This paper describes the large scale aspects of the seasonal surface heat budget and discusses itsmain forcing mechanisms in the tropical Western Pacific Ocean.The high-resolution generalcirculation model (Semtner & Chervin,1992)used in this study reproduced well the observed upper-layer thermal structure and circulation.It is shown that at least on the average of the study region(20°S-20°N,west boundary-160°E)the semiannual variation is a dominant signal for all heat budgetcomponents and is presumably due to the sun’s passing across the equator twice a year,but that thecomponents have substantial differences in amplitude.The local Ekman divergence in the region doesnot change significantly through the year.As a result,the change in surface heat content is roughlyhalf due to ocean-atmosphere heat exchange and half due to heat advection by remotely forced verti-cal motion.Horizontal currents do not play a significant role directly by advection,because the wat-er which enters the region is not very muc This paper describes the large scale aspects of the seasonal surface heat budget and discusses its main forcing mechanisms in the tropical Western Pacific Ocean. The high-resolution general circulation model (Semtner & Chervin, 1992) used in this study developed well-viewed upper-layer thermal structure and circulation. It is shown that at least on the average of the study region (20 ° S-20 ° N, west boundary-160 ° E) the semiannual variation is a dominant signal for all heat budget components and is presumably due to the sun’s passing across the equator twice a year, but that thecomponents have substantial differences in amplitude.The local Ekman divergence in the region doesnot change significantly throughout the year. As a result, the change in surface heat content is roughlyhalf due to ocean-atmosphere heat exchange and half due to heat advection by remotely forced verti-cal motion. Horizontal currents do not play a significant role directly by advection, because the wat-er which enters the re gion is not very muc