DIN CEN ISO/TR 17801:2017-11

Probably the most important primary weather factor is the effect of solar radiation on the earth's surface (global radiation). When irradiated, molecules usually absorb enough photons to break chemical bonds, initiate photochemical reactions and trigger electron transitions. The spectral irradiance of solar radiation varies locally and over time. Therefore, a reference spectrum is required as a basis for simulating the spectral irradiance of solar radiation using artificial radiation sources/radiation systems. For many years, data from CIE 85:1989 of the Commission Internationale de L'Éclairage (CIE) has been used for this purpose. Table 4 contains data for the spectral irradiance of global radiation (direct and diffuse radiation) under a cloudless sky with the sun at its highest position at equinox at sea level. However, the data in CIE 85:1989 for global irradiance only starts at 305 nm, the step size is rather coarse and the calculation key has been lost in some unexplained manner. For this reason, efforts to revise CIE 85:1989 have been ongoing for many years. The new Table 1 contains modeled data (using the SMARTS model, version 2.9.2), which was generated using a spectrum based on air mass zero (AM0), which corresponds to the extra-terrestrial spectrum of Gueymard. This Technical Report provides a reference spectrum for the field of weathering research, which allows the classification of solar simulators in the ultraviolet, visible and infrared wavelength range. The photochemical aging occurring in practice is simulated in laboratory weathering devices in a time-lapsed manner, whereby a sequence of climate episodes of maximum stress is applied. The target value for the spectral irradiance is given in the table by the spectral irradiance of global radiation (direct and diffuse radiation) at cloudless sky with the highest position of the sun at the equator at sea level during the equinox, as specified in CIE 85:1989, Table 4. This represents a realistic maximum irradiation under representative cloud-free conditions. The responsible committee is NA 054-01-04 AA "Verhalten gegen Umwelteinflüsse" ("Environmental resistance") at DIN Standards Committee Plastics (FNK).