The polar vortex is a current of cold air that circulates over the North Pole during the winter months. It is located in the stratosphere about 30 km above our heads. In early January, meteorologists have noticed that he had suddenly warmed up. In a few days, the air went from -70 ° to -20 °.
Sudden stratospheric warming this January 5 in the #stratosphere polar NH (#SSW, sudden stratospheric warming) materialized by inversion of the zonal wind at the 10hPa level (usually westerly wind replaced by east wind) and + 50 ° C in a few days vertically from the north pole. pic.twitter.com/PEyTmy6k2N
– Etienne Kapikian (@EKMeteo) January 5, 2021
This sudden warming is a phenomenon known to scientists. It is linked to a complex phenomenon of circulation of oceanic and atmospheric waves. But the one that has just happened, with + 50 ° suddenly, is classified as a major warming.
Over the last 10 days the #SPV stratospheric polar vortex has taken a bit of a battering
It’s been displaced from its usual position over the N Pole, been stretched, and even seen a small split
– Marco Petagna (@Petagna) January 5, 2021
In fact, our polar vortex is located above another softer air current: the jet stream, located in the troposphere and which influences our weather much more. Usually, the two currents turn in the same direction, from west to east. But when the vortex suddenly heats up, that waltz of two is disturbed by high winds. The polar vortex disintegrates, or even tears, instead of staying firmly in place above the North Pole. Very cold air pockets can thus descend to our latitudes, especially over Siberia and northern Europe. But since France is a buffer zone, it can also be affected, as already happened in 2012.
The winter disturbance expected for this weekend and next week remains in the classic phenomena, even if we are a little below the normal for the season. The influence of the polar vortex: really cold air currents with temperatures below minus 10 degrees. In 2012, Scandinavia even recorded a –39 ° C in central Finland. But the meteorologists stay alert to see how the vortex and the jet stream behave. They expect the consequences to be felt until February.
Still looking likely that a minimum in the surface NAM (in the short-term) will occur around Jan 26th, and seems to be associated with a downward “drip” from the negative stratospheric NAM. https://t.co/p9rT2oDzR0 pic.twitter.com/7fEp2a7AzM
– Simon Lee (@SimonLeeWx) January 21, 2021
Richard hall, a researcher in climate dynamics at the University of Bristol, has studied 40 of these sudden disturbance phenomena of the polar vortex over the past 60 years. And he reminds us that even if we are in a context of global warming, we must not believe that the duck cold in winter is over.