Quasigeostrophic turbulence in a three-layer model: effects of vertical structure in the mean shear

Abstract

For equal values of the mean vertical shear, eddy fluxes and energies are greater when the shear is concentrated at lower levels (d2U/dz2<0) than when the shear is concentrated at higher levels (d2U/dz2>0). Eddy fluxes are more sensitive to lower- than to upper-level mean temperature gradients. This relative sensitivity is a function of γ = f2Λ/(βN2H), where Λ is the mean vertical shear and H is the depth of the fluid. It is enhanced as γ is reduced, as the unstable modes become shallower, until the eddies become almost completely insensitive to the strength of the upper-layer wind for γ <0.5. -from Authors