Abstract/Summary

The ability of anthropogenic aerosols to freeze supercooled cloud droplets remains debated. Here, 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 to the nearby liquid-water clouds, the shortwave reflectance is reduced by 14% and longwave radiance increased by 4% in the glaciation-affected regions. There is an 8% reduction in cloud cover and an 18% reduction in cloud optical thickness. Additionally, daily glaciation-induced snowfall accumulations reach 15 mm. Glaciation events downwind 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.