Particle number size distributions and new particle formation events over the northern Indian Ocean during continental outflow

Abstract

Abstract The particle number concentrations, size distributions, and new particle formation (NPF) events were investigated in the South Asian outflow over the southeastern Arabian Sea (SEAS), the northern (NIO) and equatorial Indian Ocean (EIO) during the winter of 2018 based on the extensive measurements of particle number size distributions in size range 10–414 nm in the marine atmospheric boundary layer (MABL) as part of the Integrated Campaign for Aerosols, gases, and Radiation Budget (ICARB - 2018) experiment. The total particle concentrations were higher (as high as 106 cm−3; mean ~8857 ± 13425 cm−3) over the SEAS in the proximity to the continental outflow, which gradually decreased to reach the lowest values over the remote EIO (~3206 ± 4406 cm−3). Several NPF events with conspicuous bimodal size distributions and 3–10 times enhancement in nucleation particle (