1. Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland.
2. Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland.
3. Department of Physics, University of Helsinki, 00014 Helsinki, Finland.
4. Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
5. WSL (Swiss Federal Institute for Forest, Snow and Landscape Research) Institute for Snow and Avalanche Research SLF, 7260 Davos, Switzerland.
6. Helsinki Institute of Physics, University of Helsinki, 00014 Helsinki, Finland.
7. Tofwerk, 3600 Thun, Switzerland.
8. Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.
9. Aerodyne Research, Billerica, MA 01821, USA.