The heat balance in the western equatorial pacific warm pool during the westerly wind bursts: A case study

The responses of sea surface temperature (SST) in the western equatorial Pa cific warm pool to the westerly wind bursts (WWBs) play an important role i n the relationship between WWB and ENSO. By using data collected from eight buoys of TOGA (Tropical Ocean-Global Atmosphere)- COARE (Coupled Ocean-Atm osphere Response Experiment), the heat balances of the upper ocean in the w estern equatorial Pacific around 0 degrees, 156 degreesE during two WWB eve nts were calculated according to Stevenson and Niiler's (1983) method. In b oth events, SST increased before and after the WWBs, while decreased within the WWBs. The SST amplitudes approximated to 1 degreesC. Although sometime s the horizontal heat advections may become the biggest term in the heat ba lance, the variation of SST was dominated by the surface heat flux. On the other aspect, some different features of the two events are also revealed. The two cases have different variation of mixed layer depth. The depth of m ixed layer is almost double in the first case (35 in to 70 m), which is cau sed by Ekman convergence, while only 10m increments due to entrainment in t he second one, There are also differences in the currents structure. The di fferent variations of thermal and currents structure in the mixing layers a ccounted for the different variation of the heat balance during the two eve nts, especially the advection and residue terms. The seasonal variation of SST in this area is also investigated simply. The first WWB event happened just during the seasonal transition. So we considered that it is a normal s eason transition rather than a so-called anomaly. That also suggested that the seasonal distinction of the WWB is worthy of more attention in the rese arches of its relationship to ENSO.