First results from the meteor radar at South Pole: A large 12-hour oscillation with zonal wavenumber 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° 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.