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An international research team has made important steps towards improving weather forecasts, by proving they can predict unprecedented changes in the normal eastward or westward flow of air high up in the atmosphere, known as the quasi-biennial oscillation.

The quasi-biennial oscillation is one of the most repeatable wind patterns, but was unexpectedly seen to break down in February 2016. These winds are found high above the tropics in a part of the atmosphere known as the stratosphere, and their direction and strength provides forecasters with an indication of the weather to expect in Northern Europe. Westerly winds are known to increase the chance of warm and wet conditions, while easterlies bring drier and colder weather. 

The disruption in the quasi-biennial oscillation two years ago was not predicted, not even one month ahead. However, using a climate model designed for the upper atmosphere, scientists have now found that the unusual wind disruption was caused by high altitude waves originating from outside the tropics. This discovery means forecasters will now be able to predict irregularities in the quasi-biennial oscillation several weeks in advance.

Dr Scott Osprey, from the National Centre for Atmospheric Science and University of Oxford said:

“What we saw in 2016 came like a bolt from the blue: the disruption was simply was not picked up in long-range (weather) forecasts. But now we show these extreme events can be predicted weeks ahead of time which, I think, sets the standard for future forecasts.”

 

About the study:

The study was published in the Geophysical Research Letters on Friday 2 February 2018 (GMT). It was carried out by Drs. Shingo Watanabe, Eriko Nishimoto and Yoshio Kawatani at the Japan Agency for Marine-Earth Science Technology (JAMSTEC: Asahiko Taira, President) in collaboration with Prof. Kevin Hamilton at the International Pacific Research Center (IPRC) of the University of Hawaii and Dr. Scott Osprey from the National Centre for Atmospheric Science based at the University of Oxford.

The study was supported by the Japan Science and Technology Agency (JST) as part of the Belmont Forum; the “Integrated Research Program for Advancing Climate Models (TOUGOU program)” from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan; JSPS KAKENHI Grant Numbers 15KK0178,17K18816 and 26287117; the Environment Research and Technology Development Fund (2-1503) of the Environmental Restoration and Conservation Agency, Japan; and also funded under the Natural Environment Research Council (NERC) grant (GOTHAM - NE/P006779/1) under the auspices of a joint Belmont Forum and JPI-Climate program.