0Lower-stratospheric Rossby wave trains in the Southern Hemisphere:

• Main Authors: Kazuaki Nishii, Hisashi Nakamura
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2003
• Subjects: Blocking Low-frequency variability Polar-night jet Refractive index Troposphere; Austral; polar night
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.600.8470; http://www-aos.eps.s.u-tokyo.ac.jp/~nishii/paper/QJRMS-NishiiNakamura04.pdf

Behaviour 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 de ned as daily low-pass-ltered departures from the circulation varying slowly with the seasonal cycle. A wave-activity ux and refractive index for stationary Rossby waves are utilized in our analysis, each of which was dened locally for the zonally varying westerlies. Subseasonal uctuations in the lower stratosphere were often associated with zonally conned 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. Upward injection of Rossby wave activity into the stratosphere tended to occur slightly upstream or just beneath of a lower-stratospheric waveguide associated with the developed polar-night jet (PNJ), which led to the subsequent formation of a well-dened wave train downstream along that jet. The distribution of the lower-stratospheric subseasonal variability thus exhibits signicant zonal asymmetries, re ecting those in the PNJ structure and the distribution of tropospheric disturbances. Seasonal evolution of the PNJ and that of the tropospheric intraseasonal variability substantially modulated the lower-stratospheric activity of subseasonal uctuations.