Plumes of pollution from big factories can make it snow

Recent satellite images have uncovered a fascinating phenomenon where plumes of pollution from industrial factories have the power to induce snowfall and create gaps in clouds that span over extensive areas. The discovery sheds light on the intricate relationship between aerosol pollution and cloud dynamics.

It is well-established that minuscule particles of pollutants, such as soot, can influence clouds in various ways. These particles can serve as nuclei for water vapour to condense on, kickstarting cloud formation. Moreover, pollutants have the ability to modify the characteristics of existing clouds.

During research on these effects, Velle Toll from the University of Tartu in Estonia observed peculiar gaps in clouds downstream of major pollution sources. By analyzing thousands of satellite images from North America and Eurasia, Toll and his team identified 67 locations where this phenomenon occurs under specific atmospheric conditions.

Validation from weather radar confirmed that these occurrences were indeed causing snowfall. In one notable instance, a significant snowfall of up to 15 millimetres covered a vast 2200-square-kilometre area.

The process behind this snowfall initiation involves pollutant particles triggering the freezing of supercooled water droplets in clouds around them, leading to the formation of ice crystals that evolve into snowflakes. Toll explains, “And if we have water coming out of the cloud as snow, then we end up with less clouds.”

In the absence of aerosol particles, water droplets in clouds can remain in liquid form even at frigid temperatures as low as -40°C (-40°F).

The identified pollution sources primarily consist of oil refineries and factories producing metals, cement, or fertilizers. Interestingly, the researchers also observed a similar effect near four nuclear power stations that do not emit aerosol pollutants.

One hypothesis suggests that the warm air rising from these power stations may be lifting aerosol pollution from other sources, although further investigation is needed for confirmation. Toll mentions, “We don’t have a definite explanation for that.”

In theory, this aerosol-induced snowfall effect could be harnessed to intentionally trigger snowfall, but it would only be effective in regions where clouds containing supercooled liquid water droplets already exist.

Overall, the discovery of factory aerosols manipulating cloud behavior highlights the intricate interplay between human activities and atmospheric processes, offering new insights into the potential impacts of pollution on weather patterns.