The temperature difference across the cool skin of the ocean

Abstract

The temperature difference Δ T across the cool skin of the ocean was determined from radiometric measurements of surface brightness temperature and conventional measurements of temperature at a depth of 1 m. Eleven days of measurements were made from the R/P Flip in February 1974 about 800 miles north of Hawaii (35°N, 155°W). The surface brightness temperature was corrected for nonblackness of the surface to obtain an estimate of the true surface temperature. The constant λ in Saunders' (1967 a ) formula, Δ T = λ vQ / kU * was found to be λ = 6.5±0.6, where v is kinematic viscosity, Q the upward heat flux just below, the interface, k the thermal conductivity, and U * the friction velocity. The constant is independent of wind speed for winds ranging from 3 to 11 m/s. The use of subsurface rather than surface temperature in the bulk aerodynamic formulas results in an increase in the sum of the sensible and latent heat fluxes equal to 4‐5% of Q . However, the percentage change in sensible and latent heat fluxes may be much greater. Spectra of surface and subsurface sea temperature exhibit a peak at low frequencies and fall off approximately proportional to ƒ −3/2; with increasing frequency ƒ. The variability of sea surface temperature was caused about equally by the variability of subsurface temperature and the variability of Δ T . Caution should therefore be exercised in the interpretation of radiometric surface temperature measurements as representative of subsurface temperature.