Tropical-ocean-atmosphere interactions in a coupled model

Abstract

A high-resolution tropical Pacific Ocean model coupled to a medium-resolution atmospheric general circulation model has been integrated for 2 years. A seasonal cycle was included. The atmospheric model when forced with climatological seasonally varying sea surface temperatures simulates the surface stress and net surface heating over the tropical Pacific Ocean to within the uncertainty in the climatological estimates in these quantities. When coupled, however, the models drift into an annually recurring anomalous state, similar in many respects to the El Nino Southern Oscillation observed in the ocean and atmosphere. The model results emphasize the role of off-equatorial anomalies in temperature, atmospheric heating and wind response. Air—sea heat exchange is found to be dominant in determining sea surface temperature changes in these off-equatorial regions. Both cloud and evaporative feedbacks are important in the anomalous surface heat budget.