The Dynamics of the Mesosphere and Lower Thermosphere at Saskatoon (52°N)

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Abstract
The dynamics of the upper Middle Atmosphere (60–110 km) over Saskatoon (52°N, 107°W) are described, using wind data from a medium frequency radar (2.2 MHz). Seasonal variations of gravity wave intensities (8 h-10 min) and tidal amplitudes and wavelengths (24 h-8 h) are considered. Below ∼80 km, gravity wave amplitudes are larger (≲100%) in winter than in summer months and there are equinoctial minima especially for short periods: tidal amplitudes are also slightly larger (∼40%) in winter, but wavelengths are comparable with season. Between 80 and 95 km seasonal variations of gravity wave amplitudes are small, but above that height winter values are 40–100% greater. The tidal amplitudes vary in similar fashion, mainly due to large semidiurnal tides above ∼90 km. Winter tidal wavelengths also tend to be shorter than in summer above 80 km altitude. These results are compared with recent data from other middle to high-latitude radar observatories: Monpazier (44°N), Christchurch (44°S), Poker Flat (65... Abstract The dynamics of the upper Middle Atmosphere (60–110 km) over Saskatoon (52°N, 107°W) are described, using wind data from a medium frequency radar (2.2 MHz). Seasonal variations of gravity wave intensities (8 h-10 min) and tidal amplitudes and wavelengths (24 h-8 h) are considered. Below ∼80 km, gravity wave amplitudes are larger (≲100%) in winter than in summer months and there are equinoctial minima especially for short periods: tidal amplitudes are also slightly larger (∼40%) in winter, but wavelengths are comparable with season. Between 80 and 95 km seasonal variations of gravity wave amplitudes are small, but above that height winter values are 40–100% greater. The tidal amplitudes vary in similar fashion, mainly due to large semidiurnal tides above ∼90 km. Winter tidal wavelengths also tend to be shorter than in summer above 80 km altitude. These results are compared with recent data from other middle to high-latitude radar observatories: Monpazier (44°N), Christchurch (44°S), Poker Flat (65...

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