Two modes of dipole events in tropical Indian Ocean
Two modes of dipole events in tropical Indian Ocean
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热带印度洋偶极子事件的两种模态
DOI：
10.1007/s11430-009-0026-y
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发表时间：
2009-03
期刊：
影响因子：
--
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中科院分区：
文献类型：
--
作者：
通过分析印度洋偶极子事件期间热带太平洋和印度洋的地下温度和地面风应力异常的分布，揭示了印度洋偶极子事件的两种主要模态及其形成机制。(1) IOD事件期间热带印度洋地下温度异常（STA）可描述为“<”型、西向东的偶极子异常；在“<”型的东侧，热带东印度洋沿赤道向西延伸一个明显的舌状风；而在“<”型的西侧，在热带印度洋中西部，两个中心（南中心比北中心强）在赤道附近大致对称。(2) IOD事件由两个模态组成，它们具有相似的空间格局，但由于两个独立系统内的大尺度海气相互作用而具有不同的时间变率。IOD事件的第一模态起源于热带太平洋-印度洋尺度上的海气相互作用，与ENSO共存。第二模态源于热带印度洋尺度上的海气相互作用，与马斯卡林高压的位置和强度变化密切相关。强IOD事件发生在两模同相时，非同相时IOD事件减弱或消失。此外，当两个模态中的任何一个都很强时，IOD事件通常很强。(3) IOD事件是由热带印度洋异常风应力强迫引起的垂直输送，导致海水上涌和堆积。这是导致STA的主要动态过程。当赤道印度洋上空存在距平东风时，热带东印度洋的冷水上升，热带西印度洋的暖水堆积，因此热带印度洋的温跃层东浅西深。赤道地区科里奥利力引起的离赤道分量引起了印度洋赤道温跃层的浅化和冷水的上涌。另一方面，位于赤道两侧的异常反气旋环流及其旋度场，导致其旋度场中心区域暖水堆积，赤道外的赤道印度洋温跃层加深。以上三个因素导致正相IOD事件的发生。当异常西风带主导热带印度洋时，动力过程发生逆转，出现负相IOD事件。
By analyzing the distributions of subsurface temperature and the surface wind stress anomalies in the tropical Pacific and Indian Oceans during the Indian Ocean Dipole (IOD) events, two major modes of the IOD and their formation mechanisms are revealed. (1) The subsurface temperature anomaly (STA) in the tropical Indian Ocean during the IOD events can be described as a “<” -shaped and west-east-oriented dipole pattern; in the east side of the “<” pattern, a notable tongue-like STA extends westward along the equator in the tropical eastern Indian Ocean; while in the west side of the “<” pattern, the STA has opposite sign with two centers (the southern one is stronger than the northern one in intensity) being of rough symmetry about the equator in the tropical mid-western Indian Ocean. (2) The IOD events are composed of two modes, which have similar spatial pattern but different temporal variabilities due to the large scale air-sea interactions within two independent systems. The first mode of the IOD event originates from the air-sea interaction on a scale of the tropical Pacific-Indian Ocean and coexists with ENSO. The second mode originates from the air-sea interaction on a scale of the tropical Indian Ocean and is closely associated with changes in the position and intensity of the Mascarene high pressure. The strong IOD event occurs when the two modes are in phase, and the IOD event weakens or disappears when the two modes are out of phase. Besides, the IOD events are normally strong when either of the two modes is strong. (3) The IOD event is caused by the abnormal wind stress forcing over the tropical Indian Ocean, which results in vertical transports, leading to the upwelling and pileup of seawater. This is the main dynamic processes resulting in the STA. When the anomalous easterly exists over the equatorial Indian Ocean, the cold waters upwell in the tropical eastern Indian Ocean while the warm waters pileup in the tropical western Indian Ocean, hence the thermocline in the tropical Indian Ocean is shallowed in the east and deepened in the west. The off-equator component due to the Coriolis force in the equatorial area causes the upwelling of cold waters and the shallowing of the equatorial India Ocean thermocline. On the other hand, the anomalous anticyclonic circulations and their curl fields located on both sides of the equator, cause the pileup of warm waters in the central area of their curl fields and the deepening of the equatorial Indian Ocean thermocline off the equator. The above three factors lead to the occurrence of positive phase IOD events. When anomalous westerly dominates over the tropical Indian Ocean, the dynamic processes are reversed, and the negative-phase IOD event occurs.
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DOI：
10.1002/joc.986
发表时间：
2004-02
期刊：
International Journal of Climatology
影响因子：
--
作者：
W. Qian;Yafen Zhu;Jianyin Liang
通讯作者：
W. Qian;Yafen Zhu;Jianyin Liang
影响因子：
64.8
作者：
Saji, NH;Goswami, BN;Yamagata, T
通讯作者：
Yamagata, T
影响因子：
5.8
作者：
Chongyin Li;Mingquan Mu
通讯作者：
Chongyin Li;Mingquan Mu
影响因子：
1.4
作者：
Tian Ji-wei;Liu Huiqing;Q. Wei-hong
通讯作者：
Tian Ji-wei;Liu Huiqing;Q. Wei-hong
影响因子：
3.1
作者：
S. Sherwood;T. Horinouchi;Heidi A. Zeleznik
通讯作者：
S. Sherwood;T. Horinouchi;Heidi A. Zeleznik