Anthropogenic modulation of dust-dominated ice nucleation in an urban dryland city of China during winter and spring

Abstract

Abstract. Ice-nucleating particles (INPs) are crucial for cloud and precipitation modulation, yet their spatiotemporal variability and sources sampled from urban dryland regions remain poorly understood. While natural dust is recognized as a substantial source of INPs, its interaction and quantity with anthropogenic pollutants, as well as INP abundance of the mixtures, remain 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 a factor of 15 at −30 °C in an urban region. Elevated secondary inorganic aerosol was observed during winter pollution events and negatively correlated with INP activity (R = −0.71). We further refine an INP parameterization based on aerosol size (1–2.5 µm) and freezing temperature, reproducing 83 % of observations within a factor of 5. These findings underscore the need to include local aerosol heterogeneity and dust-pollution interactions in INP parameterizations for more accurate regional climate simulations.