A barotropic stability study of free and forced planetary waves /

• Main Author: Fyfe, John
• Format: Others
• Language: en
• Published: McGill University 1987
• Subjects: Rossby waves
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75433

The stability of free and forced planetary waves in a $ beta$-channel is investigated with a barotropic model. The forced waves at equilibrium result from a constant mean-zonal wind interacting with a finite-amplitude topography. === The frequencies of all infinitesimal perturbations to the equilibrium flows are determined numerically as a function of the flow parameters. The results are interpreted using a truncated spectral model and related to those of previous studies with infinite $ beta$-planes. In contrast to some earlier analytical studies we find that unstable long waves $(L sb{x}$ $>$ $L sb{y})$ exist under superresonant conditions. We also report on the existence of an interesting travelling topographic instability. === The linear instability of a weakly non-zonal flow is investigated numerically and analytically (via WKB theory). The theory reproduces the qualitative nature of the numerically-determined fastest-growing mode. === Nonlinear integrations, involving many degrees of freedom, reveal that initially-infinitesimal disturbances may grow explosively to finite-amplitude. The longer-term integrations are interpreted using a statistical mechanical model.