The Asymmetric Predictive Power of Indian Ocean Dipole for Subsequent Year's ENSO: Role of Atlantic Ocean as an Intermediary

Abstract

AbstractWe examined the Indian Ocean Dipole (IOD)'s predictive ability for El Niño‐Southern Oscillation (ENSO). Our findings indicate that positive IODs have a stronger impact on the subsequent year's ENSO compared to negative IODs. To explain this asymmetry, we proposed the “IOD‐Atlantic‐Pacific” pathway, which involves the Atlantic in boreal winter as an intermediary. The pathway comprises two stages: (a) The asymmetric “IOD‐Atlantic” connection, where positive IODs in autumn trigger winter Atlantic Niño while negative IODs cannot trigger Atlantic Niña. This asymmetry is due to the modulation of the climatological mean state on the IOD‐induced atmospheric anomalies. (b) The “Atlantic‐ENSO” connection, which is symmetric, where winter Atlantic Niño (Niña) promotes the development of La Niña (El Niño), functioning independently of ENSO's self‐oscillation behavior. The Atlantic intermediary mechanism explains the asymmetric connection between IOD and the subsequent year's ENSO and provides the IOD with independent predictive power for ENSO beyond its self‐oscillation.