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Abstract. New particle formation (NPF) and subsequent particle growth are importantsources of condensation nuclei (CN) and cloud condensation nuclei (CCN).While many observations have shown positive contributions of NPF to CCN atlow supersaturation, negative NPF contributions were often simulated inpolluted environments. Using the observations in a coastal city of Qingdao,Beijing, and Gucheng in north China, we thoroughly evaluate the simulatednumber concentrations of CN and CCN using an NPF-explicit parameterizationembedded in the WRF-Chem model. For CN, the initial simulation shows largebiases of particle number concentrations at 10–40 and 40–100 nm. Byadjusting the process of gas–particle partitioning, including the massaccommodation coefficient (MAC) of sulfuric acid, the phase changes in primary organic aerosol emissions, and the condensational amount of nitric acid, the improvement of the particle growth process yields substantially reduced overestimation of CN. Regarding CCN, secondary organic aerosol (SOA) formed from the oxidation of semi-volatile and intermediate-volatility organic compounds (S/IVOCs) is called SI-SOA, the yield of which is an important contributor. At default settings, the SI-SOA yield is too high without considering the differences in precursor oxidation rates. Lowering the SI-SOA yield under linear H2SO4 nucleation scheme results in much-improved CCN simulations compared to observations. On the basis of the bias-corrected model, we find substantially positive contributions of NPF to CCN at low supersaturation (∼ 0.2 %) over broad areas of China, primarily due to competing effects of increasing particle hygroscopicity, a result of reductions in SI-SOA amount, surpassing that of particle size decreases. The bias-corrected model is robustly applicable to other schemes, such as the quadratic H2SO4 nucleation scheme, in terms of CN and CCN, though the dependence of CCN on SI-SOA yield is diminished likely due to changes in particle composition. This study highlights potentially much larger NPF contributions to CCN on a regional and even global basis.