Vigorous New Particle Formation Above Polluted Boundary Layer in the North China Plain

Atmospheric new particle formation (NPF) is vital in climate and air pollution for its contribution to aerosols and cloud condensation nuclei; however, a vertical understanding of NPF is still limited. Here, simultaneous observations at two altitudes were conducted over the North China Plain. Despite a high aerosol loading during cold season, NPF is still frequently observed. The upper-air NPF is increasingly intensive and starts earlier as haze pollution deteriorated, and the onset time gap could exceed 3 hr. To understand the factors modulating NPF vertically, we updated the meteorology-chemistry model by incorporating state-of-the-art nucleation schemes and performed highly vertical-resolved simulations. It is revealed that vertical disparities in NPF are attributed to the pronounced stratification of sulfur dioxide, ozone, and particulate matter. As the evolution of the boundary layer, strong NPF in the upper air elevates the near-surface nucleation-mode particles. This work sheds more light on the vertical structure of NPF.