Airplanes Make it Rain (and Snow)

Posted By: The Ski Channel on July 1, 2011 1:00 pm

A recent study shows that areas near airports sometimes receive an extra dosage of rain and snow when an aircraft takes off.

The study, from the National Center for Atmospheric Research (NCAR), focuses on the “cloud seeding” phenomenon. Cloud seeding occurs when turboprop airplanes fly through mid-level clouds in sub five degree Fahrenheit temperatures and cause holes to form in clouds. The tips of the plane propellers cause the air to rapidly expand and cool, freezing to ice and falling to the ground as snow. 

Cloud seeding is more likely to happen in mid and high-latitude areas during colder months, according to NCAR scientist Andrew Heymsfield.
 
“It appears to be a rather widespread effect for aircraft to inadvertently cause some measureable amount of rain or snow as they fly through certain clouds,” Heymsfield said. “This is not necessarily enough precipitation to affect global climate, but it is likely to be noticeable around major airports in the midlatitudes.”
 
Heysmfield and company used satellite images and weather forecasting computer models to see how this phenomenon affects temperatures near six airports. They chose airports in London, Frankfurt, Paris, Seattle, Chicago, and Yellowknife (Canada), as well as Byrd Station in Antarctica.

The team decided to study the weather patterns within a 62 mile radius of those airports. It chose 62 miles because that is the distance it takes an aircraft to reach 10,000 feet, where many of the clouds are located. Cloud seeding occurred five percent of the time near the Frankfurt, DeGaulle, and O’Hare airports, while it occurred three percent of the time near the other airports.

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