When airplanes pass through clouds with supercooled water , that is, water that remains liquid below the freezing point, they pierce them and the formation of ice crystals is favored, causing snow to be produced and precipitating to the earth’s surface, as as revealed by international research, published in the journal Science .
According to experts, led by the National Center for Atmospheric Research of Colorado (USA), the phenomenoncould increase the frequency of snow around the world’s major airports. In many of them, with winter low cloud covers, the researchers recommend de-icing the planes more frequently.
To reach these conclusions, the experts analyzed 20 satellite images of a cloud cover with holes, suspended over the state of Texas (USA) on January 29, 2007. Some of these perforations were visible for more than four hours and occupied lengths greater than 100 kilometers. Later, the team consulted the file of the Federal Aviation Administration of the United States to find out which planes flew that day in that area and could have produced these perforations and channels. The aircraft they found were of all kinds: large passenger, military, small turboprop and private aircraft.
The explanation of the phenomenon is supportedon the engine propellers and on the wings. “The airplane propeller pushes the air behind it, which generates momentum around its tips,” explains Andrew Heymsfield, lead author of the study and researcher at the National Center for Atmospheric Research in Colorado (USA). This impulse, in turn, cools the air behind the propellers to 30 ° C, freezing cloud droplets and leaving a stream of small ice particles. Something similar happens with wings.
In clouds, the air temperature is around -10 ºC. If there is no dust or ice crystals (solid particles considered the core of the freezing process), the water can remain supercooled, in a liquid state, down to -40 ºC.
The work also reveals what depends on the plane creating a hole or a layer: its trajectory. “If it ascends through a layer of supercooled clouds, it will generate a hole, and if it fliesin the cloud layer (standard), will produce long channels“, maintains the expert.
