Abstract

One of the most significant environmental changes that occurs in our atmosphere, the ozone depletion in the stratosphere, produces increases in damaging UV-B radiation at the surface, especially in Antarctica. The largest populations nearest to the ozone hole region are Punta Arenas (53.0 degrees S, 70.9 degrees W, Chile) and Ushuaia (54.5 degrees S, 68.0 degrees W, Argentina) at the southern extreme of the South-American continent. The ozone trend near these locations is - 0.5% per year using the yearly averages, and - 1.2% per year using the October means. This is 2 to 5 times larger than the global average. UV-B radiation has been measured at Punta Arenas in small spectral bands, from 290 nm to 320 nm, during ''normal'' and ''perturbed'' conditions, It has been found that at Punta Arenas, during significant ozone column reductions, the largest UV-B increase occurs near 296-297 nm, which is the wavelength where the human skin has its highest sensitivity to UV-B. The relative factor of enhancement has been observed to vary between 10 and 38, depending on the values used for normalization. Ar longer wavelengths these enhancement factors are lower, until they equal unity at about 325 nm. The integrated biologically effective radiation on perturbed days is more than twice as large as the ''normal'' values.