1. Department of Physics and Atmospheric Science; Dalhousie University; Halifax Nova Scotia Canada
2. Harvard-Smithsonian Center for Astrophysics; Cambridge Massachusetts USA
3. Spectroscopie de l'Atmosphère, Chimie Quantique et Photophysique; Université Libre de Bruxelles; Brussels Belgium
4. Sorbonne Universités, UPMC Univ. Paris 06; Université Versailles St-Quentin; CNRS/INSU, LATMOS-IPSL; Paris France
5. NASA Goddard Institute for Space Studies and Lamont-Doherty Earth Observatory; Columbia University; New York New York USA