The authors are grateful to two anonymous reviewers for their constructive comments, which helped to improve this paper substantially. Also, the authors thank Dr. Daniel Graybeal for carefully proofreading an earlier draft of this paper. This work was in part supported by National Science Foundation Grants ATM-0220009 (Colucci) and SES-0525707 (Vogelsang). The reanalysis data for the SH were provided by the Climate Diagnostics Center of the National Oceanic and Atmospheric Administration, and analyzed by S-PLUS software package from Insightful Inc.
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