Multi-decadal Variability of Large-scale Circulation and its Contribution to Extreme Hydroclimate in the Mediterranean region.

The Mediterranean region, located in the transition zone between the dry subtropical and wet mid-latitude climates of Europe, is very sensitive to global climate change. Results of CMIP5 climate model experiments (Diffenbaugh and Giorgi, 2012) identify this region as a “regional climate change hotspot”, under both the intermediate and high anthropogenic forcing scenarios. However, long-term (decadal to multidecadal) climate variability has been shown to have a non-negligible contribution to the hydroclimate in this region. Models often struggle to correctly represent the mechanisms controlling Mediterranean hydroclimate and have resolutions that are too coarse to represent extreme hydroclimate. The GFDL CM2.5 model offers climate simulations represented by high temporal and spatial resolution. This study identifies the large-scale mechanisms, originating from Atlantic and Indian Ocean, which control Mediterranean mean hydroclimate. Afterwards, we quantify the impact of an internal and forced variability on those mechanisms, mean hydroclimate, and extremes.