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UP: Fachverband Umweltphysik

UP 1: Oceanography and Climate Modelling

UP 1.1: Talk

Thursday, September 2, 2021, 11:00–11:15, H3

On the Serious Limitations of Current Field Measurements and Measuring Techniques for Air-Sea Gas Exchange — •Bernd Jähne — HCI am IWR, Universität Heidelberg — Institut für Umweltphysik, Universität Heidelberg

Despite half a century of field measurements of the gas transfer velocity across the air-ocean interface, it is still not possible to provide a reliable relation between the gas transfer velocity and the parameters driving the exchange process from these measurements. The basic limitations are two-fold. Firstly, the data mainly cover only medium wind speeds and show discrepancies which are not yet understood. Secondly, none of the existing field measuring techniques is really suitable for low-wind speeds. Mass balance methods suffer from the long time constants and eddy covariance measurements from too low fluxes. Active thermography does not work either, because of the need to heat a too large patch at the water surface. The floating chamber technique is not suitable at all to measure gas transfer velocity because it cuts off the wind shear at the water surface, sensible and latent heat transfer and disturbs the wind-wave field.

In consequence, novel field measuring techniques need to be invented, which avoid the disadvantages and shortcomings of the existing technique. In addition, laboratory measurements must be performed, which simulate the oceanic conditions in an appropriate way, close the fetch-gap and wave-age gap and give direct insight into the mechanisms.