This research was supported by the National Science Foundation, Grants ATM-9123797, ATM-9500613, and OCE-9521275, and by the Air Force Office of Scientific Research, Contract F49620-92-C-0033. The computations were performed on the Cray C90 at the Pittsburgh Supercomputing Center and on the Cray Y-MP and Cray J916 at the National Center for Atmospheric Research. Discussions with Donal O’Sullivan, Jim Riley, and Pete Lombard during the course of this work are gratefully acknowledged.
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