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Influence of the Interdecadal Pacific Oscillation on Super Cyclone Activities over the Bay of Bengal During the Primary Cyclone Season
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  • Zhi Li,
  • Zecheng Xu,
  • Yue Fang,
  • Kuiping Li
Zhi Li
First Institute of Oceanography, MNR

Corresponding Author:[email protected]

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Zecheng Xu
First Institute of Oceanography, MNR
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Yue Fang
First Institute of Oceanography, State Oceanic Administration
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Kuiping Li
First Institute of Oceanography, Ministry of Natural Resources
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An obvious interdecadal change is measured in the super cyclones (SCs, categories 4 and 5) that occur from Oct-Nov over the Bay of Bengal (BoB). This change may be modulated by the interdecadal Pacific oscillation (IPO). A La Niña-like difference between the 1977–1998 (IP1) and 1999–2014 (IP2) periods forces a local Hadley circulation in the eastern tropical Indian Ocean by strengthening the Walker circulation, causing a plummeting upper-level temperatures and ultimately creating favorable thermodynamic conditions to enhance the cyclone intensity. Meanwhile, an equatorial downwelling Kelvin wave caused by heating and westerly wind differences enters the BoB rim along the coast and aptly intensifies the cyclone such that the downwelling Kevin wave and Rossby wave generated by its reflection deepen the thermocline in the BoB. The favorable atmospheric and oceanic conditions in IP2 jointly and preferentially form far more SC activities from Oct-Nov over the BoB compared to IP1.