Precipitation over coastal regions of southern France and its impacts on the regional hydrological cycle

The hydrological cycle in southern France is influenced by highly variable precipitation, which impacts the variability of soil moisture and continental runoff. The regional hydrological cycle is also significantly impacted by the Mediterranean Sea (Gulf of Lion) through moisture advection, and the strong coupling between the atmosphere and land surface affects all branches of the regional hydrological cycle, particularly due to the region's special orographic structure. The potential intensification of the regional hydrological cycle under climate change scenarios, leading to extreme hydroclimate events, is a critical factor for understanding the mechanisms of climate variability in the Mediterranean region.

In this study, long-term daily precipitation data from 1979 to 2014 for southern France was analyzed using various datasets, including data from 300 stations in the METEO-FRANCE collection, modern-era reanalysis (ERA5, JRA55), and satellite datasets. Diagnostic analysis was conducted to assess linear trends and interannual variability in total precipitation and precipitation extremes using multiple datasets. The results of this analysis allowed for the quantification of differences in variability patterns of precipitation among the datasets, highlighting their respective strengths and weaknesses. The study also examined the regional responses of soil moisture to precipitation using data from the GLEAM-GLDAS datasets besides 14 SMOSANIA stations. Finally, the representation of the observed regional hydrological cycle in historical simulations with regional (Euro-CORDEX) and global (CMIP6) climate models are analyzed. Thus, a statistical association between precipitation, soil moisture, and continental runoff is established and the role of regional atmospheric circulation and atmospheric rivers in forming multidecadal changes in the regional hydrological cycle is quantified.