1. Universidad de Castilla-La Mancha (UCLM), Instituto de Ciencias Ambientales (ICAM), 45071 Toledo, Spain
2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
3. CNR-ISAC, 40129 Bologna, Italy
4. Athens National Observatory, P.O. Box 20048, 11810 Athens, Greece
5. Atmospheric Physics Group, University of León, 24071 León, Spain