Researchers in the United States have discovered that accidental “cloud seeding” can be caused by commercial and private jetliners around the world, increasing the precipitation around major airports. When an aircraft flies through a cloud, its propellers cause an expansion and cooling of the air behind them which can cause water droplets to spontaneously cool and crystals to form. The aircraft sets off a chain reaction in the cloud that can continue on for hours after it has passed by. Though “cloud seeding” has been studied and practiced for decades as a way to induce precipitation, it seems we’ve been doing it all along without noticing.

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The researchers involved in the study — out today in the journal, Science — looked at satellite images, weather data and flight patterns from airports in Texas. “An aircraft propeller pushes air behind it, which generates thrust around the propeller tips,” said Andrew Heymsfield from the National Center for Atmospheric Research in Boulder, Colorado, a scientist involved in the study. “This thrust, in turn, cools the air behind the propellers by up to 30 degrees Celsius, freezing cloud droplets and leaving a stream of small ice particles trailing behind the propellers.”

As the aircraft flies through the cloud this effect creates canals of cold air and the crystals they produce cause extra amounts of snow precipitation in the winter, especially when there is low cloud cover around a specific airport. The researchers noted that knowing this information could lead airports to de-ice the wings of planes more to try to decrease this effect on the surrounding weather — colder wings, colder air thrusts. The researchers also discovered that this phenomenon is more common near the poles, where many of Earth’s weather monitoring systems are, and it could be skewing data that research teams are gathering in those areas. It seems that human design has quite the effect on nature and a lot of the time we don’t even notice.

Via Science Daily