The 4-day wave and transport of UARS tracers in the austral polar vortex

Upper Atmosphere Research Satellite tracer data and isentropic transport ca lculations using U.K. Meteorological Office winds initialized with these da ta show evidence of eastward-traveling waves in the polar upper stratospher e in late austral winter 1992. Microwave Limb Sounder (MLS) H2O from protot ype iterative retrievals shows a 4-day wave signal at levels from similar t o 1.5 to 0.1 hPa; a 4-day wave signal was not obvious in production retriev als of MLS H2O. At 1800 K, the 4-day wave signal in MLS H2O has a double-pe aked structure in latitude, which is reproduced in isentropic transport cal culations. The time evolution,amplitude, and phase of the 3-day wave in the transport calculations agree well with observations at high latitudes; the position and shape of the polar vortex and of H2O drawn up around the vort ex are reproduced by the transport calculations. Spectral analyses of the C ryogen Limb Array Etalon Spectrometer (CLAES) CH4 are dominated by more slo wly eastward-moving waves (similar or equal to 6-10 days), but a weak 4-day wave signature is also present between similar to 1.5 and 4 hPa. Transport calculations initialized with CH4 Show similar eastward-traveling signals, good agreement with the phase of the observed signals, and overall agreeme nt with the observed position of the vortex. The qualitative success of the transport calculations in reproducing the phase and overall time evolution of high-latitude eastward-traveling waves in the polar upper stratosphere indicates that the winds used for the transport calculations are generally reliable, and that the eastward-traveling waves identified in the MLS H2O a nd CLAES CH4 originate to a large extent from horizontal transport processe s. Examination of the vertical structure of potential vorticity shows perio ds when at the highest levels studied (around 1800 K), the;4-day wave is re sponsible for the main motion of the vortex, whereas at lower levels (at an d below similar to 1400 K) the vortex motion is characterized by a lower ea stward progression, and the 4-day wave signal contributes to motions that a re confined inside the vortex.