SOLAR ULTRAVIOLET IRRADIANCE OBSERVED FROM SOUTHERN ARGENTINA - SEPTEMBER 1990 TO MARCH 1991

A nearly continuous data set of solar ultraviolet spectral irradiance exists for Ushuaia, Argentina, latitude 54-degrees-59' S, over the per iod from mid-September 1990 to mid-March 1991. This includes a season of prolonged depletion in column ozone over Antarctica, 10-degrees or more in latitude poleward of Ushuaia. Cloudiness provides a major sour ce of variance in the measurements. When this influence is removed, th e irradiances at wavelengths between 300 and 3 10 nm are enhanced rela tive to clear sky calculations based on a 10-year ozone climatology. D uring December the average noontime irradiance at 306.5 nm. which is a good proxy for erythemal irradiance, is 45% larger than the zonal mea n climatological prediction. The largest noontime radiation levels obs erved at Ushuaia are equivalent to moving 20-degrees in latitude close r to the equator at the summer solstice.