STATIONARY ROSSBY-WAVE PROPAGATION IN A BAROCLINIC ATMOSPHERE

Observational studies of teleconnections in both solsticial seasons ha ve suggested various patterns of behaviour linked mainly to westerly j ets and equatorial westerlies. These have been interpreted using barot ropic Rossby-wave theory, and simulated using stationary forcing in ba rotropic models linearized about 300 hPa flows. In this paper the rele vant propagation behaviour is investigated using a baroclinic model wi th three-dimensional, climatological basic states. Time integrations a re performed using localized thermal forcing as a wavemaker. The propa gation results are qualitatively very similar to those obtained with t he barotropic model, though there are quantitative differences. The we sterly jets still act as strong waveguides. The shorter wavelengths an d smaller wave-activity speeds found with the baroclinic model are gen erally in better agreement with observation. Propagation into and hom the upper tropospheric equatorial westerlies in the east Pacific, prop agation across North America and propagation from Europe across the Ar abian Gulf are all found. The extent to which upper tropospheric weste rlies reach towards the equator influences the propagation into those regions. Barotropic models can only represent such behaviour if the ba sic state reflects the near-equatorial upper tropospheric zonal wind s tructure.