Examples of the Horizontal Propagation of Quasi-stationary Waves

Abstract Examples of the diagnostic of the horizontal propagation of stationary wave activity proposed by Plumb are presented for a simple model of the atmospheric response to thermal forcing in the tropics, for the observed Southern Hemisphere winter mean stationary waves and for several cases of anomalous quasi-stationary waves in both the Northern and Southern hemispheres. For the simple model, the propagation of wave activity out of the tropics is clear. From the observational data, the apparent sources of anomalous stationary wave activity are located in the regions of the major middle latitude jets and storm tracks in both hemispheres in most cases. The results suggest that midlatitude processes, such as instabilities of the jet stream or interaction with transient eddies, are the major mechanisms for forcing anomalous stationary waves. There are indications that Rossby-like wave propagation from low latitudes plays a role in forcing anomalous stationary waves associated with Southern Oscillation ev...