We thank L. Pan, F. Sassi, G. Branstator, R. Saravanan, and G. Kiladis and two anonymous reviewers for constructive comments on this paper. The National Center for Atmospheric Research (NCAR) is operated by the University Corporation for Atmospheric Research under the sponsorship of the National Science Foundation. A. Gettelman was supported at NCAR by the Advanced Study Program, the Atmospheric Chemistry Division, and the Climate and Global Dynamics Division.
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