CatRaRE: A Catalogue of radar-based heavy rainfall events in Germany derived from 20 years of data

In a warming climate, heavy rainfall is assumed to occur more frequently in the future. Extreme precipitation events are hard to observe and predict and can have devastating impact on infrastructure, housing and people. Rain gauge networks often cannot detect small-scale events, because the distances between stations are too large. In order to give a comprehensive overview on all heavy precipitation events, area-wide rainfall observations with high spatial and temporal resolution, e.g. from radar networks, are required. We present a method to extract heavy precipitation events from 20 years of radar data in Germany and collect various parameters (e.g. time, duration, location, mean and maximum precipitation, severity indices as well as meteorological, geographical and demographic information) for each event in a catalogue. In CatRaRE (Catalogue of Radar-based heavy Rainfall Events), rainfall events of 11 durations between 1 and 72 hrs are listed for the years 2001 to 2020. Two different thresholds for heavy precipitation are used: the warning level for severe weather in terms of precipitation rate from the German Weather Service and a return period of 5 years. The threshold determines their spatial distribution. While events that exceed a return period of f ve years are rather equally distributed over Germany, events based on warning level exceedance show structures linked to orography. However, this dependency decreases for short-term events that occur more randomly all over the country. Analyses reveal a large interannual variability in number and affected area of events. Despite being a dry year on average, 2018 turned out to be the year with most events. Case studies of two of the most devastating events in the last 20 years illustrate the potential of CatRaRE to examine individual events in detail. CatRaRE will be updated on an annual basis, is freely available for download and can be a useful tool for hydrologists, climatologists, and in risk management.

Automated summary

In a warming climate, the frequency of heavy rainfall events is expected to increase in the future. This study highlights the importance of radar networks and the creation of the CatRaRE catalogue for comprehensive analysis of heavy precipitation events. Spatial distribution differences were found among events based on different thresholds in Germany, with 2018 being the year with the highest number of events.