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 da ta from 1979 to 1990 have been analyzed to investigate the solar activ ity effects on upper middle atmospheric winds and tidal amplitudes. Th e period of study covers two solar maxima and a solar minimum, the con tinuous data allow a systematic analysis of solar cycle dependence on mean winds and tides. The height region of 79-97 km sampled in the stu dy shows an apparent but very weak dependence of mean winds and tidal amplitudes on solar activity variation. The observed features are fair ly consistent with the early results reported by SPRENGER and SCHMINDE R [(1969) J. atmos. terr. Phys. 31, 217]. The mean zonal wind and the semidiurnal tidal amplitudes appear to exhibit positive and negative c orrelations with the solar activity, respectively; the statistical sig nificances of these correlations are generally low. There is a biennia l periodicity evident in the zonal wind oscillations but this does not have a consistent phase relationship with the equatorial stratospheri c wind oscillations (QBO). The meridional winds and the tidal amplitud es are characterized with different and quite irregular periods of osc illations (2-5 yr). The diurnal tidal variations over the solar cycle are small and irregular, although amplitudes are slightly larger durin g the solar minimum years.