An indirect estimate of the diurnal cycle in upper ocean turbulent heat fluxes at the equator, 140°W

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Abstract
The diurnal cycle in the heat budget of the upper equatorial Pacific Ocean is studied using 26 days of special high‐resolution oceanographic and meteorological observations from a current meter mooring at 0°, 140°W. The focus is on the turbulent heat fluxes at the base of the mixed layer, which are calculated as a residual in the mean diurnal heat budget. The inferred downward heat flux at the base of the mixed layer is ∼150 W m−2, averaged over the mean diurnal cycle, and ranged from near zero in the morning and early afternoon to ∼200 W m−2 during the late afternoon until dawn. The magnitude and phasing of the mean diurnal cycle were similar for different definitions of the mixed layer depth. The inferred residual turbulent fluxes were used also to estimate the mean diurnal cycles in vertical eddy diffusivity and turbulent dissipation rate. These turbulence parameters and the heat fluxes from which they were derived have magnitudes that are broadly consistent with those estimated previously from direct microstructure measurements.