After a dramatic meteorological event currently taking place high above the North Pole, a new study led by researchers from the Universities of Bristol, Exeter and Bath is helping to shed light on the winter weather we could soon be facing.
With increasing confidence, weather prediction models predicted that a sudden stratospheric warming (SSW) event would occur on January 5, 2021, and experts have indeed confirmed that it is ongoing.
The stratosphere is the layer of the atmosphere approximately 10-50 km above the surface of the Earth. SSW events are among the most extreme atmospheric phenomena, and within a few days they can increase the temperature in the stratosphere by as much as 50 ° C. Such occurrences, sometimes resulting in snowstorms, may bring very cold weather.
A stark reminder of what an SSW can offer is the notorious “Beast from the East” of 2018.
It is possible to transmit the disruption in the stratosphere downwards, and if this persists to the surface of the Earth, it may cause a jet stream change, resulting in extremely cold weather over Europe and northern Asia.
For the signal to hit the surface, it can take several weeks or the process can take just a couple of days.
The thesis, published in the Journal of Geophysical Science and sponsored by the Research Council for the Natural Environment (NERC), involved an overview of 40 SSW events observed over the past 60 years. A new method to monitor the signal of an SSW from its onset in the stratosphere down to the surface was created by the researchers.
The results of the study, “Tracking the stratosphere-to-surface impact of Sudden Stratospheric Warmings,” indicate that split events tend to be associated with colder weather over northwestern Europe and Siberia.
The lead author of the report, Dr. Richard Hall, said that in the next week or two, there is an increased risk of severe cold and probably snow:
Around two-thirds of SSWs have a major effect on surface weather, but an extreme cold weather event is not a guarantee.
Furthermore, the SSW of today is potentially the most dangerous kind, with the polar vortex splitting into two smaller vortices of the ‘girl.’
The intensely cold weather triggered by the destruction of these polar vortexes is a stark reminder of how our weather can change unexpectedly.
Even with climate change warming our planet, these events will still occur, meaning we will need to adapt to an increasingly extreme range of temperatures,” said Dann Mitchell, associate professor of atmospheric sciences at the University of Bristol and co-author of the study.
“Our study quantifies for the first time the probabilities of when we can expect extreme surface weather following a sudden stratospheric warming (SSW) event.
These vary widely, but importantly, the impacts are faster and stronger after events where the stratospheric polar vortex splits in two, as is predicted for the event currently unfolding.
Despite this progress, there are still many questions about the mechanisms that cause these dramatic events and how they may affect the surface, and therefore this is an exciting and important area for future research,” said Dr.
William Seviour, senior lecturer in the Department of Mathematics and Global Systems Institute, University of Exeter, and co-author of the study.
Reference, “Tracking the stratosphere-to-surface impact of Sudden Stratospheric Warmings,” by Richard J. Hall, Daniel M. Mitchell, William J.M Seviour and Corwin J.
Wright, December 25, 2020, Journal of Geophysical Research.DOI: 10.1029/2020JD033881