[1] The seasonal, geographical, and altitudinal dependence of gravity wave activity in the lower stratosphere over Antarctica is presented. Gravity wave activity is estimated by calculating potential energy, E p , from radio occultation profiles obtained by the Challenging Minisatellite Payload/Global Positioning System (CHAMP/GPS) experiment. Significant seasonal variation of wave activity is observed. Smaller wave activity in summer is attributed to waves with small phase velocities experiencing critical level filtering. At other times of the year, when wave activity is large, less filtering occurs and the strong background wind is likely to cause Doppler shifting of waves to longer vertical wavelengths, which can reach larger amplitudes before saturating. Relationships between gravity wave activity and geographic location indicate that topography is a strong source for wave activity especially over the Antarctic Peninsula. However, wind rotation in this area was found to reduce the wave energy in summer at certain altitudes. A strong enhancement of wave energy is observed at the edge of the polar vortex. Again, reduced critical level filtering and Doppler shifting in the area of the jet are likely to be major causes for this finding. Possible limitations to this study due to observational filtering are discussed.

[1] A function that approximates atmospheric tidal behavior in the polar regions is described. This function is fitted to multistation radar measurements of wind in the mesosphere and lower thermosphere with the aim of obtaining a latitude-longitude-height description of the variation of tides over the whole Antarctic continent. Archival wind data sets are combined with present-day ones to fill the spatial distribution of the observations and to reduce the potential effects of spatial aliasing. Multiple years are combined through the compilation of monthly station composite days, yielding results for each month of the year. Despite potential problems associated with year-to-year variations in the tidal phase, a useful climatology of Antarctic zonal and meridional tidal wind components is compiled. The results of the fits reproduce the major features of the high-latitude tidal wind field: the dominance of the semidiurnal migrating mode in the winter months and the presence of a semidiurnal zonal wave number one component in the summer months. It is also found that the summer semidiurnal tide contains a zonal wave number zero component.

[1] This study presents the first coincident observation of inertia-gravity waves (IGWs) by lidar and radar in the Antarctic mesopause region. This is also the first known observation of two simultaneous IGWs at the same location. An Fe Boltzmann lidar at Arrival Heights (77.8 S, 166.7 E) provides high-resolution temperature data, and a co-located MF radar provides wind data. On 29 June 2011, coherent wave structures are observed in both the Fe lidar temperature and MF radar winds. Two dominant waves are determined from the temperature data with apparent periods of 7.7 AE 0.2 and 5.0 AE 0.1 h and vertical wavelengths of 22 AE 2 and 23 AE 2 km, respectively. The simultaneous measurements of temperature and wind allow the intrinsic wave properties to be derived from hodograph analyses unambiguously. The analysis shows that the longer-period wave propagates northward with an azimuth of θ = 11 AE 5 clockwise from north. This wave has a horizontal wavelength of l h = 2.2 AE 0.2 Â 10 3 km and an intrinsic period of t I = 7.9 AE 0.3 h. The intrinsic horizontal phase speed (C Ih ) for this wave is 80 AE 4 m/s, while the horizontal and vertical group velocities (C gh and C gz ) are 48 AE 3 m/s and 0.5 AE 0.1 m/s, respectively. The shorter-period wave has t I = 4.5 AE 0.3 h and θ = 100 AE 4 with l h = 1.1 AE 0.1 Â 10 3 km and C Ih = 68 AE 5 m/s. Its group velocities are C gh = 58 AE 5 m/s and C gz = 1.1 AE 0.1 m/s. Therefore, both waves propagate with very shallow elevation angles from the horizon (f = 0.6 AE 0.1 and f = 1.1 AE 0.1 for the longer-and shorter-period waves, respectively) but originate from different sources. Our analysis suggests that the longer-period IGW most likely originates from the stratosphere in a region of unbalanced flow.

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[1] This paper describes the use of EOS Microwave Limb Sounder (MLS) data to observe the field of traveling planetary waves with quasi 16 day periods. This study utilizes MLS v2.2 temperature and geopotential data between 1 January 2005 and 31 December 2008 in the range 316 hPa to 0.001 hPa (approximately 8 to 97 km) to examine these waves. Analysis demonstrates that the quasi 16 day wavefield is made up of a number of components with westward and eastward propagating s = 1 and s = 2 waves generally dominant. In the Northern Hemisphere the westward and eastward propagating s = 1 waves have similar magnitudes and are larger than the other modes, while in the Southern Hemisphere, the eastward propagating s = 1 and s = 2 waves are larger than the westward propagating wave modes. All of the modes examined display strong seasonal patterns in the temperature amplitude, significant variability in the wave activity from year to year, and the presence of strong pulse-like patterns in the activity. All of the modes also display large median temperature amplitudes poleward of 40 degrees in both hemispheres. Our analysis also demonstrates that the variability in winter from year to year is larger in the Northern Hemisphere than the Southern Hemisphere. Detailed study also suggests that the exclusion of waves from regions of negative refractive index squared likely forms much of the seasonal pattern observed. Thus, regions of strong westward wind speeds effectively exclude vertically propagating waves as expected from theory. The reflection and absorption of waves associated with critical lines is also likely to explain the frequent occurrence of standing wave patterns in the EOS MLS temperature observations. This study highlights the potential of MLS observations for observing waves from the upper troposphere to the lower mesosphere.