Surface heat balance in the equatorial Pacific Ocean: Climatology and the warming event of 1994-95

The surface heat budget in the equatorial Pacific Ocean was investigated th rough ocean model simulations, both the climatological cycle and the case o f the 1994-95 warm event. The dominant processes governing the seasonal cyc le of sea surface temperature (SST) vary significantly across the basin. In the western Pacific the annual cycle of SST is primarily in response to ne t surface heat flux. In the central basin the magnitude of the zonal advect ion term is comparable to that of the net surface heat flux. In the eastern basin the role of zonal advection is reduced and the vertical mixing and a dvection are more important. The model estimate of the vertical mixing cont ribution to the mixed layer heat budget compared well with estimates obtain ed by analysis of observations using the same diagnostic vertical mixing sc heme. During 1994-95 the largest positive SST anomaly was observed in the m idbasin and was related initially to reduced latent heat flux due to weak s urface winds and later to anomalous zonal advection. In the eastern Pacific where winds were not significantly anomalous throughout 1994-95, only a mo derate warm surface anomaly was detected. This is in contrast to strong El Nino events where the SST anomaly is largest in the eastern basin. Overall, the balances inferred from the model forced by Special Sensor Microwave/Im ager winds are consistent with the balances derived using tropical atmosphe re-ocean moorings data and Reynolds SST.