Oceanic Quasi-geostrophic Turbulence Forced by Stochastic Wind Fluctuations

Abstract

Abstract The quasi-geostrophic response to stochastic wind fluctuations is calculated using a doubly periodic nonlinear model, with a vertical resolution of three modes in most cases. The influence of various parameters on the response is investigated: space and time scale of the forcing, stratification, bottom friction and β-effect. One aim of this study is to understand the influence of nonlinear transfer, and therefore, most simulations are situated in a parameter range where nonlinearities are important. The model “pseudodispersion relation” clearly shows two regimes: a linear regime made of resonant Rossby waves for the barotropic large scales and a nonlinear regime that is dynamically similar, for example, to quasi-geostrophic turbulence forced by baroclinic instability. The forcing time scale and β-effect have little influence on the response. The most important parameter is found to be the ratio R = κ1/Kmin of the largest forced wavelength to the wavelength of the first baroclinic mode Rossby radi...