Effects of surface waves and ocean spray on the marine atmospheric boundary layer

By introducing a wave-induced component and a spray-induced component to the total stress, a mathematical model based on the Ekman theory is proposed detailing the influence of surface waves and ocean spray on momentum transport in marine atmospheric boundary layer (MABL). An analytic solution is presented for the modified Ekman model for an eddy viscosity coefficient varying linearly with height. The solution can be determined by the two-dimensional wave-number spectrum of ocean waves, the wave growth rate, the droplet flux, the geostrophic wind velocity, the Coriolis parameter and the densities of air and water. The effects of the wave-induced stress and the spray droplets on the steady near-surface wind profiles, the friction velocity and the drag coefficient in the marine atmospheric boundary layer are illustrated for different wind speeds by choosing different forms of the wave spectrum and different formulations of the wave grows rate and the droplet flux. The solutions proposed are compared with those of the model where the wave-induced stress or the spray-induced component or both of them are neglected. The solutions are also compared with the observational data. Illustrative examples and the comparisons between observations and the theoretical predictions demonstrate that the surface waves have a considerable impact for low and medium high wind speed on the near-surface mean wind profile and the turbulence structure of the marine atmospheric boundary layer. However, compared with the effect of wave-induced stress, spray droplets have more significant effects on the marine atmospheric boundary layer in the condition of very high speed.