Numerical studies of the surface-wave effects on the upper turbulent layer in the ocean

Abstract

The surface-wave effects on the structure of the ocean boundary layer are studied with a numerical boundary-layer model which consists of a closed system of equations for momentum, turbulent kinetic energy, turbulent exchange coefficient and expression for ocean stratification. Boundary conditions at the air’sea interface are calculated by use of a coupled air’sea boundary-layer model. The surface-wave effect is described by discontinuities of turbulent kinetic energy flux and mean wind energy flux across the air–sea interface. A series of numerical experiments is carried out to determine the effects of surface waves on the structure of the upper turbulent layer in the ocean. The numerical simulations demonstrate that surface waves strongly reduce a part of mean wind energy flux transmitted to the drift current and the current magnitude. These characteristics are strongly dependent on surface heat flux. The surface waves also reduce the neutral drag coefficient for a given wind speed to better match observations, but waves strongly increase turbulent kinetic energy at the ocean surface. The computations also confirm that the ratio of the mean wind energy flux transmitted to the drift current, to the total mean wind energy flux transmitted to the ocean is weakly dependent on surface heat flux. The model results are compared with observed data where available.