Upper Ocean Response to Large Wind Farm Effect in the Presence of Surface Gravity Waves

Theupper ocean responseinthe presenceofawindfarmis studied numerically,takinginto accounttheeffect of surface gravitywaves. Thefarm geometryisa simplified rigid rectangle with characteristic sizeof L aligned with the wind direction. Assuminga typicalwind deficit behindthefarm,an analytical2D U-shapedwake profileis appliedtodrive the upper ocean circulation. The shallow-water equations are modified to includefarm characteristic length, wind-wave and wave-current momentum transfer to study the circulation in the rectangular ocean basin. Solutions of this modified expressionasafunctionoftheRossby deformation radius confirmthattheupper ocean responseinthe vicinityofafarm is strongly related to the wave effects. For the numerical study, the Regional Ocean Modelling System (ROMS) and a wave-modified finite volume technique are used that the wave-modified finite volume technique shows a reasonable agreement withROMS simulation results. Numerical results for both linear and non-linearwave simulations show the existenceof horizontal shear stress gradients relatedtothe fluid motion,wave-induced stressandfarm characteristic size. The wind and wave forcing by including wind stress, Stokes drift and wave-induced stress creates symmetrical, range dependent dipoles in the upper ocean. The dipoles are sensitive to wind stress, wave forcing and L, and have tendency to become asymmetric with time. The near-surface Ekman current is affected significantly, and strong upwelling and downwelling occur.Thelinear numericalsolverresults,however,showthatthepycnoclinedepthasa responseofupper ocean to thefarm becomes weaker after almost one day. Including non-linear term, horizontal diffusion, and bottom friction leadstoa decreaseinthe strengthof eddies. But,the amplitudeof disturbancesintheleeofthefarm becomes weaker after almost three days.