Aircraft flight can make it rain and snow?!

If conditions are right, aircraft can indeed change the weather, study says

hole punch cloud
If the temperature and atmospheric conditions are right, aircraft climbing or descending can indeed make it snow or rain.     

That's the conclusion of a paper out today that states: "Ice particle production by commercial turboprop aircraft climbing through clouds much warmer than the regions where contrails are produced has the potential to modify significantly the cloud properties and effectively seed them under some conditions."  Through this seeding process, the aircraft leave behind odd-shaped holes or channels in the clouds, according to the National Center for Atmospheric Research (NCAR).   

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The NCAR paper says the precipitation from holes and channels in clouds by two commercial turboprop aircraft was documented for the first time by the National Science Foundation/NCAR C-130 aircraft

The key to these holes in the clouds: water droplets at subfreezing temperatures, below about 5 degrees Fahrenheit. As air is cooled behind aircraft propellers or over jet wings, the water droplets freeze and drop toward Earth, researchers stated. 

Researchers went on to say jet aircraft may also be producing what's known as "hole punch" clouds when flying through altocumulus with supercooled droplets at heights lower than their normal cruise altitudes where contrails can form. Commercial aircraft therefore can generate ice and affect the clouds at temperatures as much as 30°C warmer than the -40°C contrail formation temperature.

"Anytime aircraft fly through these specific conditions, they are altering the clouds in a way that can result in enhanced precipitation nearby," says Andrew Heymsfield, a scientist with NCAR.

A similar process can occur with jet aircraft, which need colder temperatures (below about -4 to -13 degrees F, or -20 to -25 degrees C) to generate the seeding effect. Air is forced to expand over the wings as the aircraft moves forward, cools, and freezes the cloud droplets, Heymsfield stated. 

Precipitation from planes may be particularly common in regions such as the Pacific Northwest and western Europe because of the frequent occurrence of cloud layers with supercooled droplets, Heymsfield says. 

Follow Michael Cooney on Twitter: nwwlayer8   

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