1. Institute for Marine and Atmospheric Research Utrecht, PO Box 80005, 3508 TA Utrecht, The Netherlands;
2. NOAA-CMDL, 325 Broadway, Boulder, CO 80305-3328, USA
3. Koninklijke Nederlandse Meteorologische Dienst, PO Box 201, 3730 AE De Bilt, The Netherlands;
4. Goddard Space Flight Center, NASA, Greenbelt, MD 20771, USA;
5. Meteorologische Dienst Suriname, Magnesiumstraat 41, Paramaribo, Surinam;
6. Max Planck Institut für Chemie, PO Box 3060, Mainz, D-55128, Germany;