Large hail frequently causes substantial damage to buildings, infrastructure and agriculture. According to Munich Re, around one-third of all natural hazard losses in Germany are caused by severe hail. As a result of anthropogenic warming and associated increases in low-level moisture and convective instability, it is generally anticipated that the likelihood of hailstorms has already increased and continue to increase in the future. Trends derived either from scarcely available direct hail observations or from model data, however, point in different direction. The objective of the project Hail-Clim as part of ClimXtreme II is to disentangle and reconcile the disparate trends identified in various data sets over past decades and to scrutinize to main reasons of the large uncertainty in the observed trends of hailstorms. We aim to reduce the uncertainty in the trends by better constraining the relationship between hailstorms and model fields (reanalysis and regional climate models) through an object-oriented approach that considers not only the occurrence of the storms but also their properties based on a radar-based tracking over 20 years. In addition, estimates of future changes will rely on an ensemble of high-resolution regional climate models for different storyline scenarios (e.g., +1.5, +2, +3 K) to quantify the uncertainty of future changes. These changes in the hazard are translated into potential extreme risk changes by applying a hail risk model developed at IMK-TRO, which shall be extended in a straightforward way to all of Germany.

Institution: Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology

Contact: Michael Kunz, Susanna Mohr, Jannik Wilhelm, Mathis Tonn