A long-term comparison of Saskatoon MF radar and Collm LF D1 mesosphere-lower thermosphere wind measurements

Monthly mean profiles of mean winds and semidiurnal amplitudes and phases i n the height range 70-110 km measured at Saskatoon (52 degreesN; 107 degree sW) and Collm (52 degreesN; 15 degreesE) between 1983 and 1998 have been in vestigated. The seasonal variations of both mean winds and tidal amplitudes and phases are similar at both stations, but there are regular differences that lead to quasi-stationary non-zonal structures. The winter semidiurnal tidal amplitudes over Saskatoon are about twice as large than over Collm a t the respective height range, but the vertical phase structure is the same . The characteristic mean wind structures as, for example, the summer south ward wind maximum or the summer mesospheric easterly jet are found to be ab out 5-10 km lower over Saskatoon than over Collm. The mean winter vertical prevailing wind gradients are stronger over Saskatoon than over Collm. On a decadal time scale the variations of the wind parameters are similar, but on the interannual time scale variations differ; in winter this indicates a possible connection with the mean stratospheric circulation. (C) 2001 Else vier Science Ltd. All rights reserved.