Winds and Wave Motions to 110 km at Mid-Latitudes. IV. Coupling Between Internal Gravity Waves and the Mean Flow

Abstract

The results of radiowave, partial reflection drift (wind) measurements from 60–110 km, for the years 1973–74, at Saskatoon, Canada (52°N, 107°W), are presented. Intensive soundings (12 profiles per hour) have provided hourly, weekly and monthly profiles for the prevailing winds and also for the amplitudes of internal gravity (I.G.) waves (τ≈60 min). A relationship between the heights of reversals of the mean flow and of maxima in the I. G. wave amplitude profiles is demonstrated for 1973 and 1974. Hourly changes in the flow are also shown to be consistent with the effects of longer period (τ≈120 min) I. G. waves and/or momentum deposition by I. G. waves (τ≲60 min). It is shown that gravity waves are a major contribution to the dynamical and energetic balance of the lower thermosphere (80–110 km).