Upper ocean heat and salt balances in response to a westerly wind burst in the western equatorial Pacific during TOGA COARE

Two volume control methods are used to analyze the upper ocean heat and salt balances in response to a westerly wind burst event in the western equatorial Pacific during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. One method uses a fixed-thickness surface layer, and the other uses an isopycnal depth as the lower boundary. Horizontal advection terms in the budget calculations are estimated using the R/V Wecoma repeat hydrographic survey data within a 133 km x 133 km region. In both methods, the upper ocean heat budget is balanced within 10 W m(-2) of the surface air-sea flux observations during a 19-day time period, which covers the December 1992 westerly wind burst and a low-wind recovery period in early January 1993. The standard error in the estimation of heat advection is 11 W m(-2). The salt budget yields a rain rate estimate of 15.4 mm d(-1) with an error bar of 4 mm d(-1). This estimate is within 20% of the optical rain gauge measurements. The advection terms are important in both the heat and salt balances. Meridional advection dominates over zonal and vertical advection, acting to decrease temperature and increase salinity in the surface layer. From the isopycnal boundary method, the diapycnal turbulent flux transports a mean heat flux of 17 W m(-2) into the thermocline. Diapycnal advection is almost equally important, so that the total heat flux into the thermocline is estimated to be more than 30 W m(-2) during the study time period. Both terms are also important in the salt budget.