Electric-Blue Clouds Appear over Antarctica
 
Dec. 23, 2013:  Data from NASA's AIM spacecraft show that noctilucent clouds
are like a great "geophysical light bulb." They turn on every year in late
spring, reaching almost full intensity over a period of no more than 5 to 10
days.
 
News flash: The bulb is glowing.
 
http://www.youtube.com/watch?v=GHpxD807kM4
 
A new ScienceCast video explores the noctilucent clouds now swirling over
Antarctica.   Play it
 
As December unfolds, a vast bank of noctilucent clouds is blanketing
Antarctica. It started on Nov. 20th as a tiny puff of electric-blue and
quickly expanded to overlie nearly the entire continent. AIM is monitoring the
progress of the clouds as they swirl and ripple around the south pole.
 
"The clouds appeared over the south pole earlier than usual this year," says
AIM science team member Cora Randall of the Laboratory for Atmospheric and
Space Physics in Colorado. "Since AIM was launched, only the 2009 season got
an earlier start.
 
http://science.nasa.gov/media/medialibrary/2013/12/23/nlc_anim1024.gif
 
Click on the image to watch the "geophysical light bulb" turn on over
Antarctica. Credit: AIM
 
Noctilucent clouds--or "NLCs" for short--are Earth's highest clouds. Seeded by
disintegrating meteoroids, they form at the edge of space 83 km above Earth's
surface. When sunlight hits the tiny ice crystals that make up these clouds,
they appear to glow electric blue.
 
Summer is when NLCs are at their brightest and most widespread.  Now is summer
in the southern hemisphere. The clouds brighten over the south pole in
November through February, and shift to the north pole in May through August.
 
Why summer?  The answer has to do with wind patterns and the flow of humidity
in our atmosphere.  Summer happens to be the time when the greatest number of
water molecules are wafted up from the lower atmosphere to mix with "meteor
smoke" at the edge of space. Ironically, summer is also the time when the
upper atmosphere is coldest, allowing the ice crystals of NLCs to form.
 
In recent years NLCs have intensified and spread.  When noctilucent clouds
first appeared in the 19th century, you had to travel to polar regions to see
them.  Since the turn of the century, however, they have been sighted as close
to the equator as Colorado and Utah.
 
Auroras Underfoot (signup)Some researchers believe this is a sign of climate
change. One of the greenhouse gases that has become more abundant in Earth's
atmosphere since the 19th century is methane.
 
"When methane makes its way into the upper atmosphere, it is oxidized by a
complex series of reactions to form water vapor," explains Hampton University
Professor James Russell, the principal investigator of AIM. "This extra water
vapor is then available to grow ice crystals for NLCs."
 
http://science.nasa.gov/media/medialibrary/2012/08/07/methane.jpg
 
A graphic prepared by Prof. James Russell of Hampton University shows how
methane, a greenhouse gas, boosts the abundance of water at the top of Earth's
atmosphere. This water freezes around "meteor smoke" to form icy noctilucent
clouds. [Larger image]
 
If this idea, one of several, is correct, noctilucent clouds are a sort of
"canary in a coal mine" for one of the most important greenhouse gases.  And
that, says Russell, is a great reason to study them.
 
Studying NLCs is the prime mission of the AIM spacecraft. Since it was
launched in 2007, AIM has made many key discoveries including the role of
meteor dust in seeding NLCs and the way NLCs are affected by long-distance
teleconnections in the atmosphere. More discoveries may be in the offing as
NASA has just extended the mission for another two years.
 
Credits:
Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit:
Science@NASA
 
More information:
 
Meteor Smoke Makes Strange Clouds -- Science@NASA
 
 
Regards,
 
Roger

--- D'Bridge 3.98
 * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)