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ABSTRACT

The Geophysical Monitoring for Climatic Change (GMCC) program of the National Oceanic and Atmospheric Administration (NOAA) operates an atmospheric monitoring observatory at Amundsen-Scott Station, South Pole. Long-term measurements of carbon dioxide, ozone, aerosols, and other background pollutants are obtained to understand their possible effects on the earth's climate. The aerosol measurement program consists of the continuous measurement of condensation nuclei (CN) concentration and aerosol scattering extinction coefficient (σsp).

During 1982, Nuclepore-filter aerosol samples were taken for subsequent analysis by the proton-induced X-ray emission (PIXE) technique with 8-h time resolution. A time series of sodium, chlorine, and sulfur concentrations shows that the sulfur and CN records are similar and that the sodium, chlorine, and σsp records are similar. Large episodes of sodium are measured at the ground in the austral winter and are apparently caused by large-scale transport from coastal regions and vertical transport to the surface during times of surface warming and weakening of the surface temperature inversion. These episodes are characterized by increases in sodium concentration, Cl/Na ratio, σsp, and particle size, and decreases in non-sea-salt sulfur concentration, suggesting a decrease in atmospheric acidity and a displacement of sulfuric acid aerosol. An analysis of back trajectories suggests transport times of several days from the Antarctic coast.

A nearly continuous record of South Pole CN measurements from 1974 to the present, and σsp measurements from 1979 to the present, has now been accumulated. The CN data show an annual cycle with a maximum exceeding 100 cm−3 in the austral summer and a minimum of about 10 cm−3 in the winter. The σsp data show an annual cycle markedly different from that of CN with a maximum in late winter, a secondary maximum in summer, and a minimum in May. Angstrom exponents calculated from the multiwavelength σsp data show a strong annual cycle suggesting larger particles in the winter than in the summer.