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

Ch. Jacobi, P. Hoffmann, D. Kürschner
2008 Annales Geophysicae  
<p><strong>Abstract.</strong> Long-period oscillations in the period range 2&amp;ndash;30 days, interpreted as planetary wave (PW) signatures, have been analysed using daily mesosphere/lower thermosphere wind measurements near 90 km over Collm (52&amp;deg; N, 15&amp;deg; E) in the time interval 1980&amp;ndash;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
more » ... ends 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.</p>
doi:10.5194/angeo-26-1221-2008 fatcat:ujg35ia5a5gpbhjk7s7skxfjxq