We wish to acknowledge fruitful discussions with Earle Williams, Walter Petersen, Kenneth Cummins, Daniel Rosenfeld, Timothy Lang, and Donald MacGorman. We are grateful to Earle Williams for providing early access to ongoing research. Earle Williams, Ted Mansell, and an anonymous reviewer provided meticulous and helpful reviews that improved the manuscript. The NLDN lightning data were obtained from Vaisala, Inc., under the direction of Jerry Guynes of TAMU. We thank Brandon Ely and Scott Steiger for assistance with IDL code. This research was supported by National Science Foundation Grants ATM-0233780 and ATM-0442011.
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