Extreme cyclones in the western Mediterranean under future climate change

The Mediterranean storm track is characterized by small but intense cyclones that can cause extreme weather events across the western Mediterranean (WMED). Thus, the aim of this study is to investigate the impact of future climate change on extreme wind, precipitation and compounding cyclones. We use a regional climate model simulation that simulates pre-industrial conditions (1821-1880) and future conditions under the representative concentration pathway RCP8.5 (2039-2098). We show that mean cyclone frequency is reduced by roughly a third in the WMED by the end of the 21st century in our simulation. For precipitation-type extreme cyclones (EXCs), future projections show increased precipitation during and after their most intense phase. During the mature phase of future precipitation EXCs, increased diabatic potential vorticity production contributes to cyclone intensity. Precipitation EXCs also appear to become more baroclinic. Wind speed EXCs are also set to become more extreme under future RCP8.5 conditions. The reason for this intensification is that wind speed EXCs are located in the left exit of a jet streak, which strengthens in the future. This provides more lift for future wind speed EXCs. For both future wind speed and precipitation EXCs, these processes also lead to a lower core pressure. Thus, we find that despite a general reduction of cyclones, precipitation and wind speed EXCs intensify in the future, implying strong socio-economic consequences for the WMED.