1. Department of Atmospheric Sciences; University of Washington; Seattle Washington USA
2. Department of Physics and Atmospheric Science; Dalhousie University; Halifax, Nova Scotia Canada
3. Harvard-Smithsonian Center for Astrophysics; Cambridge Massachusetts USA
4. Division of Engineering and Applied Sciences and Department of Earth and Planetary Sciences; Harvard University; Cambridge Massachusetts USA
5. Département de Physique, Ecole Normale Supérieure; University Abdou Moumouny of Niamey; Niamey Niger
6. Laboratoire de Physique de l'Atmosphère; Université de Cocody; Abidjan, Ivory Coast Africa
7. Centre de Recherches Hydrologiques; Yaoundé Cameroon
8. Observatoire Midi-Pyrénées; Laboratoire d'Aérologie; Toulouse France