Abstract:
The regular heating and cooling of the atmosphere drives energetic weather systems near the earth's surface. Some of this energy is propagated upwards into the middle atmosphere in a variety of wave modes, including the regular 12 hour and 24 hour tidal motion. Unlike ocean tides, which are driven by the gravitational forces of the sun and moon, the atmospheric tides are driven by the sun's daily
... heating of the atmosphere. At this latitude, the lack of solar energy during the winter considerably weakens these tides and the 12 hour component loses its distinctive periodicity. A study of the time and space structure of large scale waves in the polar mesosphere and the nature of these tidal variations, is investigated in a joint collaboration with international co-operative research projects (Russia, USA, Australia, Japan, Canada and UK). Such international co-operation is essential because these tidal and wave structures have a very large scale, much bigger than the Antarctic continent itself, and information is required from research stations spread throughout Antarctica. The waves of interest have periods of 10 hours to 3 days, which includes both inertia-gravity and Rossby wave modes. The spatial scale of the waves is determined from observations at the South Pole and Scott Base (78S). The South Pole observations were made with a Gabry-Perot interferometer - with one being installed at Arrival Heights in January 2002. The instrument measures the temperature and line of sight, wind speeds from atmospheric emissions from an altitude of about 85 - 90 kms during the polar night. The instrument scans around the pole at an elevation of about 30° and therefore provides an estimate of the wave’s zonal wave number. The Scott Base observations were recorded simultaneously with a medium-frequency, partial reflection wind radar that measures the vertical profile of the horizontal wind over Scott Base and therefore provides an estimates of the vertical wave number of the mode. The coherence between the South Pole and Scott Base is a measure of the meridional wave number and extent of the wave. The Scott Base radar cannot measure atmospheric temperature and the South Pole equipment cannot measure altitude so the two experiments are complementary. 
