Sudden warming over Arctic confuses our winter weather | NOW


In the first week of January, the Netherlands had to deal with exceptional weather: a northeasterly wind, without frost. Remarkable, meteorologists tell NU.nl. It is one of the effects of a “sudden rapid warming” of the high atmosphere that occurred around the Christmas season over the North Pole, which may also affect the rest of winter.

“I have never seen it so extreme, at the beginning of January”, KNMI climate researcher Peter Siegmund told NU.nl. He is referring to a situation in which the skates can normally be removed from the grease in the Netherlands: a persistent easterly wind. But although that brought air from Russia to the Netherlands, there was not even a degree of frost – even at night the temperature remained above 0.

This is partly because the nights were cloudy, and therefore less cold, adds his colleague Alwin Haklander. “But climate change also plays a role. The source regions of our winter cold, such as the Arctic and Russia, are warming up much faster than average.”

A temperature record of 38 degrees was set last summer within the Russian Arctic Circle, and there is still considerably less snow and ice than usual.

The exceptional weather situation meteorologist Wouter van Bernebeek from Weerplaza also noticed. This air pressure map belongs to skating weather, but ‘the cold air is gone’.

More westerly winds and more rain due to climate change

Climate change means that in winter the Netherlands is more likely to have to deal with westerly winds, which supply extra soft air from the Atlantic Ocean. The KNMI has been using new averages for the Dutch climate since 1 January. This shows that the Dutch winter has become 0.4 degrees warmer again in the past ten years, says Siegmund. There is also more rain.

If the wind does turn to the east, it also brings less cold air. But how exceptional is it actually when frost is completely absent? Haklander dug into the archives upon request and found one case that was even more extreme: January 1969, when a sustained strong easterly wind in De Bilt brought an average temperature of 4.4 degrees – above 0.

Nevertheless, the winter can still get a tail end this year, says climate researcher Michiel van Weele, also from the KNMI. The wind turned to the east because of a phenomenon meteorologists call ‘sudden stratospheric warming’. At an altitude of a few dozen kilometers above the North Pole, the temperature will then rise to 50 degrees in a very short time.

Disturbance in the stratosphere increases winter chances

This disruption took place around Christmas, says Van Weele. When that sudden warming reaches lower air layers, the westerly winds that normally revolve around the North Pole can reverse. In Europe and North America this offers a greater chance of winter weather.

“It is still too early to know how strongly the disturbance will continue to lower altitudes. But the fact that we now observe a strong warming at 30 kilometers altitude, gives a slightly higher chance of colder weather in the coming weeks. So as a winter lover you should eagerly await the long-term expectations. “

Much is still unknown about the origin of such sudden stratospheric warming. NU.nl spoke to two climate researchers from the University of Oxford who suspect that an eleven-year cycle may play a role in the intensity of the sun. We are currently one year past the minimum in this cycle, and then we have more easterly winds, weather statistics show.

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