IMPACT OF WESTERLY WIND BURSTS ON THE WARM POOL OF THE TOGA-COARE DOMAIN IN AN OGCM

A primitive equation model is used to investigate the warm pool equili brium of the tropical Pacific ocean. Attention is focused on the upper ocean. The oceanic response is described using an isothermal approach applied to warm waters contained in the TOGA-COARE domain. The heat b alance shows that all the terms, atmospheric surface fluxes, advection and diffusion, operate in the heat bugdet with different time scales. Over long periods, diffusive heat fluxes transfer heat received from the atmosphere out of the warm pool trough the top of the main thermoc line. Over short periods, the impact of westerly wind bursts modifies this balance: atmospheric heating is reversed, diffusion is enhanced a nd advective heat transports out of the warm pool operate through zona l and vertical contributions. We were able to relate the two latter pr ocesses to zonal jets and Ekman pumping, respectively. Conversely, the meridional contribution always represents a source of heat, mainly du e to the tropical wind convergence. The modelling results clearly show that except during strong wind events, entrainment cooling is not an important component of the budget. The inability to remove heat is due to the salt stratification which needs to be first reduced or even de stroyed by westerly wind bursts to activate heat entrainment into deep er layers. Finally, we suggest that the near zero estimate for the sur face heat flux entering the warm pool may be extended to longer period s including seaosnal to interannual time scale.