Anthropogenic snowfall
Anthropogenic snowfall
Industrieschnee
Description
Industrieschnee, or anthropogenic snow, is a wintertime meteorological phenomenon whereby local emissions of water vapour, usually from an industrial source, lead to snowfall downwind. In Munich (Germany), anthropological snowfall in known locally as bierschnee due to the many breweries found in close proximity to the city. The phenomenon also has been called industrial snowfall.
In Europe, it is usually associated with cold, stable, anticyclonic conditions, when surface fog (stratus) becomes super-saturated with water vapour, followed by ice nucleation and precipitation as light snow over a limited area of a few square miles.
In a comprehensive study of Industrieschnee in Switzerland spanning four consecutive winters from 1999 to 2003, an average of 4.5 days of anthropological snowfall were observed each winter at Zurich airport.
Industireschnee on parked car [Source: wiki commons. Author: Guido Radio, 26 December 2007.]
Formation process
The European context: anthropological snowfall from shallow stratus under stable anticyclonic conditions
Physically it is well known that cloud water droplets do not freeze as soon as the air temperatures drops below 0°C; in free and clean atmosphere, they do not spontaneously freeze until an air temperature of approximately -40°C has been achieved, and typically only 50% of cloud droplets are found in a frozen state at an air temperature of -20°C. However, surface fog and low cloud (anticyclonic gloom), which is a frequent visitor to lowland parts of the European continent and Britain during wintertime, has several characteristics that differentiate it from the much shorter duration clouds found in a free atmosphere, often persisting in the same location as a layer of surface stratus or stratocumulus for days at a time. in such conditions, which often occur simultaneously with poor air quality, ice nucleation may begin at much higher temperatures, typically about -7°C for European winter stratus and on occasion as high as -5°C in heavily polluted environments.
Lake effect snow and deep cold air outbreaks in cyclonic episodes
Where the surface inversion is much higher in altitude, such as in lake effect snowfall events, or in deep cold air outbreaks during cyclonic episodes, deep and more widespread snowfall may occur, extending tens of miles downwind, especially from very large industrial emission sites, due to the greater convective depth of the associated clouds.
Related articles
Further reading
- "Industrieschnee: An overview of some European anthropological snowfall events, with a case study from Bern (Switzerland), by Edward Graham, RMetS journal "Weather", January 2024.
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