20 Apr 2022
20 Apr 2022
Status: this preprint is open for discussion.

Present and future European heat wave magnitudes: climatologies, trends, and their associated uncertainties in GCM-RCM model chains

Changgui Lin1,2, Erik Kjellström1,3, Renate Anna Irma Wilcke1, and Deliang Chen2 Changgui Lin et al.
  • 1Rossby Centre, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
  • 2Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden
  • 3Department of Meteorology and the Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden

Abstract. This study investigates present and future European heat wave magnitudes, represented by the Heat Wave Magnitude Index-daily (HWMId), for regional climate models (RCMs) and their driving global climate models (GCMs) over Europe. A subset of the large EURO-CORDEX ensemble is employed to study sources of uncertainties related to choice of GCMs, RCMs and their combinations.

We initially compare the evaluation runs of the RCMs driven by ERA-interim reanalysis to the observations, finding that the RCMs are able to capture most of the observed spatial and temporal features of HWMId. With their higher resolution, RCMs can reveal spatial features of HWMId associated with small-scale processes; moreover, RCMs represent large scale features of HWMId in a satisfactory way. Our results indicate a clear added value of the RCMs in relation to their driving GCMs. Forced with the emission scenario RCP8.5, all the GCM and RCM simulations consistently project a rise in HWMId at an exponential-like rate. However, the climate change signals projected by the GCMs are generally attenuated when downscaled by the RCMs, with the spatial pattern also altered.

The uncertainty in a simulated future change of heat wave magnitudes following global warming can be attributed almost equally to the difference in model physics (as represented by different RCMs) and to the driving data associated with different GCMs. Regarding the uncertainty associated with RCM choice, representation of the orographic effects differently is a major factor. No consistent spatial pattern in the ensemble spread associated with different GCMs is observed between the RCMs, suggesting GCMs' uncertainties are transformed by RCMs in a complex manner due to the nonlinear nature of model dynamics and physics.

Changgui Lin et al.

Status: open (until 05 Jun 2022)

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  • RC1: 'Comment on egusphere-2022-215', Anonymous Referee #1, 01 May 2022 reply

Changgui Lin et al.


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Short summary
This study endorses RCMs' added-value upon their driving GCMs in representing observed heat wave magnitudes. The future increase of heat wave magnitudes projected by GCMs is attenuated when downscaled by RCMs. Within the downscaling, uncertainties can be attributed almost equally to choice of RCMs and to the driving data associated with different GCMs. Uncertainties of GCMs in simulating heat wave magnitudes are transformed by RCMs in a complex manner, rather than simply inherited.