Data of "Cloud Condensation Nuclei and the Contribution of New Particle Formation in the Yangtze River Delta of Eastern China" -version1

Cloud condensation nuclei (CCN) serve as a critical link between aerosols and clouds, with new particle formation (NPF) recognized as a major source of CCN. However, the quantitative contribution of NPF to CCN remains highly variable and insufficiently constrained by in-situ observations. To address this gap, two-year synchronized observations of CCN, particle number size distribution (PNSD), and chemical composition were conducted in an urban area of eastern China. The average CCN concentration (N_CCN) was 2220 ± 1050, 3510 ± 1500, 4050 ± 1640, and 4400 ± 1740 cm⁻³ at 0.2%, 0.4%, 0.6%, and 0.8% supersaturation, respectively. Comparisons between observed and calculated N_CCN derived from PNSD and aerosol hygroscopicity revealed uncertainties in representing the hygroscopicity of organic-rich and NPF-origin particles. N_CCN exhibited distinct diurnal variations, with concurrent anthropogenic emissions obscuring the apparent NPF contribution to CCN. By distinguishing CCN into primary and secondary components and focusing on secondary CCN, NPF-related increases were estimated at 54-71% across supersaturations of 0.2-0.8%, substantially higher than conventional estimates. Results from the complementary survival probability (SP) approach further confirmed enhanced CCN formation efficiency under warm, low-pollution conditions, consistent with higher formation rates and SP. As air quality management continues to reduce PM_2.5 mass concentrations, the organic fraction and NPF frequency are likely to increase. These trends underscore the growing importance of NPF in CCN production and the necessity for coordinated, long-term observations of CCN and NPF to improve constraints on aerosol–cloud interactions and climate effects.