ELECTRIC-BLUE CLOUDS CIRCLING ANTARCTICA
NASA's AIM spacecraft is monitoring a vast ring of electric-blue clouds circling high above Antarctica. These are noctilucent clouds (NLCs), made of ice crystals frosting specks of "meteor smoke" in the mesosphere 83 km above the frozen continent. Here is an animation from the past week:
This is the season for southern noctilucent clouds. Every year around this time, summertime water vapor billows up into the high atmosphere over Antarctica, providing the moisture needed to form icy clouds at the edge of space. Sunlight shining through the high clouds produces an electric-blue glow, which AIM can observe from Earth orbit.
"The current season began on Nov. 19th," says Cora Randall, a member of the AIM science team at the University of Colorado's Laboratory for Atmospheric and Space Physics. "Compared to previous years of AIM data, this season seems to be fairly average, but of course one never knows what surprises lie ahead, particularly since the southern hemisphere seasons are so variable."
The formation of strange clouds in the high atmosphere over remote Antarctica may seem to be of little practical interest--but that would be incorrect. Researchers studying NLCs have discovered unexpected teleconnections between these clouds and weather patterns thousands of miles away. Two years ago, for instance, Randall and colleagues found that the winter air temperature in many northern US cities was well correlated with the frequency of noctilucent clouds over Antarctica. Understanding how these long-distance connections work could improve climate models and weather forecasting--all the more reason to study eerily beautiful NLCs.