Spectral Measurements of Direct Solar Radiation and the Sky Brightness Distribution at Syowa Station, Antarctica

Abstract

Spectral measurements of the solar radiation were performed at Syowa Station (69°00′ S: 39°35′E), Antarctica, from June 1984 to January 1985 as a research project of the 25 th Japanese Antarctic Research Expedition. The spectral direct-solar radiation was measured by a sunphotometer which was equipped with eight interference filters of 330, 369, 500, 675, 776, 862, 938, and 1048 nm. The aerosol optical thickness at the 500 nm wavelength was about 0.08 as an average of the observed values during January to April 1984, but it decreased to about 0.04 during September 1984 to January 1985. These values of the aerosol optical thickness were much larger than those reported previously by several authors, and were attributed to El Chichon aerosols. The inversion of these data showed that a mono-modal volume spectrum of aerosols with the mode radius of about 0.4 μm was predominant throughout the year, and that the loading of giant particles was relatively enhanced in spring and autumn. The surface albedo around Syowa Station was estimated from measured values of the brightness and degree of polarization of skylight.