1. Earth Planetary and Space Sciences, University of California, Los Angeles, CA 90095, USA.
2. Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723-6099, USA.
3. Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, 8010 Graz, Austria.
4. NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
5. University of New Hampshire, Durham, NH 03824, USA.
6. Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109-2143, USA.
7. Southwest Research Institute, San Antonio, TX 78228-0510, USA.