印度洋偶极子与两类ElNi?o的关联及其可能机理  

THE LINKAGE BETWEEN INDIAN OCEAN DIPOLE AND TWO TYPES OF EL NI?O EVENT AND ITS POSSIBLE MECHANISMS

作　　者：董笛 何金海[1] 

机构地区：[1]南京信息工程大学大气科学学院,江苏南京210044 [2]中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室,北京100029

出　　处：《热带气象学报》2015年第2期182-192,共11页Journal of Tropical Meteorology

基　　金：国家重点基础研究发展计划(973计划)项目(2012CB417403);南京信息工程大学2014届“优秀本科毕业论文(设计)支持计划”项目;长江学者和创新团队发展计划资助(PCSIRT);江苏高校优势学科建设工程资助项目(PAPD)共同资助

摘　　要：通过合成三种具有代表性的两类ENSO指数，将El Nino事件划分为东部（EP）和中部（cP）型。利用EOF、相关分析、合成分析等方法探究了印度洋偶极子（IOD）与两类El Nino事件的关联及其产生的可能机理。研究表明，源于热带太平洋一印度洋尺度海气相互作用的IOD事件由两种型态构成，其分别与EP和CP型El Nino事件相联系。与EP型El Nino相联系的IOD事件（第一类IOD）在赤道印度洋50～150m的温跃层附近信号最强，并关于赤道呈南强北弱的准对称海温异常分布；与cP型El Nino相联系的IOD事件（第二类IOD）则在热带南印度洋海表层信号最强。在产生机理方面，EP型El Nino发展时，异常Walker环流在赤道印度洋海表面产生较强的东风应力，使赤道印度洋东部冷水上翻，西部暖水堆积；同时，赤道外南强北弱的异常反气旋环流造成旋度中心区域暖水堆积，形成第一类IOD事件。CP型El Nino发展时，异常Walker环流较弱，中心西移，赤道印度洋东风应力距平较弱，偶极子信号在赤道印度洋不显著；苏门答腊岛南部出现异常反气旋，其东侧偏南风和西侧偏北风分别将高纬冷水和低纬暖水向15～25°s的热带南印度洋输送；同时热带南印度洋东、西部风场分别有较强的辐散、辐合，使东部海温降低、西部升高，形成第二类IOD事件。After composing three representative ENSO indices, El Nino events are divided into an eastern pattern （EP） and a central pattern （CP）. By using EOF, correlation and composite analysis, the relationship and possible mechanisms between IOD and the two types of El Nino events are investigated. It shows that IOD events, originating from Indian-Pacific scale air-sea interaction, are composed of two modes, which are associated with EP and CP El Nino respectively. When it comes to sea temperature, the IOD mode related to EP El Nifio events （referred to as first type IOD） is strongest at the depth of 50 to 150 m along the equatorial Indian Ocean. Besides, it shows a quasi-symmetric distribution, stronger in the south, of the Equator. The second mode of IOD, associated with CP El Nino events, has its strongest signal in southern tropical Indian Ocean surface. In terms of mechanisms, before EP El Nino reaches its mature phase, anomalous Walker circulation produces stronger equatorial easterlies in Indian Ocean, resulting in upwelling in the east equatorial Indian Ocean, making sea temperature drop there; a couple of anomalous anticyclones （stronger in the south） form off the Equator where warm water accumulates, thus, the first type IOD event occurs. However, anomalous Walker circulation corresponding with CP El Nino is weaker and shifts its center to the west, therefore anomalous easterlies in equatorial Indian Ocean is less strong. Besides, the anticyclone south of Sumatra strengthens, the south wind east of it brings cold water from higher latitudes and north wind west of it brings warm water from lower latitudes to the 15-25°S zone. Meanwhile, there exists strong divergence in the east and convergence in the west part of south tropical Indian Ocean, making sea temperature fall and rise separately. Thus, the second type IOD lies farther south.

关 键 词：印度洋偶极子 两类El NINO事件 异常Walker环流 海气相互作用 海温异常 

分 类 号：P732[天文地球—海洋科学]