Study finds industrial aerosols can cause local snowfall by freezing clouds

Research by the University of Tartu has revealed a potential link between industrial air pollution and localized snowfall. Observations using both satellites and ground-based radar indicate that industrial facilities in North America, Europe and Asia can trigger local snowfall by causing ice to form in supercooled clouds. This phenomenon, observed near factories like copper smelters and coal-fired power plants, results from the release of aerosol particles that interact with clouds under specific atmospheric conditions. Dr. V. Toll, Associate Professor at the University of Tartu, highlighted the importance of interdisciplinary research to identify this process.

Aerosols and snow formation

Industries, including those involved in cement production, metallurgy and the burning of fossil fuels, emit aerosols, tiny solid and liquid particles that significantly affect the properties of clouds. Aerosols have been shown to increase the number of cloud droplets, thereby brightening clouds and reducing solar radiation reaching the Earth’s surface. However, the new results suggest that, under certain conditions, these particles also trigger the freezing of liquid cloud droplets, leading to snowfall downwind of industrial sites. Weather radar images taken near industrial sites in Canada and Russia show unique plumes of snow, a finding supported by satellite data indicating a simultaneous reduction in cloud cover.

Supercooling in cloud droplets

Cloud droplets can remain in liquid form at temperatures as low as -40 degrees Celsius in a process called supercooling. Only when suitable particles, such as anthropogenic aerosols, are present can these droplets freeze at temperatures between zero and -40 degrees Celsius. Toll’s team suggests that aerosol emissions, combined with heat and water vapor from industrial facilities, likely induce ice formation in clouds, leading to snowfall. Although this phenomenon has been observed at specific sites, it is unclear whether similar mechanisms affect cloud formation on a larger scale.

Further research is needed

The study, published in Science, highlights the need for further research into the role of different types of aerosols in ice nucleation processes. Future research will aim to understand whether these localized snowfalls have broader atmospheric impacts and identify the types of aerosol emissions most effective in initiating ice formation in supercooled clouds.