We are thankful to the NOAA–CIRES Climate Diagnostics Center (Boulder, CO) for providing the NCEP–NCAR reanalysis dataset and the interpolated OLR dataset from their Web site (http://www.cdc.noaa.gov/). We also thank the two reviewers for their help improving this paper. This research was in part supported by the EC Environment and Climate Research Programme (Contract: EVK2-CT-1999-00022).
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