1. Institute of Earth Sciences; The Hebrew University of Jerusalem; Israel
2. Biogeochemistry Department; Max Planck Institute for Chemistry; Mainz Germany
3. Department of Physics; University of Helsinki; Helsinki Finland
4. Earth Science Division; NASA Goddard Space Flight Center; Greenbelt Maryland USA
5. Atmospheric Composition Research Unit; Finnish Meteorological Institute; Helsinki Finland
6. Royal Netherlands Meteorological Institute (KNMI); AE De Bilt The Netherlands
7. Max Planck Institute for Meteorology; Hamburg Germany
8. Division of Nuclear Physics, Department of Physics; Lund University; Lund Sweden
9. Laboratory for Atmospheric and Space Physicsand Department for Atmospheric and Oceanic Sciences; University of Colorado Boulder; Boulder Colorado USA
10. Satellite remote sensing group; Max Planck Institute for Chemistry; Mainz Germany
11. Institute for Atmospheric and Climate Science; ETH Zurich; Zurich Switzerland
12. Institute for Meteorology; Universität Leipzig; Leipzig Germany