1. Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA
2. Department of Chemistry, University of Oregon, Eugene, Oregon, USA
3. Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
4. National Park Service, Air Resources Division, Lakewood, Colorado, USA
5. Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, Colorado, USA