Saharan dust linked to European hail events

The impact of atmospheric dust on hail formation remains poorly under-stood, with competing effects suggesting both convective enhancement throughincreased cloud condensation particles and suppression of hail activity throughenhanced ice nucleation. While high concentrations of ice nucleating particles,such as Saharan dust, are often associated with reduced hail size — motivat-ing cloud seeding efforts — empirical evidence on the influence of dust on hailfrequency is limited and regionally inconsistent.In this study, we combine a range of observational and reanalysis datasets— including CAMS reanalyses, crowd-sourced hail reports, lightning and radarobservations, and synoptic and environmental variables from ERA5, to sys-tematically investigate the relationship between Saharan dust loading and hailoccurrence across Europe. We find a strong and spatially consistent association:hail days exhibit significantly (7σ) higher dust concentrations than convectivenon-hail days, with the median dust load up to 1.8 times greater.Importantly, this dust-hail link persists across different synoptic weatherregimes, underscoring its robustness. Hail occurrence peaks at moderate dustconcentrations (38 mg m−2 or a dust optical depth of 0.033), consistent withconvective enhancement, before declining at higher values, suggesting possiblemicrophysical or radiative limitations. Crowd-sourced hail report data revealsa substantial increase in hail events on high-dust days vs. low dust days. Aninfluence of the dust concentration on the reported hail diameters was not found.When included as a predictor in statistical hail models (logistic regressionand generalized additive models), dust consistently ranks as one of the top threepredictors, with model skills improving notably.Together, our findings highlight Saharan dust as a key, yet underrecognized,factor modulating hail activity in Europe and demonstrate the need for furtherstudies on aerosoll — hail interactions.