1. Finnish Meteorological Institute, FI-00101 Helsinki, Finland
2. SRON Netherlands Institute for Space Research, 2333 CA Leiden, The Netherlands
3. Department of Earth Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
4. Department of Climate, Air & Sustainability, Netherlands Organisation for Applied Scientific Research (TNO), 3508 TA Utrecht, The Netherlands
5. Department of Environmental Sciences, Wageningen University & Research, Meteorology and Air Quality, 6700 AA Wageningen, The Netherlands
6. Institute for Marine and Atmospheric Research Utrecht IMAU, Utrecht University, Str. Princetonplein 5, 3584 CC Utrecht, The Netherlands
7. Laboratoire des Sciences du Climat et de l’Environnement, MCF–Université de Versailles Saint-Quentin, CEA-Orme des Merisiers, 91191 Gif-sur-Yvette, France
8. NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20771, USA
9. Earth System Science Interdisciplinary Center, University of Maryland, 5825 University Research Ct Suite 4001, College Park, MD 20740, USA
10. NOAA Global Monitoring Laboratory (GML), 325 Broadway, Boulder, CO 80305, USA
11. Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, Campus Box 450, Boulder, CO 80309, USA
12. Department of Earth Marine and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA