1. Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
2. Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, United States
3. Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
4. Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80523, United States
5. School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China
6. Health Canada, Ottawa, Ontario K1A 0k9, Canada