1. Science Division, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
2. Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France
3. Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany
4. Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland