Understanding the specific dynamical processes leading to extreme floods is an important but challenging task. Ruff and Pfahl used an innovative approach that allowed them to go beyond single case studies. They used operational ensemble forecasts from the ECMWF during the period 2003-2019 and focused on five major river catchments in Central Europe. Comparing extreme events (with a return period of 100 years) with more moderate events revealed important differences between the catchments. For some catchments the main factors that distinguish 100-year events were the intensity of the upper-level cutoff and surface cyclone, whereas in other catchments the main factor was an increased low-tropospheric moisture supply. The original results clearly illustrate that regional variability is substantial and no single atmospheric process can be claimed responsible for the distinction between extreme and moderate flood events.
Understanding the specific dynamical processes leading to extreme floods is an important but...
In this study, we analyse the generic atmospheric processes of very extreme, 100-year precipitation events in large central European river catchments and the corresponding differences to less extreme events, based on a large time series (~1200 years) of simulated but realistic daily precipitation events from the ECMWF. Depending on the catchment, either dynamical mechanisms or thermodynamic conditions or a combination of both distinguish 100-year events from less extreme precipitation events.
In this study, we analyse the generic atmospheric processes of very extreme, 100-year...