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 through
increased cloud condensation particles and suppression of hail activity through
enhanced 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 hail
frequency 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 radar
observations, and synoptic and environmental variables from ERA5, to sys-
tematically investigate the relationship between Saharan dust loading and hail
occurrence across Europe. We find a strong and spatially consistent association:
hail days exhibit significantly (7σ) higher dust concentrations than convective
non-hail days, with the median dust load up to 1.8 times greater.
Importantly, this dust-hail link persists across different synoptic weather
regimes, underscoring its robustness. Hail occurrence peaks at moderate dust
concentrations (38 mg m⁻² or a dust optical depth of 0.033), consistent with
convective enhancement, before declining at higher values, suggesting possible
microphysical or radiative limitations. Crowd-sourced hail report data reveals
a substantial increase in hail events on high-dust days vs. low dust days. An
influence of the dust concentration on the reported hail diameters was not found.
When included as a predictor in statistical hail models (logistic regression
and generalized additive models), dust consistently ranks as one of the top three
predictors, 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 further
studies on aerosoll — hail interactions.