Boundary-Layer Model Results for Wind-Sea Growth

Abstract

A numerical model of the boundary layer of the atmosphere above a gravity surface wave is reviewed. The model results are used to obtain an expression for the wind input, the wave growth due to the wind. This is done for wave components that propagate at an arbitrary angle to the wind. Like other purely theoretical expressions for the wind input, the wind input from the boundary-layer model is much smaller than the wind input inferred from field experiments. To study the growth of wind sea, the wind input of the third-generation wave model WAM is replaced by the wind input from the boundary-layer model. The original WAM used a wind input that was inferred from field experiments. For the wave-wave interactions the discrete-interaction approximation is used, while the dissipation is tuned to get an appropriate saturation sea state. The balance between wind input, dissipation, and wave-wave interactions in the energy-containing range of the wave spectrum in this version of the WAM is very different from the balance between these terms in the original version of the WAM. Nevertheless, in both versions of the WAM the development of the wave spectrum of growing wind sea is in agreement with experimental data. It is concluded that a wave model based on the wave boundary-layer wind-input term is quite capable of reproducing the observed growth of wind sea.