1. Department of Physics and Astronomy, Faculty of Environment, Science and Economy, University of Exeter , Exeter EX4 4QL, UK
2. Met Office , Fitzroy Road, Exeter EX1 3PB, UK
3. Maison de la Simulation, CEA, CNRS, Univ. Paris-Sud, UVSQ, Université Paris-Saclay , F-91191 Gif-sur-Yvette, France
4. Department of Earth and Planetary Science, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA
5. Department of Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA