Surface Energy Fluxes and Coupled Variability in the Tropics of a Coupled General Circulation Model

Abstract

The effect of wind-evaporative feedbacks upon ENSO, and the coupling of Pacific and Indian Ocean variability, is considered based upon a 110-yr simulation from a coupled ocean and atmosphere general circulation model. ENSO-like modes, which propagate westward, are found in the model Pacific Ocean. Examination of the SST budget shows that the modes amplify and propagate as a result of changes in the surface energy flux and upwelling rates. Surface flux variability is dominated by the solar and evaporative components, and wind-evaporative feedbacks are shown to lead to growth and westward propagation of coupled anomalies in the model Pacific, a region of mean easterly winds. Eastward propagating coupled modes in the model Indian Ocean, a region of mean equatorial westerlies, are also found and are attributed to the same feedback. Interaction of the Pacific and Indian Ocean modes through the evaporation field is demonstrated, and their relevance to observed coupled ocean-atmosphere variability is considered.