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'Atmospheric rivers' set to increase winter flooding in UK – University of Reading

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'Atmospheric rivers' set to increase winter flooding in UK

Release Date 24 July 2013

The atmospheric river that helped create the Cumbria floods of 2009

The prolonged heat wave that has bathed the UK in sunshine over the past month has given the country an unexpected taste of summer that has seemed to be missing in recent years.   

However, a new study published today (24 July) in IOP Publishing's Environmental Research Letters, has provided warnings that will chime with those accustomed to more typical British weather.

According to the study, by scientists at the University of Reading and University of Iowa, winter flooding in the UK is set to get more severe and more frequent under the influence of climate change as a result of a change in the characteristics of atmospheric rivers (ARs).

Dr Richard Allan, from the University of Reading's Department of Meteorology, said: "Previous research at the University of Reading linked flooding in the UK with vast flows of atmospheric moisture.

"The current work has exploited this knowledge in the context of climate change and has found that these atmospheric rivers become more intense in a warmer world."

ARs are narrow regions of intense moisture flows in the lower troposphere of the atmosphere that deliver sustained and heavy rainfall to mid-latitude regions such as the UK.

They are responsible for many of the largest winter floods in the mid-latitudes and can carry extremely large amounts of water: the AR responsible for flooding in the northwest of the UK in 2009 transported 4500 times more water than the average flow in the River Thames in London.

The researchers found that large parts of the projected changes in AR frequency and intensity would be down to thermodynamic changes in the atmosphere, rather than the natural variability of the climate, suggesting that it is a response to man-made climate change.

To reach these conclusions, the researchers used simulations from five state-of-the-art climate models to investigate how the characteristics of ARs may change under future climate change scenarios.

Lead author of the research, Dr David Lavers, previously at Reading but now working at Iowa, said: "ARs could become stronger in terms of their moisture transport. In a warming world, atmospheric water vapour content is expected to rise due to an increase in saturation water vapour pressure with air temperature. This is likely to result in increased water vapour transport.

"The link between ARs and flooding is already well established, so an increase in AR frequency is likely to lead an increased number of heavy winter rainfall events and floods. More intense ARs are likely to lead to higher rainfall totals, and thus larger flood events."

From Wednesday 24 July, this paper can be downloaded here >>>


For more information contact Pete Castle at the University of Reading press office on +44 (0)118 378 7391 or

Alternatively contact Michael Bishop at the IOP press office on +44(0)117 930 1032 or

Notes to editors:

The published version of the paper ‘Future changes in atmospheric rivers and their implications for winter flooding in Britain' (David A Lavers et al 2013 Environ. Res. Lett. 8 034010) is freely available online from Wednesday 24 July.

The University of Reading is ranked among the top 1% of universities in the world (THE World University Rankings 2012). Its Department of Meteorology is internationally renowned for teaching and study of atmospheric, oceanic and climate science and earth observation. Reading is involved with pioneering research on weather, climate and earth observation and is home to the Walker Institute for Climate System Research

Environmental Research Letters is an open access journal that covers all of environmental science, providing a coherent and integrated approach including research articles, perspectives and editorials.

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