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Volume 18, issue 21 | Copyright

Special issue: NETCARE (Network on Aerosols and Climate: Addressing Key Uncertainties...

Atmos. Chem. Phys., 18, 15669-15685, 2018
https://doi.org/10.5194/acp-18-15669-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 01 Nov 2018

Research article | 01 Nov 2018

Ice-nucleating ability of aerosol particles and possible sources at three coastal marine sites

Meng Si1, Victoria E. Irish1, Ryan H. Mason1, Jesús Vergara-Temprado2,a, Sarah J. Hanna1, Luis A. Ladino3,b, Jacqueline D. Yakobi-Hancock3, Corinne L. Schiller4, Jeremy J. B. Wentzell5, Jonathan P. D. Abbatt3, Ken S. Carslaw2, Benjamin J. Murray2, and Allan K. Bertram1 Meng Si et al.
  • 1Department of Chemistry, University of British Columbia, Vancouver, V6T1Z1, Canada
  • 2Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
  • 3Department of Chemistry, University of Toronto, Toronto, M5S3H6, Canada
  • 4Air Quality Science Unit, Environment and Climate Change Canada, Vancouver, V6C3S5, Canada
  • 5Air Quality Research Division, Environment and Climate Change Canada, Toronto, M3H5T4, Canada
  • anow at: Institute for Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland
  • bnow at: Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City, Mexico

Abstract. Despite the importance of ice-nucleating particles (INPs) for climate and precipitation, our understanding of these particles is far from complete. Here, we investigated INPs at three coastal marine sites in Canada, two at mid-latitude (Amphitrite Point and Labrador Sea) and one in the Arctic (Lancaster Sound). For Amphitrite Point, 23 sets of samples were analyzed, and for Labrador Sea and Lancaster Sound, one set of samples was analyzed for each location. At all three sites, the ice-nucleating ability on a per number basis (expressed as the fraction of aerosol particles acting as an INP) was strongly dependent on the particle size. For example, at diameters of around 0.2µm, approximately 1 in 106 particles acted as an INP at −25°C, while at diameters of around 8µm, approximately 1 in 10 particles acted as an INP at −25°C. The ice-nucleating ability on a per surface-area basis (expressed as the surface active site density, ns) was also dependent on the particle size, with larger particles being more efficient at nucleating ice. The ns values of supermicron particles at Amphitrite Point and Labrador Sea were larger than previously measured ns values of sea spray aerosols, suggesting that sea spray aerosols were not a major contributor to the supermicron INP population at these two sites. Consistent with this observation, a global model of INP concentrations under-predicted the INP concentrations when assuming only marine organics as INPs. On the other hand, assuming only K-feldspar as INPs, the same model was able to reproduce the measurements at a freezing temperature of −25°C, but under-predicted INP concentrations at −15°C, suggesting that the model is missing a source of INPs active at a freezing temperature of −15°C.

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Using the concentrations of ice-nucleating particles (INPs) and total aerosol particles measured at three coastal marine sites, the ice-nucleating ability of aerosol particles on a per number basis and a per surface-area basis were determined as a function of size. The ice-nucleating ability was strongly dependent on size, with larger particles being more efficient. This type of information can help determine the sources of INPs and constrain the future modelling of INPs and mixed-phase clouds.
Using the concentrations of ice-nucleating particles (INPs) and total aerosol particles measured...
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