Recirculation Gyres Forced by a Beta-Plane Jet

Abstract

A numerical model, with quasigeostrophic and barotropic dynamics, is used to study the forcing of mean flows by an unstable jet. The initially zonal jet has specified shape and transport at the western inflow boundary and is sufficiently intense and narrow that the potential vorticity gradient changes sign, giving rise to barotropic instabilities. The resulting eddies act to smooth the potential vorticity anomalies transported into the domain and produce homogenized regions in which recirculations develop to the north and south of the jet. The intensity of these recirculations, as a function of nondimensional beta, is investigated and a simple, kinematic interpretation offered.