LOW-FREQUENCY OSCILLATIONS OF FORCED BAROTROPIC FLOW

Jin and Ghil demonstrate that for topographically resonant flow, low-f requency finite-amplitude oscillations may arise from wave-wave intera ctions and topographic form drag. Their model is extended to include a zonally asymmetric vorticity source, which is shown to interact with the perturbation field to produce zonally rectified wave fluxes that d ramatically alter the Hopf bifurcation from stationary solutions to lo w-frequency oscillations. The frequency, intensity, and general charac ter of these oscillations are shown to depend crucially upon the phasi ng and relative strength of the forcings.