Anthropogenic Modulation of Dust-Dominated Ice Nucleation in an Urban Dryland City of China

Abstract. Ice-nucleating particles (INPs) are crucial for cloud formation and precipitation, yet their variability and influencing factors in urban dryland regions remain poorly understood. While natural dust is recognized as the dominant INP source, the extent to which anthropogenic pollution modulates INP abundance remains insufficiently quantified. Here, we present online observations of INPs (−15 to −35 °C), together with co-located aerosol size distribution and chemical composition in Lanzhou from winter 2024 to spring 2025. We show that long-range dust transport boosts INP concentrations by × 15 at −30 °C. Elevated secondary inorganic aerosol during pollution was enhanced and negatively correlated with INP activity (R = −0.71). We further refine a two-parameter scheme (1–2.5 µm aerosol diameter and temperature) that reproduces 83 % of observations within a factor of 5. These findings underscore the need to include local aerosol heterogeneity and dust-pollution interactions in INPs parameterizations for more accurate regional climate simulations.