Title: Astronomy Picture of the Day
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Wow, that's pretty cool.
David L.
A liberal is someone who feels a
great debt to his
fellow man, which debt he proposes to pay off with
your money. -- G. Gordon
Liddy
Astronomy Picture of the Day
Discover the cosmos! Each day a different
image or photograph of our fascinating universe is featured, along with a
brief explanation written by a professional astronomer.
2004 January 12
![See Explanation. Clicking on the picture will download
the highest resolution version available.]()
A Hole Punch Cloud Over Alabama
Credit &
Copyright: Joel Knain
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Explanation: 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. |
Tomorrow's picture: Pan the Moon
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Authors & editors: Robert Nemiroff (MTU) & Jerry
Bonnell (USRA)
NASA Official:
Jay Norris. Specific rights
apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech.
U.
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