Atmospheric Particle Number Concentrations and New Particle Formation over the Southern Ocean and Antarctica: A Critical Review

The Southern Ocean (SO) and Antarctica play important roles in the global climate. The new particle formation (NPF) alters the availability of cloud condensation nuclei (CCN), leading to impacts on the cloud reflectance and global radiative budget. In this review, we introduce the common instruments for measuring particle number concentration (PNC) and particle number size distribution (PNSD). Based on the observations over the Antarctic and some Antarctic research stations, we explored spatial and temporal characteristics of PNCs and PNSDs. From the SO to the interior of the Antarctic, the total PNCs show a decreasing trend, and the total PNCs present an obvious seasonal cycle, with the low concentration in winter (June–August) and the high concentration in summer (December–February). By summarizing the research progress over the SO and Antarctica, we discuss possible precursors of the NPF: sulfuric acid (H₂SO₄, SA), methanesulfonic acid (CH₃S(O)₂OH, MSA), dimethyl sulfide ((CH₃)₂S, DMS), iodic acid (HIO₃, IA), iodous acid (HIO₂), ammonia (NH₃), dimethylamine ((CH₃)₂NH, DMA), highly oxygenated organic molecules (HOMs) and other organics with low vapor pressure. We also explore several possible nucleation mechanisms: ion-induced nucleation of H₂SO₄ and NH₃, H₂SO₄-amines, H₂SO₄-DMA-H₂O, H₂SO₄-MSA-DMA, IA-MSA, IA-DMA, heterogeneous IA-organics nucleation mechanisms and environmental conditions required for the NPF. NPF is one of the main sources of CCN in the remote marine boundary layer, such as the SO and Antarctica. Thus, we discuss the contribution of NPF to CCN and the indirect impacts of NPF on climate. Through this review, we could better understand the PNC and NPF over the SO and Antarctica and their impacts on the global climate.