More intense and more dispersed convective cell clusters in European MCSs under higher temperatures

A number of recent catastrophic floods (e.g., Valencia, Spain) were driven by heavy, persistent rainfall from mesoscale convective systems (MCSs), which are major contributors to extreme precipitation in Europe. Understanding how MCS rainfall responds to warming is therefore critical for assessing future flood risk.  Extreme rainfall depends not only on instantaneous intensity but also on the persistence and spatial organization of precipitation. MCSs are typically a blend of intense, localized regions of “convective” precipitation alongside broader, less intense areas of “stratiform” precipitation. While extremes of both components are expected to intensify according to the Clausius-Clapeyron (CC) relationship (Da Silva & Haerter, 2025), flood-relevant rainfall additionally depends on changes in convective cluster size, number, spatial distribution, and system-scale organization.
Here, we use observational data to quantify how MCS properties scale with surface temperature in the present climate over Germany. MCSs are identified and tracked using radar precipitation and lightning observations, and convective rainfall is separated from stratiform rainfall using two independent detection methods. We examine the changes in convective cluster number, size, spatial aggregation, and system-scale characteristics with near-surface temperature.
We find that, with increasing temperature, convective clusters within MCSs become more numerous and larger, while also more spatially dispersed. Convective rainfall, typically concentrated on the southern flank of MCSs, increasingly extends northward under warmer conditions, consistent with enhanced convective instability on the northern side and slightly reduced vertical wind shear. In contrast, total MCS area, propagation speed, and convective persistence show no systematic temperature dependence.
A statistical model reproducing these temperature-dependent changes indicates that CC-driven increases in pointwise convective intensity dominate the scaling of area-averaged rainfall, explaining ~80% of the increase at mesoscale (10–100 km) scales. Increases in convective cluster size and number contribute ~20% each, while enhanced spatial dispersion partially offsets these effects (~20%).
These results constrain current-day temperature-dependent rainfall scaling and may aid the interpretation of projected extreme precipitation changes.

Da Silva, Nicolas A., and Jan O. Haerter. "Super-Clausius–Clapeyron scaling of extreme precipitation explained by shift from stratiform to convective rain type." Nature Geoscience (2025).