1. National Center for Atmospheric Research, Atmospheric Chemistry Observations and Modeling Laboratory, Boulder, Colorado, USA;
2. Department of Atmospheric Science, University of Wyoming, Laramie, Wyoming, USA;
3. Department of Chemistry, University of California, Irvine, Irvine, California, USA;
4. National Center for Atmospheric Research, Earth Observing Laboratory, Research Aviation Facility, Broomfield, Colorado, USA