Strengthening dust–cirrus relationships over Central Europe (2001–2025)

Abstract. Saharan dust is increasingly recognized as an important driver of aerosol–cloud interactions over Europe, yet its long-term influence on cloud formation remains poorly understood. This study investigates changes in the relationship between dust intrusions and upper-level cloud properties over the Carpathian Basin during the 2001–2025 period using a combination of MERRA-2 reanalysis, MODIS satellite observations, HIRS outgoing longwave radiation (OLR) data, and a database of 276 validated Saharan dust events.

The frequency of Saharan dust intrusions increased by nearly 70 % during the study period. Dust outbreaks were associated with enhanced high-cloud cover, increased cirrus reflectance, reduced effective ice particle radius, and lower OLR values. These relationships were particularly pronounced during spring, when thermodynamic conditions are most favourable for heterogeneous ice nucleation and cirrus development.

To quantify the temporal evolution of dust–cloud relationships, generalized additive models were applied to cloud and radiative variables. Atmospheric dust loading was a highly significant predictor in all seasonal models, while significant dust–time interaction terms demonstrated that cloud responses to dust have systematically strengthened over time. The strongest signals were observed for cirrus reflectance, high-cloud fraction, and OLR, indicating increasingly pronounced upper-tropospheric cloud responses under comparable dust-loading conditions.

The results suggest that Saharan dust has become an increasingly important factor influencing cloud formation and radiative processes over Central Europe. Together with growing evidence for more frequent ice-saturated and ice-supersaturated environments, the findings support the hypothesis that evolving upper-tropospheric conditions increasingly favour dust-associated cloud formation.