Growth of New Particles into Cloud Condensation Nuclei at the Summit of Mt. Fuji during Summer

Abstract

This study discussed the contribution of new particle formation (NPF) events to the number concentrations of cloud condensation nuclei (CCN) based on aerosol number size distributions measured at the summit of Mt. Fuji. The observations were made during the summer months of 2014～2019. The size distribution is measured by a scanning mobility particle sizer (SMPS), and the CCN number concentration is estimated by the number concentration of particles larger than 80 nm (N₈₀). At the summit of Mt. Fuji, the event occurred 113 times and the increase of N₈₀ was recorded 60 times out of 217 days of analysis. The N₈₀ increased by 47 to 234 cm⁻³ due to NPFs, and the increase rate was 123 to 302%. By comparing the diurnal variation of N₈₀ on days with and without NPF events, it was confirmed that the events increased N₈₀. At the summit of Mt. Fuji, the increase in N₈₀ due to NPF was small compared to some other stations, but the rate of increase was relatively high. Mode diameters grew to 80 nm in 7 of 113 events. The concentration of increase in N₈₀ is 9 to 552 cm⁻³, the increase rate is 111 to 700%. The growth period from 25 nm to 80 nm was about 2 to 12 hours, and the growth rate was about 5 to 30 nm h⁻¹. The growth characteristics depended on the particle number concentration produced by the NPF, the origin and transport route of air mass, the existing particle number concentration of N₈₀, the precursor gas concentration, and the chemical composition of the aerosol.