Installation of an European Light DOsimeter NETwork

There is great concern about the possible adverse effects on life on our planet due to a possible increase of UV-irradiance, caused by a reduction in the stratospheric ozone layer. A number of networks have already been installed or are in the planning stage to monitor solar radiation. However, most of these measurements do not satisfy the needs of the scientists who are interested more in the effects of solar radiation than in their meteorological and physical. Our European Light Dosimeter Network (ELDONET) is intended to meet those needs, by detecting whether or not significant changes in the UVB range occur over time in several regions of Europe, based on highly accurate and long term stable filter dosimeters. In contrast to some of the existing and planned networks, which provide spectrally resolved data, we will develop, build and install instruments which measure solar radiation in three well-defined channels: UV-B (280 - 315 nm, CIE definition), UV-A (315 - 400 nm) and PAR (photosynthetically active radiation (400 - 700 A0nm). The instruments and sensors will be identical for all stations in order to warrant a meaningful comparison between the data from the different sites. While the main interest is in the two UV channels we will of course measure visible radiation (PAR) for comparison as it involves only minor additional costs. In addition, measurements in the visible region provide a first easy control mechanisms to detect possible sources of error, since the ratio between the irradiances in the three channels varies only within certain limits for solar radiation. Thus, partial or complete failure of a sensor (channel) can be automatically detected. Irradiance at the earth's surface does not only depend on solar elevation and ozone content but also on atmospheric transparency, which shows usually large local and regional changes. Our network will allow us to follow also these local trends and sporadic occurrences such as mini ozone holes. The ELDONET stations are arranged along a north-south transect from Spitzbergen, (70 N) to the Canary Islands (Gran Canaria, 27 N) and extend from east to west from Greece (Korinth, 23 E) to Iceland (22 W) to cover the major light climate areas in Europe. Other stations are encouraged to join the network, which will be very easy, as the hardware and installation costs are comparatively low. Also there are no bureaucratic hurdles to overcome. Some stations will be installed at high altitude to measure the significantly higher UV-B levels compared to lower altitudes. Land-based instruments will be installed at all sites; in addition, at some sites water-proof versions will be installed in the water column to detect the irradiance experienced by the organisms growing at that specific depth.. The data generated by the different stations will be sent to Pisa, where data management is coordinated. The central server in Pisa will be responsible for data storage and processing and for the maintenance of the central FTP and WWW servers. The irradiance and dose data will be available on an instant basis to the scientific community on the World Wide Web. Each year the raw data from the stations will be copied onto CD ROMs which will then be made available to every interested user.