A Novel Blasting Fuse of Indian Ocean Dipole: Tropical Cyclone over the Bay of Bengal

Abstract The Indian Ocean Dipole (IOD) is a significant interannual variability in the Indian Ocean (IO), with global impacts on climate, agriculture, and ecosystems. Previous studies mainly link the IOD to ENSO and the anomalous Asian summer monsoon. This research investigates the potential connection between April tropical cyclones (TCs) over the Bay of Bengal (BoB) and IOD occurrences through statistical analysis, suggesting that TCs may act as a potential blasting fuse of IOD. TCs induce a negative sea surface temperature anomaly in the southern BoB, which stimulates anticyclonic Rossby wave cells on both sides of the equator and promotes northeastern wind anomalies in the central IO (CIO) located south of the equator. These wind anomalies transport warm water, resulting in an upper-ocean temperature difference between the equatorial CIO and southeastern IO. This temperature difference creates the necessary conditions for the Bjerknes feedback, facilitating the initiation and development of IOD events.