Solar ultraviolet (UV) radiation is known to have adverse effects on the biosphere including terrestrial and aquatic ecosystems as well as public health. As far as mankind is concerned, exposure to solar UV radiation is associated with skin cancer, accelerated ageing of the skin, cataract, or other eye diseases. It may also affect people?s ability to resist infectious diseases, and compromise the effectiveness of vaccination. Several plants react to increased UV radiation with reduced growth or diminished photosynthetic activity. Phytoplankton, which is the first link in the maritime food chain, may be damaged as well.
As a consequence of the observed decline in stratospheric ozone concentration UV levels are expected to increase in high- and mid-latitudes. Apart from the inherent risk of solar UV radiation, life on Earth therefore may be confronted with a further rise in UV. The anticorrelation between ozone and UV is usually partly masked by the variability in cloud cover, tropospheric pollution, or the aerosol content of the atmosphere. This fact complicates the assessment of UV trends and promotes measurements of solar UV because our ability to calculate UV radiation at the Earth?s surface for cloudy conditions is still limited.
Thus, in order to quantify the current and future impact of solar UV radiation on the biosphere, highly accurate measurements of solar spectral UV irradiance are needed. However, these types of measurements are not simple. Difficulties arise from the steep decline of the solar spectrum in the UVB range caused by the absorption of atmospheric ozone. This decline leads to escalating uncertainties in the results of measurements if the specifications of the spectroradiometers used for this purpose do not meet specific requirements or if these instruments are not maintained and deployed appropriately.
More information on UV can be found at the WMO site http://www.srrb.noaa.gov/UV or in the publications of Gunther Seckmeyer.