Atmospheric waves (≈ 10 min–30 days) in the mesosphere and thermosphere at saskatoon (52°N, 107°W), October 1978–September 1979

Partial reflection radiowave wind observations have been made continuously at Saskatoon for 1 year (September 1978–August 1979). The winds have been obtained in real-time from a twin micro-processor system, that produces profiles (32 heights from 49 to 142km) at 5-min intervals: daytime/night-time profiles normally involve values from $\text{60}\text{70}$ to 120 km.These data have been analyzed to give the daily mean wind and the amplitudes and phases of planetary, tidal (24, 12 h) and internal gravity (I.G.) waves (0.20 ? τ ? 6h). There are oscillations in the mean daily wind, with periods of 2–30 days: the disturbance from 60 to 100 km caused by the stratwarm of February and March is documented. The characteristics of the semi-diurnal tide undergo significant changes in vertical wavelength and time of maxima between summer months (May–August) and winter months (November–February): during summer the S²₂ mode (λ_z ? 150km) seems to dominate, and in other months a mixture of modes (λ_z ? 50km) exist. The diurnal tide is less regular, but during winter and spring λ_z ? 30–60 km, and for other months is very large, suggesting the S_?1¹ mode. Energy densities and scale heights (h₀) are given, and the relative magnitudes of these for the various waves are discussed with respect to height and season: there is a general trend for the growth of the wave amplitude with height (shown by h₀) to increase in the order planetary, tidal and I.G. waves (h₀, ～3–15 km): largest values are in winter and spring. Wave energies are largest in winter, decrease during spring and increase throughout late summer and fall.