Long-term variability and trends of midlatitude horizontal mesosphere/lower thermosphere winds

We analyse 43 years of mesosphere/lower thermosphere (MLT) horizontal winds obtained from a joint analysis of LF D1 lower ionospheric drift measurements from 1979 through 2006 and VHF meteor radar wind observations since 2004 at Collm (52°N, 13°E). Due to limitations of the earlier LF measurements, we restrict ourselves to the analysis of monthly mean winds near 90 km, which represents the height of maximum meteor heights as well as LF reflections in the MLT. In the 1980s and 1990s, we observe mainly positive trends of the zonal prevailing wind throughout the year, while the meridional winds tend to decrease in magnitude in both summer and winter. After 2000, no clear trends are detected. We also test Bayesian regression allowing us to model non-linear background trends with a priori unknown years of inhomogeneities. We compare these results with long-term partial reflection radar observations at Juliusruh (55°N, 13°E) since 1990. We also analyse interannual variability, and a quasi-decadal variability possibly owing to the 11-year solar cycle. These signals, however, are not stable throughout the time of observations.
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)