Planton Y. Y. auteur aut IRD Vialard Jérôme auteur aut IRD Guilyardi E. auteur aut IRD Lengaigne Matthieu auteur aut IRD McPhaden M. J. auteur aut IRD text journalArticle eng text/pdf born digital access Unusually high western Pacific Ocean oceanic heat content often leads to El Nino about 1 year later, while unusually low heat content leads to La Nina. Here, we investigate if El Nino-Southern Oscillation (ENSO) predictability also depends on the initial state recharge, and we discuss the underlying mechanisms. To that end, we use the CNRM-CM5 model, which has a reasonable representation of the main observed ENSO characteristics, asymmetries, and feedbacks. Observations and a 1007-yr-long CNRM-CM5 simulation indicate that discharged states evolve more systematically into La Nina events than recharged states into neutral states or El Nino events. We ran 70-member ensemble experiments in a perfect-model setting, initialized in boreal autumn from either recharged or discharged western Pacific heat content, sampling the full range of corresponding ENSO phases. Predictability measures based both on spread and signal-to-noise ratio confirm that discharged states yield a more predictable ENSO outcome one year later than recharged states. As expected from recharge oscillator theory, recharged states evolve into positive central Pacific sea surface temperature anomalies in boreal spring, inducing stronger and more variable westerly wind event activity and a fast growth of the ensemble spread during summer and autumn. This also enhances the positive wind stress feedback in autumn, but the effect is offset by changes in thermocline and heat flux feedbacks. The state-dependent component of westerly wind events is thus the most likely cause for the predictability asymmetry in CNRM-CM5, although changes in the low-frequency wind stress feedback may also contribute. specialized Pacific Ocean Atmosphere-ocean interaction ENSO Seasonal forecasting Climate models Interannual variability PACIFIQUE 032 021 020 34 14 5775-5793 2021 0894-8755 https://www.documentation.ird.fr/hor/fdi:010082313 10.1175/jcli-d-20-0633.1 0894-8755 [F B010082313] https://www.documentation.ird.fr/hor/fdi:010082313 https://www.documentation.ird.fr/intranet/publi/2021-08/010082313.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2021-08-31 2025-02-24 fdi:010082313 fre