ESTIMATES OF TURBULENT HEAT-FLUX AND HEAT-BUDGET IN THE UPPER LAYER OF THE WESTERN EQUATORIAL PACIFIC-OCEAN

Estimates of turbulent heat flux and heat budget in a time-dependent m ixed layer and a surface slab layer are presented using the microstruc ture data measured during the cruise of the R/V Hakuho-maru at the fix ed location of 0 degrees, 156 degrees E. Repeated profilings of the mi crostructure measurements with 3- or 6-hour intervals were carried out from November 12 to 27 in 1992. The maximum turbulent heat flux at th e bottom of the time-dependent mixed layer, which was determined as th e depth with temperature difference of 0.1 degrees from temperature at 5 m layer, is 239.1 W/m(2) downward. Mean heat flux at the bottom of the time-dependent mixed layer averaged over the analyzed period of el even days, however, was only 31.4 W/m(2) downward. Heat budget in the time-dependent mixed layer is greatly affected by advective heat flux, which reaches more than 50 percent of the net heat stored in the laye r. On the other hand, accumulated heat budget in the surface slab laye r (surface layer) about 70 m thick, defined as the layer between sea s urface and 28 degrees C isotherm, is also evaluated. Accumulated net h eat input estimated from the surface meteorological data for eleven da ys is 80 MJ/m(2). The maximum components of turbulent heat flux in the surface layer were 50 W/m(2) upward and 250 W/m(2) downward. However, the mean flux for eleven days averaged over the surface layer was onl y 9.1 W/m(2). The total heat flow at the bottom of the surface layer f or eleven days was 9.3 MJ/m(2) downward. Therefore, if we neglect the advective heat, the residue of 70.7 MJ/m(2) could contribute to a rise in temperature of the surface layer. The net heat input estimated fro m mean temperature change in the surface layer was 84 MJ/m(2). The dif ference of 13.3 MJ/m(2) could be attributed to advective heat, which c orresponds to 16 percent of the surface net heat input.