Laboratory modelling of air-sea interaction under severe wind conditions

Wind-wave interaction at extreme wind speed is of special interest now in connection with the problem of explanation of the sea surface drag saturation at the wind speed exceeding 30 m/s. The main objective of this work is investigation of factors determining momentum exchange under high wind speeds (up to U₁₀>;40 m s^-1) basing on the laboratory experiment in a well-controlled environment. Air flow velocity measurements were complemented by measurements of the wind wave spectra. The tendency to saturation of the surface drag was observed for wind speeds exceeding 25 m s^-1, accompanied by the saturation of wind wave slopes. The effect of surface drag saturation can be explained quantitatively within the quasi-linear model of the air boundary layer above the waved water surface, when the contribution of the short-wave part of the wind wave spectrum to aerodynamic resistance of the water surface is taken into account.