VARIATIONS OF MEAN WINDS AND TIDES IN THE UPPER MIDDLE ATMOSPHERE OVER A SOLAR-CYCLE, SASKATOON, CANADA, 52-DEGREES-N, 107-DEGREES-W

Saskatoon (52-degrees-N, 107-degrees-W) medium frequency (MF) radar data from 1979 to 1990 have been analyzed to investigate the solar activity effects on upper middle atmospheric winds and tidal amplitudes. The period of study covers two solar maxima and a solar minimum, the continuous data allow a systematic analysis of solar cycle dependence on mean winds and tides. The height region of 79-97 km sampled in the study shows an apparent but very weak dependence of mean winds and tidal amplitudes on solar activity variation. The observed features are fairly consistent with the early results reported by SPRENGER and SCHMINDER [(1969) J. atmos. terr. Phys. 31, 217]. The mean zonal wind and the semidiurnal tidal amplitudes appear to exhibit positive and negative correlations with the solar activity, respectively; the statistical significances of these correlations are generally low. There is a biennial periodicity evident in the zonal wind oscillations but this does not have a consistent phase relationship with the equatorial stratospheric wind oscillations (QBO). The meridional winds and the tidal amplitudes are characterized with different and quite irregular periods of oscillations (2-5 yr). The diurnal tidal variations over the solar cycle are small and irregular, although amplitudes are slightly larger during the solar minimum years.