| 摘要: |
| 热带印度洋偶极子(Indian Ocean dipole, IOD)和副热带南印度洋偶极子(Southern Indian Ocean dipole, SIOD)作为热带和副热带印度洋海气耦合的主要模态，二者联系密切。本文基于梁氏-克里曼信息流理论确定IOD与SIOD互为因果，并利用Hadley中心的海表面温度数据以及NCEP大气再分析等数据分析了1950~2021年期间前期IOD对SIOD发展的影响及其年代际变化规律。结果显示，IOD超前SIOD的相关关系在1976年和2002年前后发生了年代际转变。1950~1976年期间(P1)，二者关系不显著；1977~2002年期间(P2)，二者存在显著负相关，当IOD超前SIOD 5个月时达到最大负相关，相关系数为-0.56；2003~2021年期间(P3)，二者相关性有所减弱，相关系数为-0.33。二者关系的年代际变化可能与它们主周期的年代际变化有关。P2时期，IOD与SIOD之间存在显著的2~4a反位相一致周期，而在P1、P3时期两者没有明显的同周期。与此同时，IOD超前SIOD时二者关系的年代际变化与太平洋年代际振荡(Pacific Decadal Oscillation, PDO)的位相转换有密切联系。PDO冷位相下，副热带印度洋大气环流响应较弱，海气背景不利于IOD对SIOD事件的激发。PDO暖位相能够通过ENSO加强赤道印度洋-太平洋的Walker环流异常，与赤道东风异常有关的反气旋环流促使热带西印度洋的正海表温度异常(Sea Surface Temperature Anomalies, SSTA)向东南方向延伸，促进东南印度洋正SSTA的发展；IOD通过经向环流的垂直运动引起中纬度对流层高层辐散，产生等效正压Rossby波，与之相关的低层异常气旋环流通过“风-蒸发-海表面温度”(Wind-Evaporation-SST, WES)反馈诱导副热带西南印度洋负SSTA的发展，二者共同促进了次年冬季负SIOD事件的生成。 |
| 关键词: 印度洋偶极子，副热带南印度洋偶极子，年代际变化 |
| DOI： |
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附件 |
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| INFLUENCE OF THE TROPICAL INDIAN OCEAN DIPOLE ON THE SUBTROPICAL SOUTHERN INDIAN OCEAN DIPOLE AND ITS INTERDECADAL CHANGE |
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Shi Wenjuan1, Feng Junqiao1, Zhang Ziye2
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1.Institute of Oceanology, Chinese Academy of Science;2.Shandong University of Science and Technology
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| Abstract: |
| Indian Ocean dipole (IOD) and Southern Indian Ocean dipole (SIOD) are two dominate climatic modes in tropical and subtropical Indian Ocean, respectively. It is suggested that IOD and SIOD are causal to each other based on the Liang-Kleeman information flow. The changes in the relationship between preceding IOD and SIOD during 1950~2021 are analyzed using sea surface temperature data from Hadley Centre and NCEP atmospheric reanalysis. It is found that there is a significant interdecadal change in the IOD-SIOD relationship when the IOD leading SIOD, with interdecadal shifting around 1976 and 2002. The relationship is insignificant from 1950 to 1976 (P1). During 1977-2002 (P2), the significant negative correlation is observed between IOD and SIOD, with the highest correlation coefficient of -0.56 appearing when the former leads the latter for 5 months. From 2003 on (P3), the correlation between the two dipoles becomes weak. The interdecadal variation of the IOD/SIOD periods may contribute to the interdecadal change of the relationship between them. During P2, there is a similar 2~4a period between SIOD and IOD; whereas during P1 and P3, there is no significant resonance between them. Furthermore, there exists a close correlation between the PDO's phase transition and the interdecadal variation of IOD-SIOD relationship. During the cold phase of PDO, the atmospheric circulation response in the subtropical Indian Ocean is weak, unfavorable for the triggering of SIOD event by IOD. On the contrary, the warm phase of PDO can intensify the Walker circulation anomaly in the equatorial Indian-Pacific via ENSO, and strengthen the wind anomalies in the tropical eastern Indian Ocean, contributing to the expansion of the western tropical Indian Ocean SSTA to the southeastern Indian Ocean. Meanwhile, the IOD can also elicit the stationary equivalent Rossby wave train through the vertical motion of the meridional circulation. The associated anomalous cyclonic at low level induces a negative SSTA in SWIO by WES feedback. Finally, the negative SIOD peaks in the following winter. |
| Key words: Indian Ocean Dipole Southern Indian Ocean Dipole interdecadal change |