Sea surface gravity wave - wind interaction in the marine atmospheric boundary layer

Abstract

In this study, we investigate the turbulence structure over idealized wind-generated surface gravity waves with varying wave age using a wave-modified one-dimensional boundary layer model. To prescribe the shape of the water wave and the associated orbital velocities, we employ an empirical expression for the wave energy spectrum without assigning a prognostic equation for modelling wave evolution under the action of wind. The key element in this model is the the work done by the wave-induced momentum flux on the atmosphere in the presence of waves. This is incorporated into the airflow using an exponential decay function. Finally, we conduct a series of numerical experiments to identify wave effects on the airflow over a wavy moving interface as a function of wave age, and to check the skill of the present model in capturing wave-induced processes in the marine atmospheric boundary layer (MABL). The results obtained confirm again the significant role of wave-induced processes in influencing the MABL, for example, in modifying the wind profile. Meanwhile, it is shown that the modified one-dimensional model is sensitive to wave parameterizations and the wave energy spectrum. However, a number of uncertainties remain for further investigation, such as the choice of wave energy spectrum, wave forcing parametrization, and surface boundary conditions for momentum and energy.