1. Division of Atmospheric Physics; Max-Planck-Institute for Nuclear Physics; Heidelberg Germany
2. Department of Atmospheric Science; University of Wyoming; Laramie Wyoming USA
3. Division of Middle Atmospheric Research; Danish Meteorological Institute; Copenhagen Denmark
4. Istituto per la Scienza dell'Atmosfera e del Clima; Rome Italy
5. Ente per le Nuove Tecnologie; l'Energia e l'Ambiente, Sezione Clima, La Casaccia Research Center; Rome Italy
6. Laboratoire de Meteorologie Dynamique; Palaiseau France
7. Institute for Physics of the Atmosphere; Deutsches Zentrum für Luft- und Raumfahrt Oberpfaffenhofen; Wessling Germany