Why the warming of the stratosphere over the North Pole is causing a cooling in Europe

Why the warming of the stratosphere over the North Pole is causing a cooling in Europe
Why the warming of the stratosphere over the North Pole is causing a cooling in Europe
Anonim

Every winter, the so-called sudden stratospheric warming (SSW) occurs in the polar and subpolar stratosphere of the Northern Hemisphere. Temperatures at altitudes from 10 to 50 km can suddenly and dramatically rise in just a few days. The jump can be 40-50 degrees Celsius.

Paradoxically, these warming, disrupting the usual circulation processes, provoke a sharp cooling in the Northern Hemisphere. For example, in the winter of 2018, the UK and Ireland were hit by a wave of anomalous cold known as the "Beast from the East". In February 2019, a similar sharp cooling was observed in Canada and the United States.

Moreover, not all changes in polar vortices lead to cooling. Two years ago, warming in stratospheric polar winds preceded one of the warmest winter days in British history.

Researchers at the universities of Bristol, Exeter and Bath have come up with a new way to predict the side effects of SSP. Knowing which deviations portend a cold snap, and which ones do not, is essential for improving the accuracy of weather forecasts.

The study authors analyzed observations of 40 such fluctuations over the past 60 years. This made it possible to trace the logic of abnormal warming and cooling. The results showed that each time a large polar vortex split into two smaller ones, more severe cooling could be expected compared to other SSW anomalies.

“As anticipated, atmospheric observations show that the Arctic stratosphere is experiencing sudden warming associated with a weakening of the stratospheric polar vortex,” said Adam Scaife, head of long-range forecasts at the UK Met Office.

According to study co-author Dann Mitchell, the extremely cold weather brought by polar vortex bursts is a harsh reminder of how suddenly the weather can change.

“Even with climate change warming our planet, these events will still occur, which means we must adapt to an increasingly extreme temperature range,” concludes Mitchell.

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