Variations of mean winds and solar tides in the mesosphere and lower thermosphere over time scales ranging from 6 months to 11 yr: Saskatoon, 52°N, 107°W

Abstract

The MF radar (spaced antenna) winds technique has been used to measure mean winds at Saskatoon (52°N, 107°W), Canada for over a solar cycle. The data from 1974 to 1991 are used to study different periods of oscillation such as 24-, 12-, 6- and 3-month oscillation etc. The mean wind and tidal data are also analyzed with a special emphasis upon solar activity and the possible influence of the equatorial quasi-biennial oscillation (QBO) on mesospheric circulation. The various analyses of the data stress the solar activity influence on mean winds and semidiurnal tidal amplitudes. While a range of periods of oscillation is observed in zonal and meridional winds during 12 yr, the zonal winds are more characterized with a 2-yr period of oscillation. At certain mesospheric heights, the 26-month period least squares fits to zonal winds as well as the frequency spectra clearly indicate a QBO of the mesospheric wind pattern. The study of the amplitudes and phases of the 24-, 12-, 6- and 3-month oscillation shows that there are trends of solar modulation in some height ranges for the 12-, 6- and 3-month oscillation. © 1994.