1. Atmospheric, Oceanic and Planetary Physics, Department of Physics, National Centre for Atmospheric Science, University of Oxford, Oxford, and European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom;
2. National Centre for Atmospheric Science, University of Reading, Reading, United Kingdom;
3. Department of Meteorology, and Department of Mathematics and Statistics, University of Reading, Reading, United Kingdom;
4. Earth Science Institute, Hebrew University, Jerusalem, Israel;
5. Met Office, Exeter, United Kingdom;
6. Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, United Kingdom;
7. Department of Mathematics and Statistics, University of Exeter, Exeter, United Kingdom;
8. Department of Meteorology, University of Reading, Reading, United Kingdom