1. Science and Technology Branch, Environment Canada, Toronto, Ontario, Canada
2. Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, United States
3. Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada
4. Airzone One Ltd., Mississauga, Ontario, Canada
5. Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, United States
6. Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada