1. Research and Development; Finnish Meteorological Institute; Helsinki Finland
2. School of GeoSciences; University of Edinburgh; Edinburgh UK
3. Arctic Research Centre; Finnish Meteorological Institute; Sodankylä Finland
4. Norwegian Institute for Air Research; Tromsø Norway
5. Swedish Meteorological and Hydrological Institute; Norrköping Sweden
6. Swiss Federal Office of Meteorology and Climatology; Payerne Switzerland
7. Meteorologisches Observatorium Lindenberg, Deutscher Wetterdienst; Tauche Germany
8. National Institute for Public Health and the Environment; Bilthoven Netherlands