The influence of swell on the sea surface roughness and the growth of wind waves

The paper utilizes an extended Boussinesq wave model incorporating the wind forcing to examine the effects of swell on the spatial variation of the sea surface roughness and the growth of wind waves. We first introduce the new parameterization of the momentum flux transferred from the wind to surface gravity waves followed by an analysis of the effect of wave nonlinearity on the drag coefficient using Stokes' second-order wave theory. The time-domain Boussinesq wave model with the wind forcing is tested against the field measurements of wave growth rate in a shallow lake. Fairly good agreement between modeled and measured wave heights is obtained. Numerical experiments are then carried out to test a hypothesis for the suppression of the wave growth rate by the following swell. A simple mechanism is suggested to explain the influence of swell on the short waves observed in the numerical and laboratory experiments.