The Solar Radiation Environment of Sites at High Southern Latitudes

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Biological processes at high latitudes of the Southern Hemisphere are closely coupled to the availability of sunlight. Solar radiation in the visible wavelengths provides the energy for photosynthesis while the ultraviolet (UV) radiation can act as an inhibitor, although the magnitude of the effects are subject to debate. Over the past decade, attention has focused on high southern latitudes due to the large decline in springtime atmospheric ozone levels and the accompanying increases in solar UV irradiance. This research project will address the major factors which lead to variability in the UV and visible radiation environment at high southern latitudes using a combination of data analysis and numerical modeling. The project will utilize long-term, ground-based measurements of solar UV radiation and visible irradiance from the NSF Polar UV Radiation network, with sites located at McMurdo, Palmer and South Pole Stations, Antarctica and Ushuaia, Argentina. The earliest of these data sets began in 1988 and data collection has continued without major interruption since. The compilation will include monthly-integrated irradiances, information of short-term variability within a month, and trends over the duration of the data sets. The reported irradiances will be based on several biological weighting functions as well as selected discrete wavelengths in the ultraviolet and visible. Scientific topics to be addressed include the frequency of occurrence of unusually large UV irradiances and the change in this frequency over the duration of the data sets, the relative contributions of changes in ozone and changes in cloudiness to interannual variability in the UV radiation environment and the wavelength dependence of the attenuation associated with cloudy skies. Not only will the analyses have value to those in the atmospheric sciences community, the data will be summarized in a form valuable to biologists and ecologists studying the effects of UV radiation on biological processes.