1 Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA.
2 Atmospheric, Climate, and Earth Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA.
3 National Oceanic and Atmospheric Administration (NOAA) Chemical Sciences Laboratory (CSL), Boulder, CO, USA.
4 Department of Atmosphere, Ocean and Earth System Modelling Research, Meteorological Research Institute, Tsukuba, Japan.
5 Department of Chemistry, Colgate University, Hamilton, NY, USA.
6 Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA.
7 BAE Systems, Inc, Boulder, CO, USA.
8 Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA. chakrabarty@wustl.edu.