Size-resolved measurements of ice nucleating particles at North American and European sites

Monday, 14 December 2015: 10:35
3008 (Moscone West)
Ryan Mason1, Meng Si1, Cédric Chou1, Victoria Irish1, Robin Dickie2, Pablo Elizondo1, Rachel Wong1, Miranda Brintnell3, Michael Elsasser3, Walfried Lassar4, Kyle Pierce4, Warren Richard Leaitch3, Anne Marie Macdonald5, Andrew Platt3, Toom-Sauntry Desiree3, Roland Sarda Esteve6, Corinne L Schiller5, Kaitlyn J Suski7, Thomas Christopher James Hill7, Jonathan Abbatt8, John A Huffman9, Paul J DeMott10 and Allan K Bertram1, (1)University of British Columbia, Chemistry, Vancouver, BC, Canada, (2)University of British Columbia, chemistry, Vancouver, BC, Canada, (3)Environment Canada, Toronto, ON, Canada, (4)University of Denver, Chemistry and Biochemistry, Denver, CO, United States, (5)Environment Canada PYR, Air Quality Science Unit, Vancouver, BC, Canada, (6)CEA/CNRS-UVSQ, 5Laboratoire des Sciences du Climat et de l’Environnement, Gif/Yvette, France, (7)Colorado State University, Department of Atmospheric Science, Fort Collins, CO, United States, (8)University of Toronto, Chemistry, Toronto, ON, Canada, (9)University of Denver, Colorado, United States, (10)Colorado State University, Fort Collins, CO, United States
Ice nucleating particles (INPs) are a small fraction of the total aerosol population capable of catalyzing ice formation under atmospheric conditions, and may therefore influence the albedo and lifetime of mixed-phase and ice clouds. Compared to ambient measurements of the total number concentration of INPs, relatively little data exists on the size distribution of INPs in the atmosphere. Information on the size of INPs may be useful in source identification, modeling their transport in the atmosphere, and determining the degree to which common INP instrumentation captures the full atmospheric INP population. Measured using the micro-orifice uniform deposit impactor-droplet freezing technique (MOUDI-DFT), we report immersion-mode INP number concentrations as a function of particle size at ground-level sites in North America and Europe, including Arctic, alpine, coastal, marine, agricultural, and suburban environments. On average, more than 91 % of INPs active at -15 °C were found to be supermicron in size and 62 % were in the coarse mode (> 2.5 µm). While these percentages decreased with decreasing freezing temperature, many INPs remained in the supermicron with nearly half of those active at -25 °C belonging to the coarse mode.