ECOULEMENTS ATMOSPHERIQUES STATIONNAIRES, PERIODIQUES ET APERIODIQUES.

The authors consider the barotropic potential vorticity equation on a sphere with a simplified topography spectrally truncated to 25 components. The resulting dynamic system is studied as a function of the forcing and dissipation parameters. Steady, periodic and aperiodic solutions are obtained which exhibit some analogies with zonal and blocked atmospheric flow regimes. The bifurcations of steady solutions in phase space are explored systematically by a continuation method. Periodic and aperiodic regimes are studied by numerical integration of the time-dependent equation. The persistence of the different regimes and transitions between regimes is discussed.