Complex Influences of Tropical Indian and Atlantic Oceans on ENSO Prediction

Tropical basin interactions (TBIs) are widely involved in El Niño-Southern Oscillation (ENSO) evolution. Previous dynamical prediction studies often focused on single basin, single start month, and few events, which normally overlooked the complexity in the TBIs’ impact on ENSO prediction. To address these limitations, we conducted six sets of sensitivity hindcast experiments initializing from different seasons during 1983–2018, in which observed monthly and climatological sea surface temperatures (SSTs) over the tropical Indian (TIO) and Atlantic Ocean (TAO) are separately and synchronously prescribed. Results indicate synergistic but complicated roles of tropical SST anomalies (SSTAs) outside the Pacific in predicting ENSO. The results suggest more prominent contributions from TAO SSTAs, due to the well-captured teleconnections between ENSO and primary precursors in the North tropical and equatorial Atlantic. Conversely, the model exhibits large biases in replicating the relationship between ENSO and the basin-wide and dipole modes in the Indian Ocean, weakening the TIO SSTAs’ contributions. Moreover, SSTAs over the remote basins exert asymmetrical and phase-dependent influences on ENSO predictions; more remarkable contributions are found during La Niña and ENSO transition-development phases, indicating the TBIs’ importance in improving the spring barrier of ENSO prediction. Additionally, the impact of TBIs on ENSO prediction displays an interdecadal change; SSTAs outside the Pacific improve (degrade) El Niño prediction before (after) 2000, which may be associated with rapid warming in the TIO and TAO. Our results suggest high complexity in the TIO and TAO’s influence on ENSO prediction, stimulating future efforts for better understanding and models’ performance.