On the Self-Interaction of a Geostrophic Current and its Inertia-Gravity Normal Modes

Abstract

A shallow-water channel model on an f plane is used to study the interaction of barotropic inertia-gravity normal modes and geostrophic currents. Computed numerically are 1) the normal modes associated with a, zonal current, 2) the nonlinear wave forcing produced by the normal modes, and 3) the equilibria of the zonal current forced by the waves. A comparison is made among cases of varying wavelength and channel width as well as for various basic state currents. The behavior displayed by the normal modes and the equilibria is not radically different from that of other barotropic models. The concept of wave-mean interaction formulated here is briefly contrasted with that in the theories of Adjustment noninteraction and initialization. The results here indicate that modification of certain classical notions may be desirable if the inertia-gravity component is to he included in the dynamics.