The Instability of a Forced Standing Wave in a Viscous Stratified Fluid: A Laboratory Analogue of .the Quasi-Biennial Oscillation

Abstract

An experiment is described in which a standing internal wave is forced at the lower boundary of an annulus of salt-stratified water. At sufficiently large forcing amplitudes, the wave motion generates a strong mean azimuthal circulation which itself exhibits a long-period oscillation. Theoretical calculations, based on the wave-driven theory of the quasi-biennial oscillation of the tropical stratosphere (with suitable modifications), are performed and compared with the experimental results. Agreement is good and the study thus provides substantial confirmation of the fundamental principles of the theory.