doi:  10.3878/j.issn.1006-9895.1701.16225
印度洋冬季风异常海气环流耦合模态分析

Analysis of Abnormal Air-Sea Coupled Mode and the Indian Winter Monsoon
摘要点击 232  全文点击 225  投稿时间:2016-09-05  
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基金:  国家重点基础研究发展计划(973计划)项目2013CB956203
中文关键词:  印度洋  冬季风异常  海气环流耦合  复EOF分解
英文关键词:  Indian Ocean  Abnormal winter monsoon  Air-sea coupled circulation  Complex EOF decomposition
        
作者中文名作者英文名单位
张东凌ZHANG Dongling中国科学院大气物理研究所, 北京 100029
卢姁LU Xu中国人民解放军61741部队, 北京 100094;解放军理工大学气象海洋学院大气环流与短期气候预测实验室, 南京 211101
张铭ZHANG Ming解放军理工大学气象海洋学院大气环流与短期气候预测实验室, 南京 211101
引用:张东凌,卢姁,张铭.2017.印度洋冬季风异常海气环流耦合模态分析[J].大气科学,41(5):975-987,doi:10.3878/j.issn.1006-9895.1701.16225.
Citation:ZHANG Dongling,LU Xu,ZHANG Ming.2017.Analysis of Abnormal Air-Sea Coupled Mode and the Indian Winter Monsoon[J].Chinese Journal of Atmospheric Sciences (in Chinese),41(5):975-987,doi:10.3878/j.issn.1006-9895.1701.16225.
中文摘要:
      本文对印度洋冬季风异常海气环流耦合主要模态做了分析和讨论,得到以下结果:第一模态海面和低空大气环流的异常主要发生在东印度洋海域上空,而上层大洋环流的异常则主要反映了印度洋冬季风环流的异常,并主要体现在西向赤道暖流和东向赤道逆流上。第二模态的大气环流相应异常主要发生在孟加拉湾、阿拉伯海和赤道印度洋上空,而上层大洋环流异常除与第一模态类似外,还包括索马里暖流的明显异常。第一、二模态分别是印度洋冬季风的偏东、偏西模态,也是其主、次模态;均有约4年的年际变化,还分别有约18、22年的年代际变化;该主、次模态分别在1976年及1976、1986年有突变发生;这样印度洋冬季风有约4年的年际变化,并在1976年出现明显突变。该主、次模态的年代际变化周期也是冬季北太平洋海气联合复EOF分解第二、第一模态的年代际变化周期,这反映两大洋之间有密切联系,这是因冬季蒙古西伯利亚高压是南亚、东亚冬季风的共同源头,对两大洋的大气环流异常都有明显影响。南亚冬季风偏强时印度洋的Hadley环流和赤道辐合带上的对流均偏强,反之亦然;且该冬季风的主、次模态都如此;这也反映了南亚冬季风大气环流异常与冬季热带大气环流异常之间的耦合关系。当该主、次模态发生正、负异常变化时,近表层热带印度洋海温异常分别呈现横贯大洋的南北向跷跷板变化以及大洋东、西向的跷跷板变化;但前者是主要的。印度洋冬季风对印度洋偶极子起着抑制作用,这是该偶极子在冬季最弱的原因。在热带印度洋,大气低空垂直运动下沉、上升区域都分别大致位于该大洋近表层的下沉、上升运动区域之上,这构成了海气相互作用的负反馈机制,并有助于南亚冬季风、Hadley环流、赤道辐合带以及印度洋中冬季风环流的维持和稳定。
Abstract:
      This paper analyzes and discusses the abnormal air-sea coupled mode and the Indian winter monsoon. Main conclusions are as follows. In the first leading mode, sea surface and low level atmospheric circulation anomalies mainly occur over the eastern India Ocean, while upper ocean circulation anomalies, which embody in the westward equatorial warm current and eastward equatorial counter current, mainly reflect the winter monsoon circulation anomaly over the India Ocean. In the second leading mode, atmospheric circulation anomalies mainly occur over the Bay of Bengal, the Arabian Sea and the equatorial India Ocean; the upper ocean circulation anomalies are similar to that in the first leading mode, except that they also embody the abnormal Somali warm current. The first and second leading modes correspond to east and west modes of the Indian winter monsoon, which are also the primary and secondary modes of the Indian winter monsoon. The period of their inter-annual variation is about 4 years. The main periods of their inter-decadal variation are about 18 and 22 years respectively. The primary and secondary modes underwent mutation in 1976, and 1976 and 1978 respectively. The Indian winter monsoon has a 4-year period of inter-annual variation and underwent an obvious mutation in 1976. The inter-decadal variations of the primary and secondary modes correspond to those of the second and first modes of the winter North Pacific Air-sea combination revealed by the Complex EOF (CEOF), which reflects the close relationship of the two oceans. This is because the Mongolia-Siberian high is a common source of the South Asian and the East Asian winter monsoon, and has significant influences on atmospheric circulation anomalies over the two oceans. The South Asian winter monsoon is stronger when the Hadley circulation over the Indian Ocean and convection on the equatorial convergence belt are stronger, and vice versa. The primary and secondary modes of the winter monsoon have the similar situation. In addition, this reflects the coupling relationship between anomalies of the South Asian winter monsoon circulation and tropical circulation in the winter. When the primary and secondary modes turn to positive or negative, SST anomalies of the near-surface tropical Indian Ocean demonstrate a north-south seesaw pattern and a west-east seasaw pattern, and the former is the primary one. The Indian winter monsoon prohibits the formation of the Indian dipole, and this explains why this dipole is the weakest in the winter. In the tropical Indian Ocean, the areas of atmospheric descending and ascending motions in low levels correspond to the areas of ocean descending and ascending motions near the sea surface, which constitutes the negative feedback mechanism for the air-sea interaction. In addition, it contributes to maintenance and stability of the South Asian winter monsoon, the Hadley circulation, the equatorial convergence belt and the Indian winter monsoon circulation.
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