Wind Shear

Wind-shear-induced turbulence is very effective in enhancing the gas exchange process near the air-water interface. Laboratory measurements in open-channel flow have shown that wind can increase the reaeration rate by factors up to 10 when compared to the cases with no wind. This is clear since the wind shear is acting directly at the surface. The constant wind shear at the water surface affects the gas-transfer rate predominantly through the development of a turbulent drag velocity profile.

Saturated

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Figure 4 Concentration fluctuation profiles. Data from gas transfer experiments with grid-generated turbulence performed by Herlina and Jirka GH (2007) Turbulent gas flux measurements near the air-water interface in a grid-stirred tank. In: Garbe C, Handler R, and Jahne B (eds.) Transport at the Air Sea Interface -Measurements, Models and Parameterizations. Berlin: Springer.

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Figure 4 Concentration fluctuation profiles. Data from gas transfer experiments with grid-generated turbulence performed by Herlina and Jirka GH (2007) Turbulent gas flux measurements near the air-water interface in a grid-stirred tank. In: Garbe C, Handler R, and Jahne B (eds.) Transport at the Air Sea Interface -Measurements, Models and Parameterizations. Berlin: Springer.

Wind speeds above 3 m s-1 have been found particularly effective since they induce appreciable wave growth and wave breaking (as will be discussed later).

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