• An investigation of the dynamics of the mesopause: Fabry-Perot observations of winds and temperatures from nightglow emissions

      Conner, James F.; Smith, R. W. (1994)
      This work is a study of the behavior of tidal and planetary waves in the upper-middle atmosphere near the geographic south pole. This is accomplished with a characterization of the dynamic state of these motions. I used ground-based Fabry-Perot Spectrometer (FPS) measurements of the multiple-line, $P\sb1$(2)$\sb{c,d}$, nightglow emissions from the X$\sp2$II band of the neutral OH* molecule. I developed analytical techniques to determine a space and time distribution of spectral amplitudes and phases for the dynamic parameters of kinetic temperature and neutral wind in the OH* layer. Spectral analysis of the variations in this layer indicate the existence of two groups: a planetary wave group (periods of ${\sim}$1-10 days), with eastward phase progression, and a near semi-diurnal group (periods of ${\sim}$8-13 hours), with westward phase progression. Specific periods vary slightly for different years; this is most likely due to remote propagation conditions. Further separation of each group shows the wind oscillations exhibit wave-number one behavior with associated wave-number zero temperature oscillations, (with a few exceptions). The periodicities in the planetary group neutral wind motions are consistent with the model results of Salby, 1984, for propagation to high latitudes through realistic mean flows. The characterization of the dynamics of this layer has led to the discovery of a basic azimuthal asymmetry in the distribution of spectral amplitude for a given oscillation, that is, preferred azimuths. These preferred azimuths appear to be associated with changes in the direction, not the amplitude, of a cross-polar mean wind. This finding, in conjunction with the evanescence of some features, uncovered two cases of planetary wave dissipation. These occur when oscillations attempt to maintain their preferred alignment with a changing mean wind direction resulting in a decay of wind amplitude and a burst of thermal oscillation. Both cases occur at the same time. Coincident with these decays are enhancements in the wind and thermal energy of other, longer period, oscillations which share the same azimuthal preferences. Also coincident is an acceleration of the mean wind.