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Impact du changement climatique sur les précipitations extrêmes dans le sud-est de la France : apport des modèles résolvant la convection profonde

Abstract : The Mediterranean region and more particularly the South-East of France are affected by intense rainfall episodes during the autumn. Determining the future evolution of these events is a major scientific and societal challenge. The objective of this PhD thesis is to study at very high resolution and at climate scales the past representation and future evolution of these intense rainfall events. The approach here is based on the analysis of simulations of a family of explicit deep convection regional climate models (cprcms, 2-3 km) and on the exploitation of a new database of kilometric and hourly precipitation observations : comephore. The evaluation of the cprcms revealed a high added-value of explicit convection models compared with parameterized convection models (12.5 km) for the representation of daily and especially sub-daily extreme precipitation. The robustness of this added value has been showed to changes in cnrm-arome configurations (version, domain and model driving).The added value was also verified in 4 other rcm/cprcm pairs from the cordex fps-convection program. The study of precipitation changes based on 10-year simulations of the four cprcms did not provide a significant response of change in extreme precipitation. It is very natural climate variability is likely to dominate the future response of extreme precipitation over periods of 10 years, which implies that even at the end of the 21st century and in a scenario with high green house-gases emissions, it is likely that some decades will be wetter and others less so than decades of the current climate. It is therefore necessary to extend the simulations to increase the robustness of multi-model results. In addition, the 10-year change results with cnrm-arome are not representative of the changes over 30 years. The 30-year scenario simulation with cnrm-arome according to the rcp8.5 projection for the end of the century suggests an increase in extreme daily and especially hourly precipitation in the Cévennes and more particularly in Roussillon (+15% per degree of warming). In scenario mode, it was possible to show that cprcms can significantly change the rain response to climate change simulated by standard resolution rcms. This work is the first intensive scientific exploitation of the arome model in climate mode. The results obtained open up many possibilities for its future use to study climate at very high resolution and in particular extreme events.
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Quentin Fumière. Impact du changement climatique sur les précipitations extrêmes dans le sud-est de la France : apport des modèles résolvant la convection profonde. Climatologie. Université Paul Sabatier - Toulouse III, 2019. Français. ⟨NNT : 2019TOU30239⟩. ⟨tel-02955946⟩

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