The German Federal Office for Radiation Protection (BfS) operates a nationwide network for solar ultraviolet (UV) radiation monitoring in cooperation with the Federal Environment Agency, Germany's National Meteorological Service and other associated institutions.
Until 2017, scanning double monochromators (DM) were used within the network for spectral-resolved measurements to ensure our requirements on accuracy. However, these devices are expensive and high-maintenance. In addition, the measurement time of several minutes is a disadvantage in case of fast changing cloud conditions. An alternative system was found with a diode array radiometer using BTS technology (BTS). Comparative validation measurements of BTS and DM systems have shown that the more cost-effective BTS systems achieve sufficient stray light reduction (dynamic range) with a shorter measurement time than DM and high spectral resolution. This allows the spectral UV irradiance to be determined more accurately at fast changing cloud conditions. For this reason, further stations in the UV monitoring network were expanded with BTS diode array radiometers. One of them was installed in the high mountain region Alps, where often fast changing cloud conditions as well as the highest solar UV irradiance in Germany appear.
To inform the public about the current solar UV irradiance the BfS publishes daily courses of the UV Index as derived from the measurements of all measurement stations continuously updated over the day. However, the information is generally valid to the region of the measurement station due to the strong dependence of the solar UV irradiance on the cloudy conditions. For comprehensive information, the number of measurement stations of the German solar UV monitoring network is insufficient. To this end, the existing network is being expanded to further twenty additional stations equipped with small and low-cost UV Index sensors which achieve the desired level of accuracy for UV Index determination. The expansion is made in cooperation with the German ODL (ambient gamma dose rate) network with its 1800 stations.
In 2024 the network includes 14 stations for spectrally resolved measurements and more than 30 additional stations equipped with new broadband filter radiometer for direct measurement of the erythemal irradiance. The expansion of network with a special focus on the applied devices, the validation and the measurement results as well as the communication of the current erythemal irradiance to the public will be presented.
Sebastian Lorenz1, Markus Laufmann1, Jürgen Sotrop1, Erik Faber1, Ingo Mayer1, Cornelia Baldermann1, Daniela Weiskopf1
(1) Federal Office for Radiation Protection, Division Effects and Risks of Ionising and Non-Ionising Radiation, Oberschleissheim, Germany;