Glaciation of liquid clouds, snowfall, and reduced cloud cover at industrial aerosol hot spots.

Toll, Velle; Rahu, Jorma; Keernik, Hannes; Trofimov, Heido; Voormansik, Tanel; Manshausen, Peter; Hung, Emma; Michelson, Daniel et al. · Science · 2024

basic_science · Level V

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Abstract

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.