Solar Spectral Irradiance

..."It has become obvious that the solar spectral irradiance data on which the recommendations in the original document were based were no longer the most reliable. During the past decade a vast amount of new data has become available both through modernized measurement techniques as well as improved modelling and parameterization methods. Contrary to the situation some years ago, the stage has now been reached where results for solar spectral irradiances at ground level as measured and those obtained by reliable modeling, using extraterrestrial data as basis, show agreement to accuracies well within predictable or estimable uncertainties. It has thus become possible to calculate solar spectral irradiance levels and characteristics for any site on earth provided appropriate meteorological and atmospheric parameters are applied in reliable modeling formulas. This enables close simulation of solar irradiance characteristics for any geographical site, without the need of having to make in situ measurements."...