Temperature variations on extreme time scales
Prof. Dr. Dirk Offermann
Bergische Universität Wuppertal
Fachbereich C - Mathematik und
- Dr. Michael Jarisch
The dynamics of the middle atmosphere (10-100 km) is analyzed by studying its circulation, waves, and turbulence. These parameters are continuously varying and interacting in a complicated manner. Part of these features are subject to solar influences, and others are not. This will be studied in detail during the international CAWSES program. In the present project we specifically propose to analyze mesosphere temperature variations on very short as well as on very long time scales. We have available an extended and unique set of OH temperatures (87 km +- 5 km) which was measured at Wuppertal since 1980 and is still continued. The short period variations of these data have not been evaluated yet. We propose to do this now and to develop a gravity wave climatology on this basis. We also plan improved measurements during the project (with a peak stepping method) by which we expect to improve our analysis capability for the existing data. A special aspect of the data interpretation will be the coupling of the upper mesosphere to the middle stratosphere by gravity waves.
Analysis of very slow temperature variations (on decadal scales) has revealed a circulation change in the middle atmosphere. It appears to be linked to climatic changes in the troposphere. Continuation of the Wuppertal measurements during the present project should allow a more precise estimation of the solar cycle influence on the mesospheric temperatures. This in consequence would yield a better determination of the decadal trends (change in summer duration). On that basis we plan to analyze the suitability of the data for long-term prognoses.