Too dry, too hot, or too wet: Increasing weather persistence in European summer

Date:
December 6, 2021
Source:
Potsdam Institute for Climate Impact Research (PIK)
Summary:
Global warming makes long lasting weather situations in the Northern
hemisphere's summer months more likely -- which in turn leads
to more extreme weather events, a novel analysis of atmospheric
images and data finds. These events include heatwaves, droughts,
intense rainy periods.

Especially in Europe, but also in Russia, persistent weather
patterns have increased in number and intensity over the last
decades with weather extremes occurring simultaneously at different
locations.



FULL STORY ==========================================================================
"In our study, we show that persistent weather conditions have an
increasing similarity in summer over the North Atlantic, Europe and
Siberia, favoring more pronounced extreme weather events. In Europe
alone, about 70% of the land area is already affected by more persistent weather situations," says Peter Hoffmann from the Potsdam-Institute
for Climate Impact Research (PIK), lead author of the study published
in Nature scientific reports. "This means that people, especially in
densely populated Europe, will likely experience more and also stronger
and more dangerous weather events."

========================================================================== Prolonged sunny or rainy conditions lead to extreme events To prove
this, the scientists analysed the persistence of specific weather
conditions. They applied established image comparison methods on
atmospheric data, comparing millions of successive weather circulation
patterns worldwide over the last 40 years. They especially looked at
two individual extreme events, the 2010 heat wave over Russia and the extraordinary dry summer over Europe in 2018. "We found that weather
patterns in general are more persistent now than some decades ago," says Hoffmann. "Especially in summer, heat waves often last longer now, and
also rainfall events tend to linger longer and to be more intense. The
longer these weather conditions last, the more intense the extremes can
become, both on the warm and dry side as well as on the steady rain side."
The rise in persistent weather conditions is to a large extent due to
dynamical changes in the atmosphere as the westerly winds tend to stop
pushing forward weather systems which therefore become more persistent,
turning some sunny days into heatwaves of several weeks as well as
intensive rainfall into floods.

Climate models might underestimate rise in persistent weather patterns
Like the eye of a knowledgeable observer, the new image comparison
method systematically scans atmospheric fields and helps to assess to
which extent successive weather circulation patterns change over time or
remain stable. Fred Hattermann, co-author of the study and also scientist
at PIK, explains the potential of the new approach: "Our method crucially improves the interpretation of long-term climate impacts. When applying
the same methodology to climate model output, we do not see a comparable increase in weather persistence, especially not over Europe. Climate
models may have been a bit too conservative, underestimating the rise
in weather persistence -- thus underestimating weather extremes over
Europe." This becomes ever more important with ongoing climate change.

"Recent events and ongoing research have shown that the number
and intensity of extreme events have increased due to the global
rise in temperature," concludes Hattermann. "To counteract
this worrying trend, the goal has to be to reduce global
greenhouse gas emissions and by doing so limit climate change." ========================================================================== Story Source: Materials provided by Potsdam_Institute_for_Climate_Impact_Research_(PIK).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Peter Hoffmann, Jascha Lehmann, Bijan H. Fallah, Fred F. Hattermann.

Atmosphere similarity patterns in boreal summer show an increase
of persistent weather conditions connected to hydro-climatic risks.

Scientific Reports, 2021; 11 (1) DOI: 10.1038/s41598-021-01808-z ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211206113059.htm

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