Detailed gas exchange measurements from two circular and one linear wind/wave tunnels are presented. Heat, He, CH4, CO2, Kr, and Xe have been used as tracers. The experiments show the central importance of waves for the water-side transfer process. With the onset of waves the Schmidt number dependence of the transfer velocity k changes from k o• Sc-2/3 to k o• Sc-•/2 indicating a change in the boundary conditions at the surface. Moreover, energy put into the wave field by wind is transferred to near-surface turbulence enhancing gas transfer. The data show that the mean square slope of the waves is the best parameter to characterize the free wavy surface with respect to water-side transfer processes. 1. , • !• 0.010 ! ß ß ! ß ß o o ! ß , ß ß 10 o 10 • 10 z ?requemcy [Hz] across the free aqueous viscous boundary layer, Tellus, in press, 1985b. J•ihne, B, G. Heinz, and W. Dietrich, Measurements of the diffusion coefficients of sparingly soluble gases in water with a modified Barrer method, submitted to J. Geophlts. Res., 1986. Kanwisher, J., On the exchange of gases between the atmosphere and the sea, Deep Sea Res., I0, 195-207, 1963. Kitaigorodskii, S. A., On the theory of the equilibrium range in the spectrum of wind-generated gravity waves, J. Phys. Oceanogr.., 15, 816-827, 1983. Kitaigorodskii, S. A., On the fluid dynamical theory of turbulent gas transfer across an air-sea interface in the presence of breaking wind-waves, J. Phys. Oceanogr., I4, 960-972, 1984. Kondo, J., Parameterization of turbulent transport in the top meter of the ocean, J. Phys. Oceanogr., 6, 712-720, 1976. Lange, P. A., B. J•hne, J. Tschiersch, and J. Ilmberger, Comparison between an amplitude-measuring wire and a slope-measuring laser water wave gauge, Rev. Sci. Instrurn., 53, 651-655, 1982. Ledwell, J. R., Gas ezchange across the air-water interface, Ph.D. thesis, Harvard Univ., Cambridge, Mass., 1982. Ledwell, J. R., The variation of the gas transfer coefficient with molecular diffusity, in Gas 2•nsfer at Water Surfaces, edited by W. Brutsaert and G. H. Jirka, pp. 293-302, D. Reidel, Hingham, Mass., 1984. Liss, P.S., Processes of gas exchange across an air-water interface, Gas exchange dependency on diffusion coefficient: Direct 222Rn and SH• comparisons in a small lake, J. Geophlis. Res., 87, 546-556, 1982. Weit•er, F., Verdunstungsmessungen in einem ringf6rmigen Wind-Wasser-Kanal mir Hilfe yon Psychrometern und einem WLD-System, Staatsexamensarbeit, Inst. filr Umweltphys., Univ. Heidelberg, 1980. Witting, J., Effects of plane progressive irrotational waves on thermal boundary layers, J. l•uid Mech., 50, 321-334, 1971. Wu, J., Wind-induced drift currents, J. l•uid Mech., 68, 49-70, 1975.
