The Processes Determining the Annual Cycle of Equatorial Sea Surface Temperature: A Coupled General Circulation Model Perspective

Abstract

Abstract The origin of the annual cycle of equatorial sea surface temperature (SST) is diagnosed using a global coupled atmosphere–ocean general circulation model (CGCM) that realistically simulates this annual cycle. The simulated heat flux, wind stress, upper ocean thermal structure, and mixed-layer depth, which are critical to the correct simulation of the near-equatorial SST, are compared with observations for realism. Based on this analysis, it is concluded that the model results should be applicable to the actual coupled system in the Indian and Atlantic Oceans. In the Pacific, errors in the simulated zonal wind stress and heat flux imply that, even though the SST annual cycle is realistic, the processes that govern its evolution may be different than those found in nature. The processes controlling the annual cycle of SST in the CGCM are diagnosed with experiments in which the ocean component model is forced with the CGCM surface fluxes of heat, momentum, and freshwater. In the eastern Pacific, the...