Every winter in the northern hemisphere, a cold wind surrounds the North Pole like water around a drainage channel. It is an annual weather pattern that meteorologists are looking forward to – any significant changes could suggest that Europe is facing a serious cold. Right now, that wind is breaking in two.
Researchers at the Universities of Bristol, Exeter and Bath have come up with a new way to predict the knock-on effects of various changes in this major airflow in the stratosphere at 10 to 50 kilometers (6 to 30 miles). Above the head .
Ironically, the cause of this cold is a sudden burst of heat flowing in currents that swirl in a window of only 24 to 48 hours.
With its temperature rising by up to 40 degrees Celsius, the vortex undergoes some rapid changes, changing course or breaking dramatically into daughter vortices that push the surrounding atmosphere.
The results can be devastating. Just a few years ago, a sudden stratospheric warming (SSW) event pushed cold polar air from Siberia into Europe, providing a cell loaded with high-pressure snow, the average called the Eastern Beast.
Centered over Scandinavia, the shock of the frozen weather threw a frozen layer to the west of Britain, contributing to the chaos of transport and even a number of deaths.
That being said, not all changes in this polar vortex end in freezing conditions. Two years ago, the warming of the stratospheric polar winds preceded one of the warmest winter days in the recorded history of the United Kingdom.
Knowing what the current deviations of winter rage are and which will fade, will go a long way in making weather forecasts more accurate.
Surprisingly, such stratospheric warming events themselves are not uncommon, with records suggesting that an average of about half a dozen of these occur in the Arctic polar vortex each decade.
“Although an extremely cold event is not a certainty, about two-thirds of SSWs have a significant impact on surface weather,” said Richard Hall, a meteorologist at the University of Bristol and lead author of the new study.
Observations dating back more than six decades have provided researchers with 40 such examples of oscillations and splits in the northern stratospheric polar vortex, which inform a tracking algorithm that attempts to predict the impact each type of change will have on meteorological systems in northern hemisphere. .
The results suggest every time the polar vortex splits into two smaller winds, we can expect more severe cooling events compared to other SSW anomalies.
It is a timely result, with projected changes in air currents occurring over the weekend.
“As predicted, atmospheric observations now show that the Arctic stratosphere is experiencing a sudden warming event associated with a weakened stratospheric polar vortex,” says Adam Scaife, head of long-term predictions at the UK Met Office.
Moreover, the change has all the characteristics of the more dangerous type of SSW, which means that there is a high chance that the anticipated drop in temperature will be significant.
Having informed climate models certainly helps to improve the chances of knowing what to expect. But while modeling on this scale benefits from improved algorithms, there is still room for a lot of uncertainty when it comes to resolving precise details in the coming days.
Strangely, it may even turn out that Europe is sweating instead of shivering.
The UK recorded a record winter heat after an SSW in February 2019, after all, so the Met Office does not rule out the possibility of a similar soul in the coming weeks.
“Although the prolonged events of cold and snowy weather in February and March 2018 – nicknamed” The Beast of the East “by the British press – were linked to a sudden stratospheric warming, the record hot spell that took place in February 2019 also followed the event “says meteorologist Matthew Lehnert.
We still have some way to go before we can confidently promise in which direction the weather will go after these polar changes.
But tools like this new algorithm will improve the chances of guessing and will continue to do so as we learn more about our atmosphere.
“Despite this advance, many questions remain about the mechanisms that cause these dramatic events and how they can influence the surface, so this is an interesting and important area for future research,” says mathematician William Seviour of the University of Exeter.
This research was published in Atmospheres JGR.