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In this study, we utilized a 20-bin WRF-Chem (Weather Research and Forecast coupled with Chemistry regional model) to investigate the contributions of chemical drivers to the growth of newly formed particles, as well as to simulate the three-dimensional dynamics of new particle formation (NPF) events over the North China Plain during a summer campaign in 2019, which was reported in the accompanying paper. The model demonstrated good performance in replicating the occurrence of NPF, the growth pattern of newly formed particles, and the number concentration of particles in the size range of 10–40 nm in five events between June 29 and July 6. This period was characterized by a high frequency of NPF occurrence (>60 %). During this time, the model was also able to accurately reproduce the levels of organics in PM_1.0 relative to observations, and to reasonably replicate the levels of SO₄^2- and NH₄⁺ in PM_1.0, as well as PM_2.5 mass concentrations. Therefore, we further analyzed three NPF events with distinct particle growth characteristics: Case 1, featuring observable growth of newly formed particles to cloud condensation nuclei (CCN) size on July 1–2; Case 2, characterized by continuous growth of new particles for several hours without any net contribution to CCN on July 3; and Case 3, where no detectable continuous growth of newly formed particles was observed on July 6. In these instances, the model tended to overpredict the condensation of H₂SO₄ vapor during daytime and the formation of NH₄NO₃ during nighttime, resulting in an overestimation of the hygroscopicity parameter of nanometer particles. Nevertheless, the …