Influence of Indian Ocean Dipole and Pacific recharge on following year's El Niño: interdecadal robustness

Takeshi Izumo (1) , Matthieu Lengaigne (1) , Jérôme Vialard (1) , Jing-Jia Luo (2) , Toshio Yamagata (2) , Gurvan Madec (3)

1 PARVATI - Processus de la variabilité climatique tropicale et impacts
2 FRCGC - Frontier Research Center for Global Change
3 NEMO R&D - Nucleus for European Modeling of the Ocean

The Indian Ocean Dipole (IOD) can affect the El Niño-Southern Oscillation (ENSO) state of the following year, in addition to the well-known preconditioning by equatorial Pacific Warm Water Volume (WWV), as suggested by a study based on observations over the recent satellite era (1981-2009). The present paper explores the interdecadal robustness of this result over the 1872-2008 period. To this end, we develop a robust IOD index, which well exploits sparse historical observations in the tropical Indian Ocean, and an efficient proxy of WWV interannual variations based on the temporal integral of Pacific zonal wind stress (of a historical atmospheric reanalysis). A linear regression hindcast model based on these two indices in boreal fall explains 50 % of ENSO peak variance 14 months later, with significant contributions from both the IOD and WWV over most of the historical period and a similar skill for El Niño and La Niña events. Our results further reveal that, when combined with WWV, the IOD index provides a larger ENSO hindcast skill improvement than the Indian Ocean basin-wide mode, the Indian Monsoon or ENSO itself. Based on these results, we propose a revised scheme of Indo-Pacific interactions. In this scheme, the IOD-ENSO interactions favour a biennial timescale and interact with the slower recharge-discharge cycle intrinsic to the Pacific Ocean.

Mots clés: Air-sea interactions; Walker circulation; Interannual and interdecadal climate variability and predictability; El Niño-Southern Oscillation (ENSO); Indian Ocean Dipole; Tropical Indo-Pacific; Indian Ocean basin-wide warming/cooling (IOBW); Observational uncertainties; Warm Water Volume (WWV) recharge-discharge of the equatorial Pacific Ocean; Indian and Asian monsoons; Tropical Tropospheric Biennial Oscillation (TBO)

Domaines: Géophysique [physics.geo-ph]

Takeshi Izumo, Matthieu Lengaigne, Jérôme Vialard, Jing-Jia Luo, Toshio Yamagata, et al.. Influence of Indian Ocean Dipole and Pacific recharge on following year's El Niño: interdecadal robustness. Climate Dynamics, 2014, 42 (1-2), pp.291-310. ⟨10.1007/S00382-012-1628-1⟩. ⟨hal-00914959⟩