March 24, 2023

While temperatures have fallen well at the end of January, variations in the “polar vortex” could be responsible for cold waves. But what is this meteorological phenomenon?

An interesting phenomenon to understand temperature fluctuations? The polar vortex makes a comeback in meteorological jargon with each new cold snap. According to The Weather Channelthe polar vortex describes a depression that forms each winter, above the North and South Poles, and which could potentially generate cold waves.

Indeed, these masses of cold air swirl above the Arctic and Antarctic circles and can, at times, bring the cold down from the stratosphere towards the Earth.

On this NASA model, above, we distinguish the “surface” temperature differences, over the period from the end of December 2022 to the beginning of January 2023.

Two types of polar vortex are then distinguished. The stable stratospheric polar vortex, which will contain high altitude air masses around 30km away from the earth’s surface, and the fluctuating stratospheric polar vortex, which, due to temperature changes, tends to deform and to let a cold air descend.

Conflicting opinions

However, the causal link between the polar vortex and the appearance of extreme cold episodes is discussed among specialistsand several studies are conducted to verify the effects of this phenomenon on the thermometer.

NASA has shared the work of Judah Cohen, visiting researcher at the Massachusetts Institute of Technology and forecaster at Atmospheric and Environmental Research (AER), who defends the idea of ​​causality.

In this study dating from 2021, the scientist and his team “linked the decline of Arctic sea ice in the Barents and Kara Seas and increased snowfall in Siberia, both linked to climate change, and an increase disturbances of polar vortices and cold spells at mid-latitudes”.

For his part, the French meteorologist Guillaume Séchet nuanced the link between disruption of the polar vortex and appearance of a cold wave, taking the example of France. “The polar vortex over the North Atlantic would favor a disturbed ocean current over France, advecting mild air much more easily than cold air”, wrote the specialist, taking into account the results of the United States Agency for Oceanic and Atmospheric Observation.

That said, a weakening of the Arctic polar vortex could be observed in early February, without affecting temperatures, which should rise in the coming weeks, according to Meteo France.

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