Gas exchange experiments using time resolved UV-spectroscopy

The air sea gas exchange plays a key role in the development of the earth's climate. The oceans can act as a source or sink for climate relevant gases such as carbon dioxide, methane or dimethyl sulphide. Hydrodynamics in the viscous boundary layer at the free ocean surface and therefore the gas transfer across the interface are not well understood yet. UV-spectroscopy provides a direct and fast measuring method for gaseous or volatile tracers in the air and water phase. A wide range of hydrodynamic parameters, i.e. Schmidt numbers and solubilities is feasible with volatile hydrocarbons such as benzene or fluorobenzene. Multiple tracers may be observed simultaneously with the same non-invasive measuring technique. Laboratory experiments are performed at a 120 cm diameter circular wind-wave-facility in Heidelberg. A detailed study of gas transfer rate's dependence on the mean squared surface wave slope s^2, friction velocity u*, as well as on the Schmidt number Sc and solubility of the tracers will be performed. Also the influence of surface films or an increased viscosity is going to be examined. Preliminary results and further prospects are presented.