Behavior of quasi-stationary circulation anomalies observed in the lower stratosphere of the extratropical Southern Hemisphere during austral late winter of 1997 is studied. The anomalies are defined as daily low-pass-filtered departures from the circulation varying slowly with the seasonal cycle. A wave-activity flux and refractive index for stationary Rossby waves are utilized in our analysis, each of which was defined locally for the zonally varying westerlies.

Subseasonal fluctuations in the lower stratosphere were often associated with zonally confined wave trains emanating upward from localized, quasi-stationary anomalies in the troposphere including blocking ridges. The three-dimensional propagation of the waves was found sensitive to the structure of a local waveguide. Specifically, local overlapping of the stratospheric polar-night jet (PNJ) with a tropospheric subpolar jet acts as a "chimney" through which wave activity accumulated in the troposphere is allowed to propagate upward into the stratosphere, followed often by the formation of a zonally-propagating wave train along the PNJ. If another such chimney forms in the exit of the PNJ, wave activity associated with a lower-stratospheric wave train would be allowed to propagate downward into the troposphere, contributing to blocking formation or large-scale cyclogenesis. In fact, large-scale, quasi-stationary cyclogenesis that occurred around August 10, 1997 to the south of Australia off the Antarctic coast was a typical example, to which downward wave-activity flux from a lower-stratospheric Rossby wave train contributed substantially that had emanated from a tropospheric blocking ridge over the southwestern Pacific.

The distribution of the lower-stratospheric subseasonal variability exhibits significant zonal asymmetries, reflecting those in the PNJ structure and the distribution of tropospheric disturbances. Seasonal evolution of the PNJ and that in the tropospheric intraseasonal variability strongly modulated the lower-stratospheric activity of subseasonal fluctuations.