Resonant Excitation of Baroclinic Waves in the Presence of Ekman Friction

Abstract

The quasi-geostrophic dynamics of disturbances of a flow with a vertical shear is described by a transfer equation for potential vorticity. Wave solutions of this equation are represented by edge baroclinic waves (modes in a discrete spectrum) and singular modes in a continuous spectrum. When frequencies of these modes coincide, the effect of resonant excitation occurs in which the amplitude of baroclinic waves increases linearly. This paper studies this effect in the presence of Ekman bottom friction. It is shown that friction suppresses linear wave growth and gives rise to baroclinic waves of finite amplitude.