Solar ultraviolet irradiance observed from southern Argentina: September 1990 to March 1991

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Abstract
A nearly continuous data set of solar ultraviolet spectral irradiance exists for Ushuaia, Argentina, latitude 54°59′ S, over the period from mid‐September 1990 to mid‐March 1991. This includes a season of prolonged depletion in column ozone over Antarctica, 10° or more in latitude poleward of Ushuaia. Cloudiness provides a major source of variance in the measurements. When this influence is removed, the irradiances at wavelengths between 300 and 310 nm are enhanced relative to clear sky calculations based on a 10‐year ozone climatology. During December the average noontime irradiance at 306.5 nm, which is a good proxy for erythemal irradiance, is 45% larger than the zonal mean climatological prediction. The largest noontime radiation levels observed at Ushuaia are equivalent to moving 20° in latitude closer to the equator at the summer solstice.