Reconstruction of UV radiation over Southern Germany for the past decades
Reuder, Joachim; Koepke, Peter
A method for the reconstruction of spectral UV irradiance on the basis of radiation transfer calculations is presented. UV calculations have been performed for the time period 1968-2000 with a temporal resolution of one hour. Algorithms for the derivation of the required input parameters total ozone, aerosol, albedo and clouds have been developed to determine corresponding input data sets for the radiation transfer calculations from routine observations. The resulting spectral UV irradiances have been weighted by different action spectra. UV exposures for days, years and the growing season of crops have been obtained by integration with respect to biologically relevant time intervals. The results for two locations in Central Europe, Wuerzburg and Hohenpeissenberg, show that UV-B radiation has increased during the past decades. This increase is clearly associated with the stratospheric ozone reduction. Depending on the UV-B influence on the investigated action spectra, the increase in the annual exposure is in the order of + 2 % to + 5 % per decade. Regional differences have been found in the influence of clouds on UV radiation, indicating that the UV-B increase due to ozone reduction is enhanced by about 1 % per decade for Hohenpeissenberg and reduced by nearly the same amount for Wuerzburg.