Physical insights on future European summer heatwaves

Margot Bador1, Laurent Terray1, Julien Boé1 , Samuel Somot2

1 CERFACS, Toulouse, France 2 CNRM, Meteo-France, Toulouse, France

Motivations • Large literature showing an increase of warm extreme events and

heatwaves over the 21st century in Europe (SREX Report, IPCC, 2012 ; Bador et al. 2015, Clim. Dyn.)

• Dynamical Downscaling to better describe the land-sea contrasts, orography and local processes

Methodology

Physical insights on future European summer heatwaves

Main Question • How can the regional modeling bring physical insights on the future

European summer heatwaves ?

Methodology 1. Select an intense summer heatwave from a climate model

2. Simulate this particular heatwave with the regional model

3. Perform several simulations with constant forcings

Margot Bador

The ALADIN model • Forcings: the CNRM-CM5 climate model (member

r1i1p1), surface and lateral boundary conditions

• EuroCordex version (ALADIN V5.3, Jacob et al. 2013), configuration and domain

• Spatial resolution: 12km

• Spectral nugding: no

Regional climate modeling

Physical insights on future European summer heatwaves Margot Bador

The 2075 heatwave in the CNRM-CM5 simulation • Heatwave Severity Index (Schoetter et al. 2014, Clim. Dyn.)

The most severe heatwave of the last 3 decades of the century :

intense, large spatial extension, very long duration (more than 30 days)

European future intense heatwaves

Physical insights on future European summer heatwaves Margot Bador

A strong control by the large scale circulation and the dynamical processes • Analog analysis based on the large scale

circulation (Deser et al. 2015, sub.)

• Construction of the temperatures due to dynamical processes only

The 2075 heatwave in the CNRM-CM5 simulation

Physical insights on future European summer heatwaves Margot Bador

Configuration of the experiments • Ensemble of 20 simulations

• Duration: from the 1st of June to the 31st of August

• Initialisation: restart from the EuroCordex simulation

• Forcings: the CNRM-CM5 simulation, RCP8.5

The 2075 heatwave in the ALADIN model

Physical insights on future European summer heatwaves Margot Bador

A large spread between the members

Physical insights on future European summer heatwaves Margot Bador

Do the soil-atmosphere interactions play a role in the inter-member spread ?

Physical insights on future European summer heatwaves Margot Bador

Conclusions

Future European intense heatwaves & Regional modeling

• Regional climate modeling can bring some physical insights on heatwaves

Large ensembles are needed: based on the 19 members simulating a similar large scale circulation to the CNRM-CM5 model, a spread up to 7°C exists during the heatwave, in average over Europe

• The soil-atmosphere interactions play a role in the inter-member spread

In the case of the 2075 heatwave, largely controlled by the dynamical processes, the differences in soil moisture content before the heatwave modulate the maximum temperatures up to 5°C during the heatwave, in average over Europe

Thank you for your attention ! bador@cerfacs.fr

Physical insights on future European summer heatwaves Margot Bador

APPENDIX

Selection of future intense heatwaves