Evaluation of turbulent fluxes at the ocean surface using surface renewal theory

An internally consistent model is presented that can be used to determine the ocean surface fluxes of heat, moisture, and momentum, given bulk sea surface temperature and atmospheric temperature, humidity, and winds measured at a single level within the atmospheric surface layer. This model is based upon surface renewal theory as described by Brutsaert [1975a]. Liu et al. [1979] (hereinafter referred to as LKB) made partial use of this theory, and further improvements to the LKB parameterization have been made by Fairall et al. [1996a]. The present model includes the following improvements relative to the LKB and Fairall et al. bulk flux models: incorporation of a new time-scale parameterization for surface renewal, inclusion of capillary waves in the surface roughness model, derivation of the surface roughness scales of water vapor and heat based solely upon surface renewal theory; and incorporation of a new surface skin temperature model. The model is validated using shipborne observations of surface fluxes and surface meteorology that were obtained in the central Pacific Ocean, the western tropical Pacific, the subtropical Pacific, and the midlatitude North Atlantic. Comparisons of model results with covariance fluxes of latent heat show biases of less than 3% for all locations, with little dependence of error on wind speed; similar results are obtained for sensible heat and momentum flux. An assessment is given of the advantages of the present scheme over the LKB and Fairall et al. schemes. The model results are interpreted in the context of the physical processes involved in determining the surface roughness length and the surface renewal timescale.