1. National Research Council of Italy, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Rome, Italy
2. Molflow, Scientific, Gråbo, Sweden
3. European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), Remote Sensing and Product Division, EUMETSAT-Allee 1, Darmstadt, Germany
4. Department of Information Engineering (DIET), Università degli Studi di Roma La Sapienza, Rome, Italy