Hole in the sky?!
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- senorpepr
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Hole in the sky?!
What could create a huge hole in the clouds? Such a hole, likely hundreds of meters across, was photographed last month from a driveway near Mobile, Alabama, USA. Very unusual to see, hole-punch clouds like this are still the topic of meteorological speculation. A leading hypothesis holds that the hole-punch cloud is caused by falling ice-crystals. The ice-crystals could originate in a higher cloud or be facilitated by a passing airplane exhaust. If the air has just the right temperature and moisture content, the falling crystals will absorb water from the air and grow. For this to happen, the water must be so cold that all it needs is a surface to freeze on. The moisture lost from the air increases the evaporation rate from the cloud water droplets so they dissipate to form the hole. The now heavier ice crystals continue to fall and form the more tenuous wispy cloud-like virga seen inside and just below the hole. Water and ice from the virga evaporates before they reach the ground.
[Source: Astronomy Picture of the Day http://antwrp.gsfc.nasa.gov/apod/ap040112.html)
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- senorpepr
- Military Met/Moderator
- Posts: 12542
- Age: 41
- Joined: Fri Aug 22, 2003 9:22 pm
- Location: Mackenbach, Germany
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It's a distrail (dissipation trail; opposite of a contrail). Circular shape is caused by an airplane descending through the cloud layer. A plane cruising through a thin altostratus layer can cause a long distrail. Prof Steve Ackerman at UW-Madison assigned a final project last semester, and the class is submitting a manuscript on a MODIS-observed distrail over WI in Nov.
Some more great shots...from above this time!
http://cimss.ssec.wisc.edu/goes/misc/distrails/031121.html
Some more great shots...from above this time!
http://cimss.ssec.wisc.edu/goes/misc/distrails/031121.html
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