Irradiance spectral

The effective biological dose (Ee 18) at local apparent noon for each chamber was estimated by multiplying the relative biological efficiency for photoinhibition [epi(X)] by the available spectral irradiance [E(X)], and integrating with respect to wavelength (X, 290-400 nm) ... 

The downward spectral irradiance data [Ed(X), the ambient UV radiation] were generated with the atmospheric model of Frederick and Lubin (27) and ozone levels measured during the course of this study (J.E. Frederick, pers. commun.). The relative degree of UV enhancement (%ENH) for each chamber was calculated as follows ... 

Balu M, Padilha LA, Hagan DJ, Van Stryland EW, Yao S, Belfield K, Zheng S, Barlow S, Marder S (2008) Broadband Z-scan characterization using a high-spectral-irradiance, high-quality supercontinuum. J Opt Soc Am B 25 159-165... 

CIE Publication No. 85 [2] provides data on solar spectral irradiance for typical atmospheric conditions. A condensed version of a table for maximum global irradiance at the equator is given in ISO 4892-1 [3]. Reference solar spectral irradiance can be found in ISO 9845-1 [4] and analytical expressions for daily solar profiles are given in IEC 61725 [5], but this sort of data cannot generally be used to provide simplistic average acceleration factors. 

CIE TC2-17, Solar Spectral Irradiation, Publication CIE 85, Wien, Austria, 1989. 

ISO 9845-1, Solar energy - Reference solar spectral irradiance at the ground at different receiving conditions - Part 1 Direct normal and hemispherical solar irradiance for air mass 1,5 (available in English only), 1992. 

The general requirements for accelerated weathering apparatus are given in ISO 4892-1 [29], whilst ISO 4892 Parts 2-4 [26-28] deal more specifically with xenon arcs, fluorescent tubes and carbon arcs respectively. ISO 4892 refers to ISO 9370 [30] (Instrumental determination of radiant exposure in weathering tests), and CIE publication 85 (Solar spectral irradiance) [31]. 

The spectral irradiance of a typical mercury xenon lamp is shown in Figure 45. There is a characteristic high intensity mercury emission at 313 nm and a low intensity emission at 334 nm The MUV projection printing tools isolate these two lines through insertion of band-pass filter sets into the optical path, such that little or no light to the blue of 300 nm or to the red of 350 nm is transmitted to the resist surface. The transmission of a filter set of this sort for the Perkin Elmer Micralign 500 is shown in Figure 46. 

Figure 45. The relative spectral irradiance of a high pressure mercury xenon lamp of the sort commonly used in optical aligners.

Fig. 3.19a Solar spectral irradiance (global AM 1.5) and the fraction of the irradiance above A,niin where A,niin is the minimum wavelength at which the spectral irradiance has a measurable value [101],...

The use of various types of dosimeters, more or less well calibrated, which convert the photonic energy collected in a specific waveband (variable from one device to another) into an electric signal has led to a situation where comparison of experimental conditions in different laboratories is sometimes impossible. The most rigorous approach would be spectro-radiometry measuring genuine spectral irradiance, but this method requires expensive devices. A comprehensive document has been issued... 

Lean, J. L., O. R. White, and A. Skumanich, On the Solar Ultraviolet Spectral Irradiance during the Maunder Minimum, Global Biogeochem. Cycles, 9, 171-182 (1995b). 

McKenzie, R. L., W. A. Matthews, and P. V. Johnston, The Relationship between Erythemal UV and Ozone, Derived from Spectral Irradiance Measurements, Geophys. Res. Lett., 18, 2269-2272 (1991). 

FIGURE 16.6 Spectral irradiation of unfiltered solar simulator compared to zero air mass solar spectral irradiance (adapted from Winer et al., 1979). 

Absorbance An index of the light absorbed by a medium compared to the light transmitted through it. Numerically it is the logarithm of the ratio of incident spectral irradiance to the transmitted spectral irradiance. 

Spectral irradiance Irradiance at a given wavelength per unit wavelength integral, expressed in W/cm /nm measured usually with a spectroradiometer. 

In this way, the spectral irradiance measured at the Earth s surface at a normal incidence for a wavelength X is given by ... 

IaX is the diffuse spectral irradiance on a horizontal surface due to aerosol,... 

Igx is the spectral irradiance reflected from the air-ground system,... 

The model was initially compared with LOWTRAN 7 (5) results and with Brewer spectrophotometer measurements carried out at Lisbon in 1990. LOWTRAN-MESTRad results show a reasonable good agreement over 290-400 nm range with a mean difference of about 10%. Figure 4 shows de Model/LOWTRAN ratios for direct, diffuse and global spectral irradiances computed for the same conditions of ozone (332 Dobson Units), solar zenith angle (45.2°) and aerosol optical depth (0.0). 

Figure 4. MESTRad/LOWTRAN ratios for direct, diffuse and global spectral irradiances computedfor the same conditions of ozone (332 Dobson Units), solar zenith angle (45.2 °) and aerosol optical depth at 500 nm...

UV-B spectral global irradiance and total ozone direct sun measurements carried out at Lisbon during 1990 with a MARK 11 Brewer ozone spectrophotometer and with clear-sky conditions were used for comparison at several zenith angles, total ozone and aerosol conditions. However, because aerosol optical depth measurements were not available at this time it was decided to use T5oo=0.0 for the model input. The results of the Model/Brewer ratios for global spectral irradiances are shown in Figure 5. The results are similar and consistent with the earlier LOWTRAN 7 (6) comparison, where the ratio approaches to unity as the wavelength increases,... 

Figure 5. MESTRad/Brewer global spectral irradiance ratios computedfor several clear-sky days during 1990 at Lisbon (tsw=0.0).

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