An algorithm to evaluate solar irradiance and effective dose rates using spectral UV irradiance at four selected wavelengths

The paper shows a semi-analytical method for environmental and dosimetric applications to evaluate, in clear sky conditions, the solar irradiance and the effective dose rates for some action spectra using only 4 spectral irradiance values at selected wavelengths in the UV-B & UV-A regions (305, 320, 340 and 380 nm). The method, named WL4UV, is based on a reconstruction of an approximated spectral irradiance that can be integrated, to obtain the solar irradiance, or convoluted with an action spectrum to obtain an effective dose rate. The parameters required in the algorithm are deduced from archived solar spectral irradiance data. This database contains measurements carried out by some Brewer spectrophotometers located in various geographical positions, at similar altitudes, with very different environmental characteristics: Rome (Italy), Ny Ålesund (Svalbard Islands, Norway), Ushuaia (Tierra del Fuego, Argentina). To evaluate the precision of the method, a double test was performed with data not used in developing the model. Archived Brewer measurement data, in clear sky conditions, from Rome and from the National Science Foundation UV data set in San Diego (Ca, USA) and Ushuaia, where SUV 100 spectroradiometers operate, were drawn randomly. The comparison of measured and computed irradiance has a relative deviation of about ± 2%. The effective dose rates for action spectra of Erythema, DNA and non-Melanoma skin cancer have a relative deviation of less than about 20 % for solar zenith angles less than 50°.