The quasi two-day wave (QTDW) at 82–97km altitude over Collm (51° N, 13° E) has been observed using a VHF meteor radar. The long-term mean amplitudes calculated using data between September 2004 and August 2014 show a strong summer maximum 5 and a much weaker winter maximum. In summer, the meridional amplitude is slightly larger than the zonal one with about 15ms°1 at 91 km height. Phase differences are slightly greater than 90° on an average. The periods of the summer QTDW vary between 43 and 52H during strong bursts, while in winter the periods tend to be more diffuse. On an average, the summer QTDW is amplified after a maximum of 10 zonal wind shear which is connected with the summer mesospheric jet and there is a possible correlation of the summer mean amplitudes with the backgound wind shear. QTDW amplitudes exhibit considerable inter-annual variability, however, a clear relation between the 11 year solar cycle and the QTDW is not found.

The quasi two-day wave (QTDW) at 82–97km altitude over Collm (51° N, 13° E) has been observed using a VHF meteor radar. The long-term mean amplitudes calculated using data between September 2004 and August 2014 show a strong summer maximum 5 and a much weaker winter maximum. In summer, the meridional amplitude is slightly larger than the zonal one with about 15ms°1 at 91 km height. Phase differences are slightly greater than 90° on an average. The periods of the summer QTDW vary between 43 and 52H during strong bursts, while in winter the periods tend to be more diffuse. On an average, the summer QTDW is amplified after a maximum of 10 zonal wind shear which is connected with the summer mesospheric jet and there is a possible correlation of the summer mean amplitudes with the backgound wind shear. QTDW amplitudes exhibit considerable inter-annual variability, however, a clear relation between the 11 year solar cycle and the QTDW is not found.

Collm meteor radar (MR) winds have been analyzed with respect to quasi 2-day wave (QTDW) amplitudes and phases. Two methods have been considered, one of them taking into account the varying period and the other one assuming a fixed period of 48 h. While the use of a fixed period leads to a slight underestimation of amplitudes, the seasonal cycle, the inter-annual variability, and the distribution of amplitude and phase diffferences between the zonal and meridional horizontal component are similar for both methods. One may conclude that the use of a fixed period is justified for analyzing QTDW amplitudes and phases as long as only qualitative results are required.

Mesopause region winds have been measured by the low-frequency (LF) method at Collm until 2008. Since 2004, meteor radar (MR) measurements have been performed also. The LF and MR data set are combined to obtain a continuous time series of monthly zonal prevailing winds from 1979 through 2013 at about 90 km altitude. It has been found that, on a monthly time scale, the difference between zonal prevailing winds measured by LF and MR are small. During the 35-yr time interval considered, the zonal winds show positive trends towards more westerly winds throughout the year except for spring. There is a tendency that in spring and summer the trends are changing from more positive to small or negative after 1995. There is a possible influence of the 11-year solar cycle, most visible during early summer and early winter, and the effect weakens during recent years.

Seit Juli 2004 wird an der Außenstelle Collm der Universität Leipzig kontinuierlich ein Meteorradar zur Messung des Windes und der Temperatur im Höhenbereich 80-100 km betrieben. Die Messungen dienen der Überwachung der Dynamik der Mesopausenregion, und ihrer Änderungen auf Zeitskalen von Tagen und Jahren. Erste Ergebnisse vom Herbst 2004 werden dargestellt, verglichen mit den ebenfalls am Collm durchgeführten Langewellenreflexionswindmessungen. Die Ergebnisse zeigen, dass die vertikale Struktur des Windsystems und die Variationen von Tag zu Tag qualitativ übereinstimmen. Die mit dem Meteorradar gemessenen Gezeitenamplituden sind jedoch systematisch größer als diejenigen, die mit dem Langewellenverfahren gemessen wurden.

Results of mesosphere/lower thermosphere wind measurements over Collm in 2007, carried out with a meteor radar (MR) and the LF D1 method in 2007 are presented. The seasonal cycles of wind parameters are in qualitative agreement with other years, but strong southward winds are noted in the first half of the year. The tidal amplitudes are lower than on a long-term average. Trend analyses of the LF winds show an increase of the zonal prevailing wind throughout the year, a decrease of the meridional Brewer-Dobson-circulation, and a tendency of the semidiurnal tidal phases towards later times, possible in connection with middle atmosphere cooling. However, these trends seem to decrease in recent years. The LF winds are in good agreement with modern empirical models, partly owing to the fact that these models base on LF and similar wind measurements. MR winds are usually stronger, which is especially the case with the semidiurnal tide. / Es werden die Ergebnisse von Meteorradar- und LF D1-Windmessungen im Mesopausenbereich über Collm im Jahre 2007 vorgestellt. Der Jahresgang der Windparameter ist in qualitativer Übereinstimmung mit denjenigen anderer Jahre, aber deutliche nach Süden gerichtete Winde werden in der ersten Hälfte des Jahres festgestellt. Trendanalysen der Windparameter zeigen eine Zunahme des Zonalwindes, eine Abnahme des Meridionalwindes, und eine Tendenz zur Verschiebung der halbtägigen Gezeiten zu späteren Zeitpunkten, was in Übereinstimmung mit einer Abkühlung der Atmosphäre ist. Diese Trends weisen in den letzten Jahren jedoch eine Tendenz zur Verringerung auf. Die mit der LF D1-Methode gemessenen Winde sind in guter Übereinstimmung mit empirischen Modellen, was jedoch zum Teil darauf zurück zu führen ist, dass diese Modelle auch auf Collmer Daten beruhen. Meteorradars messen im Allgemeinen stärkere Winde, dies zeigt sich vor allem bei den halbtägigen Gezeiten.

Time series of mesosphere/lower thermosphere half-hourly winds over Collm (51.3°N, 13.0°E) have been obtained from 1984 – 2008 by low frequency spaced receiver measurements and from 2004 to date by very high frequency meteor radar Doppler wind observations in the height range 82 – 97 km. From half-hourly differences of zonal and meridional winds, gravity wave (GW) proxies have been calculated that describe amplitude variations in the period range of 1 – 3 hours. After applying corrections to account for instrumental differences, GW climatology and time series have been obtained. The mean GW activity in the upper mesosphere shows maximum amplitudes in summer, while in the lower thermosphere GWs maximize in winter. Positive/negative long-term trends are visible in winter/summer. Interannual and quasi-decadal variations of GW amplitudes are also visible, but these are intermittent. / Zeitreihen von halbstündlichen Winden der Mesosphare/unteren Thermosphare über Collm (51,3 ¨ °N, 13,0°E) wurden von 1984 bis 2008 durch LF-Driftmessungen und von 2004 bis heute durch VHF-Meteorradarmessungen im Höhenbereich von 82 – 97 km gewonnen. Aus halbstündlichen Differenzen von zonalen und meridionalen Winden wurden Proxies für Schwerewellen (GW) berechnet, welche Amplitudenvariationen im Periodenbereich von 1 – 3 Stunden beschreiben. Nach Korrekturen zur Berücksichtigung instrumenteller Unterschiede wurden GW-Klimatologie und Zeitreihen erstellt. Die mittlere GW-Aktivitat in der oberen Mesosphäre zeigt Maxima im Sommer, wahrend in der unteren Thermosphäre GW-Maxima im Winter auftreten. Positive/negative Langzeittrends sind im Winter/Sommer sichtbar. Interannuale und quasi-dekadische Variationen der GW-Amplituden sind ebenfalls sichtbar, aber nicht durchgehend erkennbar.