El Nino-Southern Oscillation (ENSO) Interactions with Tropical Atlantic and Indian Oceans

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The El Niño-Southern Oscillation (ENSO) is the dominant interannual variability in the Earth’s climate. Current understanding of the interactions between ENSO and tropical Atlantic and Indian Ocean is limited. However, these interactions are seemingly crucial for accurate prediction of ENSO structure and evolution and its global impact. Current operational models have difficulty accurately predicting ENSO and its interactions with climate modes in other ocean basins. Through observational analyses and numerical modeling tasks, results from this award may reveal key physical processes behind these interactions and advance our current knowledge of ENSO dynamics, pan-tropical climate interactions, and general large-scale atmosphere-ocean interactions. This in turn may provide additional metrics to assess and improve global model representations of ENSO and its influence on weather events.The award has three research thrusts. The first thrust investigates the relative roles of ENSO-induced extratropical and tropical forcing of sea surface temperature anomaly (SSTA) in the tropical North Atlantic (TNA) and how the TNA SSTA may feedback to ENSO through induced Rossby and Kelvin wave responses. Observational analyses and idealized model experiments will be performed. The second thrust examines the interaction between Atlantic Niño and ENSO. A composite analysis will be conducted to elucidate the formation mechanisms of Atlantic Niño under preceding El Niño and La Niña conditions. Coupled and uncoupled model experiments will be carried out to investigate how ENSO influences Atlantic Niño and how Atlantic Niño impacts subsequent ENSO evolution and to what extent model bias in sea surface temperature affects the remote Atlantic forcing. The third thrust investigates how ENSO influences the Indian Ocean dipole (IOD) and to what extent Indian Ocean basin warming contributes to El Niño turnabout. Focus will be placed on the effect of equatorially symmetric and antisymmetric circulation responses to El Niño during its developing summer and linear and nonlinear wind responses to the boreal winter IDO rainfall pattern.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.