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通过合成三种具有代表性的两类ENSO指数,将El Ni?o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 Ni?o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-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 Ni?o事件相联系。与EP型El Ni?o相联系的IOD事件(第一类IOD)在赤道印度洋50~150 m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 Ni?o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 Ni?o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 Ni?o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。
By combining the three representative ENSO indices, El Niño events are divided into eastern (EP) and central (CP) types. Using EOF, correlation analysis, synthetic analysis and other methods to explore the Indian Ocean Dipole (IOD) and two types of El Ni? O event association and its possible mechanism. The results show that the IOD events originated from the tropical Pacific-Indian Ocean air-sea interaction consist of two types, which are related to the El Niño events of EP and CP, respectively. The IOD event associated with EP El Niño (Type IOD) has the strongest signal near the thermocline between 50 and 150 m in the equatorial Indian Ocean and the quasi-symmetric SST anomaly with strong south to north weakness in the equatorial region. The IOD event associated with El Niño CP (Type IIOD) is the strongest signal in the surface sea of the tropical South Indian Ocean. In terms of the mechanism of production, the EP Walker circulation produces a strong easterly stress on the surface of the equatorial Indian Ocean, causing the cold water in the equatorial Indian Ocean to flip up and the western warm water to accumulate. Meanwhile, the strong south weakness of the equatorial South The anomalous anticyclone circulation caused the warm water to accumulate in the central area of curl, forming the first type of IOD event. In the development of El Niño CP, the anomalous Walker circulation is weaker and the center moves westward. The easterly anomalies of the easterly wind in the equatorial Indian Ocean are weaker and dipole signals are not significant in the equatorial Indian Ocean. Abnormal anticyclones appear in the southern Sumatra, The southerly winds and the westward northerly winds respectively send high-latitude cold water and low latitude warm water to the tropical South Indian Ocean at 15-25 ° S. At the same time, the wind fields in the east and west of the tropical South Indian Ocean have stronger divergence, convergence, So that the eastern sea temperature decreased, the western rise, the formation of the second type IOD events.