1. CEN, Meteorological Institute University of Hamburg Hamburg Germany
2. Institute of Geosciences and Earth Resources (IGG) National Research Council (CNR) Turin Italy
3. Institute of Atmospheric Sciences and Climate (ISAC) National Research Council (CNR) Bologna Italy
4. Department of Mathematics and Statistics University of Reading Reading UK
5. Centre for the Mathematics of Planet Earth University of Reading Reading UK
6. Geosciences Department and Laboratoire de Météorologie Dynamique (CNRS and IPSL), Ecole Normale Supérieure and PSL University Paris France
7. Department of Atmospheric & Oceanic Sciences University of California Los Angeles CA USA