Cloud‐Mediated Dust Effects Dominate Photovoltaic Performance Losses in Southern Europe

Saharan dust outbreaks are a major source of atmospheric variability over Southern Europe and are known to reduce photovoltaic (PV) power generation through aerosol‐induced attenuation of solar radiation. However, the relative importance of direct dust radiative effects and indirect aerosol–cloud interactions remains poorly constrained. Here, we investigate dust impacts on national‐scale PV performance in Spain, Italy, and Greece during 2020–2025 by combining hourly PV generation data, MERRA‐2 dust reanalysis, CAMS irradiance products, and MODIS cirrus cloud observations. A quadratic bootstrap mediation framework was applied to separate direct dust effects from indirect cirrus‐mediated pathways. PV performance ratios (PR) decrease systematically with increasing dust loading, with the strongest reductions occurring when elevated dust concentrations coincide with enhanced cirrus cloudiness. Under combined dust–cirrus conditions, annual mean PR values decline to approximately 0.63 in Spain, 0.53 in Italy, and 0.49 in Greece, accompanied by strong suppression of direct irradiance and increased diffuse radiation fractions. Satellite observations reveal increasing cirrus reflectance and decreasing effective ice particle radius with increasing dust loading, consistent with dust‐enhanced heterogeneous ice nucleation and cirrus cloud modification. Mediation analysis demonstrates that the indirect cirrus‐mediated effect is statistically significant and dominates PV generation losses in all three countries, whereas direct dust effects are weak, and partially compensating due to enhanced diffuse radiation. These results indicate that cloud‐mediated aerosol effects, rather than direct dust extinction alone, represent the dominant mechanism controlling PV performance losses across Southern Europe, with important implications for solar‐energy forecasting and renewable‐dominated power systems.