1. Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology (ETH), Winter-thurerstrasse 190, CH-8057 Zurich, Switzerland.
2. Pacific Northwest National Laboratory, Post Office Box 999, Richland, WA 99352, USA.
3. National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305, USA.
4. Bureau of Meteorology, Melbourne, Victoria 3001, Australia.
5. Estonian Meteorological and Hydrological Institute, 61602 Toravere, Estonia.