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), a prominent feature of the mesosphere mainly around solstices, is simulated with the COMMA-LIM Model (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology). The calculations are made approximately one month after the summer solstice in the Northern Hemisphere when the QTDW reaches its maximum in the mesosphere and lower thermosphere. The results show that the QTDW produces a moderate westward forcing of the zonally averaged flow and a poleward driving of the residual mean meridional circulation. / Die Quasi Zwei-Tage Welle (QTDW), eine deutliche Erscheinung in der Mesosphäre kurz nach dem Sommer Solstitium, wird mit dem COMMA-LIM Modell (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology) simuliert. Die Zwei-Tage Welle wurde unter Juli-Bedingungen an der unteren Modellgrenze angeregt, zu der Zeit, zu der sie ihr Maximum in der Mesosphäre und unteren Thermosphäre erreicht. Die Ergebnisse zeigen eine sich westwärts ausbreitende Welle, die auf den Grundstrom eine moderate Beschleunigung nach Westen ausübt. Die residuelle mittlere Meridional Zirkulation erfährt dadurch eine zum Pol gerichtete Triebkraft.

The quasi two-day wave (QTDW), a prominent feature of the mesosphere mainly around solstices, is simulated with the COMMA-LIM Model (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology). The calculations are made approximately one month after the summer solstice in the Northern Hemisphere when the QTDW reaches its maximum in the mesosphere and lower thermosphere. The results show that the QTDW produces a moderate westward forcing of the zonally averaged flow and a poleward driving of the residual mean meridional circulation. / Die Quasi Zwei-Tage Welle (QTDW), eine deutliche Erscheinung in der Mesosphäre kurz nach dem Sommer Solstitium, wird mit dem COMMA-LIM Modell (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology) simuliert. Die Zwei-Tage Welle wurde unter Juli-Bedingungen an der unteren Modellgrenze angeregt, zu der Zeit, zu der sie ihr Maximum in der Mesosphäre und unteren Thermosphäre erreicht. Die Ergebnisse zeigen eine sich westwärts ausbreitende Welle, die auf den Grundstrom eine moderate Beschleunigung nach Westen ausübt. Die residuelle mittlere Meridional Zirkulation erfährt dadurch eine zum Pol gerichtete Triebkraft.

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.