Winds and Wave Motions to 110 km at Mid–Latitudes I. Partial Reflection Radiowave Soundings, 1972–73

Abstract

Measurements of winds (60?110 km) for Saskatoon, Canada (52N, 107W), have been obtained from a partial reflection radiowave system. Closely spaced atmospheric soundings (12 per hour) for heights between 51?117 km with 3?km height resolution, were made between August 1972 and September 1973. The median of the wind profiles for a given hour has been identified mainly as the prevailing wind, and the irregular components from each profile as internal atmospheric gravity waves (30<τ<60 min, 12<?<30 km). The amplitudes and shears of the irregular winds have their largest values in winter. A diurnal variation has been found, showing a minimum in amplitude and shear values near noon for all seasons; this variation is especially noticeable above 90 km. Comparisons of seasonal variations in the prevailing zonal and meridional winds, with the amplitudes of the irregular winds, suggest interactions involving critical layers and momentum transfer. Tropospheric weather systems are considered in relation to the gravity wave amplitudes.