Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada

Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA

Department of Physics, University of Helsinki, Helsinki, Finland

Department of Chemical Engineering, Columbia University, New York, NY, USA

Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA

Atmospheric Sciences Division, Brookhaven National Laboratory, Building 815E, Upton, NY, USA

Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA

Department of Civil Engineering, Indian Institute of Technology, Kanpur, India

Environment Canada, Toronto, Ontario, Canada

School of Earth and Environment, University of Leeds, Leeds, UK

Department of Applied Environmental Science and Bert Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden

Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada

Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA