Rare Atmospheric Wave Supercharges Noctilucent Clouds Over the Southern Hemisphere

A rare atmospheric wave nearly half as wide as Earth itself is supercharging noctilucent clouds (NLCs) in the southern hemisphere. NASA’s AIM spacecraft detected the phenomenon in a series of south polar images spanning Nov. 24th through Dec. 3rd. “This is a clear sign of planetary wave activity,” says AIM principal investigator James Russell of Hampton University, which manages the Aeronomy of Ice in the Mesosphere mission for NASA. On Dec. 1st, skywatchers from New Zealand reported the appearance of blue-ish clouds, a rare sighting for latitude of 45S. Noctilucent clouds over Antarctica itself are nothing unusual. They form every year around this time when the first wisps of summertime water vapor rise to the top of Earth’s atmosphere. Molecules of H2O adhere to specks of meteor smoke, forming ice crystals 83 km above Earth’s surface. But these NLCs are different. They’re unusually strong and congregated in a coherent spinning mass. Southern hemisphere NLCs are seldom seen outside Antarctica, so this is a rare event. Sky watchers in south island of New Zealand, Tasmania, southern Chile/Argentina and the Falkland Islands should be alert for an electric-blue glow on the western horizon after sunset.



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