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Ann. Geophys., 26, 1221-1232, 2008
www.ann-geophys.net/26/1221/2008/
© European Geosciences Union 2008
Trends in MLT region winds and planetary waves, Collm (52° N, 15° E)
Ch. Jacobi1, P. Hoffmann1, and D. Kürschner2
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.
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