FIRST RESULTS FROM THE METEOR RADAR AT SOUTH-POLE - A LARGE 12-HOUR OSCILLATION WITH ZONAL WAVE-NUMBER ONE

The first mesopause-region (ca. 92+/-5 km) wind measurements from the meteor radar at Amundsen-Scott Station at South Pole are described. Measurements are made along four orthogonal azimuth directions approximately 2 degrees from the geographic South Pole. A large (+/-20 ms(-1)) oscillation in the northward wind is observed, with 12-hour period and zonal wavenumber one. A similar wave was observed during August 1-13, 1992 at South Pole by Hernandez et al. (1993) using optical methods. The predominant semidiurnal tide in the atmosphere is migrating with the apparent motion of the sun, with s = 2. The s = 1 oscillation is interpreted here to result from the nonlinear interaction between the migrating semidiurnal tide and a stationary wave with s = 1. The present mechanism represents an alternative to the gravity-wave driven 'pseudotide' theory put forth by Walterscheid et al. (1986) to explain the occurrence of unexpectedly large semidiurnal tidal oscillations at high latitudes.