Early arrival of rare, iridescent polar stratospheric clouds over Europe

An early outbreak of polar stratospheric clouds, known for their intense iridescence, was reported over parts of northern Europe on December 17, 2023.

A remarkable display of polar stratospheric clouds (PSCs) graced the skies over parts of northern Europe on December 17, 2023. Chad Blakley of Lights over Lapland shared his awe with SpaceWeather.com, emphasizing the magical quality of these winter occurrences.

“We just witnessed a spectacular display of polar stratospheric clouds,” Blakley said. “It’s that magical time of year again.”

PSCs, also known as nacreous clouds, are a rare atmospheric phenomenon; the stratosphere typically lacks the moisture needed for cloud formation. However, when temperatures in the Arctic stratosphere plummet to around -85 °C (-121 °F), sparse water molecules can combine to form ice crystals. These crystals, illuminated by high-altitude sunlight, then paint the sky with colors that are often compared to those of the aurora borealis.

NASA’s polar stratosphere forecast models confirm that recent temperatures have been conducive to the formation of the vibrant Type II PSCs:

Typically observed only a few times during an Arctic winter, and most commonly in January, the December sighting suggests an early and possibly active season for PSCs, hinting at further displays to come.

References:

¹ An outbreak of polar stratospheric clouds – SpaceWeather – December 18, 2023

Featured image credit: Pekka Lähteenmäki. Photo taken on December 17, 2023 @ Helsinki, Finland (via SpaceWeather)