Modern polymeric materials possess an ever increasing potential in a large variety of outdoor objects and structures
offering an alternative for many traditional materials. In outdoor applications, however, polymers are subject to a
phenomenon called weathering. This is primarily observed as unwanted property changes: yellowing or fading, chalking,
blistering, and even severe erosion of the material surface. One of the major weathering factors is UV radiation.
In spring 2005, the Finnish Meteorological Institute with its research and industrial partners launched a five-year
material research project named UVEMA (UV radiation Effects on MAterials). Within the framework of the project, a
weathering network of seven European sites was established. The network extends from the Canary Islands of Spain
(latitude 28.5°N) to the Lapland of Finland (latitude 67.4°N), covering a wide range of UV radiation conditions. Since
autumn 2005, the sites of the network have been maintaining weathering platforms of specimens of different kinds of
polymeric materials. At the same time, the sites have been maintaining their long-term monitoring programmes for
spectrally resolved UV radiation. Within UVEMA, these data are used for explaining the differences between the
degradation rates of the materials at each site and for correlating the UV conditions in accelerated ageing tests to those
under the Sun.
We will present the objectives of the UVEMA project aiming at deeper understanding of the ageing of polymers and
more reliable assessments for their service life time. Methodologies adopted within the project and the first results of the
project will be summarized.
An Antarctic UV-monitoring network established in 1999 as a Spanish-Finnish-Argentinian co-operation consists of multiband filter radiometers located at Belgrano, Marambio, and Ushuaia. To provide with quality controlled and assured calibrated groundbased Antarctic UV data, bi-weekly lamp tests were used on every site and visits of travelling reference instruments on two of the sites. Along the six years of operation, the sensitivity in some of the instrument channels was found to drift up to 61%. In both stations, always the same channels showed the best stability or worst instability. The rigorous quality assurance programme ensured that reliable time series of solar data could be produced, however. The most recent Antarctic ozone depletion period of 2005/2006 was studied by comparing OMI satellite-based erythemally weighted daily doses with the measured polynomial corrected data for August 2005-March 2006 for Ushuaia and Marambio. The root mean square (RMS) of difference between the groundbased and satellite-retrieved daily doses was on monthly basis smaller for Ushuaia (19 - 28 %) than for Marambio (17-58 %), possibly due to e.g. bigger heterogeneity of the ground albedo, and variability of the cloudiness. Our final task of combining the polynomial corrected lamp calibration factors and the traveling reference calibration factors, to produce the final calibrated Antartic UV data, is discussed, too.
Multiband filter radiometers (MBFRs) are extensively used in national networks for UV climate monitoring and information to the public about the potential risk of solar UV exposure. In order to provide an international, uniform expression of the Global UV index measurements, a harmonized calibration scale is needed. In this paper we present the results of the first international intercomparison of MBFRs held in Oslo in 2005. The purposes are to evaluate the UV-index scale of different radiometers and to provide a harmonized UV-index scale based on the radiometers individual directional and absolute spectral response functions. In total 43 MBFR radiometers and 4 high resolution spectroradiometers were assembled, representing UV-monitoring networks operated by institutions in US, Spain, Greece, Poland, Belgium, UK, Austria, Norway, Sweden and Finland. The radiometers are operating worldwide, with stations in the Antarctica and Arctic, North- and South-America, Africa, Europe, Middle-East and Nepal. All sky conditions were realized during the campaign period. The agreement between the users' own processed UVI and the reference is generally very good; within ±5% for 22 out of 26 data sets (75%) and ±10% for 23 out of 26 (88%). Solar zenith dependent discrepancies and drift in the users' UVI scales is seen, but the performance of most radiometers is generally very good. All the objectives planned for the intercomparison were fulfilled and the campaign considered a success.