CONDENSATION NUCLEUS SIZE DISTRIBUTION AT MAWSON, ANTARCTICA - MICROPHYSICS AND CHEMISTRY

This work examines the annual evolution of the condensation nucleus (CN) size distribution and its relationship with other aerosol microphysical and chemical parameters in the lower atmosphere over Antarctica. Good agreement is observed between the seasonal cycles of aerosol volume and non-sea-salt sulfate. Changes between periods with strong bimodality and periods with a weak or missing nucleus mode are interpreted in terms of a seasonally varying precursor sulfur source strength and aerosol surface area. Although there are very limited measurements of SO2 concentration for this region, conditions under which these are consistent with the observed SO4 levels are considered. Overall, the observed relationships between microphysical and chemical properties of the aerosol strongly support the notion that the dominant source of nuclei in remote southern locations, including Antarctica, is maritime and that these nuclei result from the oxidation of dimethyl sulfide to methane sulfonate and sulfate.