Articles | Volume 26, issue 5
Ann. Geophys., 26, 1221–1232, 2008
https://doi.org/10.5194/angeo-26-1221-2008

Special issue: The fourth IAGA-ICMA-CAWSES Workshop "Long-Term Changes and...

Ann. Geophys., 26, 1221–1232, 2008
https://doi.org/10.5194/angeo-26-1221-2008

  28 May 2008

28 May 2008

Trends in MLT region winds and planetary waves, Collm (52° N, 15° E)

Ch. Jacobi1, P. Hoffmann1, and D. Kürschner2 Ch. Jacobi et al.
  • 1Institute for Meteorology, University of Leipzig, Stephanstr. 3, 04103 Leipzig, Germany
  • 2Faculty of Physics and Earth Sciences, University of Leipzig, Collm Observatory, 04779 Wermsdorf, Germany

Abstract. Long-period oscillations in the period range 2–30 days, interpreted as planetary wave (PW) signatures, have been analysed using daily mesosphere/lower thermosphere wind measurements near 90 km over Collm (52° N, 15° E) in the time interval 1980–2005. Interannual and interdecadal variability of PW are found. Since the 1990s, a tendency for larger zonal amplitudes compared to meridional ones has been observed, i.e. some long-term trends are visible, which are positive in the zonal component, but negative in the meridional component. There is a tendency of the trend to be non-linear for waves with periods lower than 7 days, so that a climatic transition appears around 1990, with smaller changes before and after that time. A solar cycle effect on PW is weak, but there is a tendency for a positive correlation between solar flux and wave activity, if a time lag of PW activity with respect to the solar flux of about 2 years is taken into consideration.