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Hole-Punch Clouds: Mystery Solved

June 17, 2010

Any guesses what punched that hole in the cloud? Well, researchers have been looking for the answer for a while and airplanes have been the main suspect for this phenomenon. New research study confirms that planes, both propellers and jet planes , can cause formation of these shapes in the clouds named as “hole-punched clouds ” or “punched hole clouds” as a result of enhanced precipitation effect. These clouds have also been linked to UFO sightings in past, most famous one being in Moscow during October 2009.

Let’s try to understand how planes can trigger this phenomenon. We all know water freezes at 0 degree C, but due to lack of any dust particles or any other surface in higher altitudes, water can be in liquid form even below zero degrees or in other words it can exist in supercooled state. Now any particle which can work as seed particle can trigger the formation of ice and airplanes can provide the seed particles. Exhaust of jet planes generate tiny particles which can trigger ice formation, while propeller planes causes sudden pressure drop leading to sudden cooling to about -50 degrees C resulting in formation of ice which acts as trigger. As water precipitates, it sucks humidity from surrounding area and form larger ice particles and eventually fall down as snowfall, leaving a hole in the cloud.

Previous research also suggests that propeller planes could make snow fall when they flew through supercooled clouds, where water droplets remain liquid despite subfreezing temperatures. But until recently, a direct connection between airplanes, hole-punch clouds and snowfall was missing. Now, a team of atmospheric scientists report observing all three in the June Bulletin of the American Meteorological Society. [Wired]

 

Andrew Heymsfield from National Center for Atmospheric Researchand team flew in one of snowfall region resulting from hole-punched clouds accidentally while doing some cloud study. Their turboprop plane loaded with instruments took video and images of the cloud while on the ground unexplained snowfall was recorded near Denver International airport.

A subsequent review of flight track records from the Federal Aviation Administration revealed that turboprop planes operated by two airlines flew close to the hole-punch location, following a standard flight path that produced the subsequent band of snow. Snow crystals began falling about five minutes after the second aircraft flew through the cloud. The snowfall, in a band about 20 miles long and 2.5 miles wide, continued for about 45 minutes, resulting in about two inches of snow on the ground. The researchers also examined data from onboard spectrometers that profiled the snowflakes within the band of snow beneath the hole punch. These plate-shaped crystals showed evidence of riming (accumulation of liquid water), whereas ice particles elsewhere in the cloud showed little or no riming.

“This tells us that the aircraft literally ‘seeded’ the cloud just by flying through it,” Heymsfield says.

“This apparently happens frequently, embedded in the cloud layers,” Heymsfield says. “You wouldn’t necessarily see it from satellite or from the ground. I had no idea this was happening. I was sitting in back of the plane. And then this data set just fell in our laps. It was a lucky break.” [UCAR News]

Photo Credit: Flickr user mullerb; Used under Creative Commons License

Filed under: Research,Science,Uncategorized

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1 Comment Leave a Comment

  • 1. Science Is Beautiful &raq&hellip  |  December 28, 2010 at 11:02 pm

    […] image of Hole Punch clouds formed over West Virginia clouds during Dec of 2009.  In one of my earlier post, I have discussed the mechanism of such cloud formation. We all know water freezes at 0 degree C, […]

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