Glaciation of liquid clouds, snowfall, and reduced cloud cover at industrial aerosol hot spots.
Velle Toll, Jorma Rahu, Hannes Keernik, Heido Trofimov, Tanel Voormansik, Peter Manshausen, Emma Hung, Daniel Michelson, Matthew W Christensen, Piia Post, Heikki Junninen, Benjamin J Murray, Ulrike Lohmann, Duncan Watson-Parris, Philip Stier, Norman Donaldson, Trude Storelvmo, Markku Kulmala, Nicolas Bellouin
Author Information
Velle Toll: Institute of Physics, University of Tartu, Tartu, Estonia. ORCID
Jorma Rahu: Institute of Physics, University of Tartu, Tartu, Estonia. ORCID
Hannes Keernik: Institute of Physics, University of Tartu, Tartu, Estonia. ORCID
Heido Trofimov: Institute of Physics, University of Tartu, Tartu, Estonia. ORCID
Tanel Voormansik: Institute of Physics, University of Tartu, Tartu, Estonia.
Peter Manshausen: Department of Physics, University of Oxford, Oxford, UK. ORCID
Emma Hung: Environment and Climate Change Canada, Toronto, ON, Canada. ORCID
Daniel Michelson: Environment and Climate Change Canada, Toronto, ON, Canada. ORCID
Matthew W Christensen: Atmospheric, Climate, and Earth Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA. ORCID
Piia Post: Institute of Physics, University of Tartu, Tartu, Estonia. ORCID
Heikki Junninen: Institute of Physics, University of Tartu, Tartu, Estonia. ORCID
Benjamin J Murray: Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK. ORCID
Ulrike Lohmann: Institute of Atmospheric and Climate Science, ETH Z��rich, Z��rich, Switzerland. ORCID
Duncan Watson-Parris: Scripps Institution of Oceanography, University of California, San Diego, Ja Jolla, CA, USA. ORCID
Philip Stier: Department of Physics, University of Oxford, Oxford, UK. ORCID
Norman Donaldson: Environment and Climate Change Canada, Toronto, ON, Canada. ORCID
Trude Storelvmo: Department of Geosciences, University of Oslo, Oslo, Norway. ORCID
Markku Kulmala: Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki, Finland. ORCID
Nicolas Bellouin: Department of Meteorology, University of Reading, Reading, UK. ORCID
The ability of anthropogenic aerosols to freeze supercooled cloud droplets remains debated. In this work, we present observational evidence for the glaciation of supercooled liquid-water clouds at industrial aerosol hot spots at temperatures between -10�� and -24��C. Compared with the nearby liquid-water clouds, shortwave reflectance was reduced by 14% and longwave radiance was increased by 4% in the glaciation-affected regions. There was an 8% reduction in cloud cover and an 18% reduction in cloud optical thickness. Additionally, daily glaciation-induced snowfall accumulations reached 15 millimeters. Glaciation events downwind of industrial aerosol hot spots indicate that anthropogenic aerosols likely serve as ice-nucleating particles. However, rare glaciation events downwind of nuclear power plants indicate that factors other than aerosol emissions may also play a role in the observed glaciation events.
