Upper Troposphere / Lower Stratosphere (UTLS)
- The research group’s field activities mainly focus on measurements in altitudes of the Upper Troposphere/Lower Stratosphere (UT/LS) by using airborne platforms with advanced ceiling such as the Russian M55 Geophysica. Further instrumental applications were realized on board the French ATR-42, the British BAe-143, and the German HALO (G550), Falcon-20, Learjet 35A and Partenavia P68. The group works with condensation particle detectors and optical particle counters in the submicron particle size range. Impactors are used for sampling aerosols for offline analysis with SEM, ESEM, NanoSIMS techniques. Cloud particles are probed with forward scattering particle spectrometers and shadow cast imaging sensors and digital holography.
- Holography is a tool to examine the local environment surrounding cloud particles, either in-situ in atmospheric clouds or in laboratory or wind-tunnel simulated clouds. One can examine, for example, the three-dimensional clustering of cloud particles due to turbulence and the local spatial structure of mixed phase clouds (i.e. how are water droplets distributed about the ice particles in mixed-phase clouds). Because one can measure thousands of particles in a local sample volume (a single hologram), one can also estimate a local size distribution on cm-scales and also how local size distributions vary with position inside a cloud.
- The world wide unique facility of our research group, the Mainz vertical wind tunnel allows one to freely suspend various hydrometeors as for example rain and cloud drops, ice particles, and snow flakes in a vertical air stream so that no wall effects are to be expected. As the hydrometeors are levitated at their terminal velocities the ventilation coefficients are in the real-atmospheric order. In the wind tunnel single events with individual hydrometeors are observed. Environmental conditions such as air speed, temperature, humidity and depending on the study, concentrations of trace gases or aerosol particles are controlled exactly and continuously recordered. To perform experiments with the ice phase the wind tunnel air can be cooled down to -30°C. The air humidifying is possible up to the saturation level. The air speed can reach values up to 40 m/s; allowing the whole range of hydrometeors, starting with small drops having radii between 30 und 500 µm, large drops with equivalent radii up to 3 or 4 mm, ice crystals, snow flakes, graupels and even large hailstones, can be floated. The Mainz vertical wind tunnel is therefore an outstanding tool for microphysical and chemical investigations of hydrometeors. Read more...