Long-term (1936-2003) ultraviolet and photosynthetically active radiation doses at a north Norwegian location in spring on the basis of total ozone and cloud cover

We have reconstructed a homogeneous and consistent 68-year time series of ultraviolet (UVR) and photosynthetically active radiation ( PAR) doses for the spring period at a marine location in northern Norway. The time series is simulated mainly on the basis of the Tromso total ozone series and routine meteorological observations of cloud cover. All other relevant input parameters were fixed at realistic values determined by local measurements and climatology. Our approach is applicable to a wide range of locations worldwide where routine ozone measurements and cloud observations are done. For the whole period 1936 2003, we find trends of + 4.5%, + 2.8% and + 1.3% per decade for the monthly UVB doses in March, April and May, respectively. UVA and PAR doses, which are not affected by total ozone, reveal smaller trends (+ 1 - 2% per decade) in March and April, while the May trend is comparable to UVB. At shorter term, however, the radiation trends were very variable.