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A heat stroke in the polar vortex threatens a new cold wave over Europe


A heat stroke in the polar vortex threatens a new cold wave over Europe

A heat stroke in the polar vortex threatens a new cold wave over Europe

A dramatic meteorological event is taking place over the North Pole: a sudden warming above 10 kilometers above the earth’s surface has raised the temperature suddenly by 50ºC.

Meteorologists call this episode Sudden Stratospheric Warming (SSW) and it happened suddenly in the early days of the new year.

In December, the stratospheric temperature was -70ºC, but the peak of heat has raised the thermometer to -20ºC on Tuesday, January 5, according to a release from the University of Bristol.

Although this episode is not the first time it has occurred, it has severe climatic consequences: in early 2012 and 2018, two intense cold waves affected Europe as a consequence of sudden warming in the stratosphere.

The one in 2018 was known as the “beast from the East” and set record cold temperatures in various parts of the old continent.

Atmospheric circulation patterns

Atmospheric circulation patterns The World Meteorological Organization then explained that the phenomenon was related to large-scale atmospheric circulation patterns and to sudden stratospheric warming recorded in the stratosphere above the North Pole.

That episode of stratospheric warming caused a division in the polar vortex that generated cold winds from Siberia and impacted the temperatures of Europe.

A similar scenario may occur this winter, scientists warn in an article published in the journal JGR Atmospheres.

They explain in their article that SSWs are extreme atmospheric regimes that can have a signature on the Earth’s surface climate up to 40 days after the onset of the event in the stratosphere.

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60-year follow-up

60-year follow-up The study looked at 40 SSW events that occurred over the past 60 years and warns that the polar vortex split is associated with cooler weather in northwestern Europe and Siberia.

Study author Dann Mitchell explains that “the extremely cold weather brought by these polar vortex breaks is a stark reminder of how suddenly our climate can change.”

He adds that even with climate change warming our planet, these events will continue to occur, which means that we must be able to adapt to an increasingly extreme range of temperatures.

Another of the study’s authors, William Seviour, is even more categorical: “the impacts appear faster and stronger after events in which the stratospheric polar vortex splits in two, as can occur in the event that is currently unfolding. ”

Shifting polar vortex

Shifting polar vortex He polar vortex It is a large-scale cyclone located near the terrestrial polar zones: it is located in the middle and upper troposphere and the stratosphere.

When winter comes, the northern hemisphere receives less ultraviolet radiation, an integral part of the sun’s rays. So temperatures drop, especially in the extreme north of the planet.

These temperature differences generate the so-called stratospheric jet stream, which is formed not only by atmospheric warming, but also by the rotation of the planet.

When an SSW occurs, there is a change in the circulation of strong winds around the polar vortex and even a reversal of the air current.

The cold is then trapped in the jet stream and can descend to lower latitudes, causing the familiar cold waves that, again, threaten much of the Northern Hemisphere.

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Reference

Reference Tracking the stratosphere‐to‐surface impact of Sudden Stratospheric Warmings. Richard J. Hall et al. JGR Atmospheres, December 2020. DOI:https://doi.org/10.1029/2020JD033881

Photo: Lorri Lang. Pixabay.


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