ABSTRACT
ABSTRACT: During the 1970s scientists’ concern about the effects of anthropogenic emissions on the ozone layer started. Later, in the middle 1980s, ozone depletion over Antarctica during the spring was discovered. Satellite and ground based measurements indicated a pronounced increase in ozone destruction inside the polar vortex until the middle 1990s. Stratospheric ozone concentration and UV-B radiation at the earth’s surface are inversely related. However, other factors such as solar zenith angle, cloud cover and aerosols also affect solar irradiance measured at ground level and, hence, variations of UV-B radiation at the earth’s surface are not easily derived only from ozone concentrations. Spectral measurements of solar radiation are essential in UV-B studies, since they provide detailed information on the environmental conditions. In 1988, the National Science Foundation (US) initiated the activities of the NSF UV Radiation Monitoring Network. Four spectro-radiometers (SUV-100) were installed in Antarctic and Sub-Antarctic stations (South Pole, McMurdo, Palmer and Ushuaia). This network was later augmented by installing two new spectro-radiometers (Barrow, Alaska and San Diego, California). A time series of approximately ten years is now available from all stations. This database constitutes the basis for atmospheric studies and provides supporting data for biological research. Nevertheless, the time series for these measurements are still relatively short to determine trends. However, systematic measurements of total ozone column have been performed since the late 1950s at ground stations and, since the late 1970s, global coverage is available from instruments installed on satellites (Nimbus-7, Meteor-3, Adeos, Earth-Probe, Gome). Long-term ground level irradiance time series provided by broadband instruments (Pyranometers, UV and erythemally weighted) are also available from many sites around the world. Using a multi-regressive model, we were able to extend narrow-band and biologically weighted irradiances, from total ozone column and ground level irradiance measured by broadband instruments. Data from pyranometers belonging to the NOAA/CMDL surface radiation budget was used to obtain a time series of narrowband and biologically weighted irradiance for South Pole, dating back to the late 1970s. In this paper, we will present a discussion on the evolution of the ozone hole and UV-B irradiances over Antarctica, during the past decades, using the above-discussed data sets.
