Assessment of spectral UV radiation at Marambio Base, Antarctic Peninsula

Abstract

This study aims to assess the dependence of spectral UV radiation on different atmospheric and terrestrial factors, including solar zenith angle, ozone, and cloud cover, in the southern polar environment. For this purpose, 23g260 spectra (300-363gnm), obtained by the B199 Mk-III Brewer spectrophotometer at Marambio Base, Antarctic Peninsula region, over the period 2010-2020, were studied. A neural network model was developed to investigate the effects of the explanatory variables at 127 wavelengths in the interval 300-363gnm, with a 0.5gnm sampling interval. Solar zenith angle (SZA) proved to be the most important parameter, followed by cloud cover, total ozone column (TOC), and surface albedo. The relative SZA effect is greatest at the shortest wavelengths, where a 1g decrease in SZA results in a 6g%-18g% increase in UV irradiance (305gnm). TOC particularly affects the short wavelengths below approximately 320-325gnm, when for example at 305gnm a 10gDU decrease in TOC causes a 7g%-13g% increase in UV irradiance. The large-scale ozone holes (e.g., in 2011-2012, 2014-2015, 2018-2019) caused the spectral UV irradiance at very short wavelengths to peak in spring, whereas in other seasons (e.g., 2010-2011, 2012-2013), the maxima at all wavelengths were recorded in summer (November to January). Absorption of UV radiance by the ozone also affected the temporal distribution of very high spectral UV irradiances (i.e., highest 10g% of the distribution), when at 305gnm they were observed both in spring and summer months, and at 340gnm they occurred mostly in summer. The effect of cloud cover was strongest near the fully cloudy sky and in the summer months, when the Antarctic clouds tend to be thickest.