A model of air-sea gas exchange incorporating the physics of the turbulent boundary layer and the properties of the sea surface

The model presented contains interfacial, bubble-mediated, ocean mixed layer, and remote sensing components. The interfacial (direct) gas transfer dominates under conditions of low and-for quite soluble gases like CO₂- moderate wind speeds. Due to the similarity between the gas and heat transfer, the temperature difference, ΔT, across the thermal molecular boundary layer (cool skin of the ocean) and the interfacial gas transfer coefficient, K_int are presumably interrelated. A coupled parameterization for ΔT and K_int has been derived in the context of a surface renewal model [Soloviev and Schluessel, 1994]. In addition to the Schmidt, 5c, and Prandtl, Pr, numbers, the important parameters are the surface Richardson number, Rf₀, and the Keulegan number, Ke. The more readily available cool skin data are used to determine the coefficients that enter into both parameterizations. At high wind speeds, the Ke-number dependence is further verified with the formula for transformation of the surface wind stress to form drag and white capping, which follows from the renewal model. A further extension of the renewal model includes effects of solar radiation and rainfall. The bubble-mediated component incorporates the Merlivat et al. [1993] parameterization with the empirical coefficients estimated by Asher and Wanninkhof [1998]. The oceanic mixed layer component accounts for stratification effects on the air-sea gas exchange. Based on the example of GasEx-98, we demonstrate how the results of parameterization and modeling of the air-sea gas exchange can be extended to the global scale, using remote sensing techniques.