The authors are very grateful to Mark Serreze (University of Colorado, Boulder) for providing us with his cyclone identification/tracking program (FORTRAN codes) and useful advice regarding the use of the program. The authors are greatly indebted to Yang Feng for his excellent computing support and to Bin Yu and Walter Skinner for their useful internal review of an earlier version of this manuscript. The authors wish to thank the two anonymous reviewers for their constructive review comments.
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