Understanding and modelling the REgional climate system ModEls in the Mediterranean for BEtter water-related Risk prevention in the context of global change – REMEMBER

The Mediterranean basin has quite a unique character that results both from physiographic and climatic conditions and historical and societal developments. Because of the latitudes it covers, the Mediterranean basin is a transition area under the influence of both mid-latitudes and tropical variability. Because in such transition area, the Mediterranean basin is very sensitive to global climate change at short (decadal) and long (millennial) time scales. Regarding on-going climate change, the Mediterranean area is considered as one major “hot-spots” with an increase in the interannual rainfall variability and strong warming and drying. The vulnerability of the Mediterranean population may thus increase with higher probability of occurrence of events conducive to floods and droughts which are among the most devastating natural hazards. In the context of global warming, sea level rise is also of major concern since the Mediterranean basin has one of the most crowded coasts in the world and demographic projections suggest that urban coastal population could reach 176 million people and the number of tourists per year could grow up to 350 million by 2025. This continuing migration towards coastal areas makes the Mediterranean one of the most vulnerable region to risks inherent to rising sea level.

The motivation of the project is thus to understand and model the Mediterranean climate system and specifically the processes leading to heavy precipitation and floods, heat waves and droughts and sea-level rise, not only as separate processes within each Earth compartment, but as coupled mechanisms with feedback loops. This is indeed crucial to characterize how these processes will respond to climate change, in order to make decision on development of adaptation strategies to face risks related to changing climate. First, it relies on the analysis of a first set of simulations performed with the three French stand-alone and coupled regional climate models in the frame of HyMeX and MED-CORDEX programs (stream1 simulations) and on the quantification of the multi-model uncertainty. Second, it consists in improving the stand-alone models with new common parameterizations for precipitation and air/sea fluxes, and river routing, multi-layer soil, groundwater, vegetation, irrigation and sea-level schemes. Last, it consists in integration these improvements in regional climate system models to produce and analyse a new set of regional simulations (hindcasts and IPCC CMIP5 scenarios) for the Mediterranean climate (stream 2 simulations) which will hopefully better represents heavy precipitation and floods, heat waves and droughts and sea-level evolution.

However, regional climate simulations are often biased and correction methods have to be applied to provide relevant information for end-users. Modelling the full climate systems by coupling sophisticated models of the different compartments is an a priori necessity to accurately simulate the regional climate but biases of each model can propagate and therefore affect the simulated regional climate. A last objective of the project is thus to quantify the potential added-value of fully coupled regional climate system models with respect to stand-alone regional climate models to provide relevant indicators to provide information tailored to the needs of policymakers and society actors. The REMEMBER project will make use of the new observation datasets collected in the frame of HyMeX and can be seen as the French contribution and support to the HyMeX and MED-CORDEX programs. This project is thus to be conducted in strong collaboration with European and Mediterranean partners and will benefit from the visibility of such programs for the dissemination of the results.