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Land-Atmosphere Interactions Exacerbated the Drought and Heatwave over Northern Europe during Summer 2018
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  • Paul A Dirmeyer,
  • Gianpaolo Balsamo,
  • Eleanor Blyth,
  • Ross Morrison,
  • Hollie Cooper
Paul A Dirmeyer
George Mason University

Corresponding Author:pdirmeye@gmu.edu

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Gianpaolo Balsamo
ECMWF Model Division/Physics
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Eleanor Blyth
UK Centre for Ecology and Hydrology
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Ross Morrison
Centre for Ecology and Hydrology
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Hollie Cooper
UK Centre for Ecology & Hydrology
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The 2018 drought and heatwave over Europe was exceptional over northern Europe, with unprecedented forest fires in Sweden, searing heat in Germany and water restrictions in England. Monthly, daily and hourly data from ERA5, verified with soil moisture and surface flux measurements over Britain, are examined to investigate the subseasonal-to-seasonal progression of the event and the diurnal evolution of tropospheric profiles to quantify the anomalous land surface contribution to heat and drought. Data suggest the region entered a rare condition of becoming a “hot spot” for land-atmosphere coupling, which exacerbated the heatwave across much of northern Europe. Land-atmosphere feedbacks were prompted by unusually low soil moisture over wide areas, which generated moisture limitations on surface latent heat fluxes, suppressing cloud formation, increasing surface net radiation and driving temperatures higher during several multi-week episodes of extreme heat. We find consistent evidence in field data and reanalysis of a breakpoint threshold of soil moisture at most locations, below which surface fluxes and daily maximum temperatures become hypersensitive to declining soil moisture. Similar recent heatwaves over various parts of Europe in 2003, 2010 and 2019, combined with dire climate change projections, suggest such events could be on the increase. Land-atmosphere feedbacks may play an increasingly important role in exacerbating extremes, but could also contribute to their predictability on subseasonal time scales.
Jun 2021Published in AGU Advances volume 2 issue 2. 10.1029/2020AV000283