1. National Oceanic and Atmospheric Administration, Aeronomy Laboratory, R/AL7, 325 Broadway, Boulder, Colorado 80305, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, Harvey Mudd College, Claremont, California 91711, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida 33149, and Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720