Water Vapour and Clouds
The Earth's radiation budget is particularly sensitive to changes in water content and cloud cover during the tropopause. In this altitude region, on the one hand the exchange of water vapour between troposphere and stratosphere takes place, and on the other hand cirrus clouds form. Since both the water vapour and the cirrus clouds influence the radiation balance of the atmosphere, current research is being carried out both on the water vapour exchange processes and on the formation and life cycle of the cirrus ice particles. New insights are gained during national and international airplane and balloon measurement campaigns and at the AIDA cloud chamber. During the campaigns, e.g. the ice water content of the cirrus and the humidity content of the air is recorded with the high-precision measuring instruments FISH and CFH. The NIXE-CAPS and NIXE-Balloon instruments measure the number and size of the ice crystals. The measurement data is archived in the JULIA data base, that contains quality-checked water vapor, other trace gas and cloud measurements from numerous international measurement campaigns. For a better interpretation of the measurements and for the large-scale representation of water vapour transport and cirrus clouds, simulations are carried out with the detailed spectral microphysical cirrus model MAID and the large-scale Lagrangian Cirrus Model CLaMS-Ice, in cooperation with the working group 'Theory and simulation' at the IEK-7 and the Johannes-Gutenberg University Mainz within the framework of the Gutenberg Research College.