Objectives

In the mesopause region (80 - 100 km) both tidal and planetary wave activity are subject to considerable long-term variability. This variability already has been investigated separately by means of long-term ground-based wind and absorption measurements, as it is reported in literature. However, the interpretation of these mesopause region upper middle atmosphere changes in terms of a connection with the overall atmospheric variability and to global climate change is not possible as long as the coupling processes and interaction mechanisms are not fully understood. To provide this knowledge the objectives of the project thus are:

(1) Estimating the day-to-day variability of the semidiurnal tide in the period range of planetary waves and the interannual variability of this modulation from different ground-based mesopause wind measurements, thus obtaining reliable results through cross-checks of the data.

(2) Analysing case-studies through co-ordinated measurements at several measuring sites. This is necessary to provide information of the tidal and wave parameters as the horizontal wavenumber.

(3) Investigating theoretically the interaction of tides and planetary waves using realistic wave parameters from the measurements to give insight to the wave-tidal interactions.

Within this project thus an important step towards a better understanding of middle atmosphere dynamics and a reliable description of atmospheric dynamics with respect to climate modelling will be performed.

The project is scheduled for the years 1998 - 2000. Three measuring campaigns of winds in the 80 - 100 km height region over Europe have been carried out during this period.

last change: 9.9.1999