High-Resolution Spectral UV Monitoring and Atmospheric Transfer Modeling in the Netherlands
During the past decade a decrease in stratospheric ozone has been observed over large parts of the globe. Stratospheric ozone is the primary absorber of solar UV-B and UV-C and serves as a partially-protective shield against harmful UV irradiance in the biosphere. Decreased levels of ozone appear to increase the levels of harmful UV-B (280–315 nm) in the biosphere, leading to a variety of adverse effects on human health and on aquatic and terrestrial ecosystems. Changes in other atmospheric parameters, like aerosol content, cloud cover, and tropospheric ozone could also influence UV-B irradiance at ground level. High resolution spectral monitoring data are necessary to detect the present biologically-effective UV irradiance and to investigate the possible trends in effective UV. The advantage of spectral measurements is that the data can be used for evaluations with various biological action spectra.
A project was started in the Netherlands to gain knowledge of the present biologically-relevant UV climate and its dependence on atmospheric conditions. The measurements will be used to validate atmospheric UV transfer models; long-term monitoring should provide information on trends in the biologically-relevant UV. To meet these aims, a UV spectrometer system consisting of a highly accurate scanning double monochromator especially for the biologically-relevant UV-B region with a focal length of 50 cm, grating with 24001/mm, linear dispersion 0.375 nm/mm, and a multichannel detection system (diode array) for UV-A radiation measurements. Spectral coverage of the combined system ranges from 290–450 nm. UV monitoring needs will be outlined from the perspective of effect evaluations; preliminary results from the RIVM measurement system will be shown and the necessary international collaboration will be discussed.