Preprints
https://doi.org/10.5194/esd-2021-49
https://doi.org/10.5194/esd-2021-49

  22 Jul 2021

22 Jul 2021

Review status: this preprint is currently under review for the journal ESD.

Atmospheric Rivers in CMIP5 climate ensembles downscaled with a high resolution regional climate model

Matthias Gröger1, Christian Dieterich1, Cyril Dutheil1, Markus Meier1,2, and Dmitry Sein3,4 Matthias Gröger et al.
  • 1Department of Physical Oceanography and Instrumentation, Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, 18119, Germany
  • 2Research and Development Department, Swedish Meteorological and Hydrological Institute, Norrköping, 601 76, Sweden
  • 3Shirshov Institute of Oceanology, Russian Academy of Sciences; Moscow, Russia
  • 4Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research; Bremerhaven, Germany

Abstract. Atmospheric rivers (AR) are important drivers of heavy precipitation events in western and central Europe and often associated with intense floods. So far, the ARs response to climate change in Europe has been investigated by global climate models within the CMIP5 framework. However, their spatial resolution between 1 and 3° is too coarse for an adequate assessment of local to regional precipitation patterns. Using a regional climate model with 0.22° resolution we downscale an ensemble of 24 global climate simulations following the greenhouse gas scenarios RCP2.6, RCP4.5, RCP8.5.

The performance of the model was tested against ER-I reanalysis data. The downscaled simulation notably better represents small-scale spatial characteristics which is most obvious over the terrain of the Iberian Peninsula where the AR induced precipitation pattern clearly reflect eat-west striking topographical elements resulting in zonal bands of high and low AR impact. Over central Europe the model simulates a less far propagation of ARs toward eastern Europe compared to ERA-I but a higher share of AR forced heavy precipitation events especially Norway where 60 % of annual precipitation maxima are related to ARs.

We find ARs more frequent and more intense in a future warmer climate especially in the higher emission scenarios whereas the changes are mostly mitigated under the assumption of RCP2.6. They also propagate further inland to eastern Europe in a warmer climate. In the high emission scenario RCP8.5 AR induced precipitation rates increase between 20 and 40 % in western central Europe while mean precipitation rates increase by maximal 12 %. Over the Iberian Peninsula AR induced precipitation rates slightly decrease around −6 % but mean rates decrease around −15 %. The result of these changes is an overall increased contribution of ARs to heavy precipitation with greatest impact over Iberia (15–30 %).

Over Norway average AR precipitation rates decline between −5 to −30 %. These reductions most likely the originate from regional dynamical changes. In fact, over Norway we find ARs originating from > 60° N are reduced by up to 20 % while those originating south of 45° N are increased. Also, no clear climate change signal is seen for AR related heavy precipitation and annual maximum precipitation over Norway where the uncertainty of the ensemble is quite large.

Matthias Gröger et al.

Status: open (until 17 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esd-2021-49', Anonymous Referee #1, 23 Aug 2021 reply
    • AC1: 'Reply on RC1', Matthias Gröger, 28 Aug 2021 reply
  • RC2: 'Comment on esd-2021-49', Anonymous Referee #2, 16 Sep 2021 reply
  • RC3: 'Comment on esd-2021-49', Anonymous Referee #3, 19 Sep 2021 reply

Matthias Gröger et al.

Matthias Gröger et al.

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Short summary
Atmospheric Rivers transport high amounts of water from subtropical regions to Europe. They are an important driver of heavy precipitation and flooding. Their response to a warmer future climate has so far been assesed only by global climate models. In this study we apply for the first time a high resolution regional climate model that better resolves small scale land – atmosphere interactions.
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