Influence of transient atmospheric circulation on the surface heating of the western Pacific warm pool

Trade and monsoonal winds converge to regions of the highest sea surface temperature (SST) in the equatorial western Pacific. These regions have the largest cloud cover and smallest wind speed. Both surface solar heating and evaporative cooling are weak. Data on surface heat fluxes show that the reduced evaporative cooling due to weakened winds exceeds the reduced solar heating due to enhanced cloudiness. The result is a maximum surface heating in the strong convective and high SST regions, which follow the seasonal march of the sun. As the Sun moves away from a convective region, the strong trade and monsoonal winds set in, and the evaporative cooling enhances, resulting in a net cooling of the surface. We conclude that the seasonal variation of evaporation associated with the seasonal variation of trade and monsoonal winds is one of the major factors that modulate the SST distribution of the Pacific warm pool.