[13] Thus, investigating the temporal variations of the dates of equinoctial circulation rearrangements and winter/summer circulation periods duration in the midlatitude lower thermosphere, we have revealed their high variability and some regional (longitudinal) differences. Nevertheless, the tendency to a systematic increase of the autumn rearrangement duration in East Siberia and of the spring rearrangement duration in central Europe should be mentioned. As a rule, the duration of the winter circulation over Siberia is longer than over Europe. Also, the most interesting result is that the summer circulation duration has a tendency (trend) to a systematic decrease in the both regions.
[14] Comparing these results for the lower thermosphere with the results for the stratosphere [Langematz et al., 2003] and for the mesosphere [Offermann et al., 2003, 2004], we may conclude that the trends of the "summer duration" can depend on the height and can be reversed. It is still not clear whether these trends are related to an anthropogenic influence. The only appropriate way to check this suggestion is via further investigations of multiyear temperature and wind data and study of physical mechanisms.
Citation: (2005), Indications of long-term changes in the lower thermosphere prevailing zonal wind regime, Int. J. Geomagn. Aeron., 5, GI3010, doi:10.1029/2004GI000085.
Copyright 2005 by the American Geophysical Union