Planes flying over rain or snow can intensify the precipitation by as much as 10-fold, according to a new study.

Researchers at the University of Helsinki and the Finnish Meteorological Institute find that the rain- and snow-bursts are not caused by emissions from the aircraft but are the peculiar consequence of the aircrafts’ wings passing though clouds of supercooled water droplets in cloud layers above a layer of active rain or snow.

Under the right conditions, this effect can boost rain and snow storms over airports, where many planes intersect the cloud layer on approach and descent.

“The interesting thing about this feature is that it is caused by aircraft, but it is not caused by pollution,” said Dimitri Moisseev, a researcher at the University of Helsinki and the Finnish Meteorological Institute and the lead author of the new study in AGU’s Journal of Geophysical Research: Atmospheres. “Even if there would be absolutely ecological airplanes, which don’t have any combustion, no fuel or anything, it would still happen.”

Moisseev says the study could help meteorologists “nowcast” natural rain and snow conditions 2 to 6 hours into the future, which is essential for airport operations.

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