Measurement Report: Vertical New Particle Formation Profile observed at 356 m Shenzhen Meteorological Tower

Abstract. Vertical measurements of New Particle Formation (NPF) are essential yet scarce for understanding the role of ultrafine particles in lower boundary layer atmospheric processes. This study presents comprehensive vertical observations conducted at the 356 m Shenzhen Meteorological Tower, utilizing mobility particle size spectrometers (SMPS and Nano-SMPS) at five heights (5–350 m) during two intensive observation periods (IOPs) in 2023. Results reveal distinct vertical dependencies in NPF characteristics. The NPF occurrence frequency was higher at ground level, while the particle growth rate (GR) was significantly enhanced aloft, increasing from 9±4 nm h⁻¹ at the surface to 14±4 nm h⁻¹ at 320 m. The vertical structure of NPF was classified into four types, which were closely related to the condensation sink (CS) higher at ground 0.04 s⁻¹ than aloft 0.02 s⁻¹. Turbulence promoted near- surface nucleation with peak growth rates up to ~13 nm h⁻¹ (average 9±4 nm h⁻¹ at 5 m) and enhanced growth in the middle layers with GR values of 7–8 nm h⁻¹ at 100–200 m (e.g., 8 nm h⁻¹ at 100 m and 200 m, and 5–8 nm h⁻¹ at 150 m), while growth rate at 350 m was mostly within 4 nm h⁻¹. Furthermore, the upper tower environment contributed more effectively to the conversion of new particles into cloud condensation nuclei, as supported by the significantly higher GR at 320 m (14±4 nm h⁻¹) compared to the surface (9±4 nm h⁻¹), indicating that particles aloft can grow into CCN active sizes more rapidly despite weaker turbulence at the highest levels. This work provides critical insights into aerosol vertical transport process and CCN production in the urban boundary layer.