This is the first of two papers reporting measurements made near Scott Base, Antarctica, during the spring of 1990 (October--November). The present paper describes the hourly and daily variations of the light falling on a horizontal surface, with the incident light divided into two components, that from the Sun directly and that from the sky. The light has been separated into four wavelength bands covering the blue to the UVB region of the spectrum. The intensities have been compared with values measured in Wellington. New Zealand. A simple air mass dependence has been found which fits the complete data set once a surface albedo parameter is taken into account, which provides an easy estimate for the daily average illumination throughout the year. The paper also correlates the changes in the UV and UVB with changes in upper atmosphere ozone concentration and compares the total daily UV dose in the Antarctic with that at Wellington, a typical mid-latitude site. ¿ American Geophysical Union 1992