Record breaking heatwaves and droughts in North America and Western Europe, torrential rainfalls and floods in South-East Europe and Japan - the summer of 2018 brought a series of extreme weather events that occurred almost simultaneously around the Northern Hemisphere in June and July.
Record breaking heatwaves and droughts in North America and Western Europe, torrential rainfalls and floods in South-East Europe and Japan - the summer of 2018 brought a series of extreme weather events that occurred almost simultaneously around the Northern Hemisphere in June and July. These extremes had something in common, a new study by an international team of climate researchers now finds: the events were connected by a newly identified pattern of the jet stream encircling the Earth.
The jet stream formed a stalled wave pattern in the atmosphere which made weather conditions more persistent and thus extreme in the affected regions. The same pattern also occurred during European heat waves in 2015, 2006 and 2003, which rank among the most extreme heatwaves ever recorded. In recent years, the scientists observed a clear increase of these patterns.
The jet stream, about 10 km high up in the atmosphere, steers large scale weather systems from west to east around the globe. The wind system can develop large meanders, so-called Rossby waves, and occasionally these waves stay in place for weeks. Under these conditions warm sunny days can turn into a heat wave and drought, and rainy days into a flood. “Our study shows that the specific locations and timing of the 2018 summer extremes weren’t random but directly connected to the emergence of a re-occurring pattern in the jet stream that stretches around the entire Northern Hemisphere,” says lead author Kai Kornhuber from the University of Oxford's Department of Physics and the Potsdam Institute for Climate Impact Research (PIK).
Read more at University of Oxford
Photo credit: giselaatje via Pixabay
