Cretat J. auteur aut IRD Terray Pascal auteur aut IRD Masson S. auteur aut IRD Sooraj K. P. auteur aut IRD text journalArticle eng text/pdf born digital access The intrinsic precursors and timescale of the tropical Indian Ocean Dipole (IOD) are examined with the help of a partially coupled global experiment with decoupled SST over the tropical Pacific. The IOD does exist in the absence of sea surface temperature interannual variability in the tropical Pacific in our modeling framework, but has weaker amplitude and damped Bjerknes feedback. However, IOD variability is much more biennial in the absence than presence of El Nio Southern Oscillation, especially in the eastern equatorial Indian Ocean (IO). Such biennial rhythm results mainly from two mechanisms internal to the IO. The tropical ocean dynamics play a key role in the biennial anomalies during boreal winter with a sudden reversal of thermocline anomalies in the eastern equatorial IO forced by intraseasonal disturbances reminiscent of the Madden-Julian Oscillation (MJO). However, this preconditioning is not sufficient for triggering IOD events in the next boreal spring per se. The main trigger for pure IODs relates to tropical-extratropical interactions within the IO. Convection and diabating heating associated with negative IODs promote a Gill-type tropical response, excite mid-latitude wave-trains and subtropical blocking in the Southern Hemisphere that trigger positive subtropical IOD events during boreal winter. The latter promotes cold SST and anticyclonic circulation anomalies over the southeast IO that persist and migrate northeastward, triggering positive IOD events during the next boreal spring. Accounting for the complementary influence of tropical ocean dynamics coupled to MJO and tropical-extratropical ocean-atmosphere interactions may thus help improving IOD predictability. specialized Biennial variability Coupled climate model Indian Ocean Dipole MJO Ocean dynamics Tropical-extratropical interactions OCEAN INDIEN ZONE TROPICALE 032 51 4 1311-1332 2018 0930-7575 https://www.documentation.ird.fr/hor/fdi:010073687 10.1007/s00382-017-3956-7 0930-7575 [F B010073687] https://www.documentation.ird.fr/hor/fdi:010073687 https://www.documentation.ird.fr/intranet/publi/2018/08/010073687.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2018-09-12 2023-07-11 fdi:010073687 fre