1. National Oceanography Centre, Empress Dock, Southampton SO14 3ZH, UK.
2. National Oceanic and Atmospheric Administration (NOAA)–Atlantic Oceanographic and Meteorological Laboratory (AOML)/Physical Oceanography Division, 4301 Rickenbacker Causeway, Miami, FL 33149, USA.
3. Rosenstiel School of Marine and Atmospheric Sciences (RSMAS), University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA.
4. Max Planck Institute for Meteorology, Bundesstrasse 53, D-20146 Hamburg, Germany.