Mediterranean compound extremes and their link to Mediterranean cyclones

Mediterranean weather extremes are often driven by regional low-pressure systems, here under the name of Mediterranean cyclones. In this work we take a Lagrangian (cyclone-centred) and a Eulerian (geographical) perspectives on the association between bi-variate compounds of rain-wind and wave-wind extremes and Mediterranean cyclones. Our aim is to provide new insight on the processes driving the compounding of extreme weather conditions in the extended Mediterranean region. Three main research questions are adressed.
(i.) What is the average spatial distribution of compound extremes around cyclone centres?
(ii.) How is the regional compound frequency modulated by the presence of cyclones?
(iii.) Is the presence of cyclonic air-streams (warm conveyor belts and dry intrusions) and fronts relevant for triggering compound extremes?
The results are strongly dependent on the compound type, on the cyclone class and on the season and region of occurrence. We find that in transition seasons compound extremes are far rarer than in the winter season, and that they are mostly associated with a nearby low-pressure centre. The fraction of cyclone-related compounds is weaker during the winter season, even though winter baroclinic cyclones are associated with the highest frequency and spatial extension of compound extremes. Finally, the presence of warm conveyor belts (inflow and ascent), dry intrusion outflow and cold fronts around the cyclone centre is shown to be important for the occurrence of regional compound extremes across all seasons. Warm conveyor belt ascent regions show high occurrence of both types of compound extremes; wave-wind compounds are also favoured in regions of dry intrusion outflow.