1. a School of Informatics and Multimedia Technology , University of North London , 166-220 Holloway Road, London, N7 8DB, UK
2. b Earth Observation Science Group, Department of Physics and Astronomy , University of Leicester , Leicester, LE1 7RH, England, UK
3. c Rutherford Appleton Laboratory , Atmospheric Science Group , Chilton, Oxfordshire, OX13 3DB, England, UK