ERA-40 data were provided by the European Centre for Medium-Range Weather Forecasts from their Web site at http://data.ecmwf.int/data/d/era40_daily/. NCEP–NCAR reanalysis data were provided by the NOAA–CIRES Climate Diagnostics Center, Boulder, Colorado, from their Web site at http://www.cdc.noaa.gov. Interpolated OLR data were also provided by NOAA–CIRES from the same Web site. This work was supported by NSF Grant ATM-0212685.
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