Strengthening impacts of spring sea surface temperature in the north tropical Atlantic on Indian Ocean dipole after the mid-1980s
Strengthening impacts of spring sea surface temperature in the north tropical Atlantic on Indian Ocean dipole after the mid-1980s
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20世纪80年代中期以后北热带大西洋春季海表温度对印度洋偶极子的影响增强
DOI：
10.1007/s00382-021-06128-6
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发表时间：
2022-01
期刊：
影响因子：
4.6
通讯作者：
Sheng Chen
中科院分区：
文献类型：
--
作者：
Guangli Zhang;Xin Wang;Qiang Xie;Jiepeng Chen;Sheng Chen
摘要 众所周知，印度洋偶极子（IOD）与厄尔尼诺南方涛动（ENSO）密切相关。本研究发现，春夏季北热带大西洋（NTA）海面温度（SST）异常可以促进20世纪80年代中期以来的IOD以及ENSO的发展。 20世纪80年代中期以后，由于吉尔型罗斯贝波响应，春季和夏季凉爽的NTA海温异常可能会激发副热带东北太平洋上空的反气旋环流。西太平洋地区依次出现低层气旋性环流。气旋环流东南侧的异常低层西南风降低了气候风速，因此出现温暖的海温异常，并通过风蒸发海温（WES）反馈延伸到热带中部太平洋。导致印太地区沃克环流发生变化，热带印度洋东部出现异常下降，热带太平洋中部出现异常上升。异常沃克环流的下降分支在苏门答腊岛沿岸产生地表东南风异常，并抬升热带印度洋东部的温跃层，从而在秋季产生正 IOD 事件。这种跨流域机制得到了 NTA 上温海温扰动的耦合模型实验的支持。相比之下，虽然在20世纪80年代中期之前，NTA冷海温异常可以通过半球间经向环流诱发赤道东太平洋暖海温异常，但热带印度洋的响应却相当弱。此外，20世纪80年代中期以后NTA-IOD关系的增强被认为是全球变暖背景下海温平均状态变化的结果，这已被两个不同平均海温背景的耦合模型实验所证实。
AbstractIt is well known that the Indian Ocean dipole (IOD) is closely related to El Niño-Southern Oscillation (ENSO). In this study, it is found that spring–summer north tropical Atlantic (NTA) sea surface temperature (SST) anomalies can contribute to the development of the IOD since the mid-1980s as well as ENSO. After the mid-1980s, an anticyclonic circulation over the subtropical northeastern Pacific could be excited by cool NTA SST anomalies in spring and summer due to a Gill-type Rossby-wave response. A low-level cyclonic circulation appears in the west Pacific in turn. The anomalous lower-level southwesterlies on the southeastern flank of the cyclonic circulation reduce the climatological wind speed, and thus, warm SST anomalies appear and extend to the central tropical Pacific via the wind-evaporation-SST (WES) feedback. As a result, Walker circulation over the Indo-Pacific region is changed, with anomalous descending in the eastern tropical Indian Ocean and ascending in the central tropical Pacific. The descending branch of anomalous Walker circulation generates surface southeasterly wind anomalies along the coast off Sumatra and lifts the thermocline in the eastern tropical Indian Ocean, which produces a positive IOD event in autumn. Such a cross-basin mechanism is supported by a coupled model experiment with warm SST perturbations over the NTA. In contrast, although cold NTA SST anomalies can induce warm SST anomalies in the eastern equatorial Pacific through interhemispheric meridional circulation before the mid-1980s, the responses in the tropical Indian Ocean are rather weak. In addition, the enhancement in the NTA-IOD relationship after the mid-1980s is suggested to result from the changes in the SST mean state under the context of global warming, which is confirmed by two coupled model experiments with different mean SST backgrounds.
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