Poster Open Access

The Heidelberg Aelotron - new perspectives for laboratory investigations of small-scale air-sea interaction

Jähne, Bernd; Schimpf, Uwe; Balschbach, Günther; Garbe, Christoph; Degreif, Kai

A large annular wind/wave facility with quasi unlimited fetch has been built at the Institute for Environmental Physics University of Heidelberg, Germany. The facility is designed to perform detailed studies of small-scale air-sea interaction. It is optimized for imaging short wind waves, accurate measurements of gas transfer velocities and to deploy infrared imaging techniques.

The annular water channel has an outer diameter of 10 m and a width of 0.65 m. It is 2.4 m high and can be filled with water up to a height of 1.2 m, which corresponds to a water volume of approximately 21 m3. Wind is generated by a rotating paddle wheel up to 15 m/s. The air space is gas tight and the walls are insulated. Experiments can be performed with deionized water, artificial sea water, surfactants, and reactive gases. An air conditioning system controls independently humidity and air temperature. In conjunction with an air flushing system net heat fluxes at the water surface can be adjusted from -500 to 1000 W/m2. A water current with a speed up to 0.5 m/s against the wind direction can be generated separately by a set of thrusters.

Air temperature, water temperature, relative humidity, water current and wind speed are continuously monitored. Standard measurements techniques include a color imaging slope gauge (mean square wave slope and wave spectra), an infrared imaging system (heat transfer velocity), and infrared absorption spectroscopy (gas transfer velocities of He, H2, N20, and F12).

We plan to focus in the next decade on measurements revealing the mechanism of air-sea gas transfer including the effects of surfactants and waves. The experimental possibilities of the facility are detailed to show the opportunities for international cooperation.

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