏降水异常的影响  

The Impact of Water Vapor Transport on the Summer Monsoon Onset and Abnormal Rainfall over Yunnan Province in May

作　　者：陈艳[1] 丁一汇[2] 肖子牛[3] 晏红明[4] 

机构地区：[1]南京信息工程大学大气科学系,南京210044 [2]中国气象局国家气候中心,北京100081 [3]中国气象局国家气象中心,北京100081 [4]云南省气象科学研究所,昆明650034

出　　处：《大气科学》2006年第1期25-37,共13页Chinese Journal of Atmospheric Sciences

基　　金：九五"国家攀登A项目南海季风试验SCSMEX;国家重点基础研究发展规划项目2003CB415101;云南省气象局青年研究基金"云南初夏干旱的模式预测方法集成研究

摘　　要：主要利用1961-2000年云南120个站的逐日降水资料和NCEP／NCAR再分析资料，研究水汽输送对云南夏季风爆发和初夏5月降水异常的影响。结果表明，5月份云南上空为一致的西南风水汽输送，主要由来自印度半岛北部的副热带西风水汽输送和热带印度洋至孟加拉湾的西南风水汽输送汇合而成，而来自南海地区西太平洋副高西侧转向的偏南水汽输送是构成云南东部地区水汽输送的重要分支。5月下旬云南夏季风爆发期间，热带印度洋至孟加拉湾地区的水汽输送显著增强，云南上空增湿明显，这为季风爆发提供了必要的水汽条件，而东亚中纬地区冷空气的入侵则可能是触发季风降水的重要机制。进一步研究发现，云南5月降水量显著的年际变化也与大尺度水汽输送异常密切相关，即当热带印度洋至孟加拉湾地区的水汽输送强，而南海至东亚大陆地区的水汽输送弱时，降水量偏多，反之偏少。Although the partial westerlies prevails perennially at low level over Yunnan Plateau, it exhibits prominent dry and wet seasons influenced by the monsoon climate. The conspicuous fluctuations of precipitation tend to cause severe disasters, especially in May, the critical early summer period for spring crops growing. As one of the most significant factors contributing to rain, the impact of water vapor transport （WVT） on the summer monsoon onset and the possible relationship between WVT and abnormal rainfall in May are investigated. The primary datasets analyzed in this study include the 1961 - 2000 observational precipitation at 120 stations scattered in Yunnan Province of China, NCEP/NCAR reanalysis data, 1979 - 2000 CPC （the Climate Prediction Center） Merged Analysis of Precipitation （CMAP） and Outgoing Longwave Radiation （OLR）. The climatological distribution of vertically integrated WVT vectors in May presents that Yunnan is generally overlaid by southwestern WVT, which mainly consists of the subtropical westerly from the northern part of Indian subcontinent and southwesterly from the tropical Indian Ocean （TIO） and the Bay of Bengal （BOB）. In addition, the partial southerly WVT that turns around the west flange of the western Pacific subtropical high is one of the important branches over the eastern part of Yunnan Province. The results show that the average date of the summer monsoon onset in Yunnan is 28 May, identified by a criterion of Yunnan precipitation index. During the summer monsoon onset, the WVT over TIO and BOB greatly intensifies, strengthening the WVT over the western part of Yunnan accordingly. However, the WVT weakens over the eastern part associated with a cyclonic variation over the northwestern South China Sea （SCS）. Consequently, the specific humidity over Yunnan increases rapidly, providing necessary moisture condition for the monsoon onset. Meanwhile, the composite result also reveals that cold surges from the mid-latitude may play a crucial role in trigg

关 键 词：水汽输送 夏季风 云南初夏降水 

分 类 号：P463[天文地球—大气科学及气象学]