Display of Polar Stratospheric Clouds (PSCs) in the Arctic

December 23, 2023

Over a period of more than three days, the Arctic skies have been adorned with an extraordinary celestial display—rare “rainbow clouds,” scientifically known as Polar Stratospheric Clouds (PSCs). This captivating phenomenon was observed in various locations, including Norway, Sweden, Finland, Alaska, and even as far as Scotland. The appearance of these vibrant clouds, starting on December 18 and continuing until December 20, has been attributed to an unusual cold snap in the region.

Spectacular Colors Above Gran, Norway

Photographs of the PSCs above Gran in Norway were captured by Ramunė Šapailaitė, who described the colors as “spectacular.” The clouds were visible throughout the day, with the colors intensifying just before sunset. The images, taken with a phone, revealed the rainbow hues and iridescent shimmer characteristic of PSCs.

Formation of Polar Stratospheric Clouds (PSCs)

PSCs form when water vapor enters the stratosphere, and temperatures are cold enough for the vapor to condense. In the winter season, high latitudes experience minimal solar radiation, leading to a significant drop in temperatures during the polar night. Under these conditions, PSCs can develop, trapping outgoing longwave radiation and emitting some of it back towards the Earth’s surface, hindering atmospheric cooling.

Increasing Frequency in the Arctic

According to Harvard University, PSCs are occurring with increasing frequency in the Arctic. There are two main types of PSCs: those formed from a mix of ice crystals and nitric acid, producing less spectacular colors, and those composed of pure ice crystals, resulting in more vivid and vibrant colors. The rainbow clouds observed in the Arctic on December 18 were identified as type 2 PSCs.

Scientific Significance and Beauty of PSCs

Polar Stratospheric Clouds not only offer a stunning visual spectacle but also hold scientific significance. The increasing frequency of their occurrence in the Arctic raises questions about the region’s atmospheric conditions and climate dynamics. As the mesmerizing display of rainbow clouds captures the attention of onlookers, scientists continue to study and understand the underlying processes contributing to this rare atmospheric phenomenon.

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