Why Does This Cloud Have a Hole in it?

3 photos
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Eric Grant
WHAT IS IT?
This rare atmospheric phenomenon has several different names, but is best known as a “Hole Punch Cloud” or a “Fallstreak Hole”. They are seen in altocumulus type clouds like the one above or in cirrocumulus clouds found at higher altitudes.
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Eric Grant
WHAT CAUSES IT?
nWhen the temperature in a cloud is below freezing, but there is no nuclei (dust, smoke, microscopic insect) present for an ice crystal to form around the super-cooled water droplets making up the cloud will remain suspended in the air. It is believed something triggers a rapid deep freeze of these super-cooled water droplets creating ice crystals which eventually fall from the cloud creating the appearance of a circular hole. In some instances light snow has been reported falling from the expanding punch hole.
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NASA
WHY A CIRCLE?
nAirplanes may be the main culprit. As they pass through the super-cooled water droplets in a cloud the air cools instantly leaving behind a visible line of ice crystals known as condensation trails. These ice crystals continue to grow and eventually fall to Earth from the hole in the cloud where the plane had flown through.
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