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Abstract. This paper describes the various physical processes relating near-surface atmospheric and oceanographic bulk variables; their relationship to the surface fluxes of momentum, sensible heat, and latent heat; and their expression in a bulk flux algorithm.The algorithm follows the standard Monin-Obukhov similarity approach for near-surface meteorological measurements but includes separate models for the ocean's cool skin and the diurnal warm layer, which are used to derive true skin temperature from the bulk temperature measured at some depth near the surface.

To obtain bulk surface flux estimates approaching the _+10 W m -: accuracy desired for the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (COARE) program, bulk water temperature data from ships and buoys must be corrected for cool-skin and diurnal warm-layer effects. In this paper we describe two simple scaling models to estimate these corrections. The cool-skin model is based on the standard Saunders [ 1967] treatment, including the effects of solar radiation absorption, modified to include both shear-driven and convectively driven turbulence through their relative contributions to the near-surface turbulent kinetic energy dissipation rate. Shear and convective effects are comparable at a wind speed of about 2.5 m s -•. For the R/V Moana Wave COARE data collected in the tropical western Pacific, the model gives an average cool skin of 0.30 K at night and an average local noon value of 0.18 K. The warm-layer model is based on a single-layer scaling version of a model by Price et al. [1986]. In this model, once solar heating of the ocean exceeds the combined cooling by turbulent scalar heat transfer and net longwave radiation, then the main body of the mixed layer is cut off from its source of turbulence. Thereafter, surface inputs of heat and momentum are confined to a depth Dr that is determined by the subsequent integrals of the heat and momentum. The model assumes linear profiles of temperature-induced and surface-stress-induced current in this "warm layer." The model is shown to describe the peak afternoon warming and diurnal cycle of the warming quite accurately, on average, with a choice of a critical Richardson number of 0.65. For a clear day with a 10-m wind speed of 1 rn s -•, the peak afternoon warming is about 3.8 K with a warmlayer depth of 0.7 m, decreasing to about 0.2 K and 19 rn at a wind speed of 7 m s -•. For an average over 70 days sampled during COARE, the cool skin increases the average atmospheric heat input to the ocear/by about 11 W m-:; the warm layer decreases it by about 4 W m -: (but the effect can be 50 W m -: at midday). 1. Introduction Sea surface temperature (SST) is a key variable driving air-sea interaction. SST and air-sea fluxes were a dominant component of the study of the tropical western Pacific warm pool in the Tropical Ocean-Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) held in 1992-1993 [Webster and Lukas, 1992]. Uncertainties in air-sea temperature difference represent a major uncertainty in assessing the heat balance of the warm pool [Lukas, Paper number 95JC03190. 0148-0227/96/95JC-03190505.00 1989]. Fairall et al. [1996a] have shown that to estimate this heat balance to an accuracy of 10 W m '2 requires specification of the SST to an accuracy of _+0.2 K. Bulk flux routines are based on the empirical relationship between the turbulent fluxes and the air-sea contrasts of wind, humidity, and temperature; the SST is the lower thermal boundary condition. Logically• the proper temperature is taken at the air-sea...

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