Sudden stratospheric warming

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The sudden stratospheric warming ( english sudden stratospheric warming ) is a known since 1952, first from Berlin meteorologist Richard Scherhag as Berlin phenomenon appearance in weather that described stratosphere of the northern hemisphere .

description

In the winter months , a polar vortex forms in the polar stratosphere due to the negative radiation balance in the polar region , with strong westerly winds at the southern boundary. The temperatures in the lower stratosphere (at an altitude of around 20 km) are on average below −70 ° C.

This structure, which predominates in winter, is severely disturbed on average every two years, but at irregular intervals. With this strong heating ( Major Warming ), the temperature of the stratosphere increases within a few days to more than 50 degrees and reaches higher values than in more southerly latitudes. This sudden warming is associated with a reversal of west to east winds and thus a collapse of the polar vortex. This is followed by an equally abrupt cooling.

The consequence of sudden stratospheric warming is, among other things, a weakening of the pressure difference between the Iceland low and the Azores high . However, this determines the prevailing wind direction for Central Europe and thus whether the winter in Europe is cold or mild. A sudden warming of the stratosphere favors weather conditions that favor the penetration of cold mainland air from the east to Central Europe.

causes

The cause of the sudden, irregular stratospheric warming is the interaction between the North Atlantic , the troposphere and the stratosphere. An increased number of sudden stratospheric warming occurs when the flow of heat from the North Atlantic into the atmosphere is increased.

Differentiation to similar phenomena

In meteorology, three forms of sudden stratospheric warming are distinguished:

  • Major Warming , perceptible as an anomaly of the weather ; only this is referred to as the Berlin phenomenon or the Berlin phenomenon .
  • Several times per winter, weaker stratospheric warming occurs ( minor warming ). These bring a temperature increase of at least 25 degrees within a week and can occur in all layers of the stratosphere. They have no influence on the stability of the polar vortex.
  • As a final Warming refers to the warming at the end of winter March to May The polar vortex collapses without being restored afterwards.

See also

literature

  • Martin Kappas: Climatology. Climate Research in the 21st Century - a Challenge for Natural and Social Sciences. Spektrum Akademischer Verlag, Heidelberg 2009. ISBN 978-3-8274-1827-2

Individual evidence

  1. R. Scherhag: The “Berlin Phenomenon” and the Geophysical Year (PDF; 67 kB). Supplement to Berliner Wetterkarte 137, 1958, accessed on February 15, 2011
  2. Meteorologists from the Free University discover the cause of cold and warm winter periods . Press release of Freie Universität Berlin No. 13/2011 from January 17, 2011, accessed on February 15, 2011
  3. Peter Rüegg: Warming in the stratosphere creates cold winters. In: ethz.ch. ETH Zurich , January 29, 2019, accessed on January 29, 2019 .
  4. M. Kappas, p. 207

Web links