Dipl.-Met. Matthias Voigt

Ph.D. student in the group Theoretical Cloud Physics, headed by Prof. Peter Spichtinger.

Properties of cirrus clouds may vary on a short spatial scale. The aim of my work is to investigate the sources of these inhomogeneities. My work takes place in the context of the AIRTOSS project where cirrus clouds over North and Baltic sea were probed in may and september 2013 by in situ measurements of particles and radiation with an aircraft and a towed sensor shuttle. During the field campaign our group supported the experimental groups with evaluation of numerical weather predictions and flight planning. I contribute to the analysis of the campaign by carrying out numerical simulations that are compared to the measurements in order to investigate the most probable scenario for the source of the inhomogeneities.

The meteorological conditions leading to the cirrus formation are investigated using meteorological analyses as obtained from the European Centre for Medium-Range Forecasts (ECMWF). The ECMWF wind fields are used to calculate backward trajectories. From these calculations the large-scale/mesoscale motions are derived. The meteorological analyses and measurements (temperature, wind, humidity) are used as initial conditions for cirrus cloud resolving simulations where the small scale motions are analyzed. We use a LES model, including a state-of-the-art ice microphysics scheme for 2D and 3D idealized and quasi-realistic simulations. In order to address the impact of dynamics vs. microphysics, we investigate different environmental conditions. The microphysical and macrophysical properties of the simulated cloud are finally compared to the measurements, in order to get some information about the most probable scenarios.