Stronger thunderstorms and more hail through climate warming?

Germany is moving toward a future marked by rising temperatures driven by climate change and potentially cleaner air resulting from electrification and stricter emission standards. These shifting environmental conditions raise an important question: How will severe convective storms evolve in a warmer, less polluted atmosphere? This study investigates that question by simulating three supercell events at high resolution using the ICOsahedral Non-hydrostatic (ICON) model.

The selected cases were observed during the Swabian MOSES field campaigns in 2021 and 2023. To assess how these storms might change in a warmer climate, the simulations apply the pseudo-global warming method, which modifies atmospheric conditions according to projected temperature increases. Furthermore, the study incorporates aerosol effects on clouds and precipitation by using a two-moment microphysics scheme. Four warming scenarios were tested, allowing a detailed examination of both thermodynamic and microphysical responses.

Overall, the simulations show that higher temperatures enhance convective activity. Warmer conditions promote stronger updrafts, support more vigorous storm development, and lead to more frequent and intense supercell formation. As a result, precipitation amounts increase substantially, and extreme events—such as flash flooding and severe hailstorms—become more pronounced. In several cases, rainfall increases exceed 7% per degree of warming, surpassing the rates predicted by the Clausius–Clapeyron relationship. This super-Clausius–Clapeyron scaling suggests that storm dynamics and microphysical processes further amplify rainfall beyond what is expected from thermodynamic moisture increases alone.

A notable finding concerns hail formation. Under lower cloud condensation nuclei (CCN) concentrations, hailstones grow significantly larger, and the spatial extent of large hail expands by up to 400%. This indicates that, although cleaner air may reduce aerosol loads, it can also create conditions that favor more intense and widespread hail events. Lower CCN levels also correspond to a reduced ratio of cold-to-warm rain formation and lower precipitation efficiency. Interestingly, these aerosol-related effects remain consistent across all warming scenarios, implying that aerosol influences on storm microphysics are robust and largely independent of temperature changes.

Taken together, the results suggest that Germany—and central Europe more broadly—may face more intense convective weather in a future warmer climate. Stronger supercells, heavier rainfall, larger hail, and more frequent flash floods could all become increasingly common, underscoring the need for improved forecasting, risk assessment, and adaptation strategies as environmental conditions continue to evolve.

The pre-print of the accepted article can be found at: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3069/egusphere-2025-3069.pdf