Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 47, Issue 18, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2020GL090079
Keywords
Indian Ocean Dipole; thermocline warming; ENSO; oceanic Rossby waves; Bjerknes feedback; wind-evaporation-SST feedback
Categories
Funding
- National Natural Science Foundation of China [41830538, 41525019, 41976024]
- Chinese Academy of Sciences [XDA15020901, 133244KYSB20190031, ZDRW-XH-2019-2]
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) [GML2019ZD0303, GML2019ZD0306, 2019BT2H594]
- CSIRO
- Earth Systems and Climate Change Hub of the Australian Government's National Environmental Science Program
- QNLM
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The 2019 positive Indian Ocean Dipole (IOD) was the strongest event since the 1960s which developed independently without coinciding El Nino. The dynamics is not fully understood. Here we show that in March-May, westward propagating oceanic Rossby waves, a remnant consequence of the weak 2018 Pacific warm condition, led to anomalous sea surface temperature warming in the southwest tropical Indian Ocean (TIO), inducing deep convection and anomalous easterly winds along the equator, which triggered the initial cooling in the east. In June-August, the easterly wind anomalies continued to evolve through ocean-atmosphere coupling involving Bjerknes feedback and equatorial nonlinear ocean advection, until its maturity in September-November. This study clarifies the contribution of oceanic Rossby waves in the south TIO in different dynamic settings and reveals a new triggering mechanism for extreme IOD events that will help to understand IOD diversity.
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