Land-sea contrast in present and projected precipitation extremes in the Mediterranean region

Significant observational evidence supports the interpretation of the Mediterranean region as a hotspot region for climate change, including a variation in the frequency and intensity of extreme events such as heatwaves, droughts, or heavy precipitation. This has been observed particularly in the most recent decade, and has an example in the year 2022, which has shown a spread and persistent occurrence of high temperatures, low precipitation, droughts, and extreme precipitation events. Characterizing the pattern of extreme events is important for future prevention strategies against climate and weather events associated to high risk of catastrophes such as floods, landslides, and droughts, which all heavily affect populations and economies. This is even more crucial for the Mediterranean region, as it is a vulnerable region for climate change and one of the most densely populated areas in the world. In the most recent years, considerable attention has been paid to the geographical, topographical, and temporal patterns of extreme event variation throughout the Mediterranean region, although their rarity and local character have made it difficult to observe statistically significant changes. This is true especially above the sea since there are fewer weather stations and a reduced interest in weather and climate far from populated lands, leading to scarce data. This is reflected on the fact that many datasets do not even include data from the sea, such as E-OBS. The aim of this study is to analyse present and projected land and sea precipitation extremes in the Mediterranean region, with a particular focus on possible difference between land and sea extreme event patterns. In order to perform such study, several gridded datasets chosen because of their homogeneous coverage of the area were used, one representative for each type of climate data: ERA5 for reanalysis, E-OBS for station interpolation data, TRMM for satellite data, and CMIP5 for model data. The data and methodology were discussed in Chapter 3. Several analyses were performed on these data to investigate changes in mean climate variables (Chapter 4) and in extremes (Chapter 5), while also characterizing the type of precipitation that drives extreme events in the Mediterranean region. Three case study areas in the Mediterranean region where an increase of extreme precipitation was observed in the recent past were then investigated more in depth to analyse changes in atmospheric circulation during extreme events. Finally, results from an ensemble of global climate models were used to analyse the extreme indices projected to the end of the century (Chapter 7) and provide a preliminary outlook on the future change of extreme events in the Mediterranean region.