1. National Oceanography Centre, Empress Dock, Southampton, SO14 3ZH, UK.
2. Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, USA.
3. National Oceanic and Atmospheric Administration Atlantic Oceanographic and Meteorological Laboratory, 4301 Rickenbacker Causeway, Miami, FL 33149, USA.
4. Max-Planck-Institut für Meteorologie, Bundesstraße 53, 20146 Hamburg, Germany.