RECIRCULATION GYRES FORCED BY A BETA-PLANE JET

A numerical model, with quasigeostrophic and barotropic dynamics, is u sed to study the forcing of mean hows by an unstable jet. The initiall y zonal jet has specified shape and transport at the western inflow bo undary and is sufficiently intense and narrow that the potential vorti city gradient changes sign, giving rise to barotropic instabilities. T he resulting eddies act to smooth the potential vorticity anomalies tr ansported into the domain and produce homogenized regions in which rec irculations develop to the north and south of the jet. The intensity o f these recirculations, as a function of nondimensional beta, is inves tigated and a simple kinematic interpretation offered.