Aufteilung des Transferwiderstands zwischen Luft und Wasser beim Austausch flüchtiger Substanzen mittlerer Löslichkeit zwischen Ozean und Atmosphäre

The main focus of this thesis is the investigation of the air-water exchange of volatile tracers of medium solubility. The transfer resistances of tracers with a broad spectrum of solubilities were measured in experiments at the Aeolotron wind-wave facility. The dependence of transfer resistances on friction velocity and mean square slope is studied for both clean water and water with an added surfactant. It becomes clear that neither friction velocity nor mean square slope alone can be used to describe gas exchange for both cases. In addition Schmidt number scaling for tracers with medium solubility was investigated. Schmidt number scaling is a common method to compute the transfer resistance of a tracer using another one. This requires that the air-side or water-side transfer resistance are negligible. This is not the case for tracers with medium solubility. Here an extended Schmidt number scaling method is tested experimentally for the first time. The air-sided resistance is determined by the Schmidt number scaling with a very well soluble reference-tracer (Methanol, alpha = 5470). Accordingly the water-sided resistance is calculated with a water-sided controlled reference-tracer (N2O, alpha = 0.6). The total resistance is obtained using both parts of the resistance and the partitioning equation of Liss and Slater (1974). The comparison of computed and measured resistances shows good agreement. Finally, a simple function to empirically describe the ratio of air-sided to total resistance in dependence of friction velocity and solubility is presented.