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Abstract:
Recent studies have focused on the relationship between global warming and extreme precipitation events. The risk of flooding is increasing due to global warming, since warmer air temperatures accommodates more moisture content according to Clausius-Clapeyron relation. One of the major flood sources is known as Vb cyclones, i.e. cyclones travelling through the Mediterranean then moving northwards on the eastern flank of the Alps towards central Europe. In this study, the convection process during major Vb events is investigated. Two detection methods for convection are used. The first is Lagrangian convection tracking method (Purr et al. 2021) and the second is mid-tropospheric vertical velocity and vorticity method (Poujol et al. 2019) on convective-permitting simulations (3km resolution) driven by ERA5 reanalysis data for selected Vb cases. The results show that at least one third of the total amount of rainfall is produced by convection. Both methods show similar patterns and comparable amplitudes of convective precipitation. The second method is tuned to detect convective precipitation on a lower resolution parameterised-convection simulations. A comparable fraction due to convection during a Vb event is identified and the method is applied on more events to allow statistical significance. Convection is investigated in a warmer climate scenario, and it is found that convective fraction increases as high as two thirds of precipitation during Vb-events accounting for the global warming signal. This concludes that while the mean precipitation rate decreases due to global warming, extreme localised convection increases indicating more risk of flooding events in central Europe.
