Much of the work this paper is based on was conducted when the authors were at The Florida State University, where they were supported by NSF Grant ATM-0003136, and NOAA Grant NA06GP0023. EC was also supported by a CRC award at FSU, and NSF Grant ATM-0296076 at SUNYSB. NH would also like to acknowledge the hospitality provided by Professor R. Lindzen at MIT.
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