Insights from hailstorm track analysis in European climate change simulations

Abstract. Hailstorms are among the most destructive weather events, posing significant threats to infrastructure, agriculture, and human life. This study applies hailstorm-tracking diagnostics to kilometer-scale, decade-long climate simulations over Europe using the COSMO v6 model driven by ERA5 reanalyses. Convection is treated explicitly, and hail is modeled online with the HAILCAST parameterization. Simulations represent current and future climate simulations, the latter corresponding to a 3 K global temperature increase implemented via a pseudo-global warming approach.

We analyze high-frequency hail output at 5 min intervals, which enables tracking ~40 k hailstorms in Europe in current and future climate simulations each. Storm track properties include length, duration, hail size, and spatial distribution, while three-dimensional environmental variables along these tracks yield storm-centered composites of hailstorm structure and allow for the examination of storm-inflow environments. Our analysis reveals significant shifts in the characteristics of hailstorms under the future climate scenario. Notably, hail frequency trends vary across Europe, but the trends in hailstorm environments are comparatively uniform. The most striking results are: (i) hail swath areas are projected to change both in terms of frequency and spatial extent, with a two-fold increased frequency of storms producing ~50 mm and larger hail diameters. Per-storm hail swath areas generally expand by 15–30 %, with swath area increases being more important for smaller hail, while frequency changes dominate for larger hail. (ii) The effect of increased hail melting due to the higher elevation of the 0 °C level on the storm maximum hail diameters is found to be minor. (iii) Precipitation and wind hazards accompanying hailstorms are expected to increase on average by 20 % and 5 %, respectively, while extreme hail-precipitation compound events, i.e., hail with a diameter of at least 30 mm followed by 50 mm h^-1 are projected to be twice as frequent in the future.