Size distribution of Antarctic submicron aerosols

The method and results of the observation of the size distribution of submicron aerosols carried out at Syowa station (69°00”S, 39°35”E) in the sunlit months from August to December in 1978 are described. The most important finding in this series of observations is that the bimodal size distribution with a trough at around 10^-6 cm in radius is seen in almost all observations. The prevalence of the bimodal size distribution observed at Syowa station in the sunlit months gives evidence of new particle formation in the Antarctic troposphere. Based on simplified theoretical calculations, it is concluded that the production rate of new particles is about 4 X 10^-4 cm^-3 s^-1 in the summer in Antarctica which for instance could be yielded by homogeneous conversion of an SO₂ concentration of 1 μg m^-3 at a rate of 0.5% hr^-1. The most plausible precursors of SO₂ involved in this process seem to be rather inert gases such as COS, CS2, etc. DMS plays a small rôle in this new particle formation process, although it does play an important rôle in maintaining the aerosol mass concentration in the Antarctic atmosphere.