AN INDIRECT ESTIMATE OF THE DIURNAL CYCLE IN UPPER OCEAN TURBULENT HEAT FLUXES AT THE EQUATOR, 140-DEGREES-W

The diurnal cycle in the heat budget of the upper equatorial Pacific O cean is studied using 26 days of special high-resolution oceanographic and meteorological observations from a current meter mooring at 0 deg rees, 140 degrees W. The focus is on the turbulent heat fluxes at the base of the mixed layer, which are calculated as a residual in the mea n diurnal heat budget. The inferred downward heat flux at the base of the mixed layer is similar to 150 W m(-2), averaged over the mean diur nal cycle, and ranged from near zero in the morning and early afternoo n to similar to 200 W m(-2) during the late afternoon until dawn. The magnitude and phasing of the mean diurnal cycle were similar for diffe rent definitions of the mixed layer depth. The inferred residual turbu lent fluxes were used also to estimate the mean diurnal cycles in vert ical eddy diffusivity and turbulent dissipation rate. These turbulence parameters and the heat fluxes from which they were derived have magn itudes that are broadly consistent with those estimated previously fro m direct microstructure measurements.