1. a Department of Atmospheric Science, University of Wyoming, Laramie, Wyoming
2. b Laboratory of Atmosphere and Space Physics, University of Colorado Boulder, Boulder, Colorado
3. c Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado
4. d Department of Chemistry, University of Colorado Boulder, Boulder, Colorado
5. e Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado
6. f National Center for Atmospheric Research, Boulder, Colorado