01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-04-0148 |
| Title of Abstract | The multi-year negative Indian Ocean Dipole of 2021-2022 |
| Authors | Ankur Srivastava*, Gill M. Martin, Maheswar Pradhan, Suryachandra A. Rao, Sarah Ineson |
| Organisation | Indian Institute of Tropical Meteorology, Pune |
| Address | IITM, Dr. Homi Bhabha Road, Pashan Pune, Maharashtra, India Pincode: 411008 E-mail: ankur@tropmet.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | During 2021 and 2022, the Indian Ocean experienced persistent negative Indian Ocean Dipole (nIOD) conditions, with the 2022 event being the strongest on record. The Dipole Mode Index remained negative from the summer of 2021 through early winter 2022- an unprecedented 19-month duration- marking the first documented multi-year nIOD. This event co-occurred with the triple-dip La Niña of 2020-2022. In this study, we investigate the mechanisms underpinning this prolonged nIOD. Beginning in summer 2021, the tropical Indian Ocean (TIO) experienced dominant westerly wind anomalies that persisted until the end of 2022, accompanied by a record number and duration of westerly wind bursts (WWBs). These anomalous westerlies were supported by the prevailing La Niña state and enhanced convection over the eastern TIO associated with tropical intraseasonal oscillations. WWBs occurring outside their climatological peak months, along with strong westerly anomalies, altered the strength of zonal currents and Wyrtki jets in the TIO. The resulting heat and mass redistribution deepened the thermocline in the eastern TIO, sustaining the nIOD. Anomalous westerly activity in spring 2022 acted as a bridge between the two nIOD phases, extending the event's duration to record length. This multi-year nIOD mitigated the potential for excess Indian summer monsoon rainfall by offsetting the monsoon-favourable modulation of the Walker circulation with anomalous subsidence over India, driven by nIOD-induced changes in the regional Hadley circulation. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Wyrtki jets, negative Indian Ocean Dipole, Triple-dip La Nina, Indian Monsoon |
| For Awards | yes |
| Date Of Birth | 09-02-1991 |
| ECSN Registration Number | IIOE2-ECSN-0125 |