Georgia Sotiropoulou, Ecole Polytechnique Federale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory of Atmospheric Processes and their Impacts (LAPI), Lausanne, Switzerland, Athanasios Nenes, Ecole Polytechnique Federale de Lausanne, School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory of Atmospheric Processes and their Impacts (LAPI), Lausanne, Switzerland; Foundation for Research and Technology, Patras, Greece, Annica Ekman, Stockholm University, Department of Meteorology, Stockholm, Sweden, Julien Savre, Ludwig Maximilians University of Munich, Munich, Germany, Sylvia Sullivan, Columbia University of New York, Department of Earth and Environmental Engineering, New York, NY, United States, Tom Lachlan-Cope, NERC British Antarctic Survey, Cambridge, United Kingdom and Gary Lloyd, University of Manchester, Manchester, United Kingdom