First aerosol optical thickness measurements at Dome C (East Antarctica), summer season 2003–2004

In the framework of a calibration project concerning satellite sensors over a remote site of inland Antarctica, the temporal variations of atmospheric aerosol properties have been investigated in relation to their strong influence on the transfer of visible radiation. For this, a sunphotometer was installed at Concordia station (75°S, 123°E, 3200 m a.s.l.) on the Antarctic plateau during summer season 2003–2004. Meteorological parameters were recorded for the same period. Very low aerosol optical thickness values were observed with a mean AOT of 0.02 at 440 nm and 0.007 at 870 nm for clear sky conditions, and a small standard deviation. Angstrom coefficients were high with an average of 1.65 at 440 nm. These values reflect the high purity of the atmosphere and the small size of particles, mainly sulfate aerosols. Higher AOT values are observed under diamond dust conditions (0.025 at 440 nm and 0.013 at 870 nm). Temporal variations are also observed at the daily and seasonal levels. Dome C, therefore, appears to be an excellent site for satellite sensor calibration as well as investigations concerning the background atmospheric composition and global atmosphere changes caused by human activities.