Influence Of Ocean-Atmospheric Waves On The Major Interannual Sea-Surface Temperature Mode In The Tropical Indo-Pacific

The El Ni(?)o-Southern Oscillation(ENSO)and the Indian Ocean Dipole(IOD)are both the phenomenon related to the coupled instabilities' development of large-scale ocean-atmosphere interaction.We decompose the high-frequency oceanic waves into basic and anomalous parts based on the scale interaction;by diagnosing the interannualscale statistical features of anomalous structures and heat flux,the specific physical processes and mechanisms of high-frequency waves' thermodynamic feedback on the interannual temperature are investigated,and characteristics of its influence on ENSO are summarized.Via a multi-factor model,the relevant mechanisms of coupled instabilities in the Indian Ocean and their potential contribution to the IOD predictability are clarified.The main conclusions are as follows:The high-frequency wind-induced ocean response is most significant at the 30–90-day frequency band,which manifests as the tropical Kelvin waves in the Pacific Ocean.Apparent feedback exists between the oceanic Kelvin waves and the interannual temperature of the mixed layer of central and eastern equatorial Pacific.The feedback amplitude is asymmetric between the positive and negative ENSO phases.The feedback efficiency is the highest when the interannual temperature of the mixed layer of central and eastern equatorial Pacific shows a weak anomaly.In that case,the feedback could trigger and maintain the ENSO development while delaying its decay.This feedback may also interfere with the ENSO phase-locking behavior.The feedback-induced variation of interannual temperature in April-June is significantly correlated with the Ni(?)o3.4 index within one year,which may provide considerable predictability of the interannual ENSO prediction.The background can modulate thermodynamic and dynamic structures of the oceanic Kelvin wave.The anomalous structure will induce heat flux along the thermocline in the interannual band,which finally results in positive feedback on ENSO under both phases.However,the high-order term heat flux results in positive feedback on El Nino but negative feedback on La Nina,which is a critical reason for the feedback asymmetry.The Recharge Oscillator mechanism and the Delay Oscillator mechanism in the Indian Ocean can only explain the development of partly specific IOD events.The IOD's coupled instabilities majorly come from the response to ENSO and stochastic forcing rather than the two-year oscillation mode of large-scale ocean-atmosphere coupling.Therefore,the latter can provide additional but limited IOD predictability.