We thank David Baumhefner and Thomas Mayer of the National Center for Atmospheric Research (NCAR) for their help in performing the model integrations. We also appreciate the thoughtful comments of the anonymous reviewers. Many of the computational analyses were performed at NCAR. We would like to acknowledge the Scientific Computing Division of NCAR for computer time. NCAR is sponsored by the National Science Foundation. This study is based on work supported by the National Science Foundation under Grants ATM-9411188 and ATM-9634667.
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