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)