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A. H. Manson, J. B. Gregory, and D. G. Stephenson

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<λ<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.

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A. H. Manson, J. B. Gregory, and D. G. Stephenson

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).

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A. H. Manson, J. B. Gregory, C. E. Meek, and D. G. Stephenson

Abstract

The behavior of the daily noon winds at 52°N, 107° W (Saskatoon, Canada) at altitudes from 52 km to about 110 km are studied for the interval September 1974–Apzil 1975. These data are compared with ROCOB temperatures and winds (≲55 km) for Churchill (94°N, 59°W). The thermal wind equation and running cross-correlation analysis are used to demonstrate the seasonal variations of the meridional temperature gradient, and of coupling, within the stratosphere, mesosphere and thermosphere. The effects of the stratospheric warming of January 1975 are also investigated. The correlations were dominated by this event, and show that coupling occurred between the stratosphere (20–30 mb) and mesosphere/thermosphere (≲100 km) during the first half of January. Spectral analysis for two intervals before and after the stratwarm show that coupling was more significant during the late winter; periods near 2–3, 4–5 and ≳20 days were involved.

Comparisons between daily mean winds and daily noon winds show that up to 100 km the daily variations are well represented by the noon data; above 100 km the daily variations are less reliable but trends are well represented by the noon data.

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