On the evolution of the western equatorial Pacific warm pool during the TOGA COARE IOP.

摘要

Upper ocean temperature and salinity variability in the western equatorial Pacific warm pool has been the subject of considerable study because it is linked to important climate phenomena, e.g. El Nino-Southern Oscillation (ENSO) events. In this work, the evolution of the upper ocean in the western equatorial Pacific warm pool at 1.75°S, 156.0°E is investigated for the three ∼20-day R/V Wecoma survey cruises made during the TOGA COARE IOP, Nov 1992--Feb 1993. Three ocean layers are considered: the surface mixed layer (SML) in which density is within 0.01 kg m-3 of the surface density, a 50 m fixed depth layer, and the upper ocean layer (UOL) between the sea surface and the sigmatheta = 22.0 kg m-3 isopycnal. The average depths of the SML and UOL were 25 m and 77 m, respectively.;Episodes of sustained winds are important in predicting ocean heat and salt variability because the combination of strong currents together with even modest lateral gradients can result is sizable advective fluxes. On the second survey cruise, the near-equatorial oceanic response to a sustained westerly wind event generated strong meridional cooling that was somewhat compensated by warming associated with moderate to was somewhat compensated by warming associated with moderate to strong equatorial downwelling of 10 to 20 m day-1. Subsurface shear driven turbulence at ∼2.1°S appears to be the genesis of at least one of the meridional fronts. Advection was the dominant term in the 50 m and UOL layer heat and salt budgets for this period.;The three cruise average heat advection estimates were not significantly different from zero. Salt advection, however, appears to be important in maintaining the warm pool salinity and suggests that ocean circulation is likely important in the long term budget. A somewhat surprising result was that the penetration of radiant energy below the base of the SML averaged -52 Wm-2 and was the dominant flux term in the SML heat budget. For this same period, the net surface and turbulent heat fluxes averaged 14 Wm-2 and -11 Wm-2, respectively.