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研究了印度洋Dipole事件期间热带太平洋-印度洋海洋次表层海温异常和海面风应力异常分布主要型,揭示了Dipole事件的两种模态,探讨了其形成机制,得到如下结果:(1)印度洋Dipole事件在热带印度洋次表层海温异常表现为“<”型的东西向偶极子分布,“<”以东的热带东印度洋为沿赤道呈舌状西伸的显著海温异常中心,“<”以西的热带中西印度洋为反号的、以赤道为准对称的南强北弱显著海温异常中心.(2)印度洋Dipole事件由两种模态构成,二者具相同空间分布但具不同的时间变率,它们是两个独立的大尺度海气相互作用的结果.Dipole事件第一模态源于热带太平洋-印度洋尺度海气相互作用,它与ENSO事件共存.Dipole事件第二模态起因于热带印度洋尺度海气相互作用,它与Mascarene高压位置和强度变化紧密联系.当二者位相一致时,产生强Dipole事件,二者位相相反时,Dipole事件很弱或消失,一者较强时,Dipole事件一般也较强.(3)印度洋Dipole事件是热带印度洋海面异常风应力强迫的结果,海面异常风应力作用下产生的垂直输送导致海水堆积和涌升是造成次表层海温异常的主要动力过程.当赤道印度洋为异常东风时,热带东印度洋冷海水上升,热带西印度洋暖海水堆积,热带印度洋温跃层东浅西深;由于Coriolis力的作用,赤道海域离赤道流造成冷海水上升,赤道印度洋温跃层变浅;赤道两侧热带印度洋异常反气旋环流及旋度场,造成该异常旋度中心区域暖海水堆积,赤道外热带印度洋温跃层加深.三者共同作用产生正位相Dipole事件.热带印度洋为异常西风时,动力过程相反,产生负位相Dipole事件.
During the Dipole event in the Indian Ocean, the dominant subtropical oceanic surface temperature anomalies and sea surface wind stress anomaly distributions in the tropical Pacific-Indian Ocean were revealed. Two modes of Dipole event were revealed and their formation mechanisms were discussed. The results are as follows: (1) Dipole The subtropical oceanic anomalies in the tropical Indian Ocean show an east-west dipole distribution of “<” type. The tropical East Indian Ocean to the east of the “<” is a prominent SST anomaly that extends tongue-like along the equator (2) The Dipole event in the Indian Ocean consists of two modes, and both of them have the same space, which is opposite to the tropical central and western Indian Ocean to the west of the “” Distribution but with different time variability, they are the result of two independent large-scale air-sea interactions.The first mode of Dipole event originated from tropical Pacific-Indian Ocean scale air-sea interaction which co-exists with ENSO event.The Dipole event The second mode is due to the interaction of tropical Indian Ocean scale with air-sea and it is closely related to the change of position and intensity of Mascarene high pressure. When the two phases are consistent, the strong Dipole event is generated. When the two phases are opposite, the Dipole event is weak or (3) The Dipole event in the Indian Ocean is the result of abnormal wind stress in the tropical Indian Ocean sea surface. Vertical transport caused by abnormal wind stress in the sea surface leads to seawater accumulation and ascent When the equatorial Indian Ocean is anomalous east wind, the cold seawater in the tropical East Indian Ocean rises, the warm western Indian Ocean accumulates in the tropical Indian Ocean and the eastwestern shallow thermocline in the tropical Indian Ocean becomes west-deep. Due to the Coriolis force, the equatorial sea area The cold sea water rose from the equatorial stream, and the thermocline became shallow in the equatorial Indian Ocean. The anomalous anticyclone circulation and curl field in the tropical Indian Ocean on both sides of the equator resulted in the accumulation of warm seawater in the central area of the abnormal curl and the deepening of the thermocline over the equatorial Indian Ocean. When the tropical Indian Ocean is anomalous westerlies, the dynamic process is opposite, resulting in the negative phase Dipole event.