Rare industrial snowfall in UK thought to be caused by pollution

A rare phenomenon known as industrial snow appears to have occurred near Heathrow Airport earlier this year, a study has revealed.

Satellite imagery showed three large white bands on the ground in parts of Surrey, despite relatively dry conditions in the area at the time. The snowfall recorded on January 23 was near industrial facilities southeast of Heathrow Airport.

Dr. Julian Meyers, an independent weather and climate consultant who saw the snow and wrote the study, said the only real explanation is that pollution triggered the snowfall.

Man-made or industrial snow occurs when moisture in the air condenses around tiny pollution particles, such as forming snowflakes. The conditions have to be just right, with temperatures low enough and enough moisture in the atmosphere. Only a handful of cases have been reported in the UK.

Meyers said it started on a cold morning, recalling how his village of West Molesey in Surrey was enveloped in icy fog. It dawned on me that this wasn’t just frost.

Upon closer inspection, he discovered that the snow was very dry, like dried coconuts, and that unlike frost, it seemed to have been deposited on the surface from above. Meyers said this was initially confusing because the area was under a ridge of high pressure and little rain was expected at the time.

A colleague alerted him to a satellite image of eastern Surrey taken on the morning of Jan. 23, which showed three bands of what looked like light snow. Mace hypothesized that a breeze pushed industrial snow north-northwest, where it was deposited along these tracks.

Satellite imagery also shows a few passing clouds. However, it is unlikely that the snow is formed by clouds in a more typical way, said Giles Harrison, a professor in the Department of Meteorology at the University of Reading, who was not involved in the work. For regular snow to fall, a front would have to move through the area, but there is no evidence of this.

Mays said factors other than industrial pollution from ground sources may have influenced the day’s events. These include potential ice trails left behind by planes entering and exiting the airport. Moisture from nearby reservoirs may also have an impact.

But, he added, the evidence suggests something is causing the water droplets in the fog to expand and freeze, turning into snowflakes. Contamination is thought to provide toeholds, or nucleation sites, that enable water droplets to form ice crystals.

“It’s pretty special,” Harrison said. He co-authored a 2009 study on early reports of industrial snowfall in the UK. One of the incidents related to emissions from a cider factory. One local was quoted in the study as saying: It snowed, and the snow smelled like apples.

Harrison added that industrial snowfall is not typically predicted, which is why it might surprise observers.

This phenomenon has also been reported in the United States. A 2014 case in Amarillo, Texas, was blamed on steam from a large power plant that was thought to have turned to snow in the frigid February air. A spokesman for the local energy company told the Amarillo Global News at the time that people working at the plants had been noticing this for years.

Harrison said such unusual snowfalls were likely to become even rarer in the UK as average temperatures were expected to continue to rise due to global warming.

Mays added that his witnessing of the phenomenon was definitely an accident, considering how small the snowfall was. “If I lived a mile and a half away, I probably wouldn’t notice it,” he said.