1. National Oceanic and Atmospheric Administration, Geophysical Fluid Dynamics Laboratory, Princeton, NJ 08540–6649, USA.
2. Universite Pierre et Marie Currie/CNRS/IRD/MNHN LOCEAN-IPSL, Paris, France.
3. National Centre for Atmospheric Sciences-Climate, Department of Meteorology, University of Reading, Reading, UK.
4. National Center for Atmospheric Research, Boulder, CO, USA.