1. Meteorological Institute, Ludwig-Maximilians-Universität, Theresienstr. 37, 80333 Munich, Germany;
2. Institute of Atmospheric Physics, German Aerospace Center (DLR), Oberpfaffenhofen, 82234 Wessling, Germany;
3. Leibniz Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig, Germany;
4. Institute for Atmospheric Physics, Johannes Gutenberg University, Becherweg 21, 55099 Mainz, Germany