Quasi-two-year oscillation

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Time-height plot of the monthly and zonally averaged zonal wind u between 1981 and 1991 near the equator. West winds are shown in red, east winds in blue and the zero line is shown in black. The altitude range corresponds to about 20 to 35 km. Data source: FU Berlin

The  quasi-biennial oscillation ( QBO for short, from the English “quasi-biennial oscillation”), also quasi-biennial oscillation , is a quasi- periodic atmospheric wave of the zonal wind in the equatorial stratosphere of the earth .

Occur

It appears at an altitude of around 16 to 40 kilometers with a maximum at around 20 to 25 kilometers and is characterized by an east-west wind reversal. Since observations began in 1953, the period has fluctuated between 22 and 34 months, with the mean period being 27 months. Their east wind phase lasts longer in the upper layers and shorter in the lower layers than their west wind phase. The east winds are stronger than the west winds, with a strength of −30 m / s (east wind) to +15 m / s (west wind).

In the westerly wind phase the polar vortex and the jet stream intensify , with more Atlantic lows and mild westerly weather for Europe.

At the end of 2015 - mid-2016, the change did not occur for the first time since the observations began. As of August 2016, the cause of the interruption is unknown.

Research history

The German meteorologist Arthur Berson observed westerly winds in the lower stratosphere during his aerological East Africa expedition in 1908 when pilot and recording balloons rose . This contradicted the assumption that stable easterly winds prevail at the equator at this altitude, as observed after the eruption of Krakatau in 1883 based on the direction of its smoke and dust cloud. This riddle initially remained unsolved until radiosonde stations were set up near the equator as part of the International Geophysical Year at the end of the 1950s. Initial data analyzes indicated the existence of an oscillating zonal wind. The theory of QBO was set up from 1968 by Richard Lindzen and James Reed Holton (1938–2004).

meaning

The QBO plays an important role in relation to the effects of the variability of solar activity on the earth's atmosphere and thus also on the global climate .

Via the polar vortex and the overturning of the synoptic waves of the jet stream (east wind phases), the QBO probably correlates with shorter-term periods of Arctic  (AO) and North Atlantic Oscillation  (NAO), and is integrated into the global context of teleconnection .

Web links

Individual evidence

  1. ↑ a b The Quasi-Biennial-Oscillation (QBO) data series , Institute for Meteorology at the Free University of Berlin , accessed on May 28, 2013
  2. ↑ Quasi-biennial oscillation. wetteronline.de: Weather dictionary.
  3. ↑ PA Newman, L. Coy, S. Pawson, LR Lait: The anomalous change in the QBO in 2015-2016 . In: Geophysical Research Letters . August 2016, doi : 10.1002 / 2016GL070373 .
  4. ^ Arthur Berson: Report on the aerological expedition of the Royal Aeronautical Observatory to East Africa in 1908 . Vieweg, Braunschweig 1910