Winds and waves (10 min‐30 days) in the mesosphere and lower thermosphere at Saskatoon (52°N, 107°W, L = 4.3) during the year, October 1979 to July 1980

Abstract

Winds from a medium frequency (2.2 MHz) radar, operating as a partial reflection drifts system, have been obtained for four seasons of 1979/1980. Harmonic and spectral analyses have been used to provide monthly profiles of zonal and meridional winds, and the amplitudes and phases of 12 and 24 hour tides, at heights from 70 to 110 km. There are distinctive changes in tidal vertical wavelengths and phases between winter‐ and summer‐like months. Fluctuations of the mean daily wind and the tides during the stratwarm of February 1980 are documented. Oscillation of the wind, for all seasons, with periods from 2 to 30 days, are related to Rossby periods for atmospheric normal modes. Energy densities for oscillations appropriate to waves ranging in scale from gravity, through tidal, to planetary waves are evaluated by month and are compared with turbulence parameters for energy dissipation rates and vertical eddy diffusion coefficients. There are winter maxima and summer secondary maxima in both energy densities and turbulence parameters, which suggest a relationship between certain waves and the creation of turbulence.