January 24, 2022 1:55 pm

Where are the noctilucent clouds at the South Pole?

Francisco Martin Leon 2 min
AIM satellite image showing the absence of NLC as of November 23, 2021

But as current data from NASA’s AIM spacecraft, image above, shows, the noctilucent zone is empty.

NLCs are the highest clouds on Earth. Seeded by meteoroids, they float on the edge of space about 83 km above ground. Clouds form when wisps of water vapor rise into the mesosphere in summer, allowing water to crystallize around the specks of meteor smoke.

The southern season for NLCs typically runs from November to February. So where are they?

To find the answer, Lynn Harvey of the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado analyzed data from NASA’s microwave probe. Found “a heat wave in the mesosphere”:

Evolution of temperatures in the mesosphere. See text for details

The temperature in 2021 is higher than in other years“says Harvey, whose graph compares the temperature for each year since AIM was launched in 2007.

Noctilucent clouds require extreme cold; otherwise, the water molecules will not adhere to the meteoroids. So a heat wave, even a brief one, is enough to delay the start of the NLC season.

Distinguished University of Colorado professor Cora Randall makes this prediction: “If I had to put a date on it, I would say that the season will start on December 1, but with great uncertainty. Stay tuned for a more conservative statement ! “


This entry was published in Reports on 27 Nov 2021 by Francisco Martín León


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