Effect of cloudless sky parameters on global spectral solar radiation within 0.3-1.1 μm region

The aim of this study is to evaluate the effect of cloudless sky parameters on global spectral solar radiation over the complete solar spectrum (0.3-1.1 μm) in Bangi, Malaysia using SPCTRAL2 parametric model written by MATLAB. The results show that there is a noticeable attenuation in the various spectral global solar irradiance regions when the solar zenith angle becomes larger than 50°. The global solar irradiance at a solar zenith angle 80° has a value of about 146 W m ^-2 μm at a wavelength of 0.46 μm but it increases to about 525 W m ^-2 μm ^-1 at a solar zenith angle 10° at the same wavelength. The impact of water vapor on spectral global solar radiation is clear in the visible and near infrared wavelengths between 0.55 and 1.0 μm does not affect the spectral UV. Whereas the ozone effect is especially within the wavelength ranged between (0.3-0.35 μm and 0.49-0.73 μm and there is a strong absorption in monochromatic wavelength 0.469, 0.610 and 0.645 μm. finally the turbidity parameter β has a strong influence on the spectral global solar radiation. The effect of the turbidity parameter β becomes strong when β is equal to 0.20 (turbid) or more and this is due to the increment in the air pollution in the atmosphere. However, the wavelength exponent α, has only a minor influence on spectral irradiance. The overall results of this case study show that the spectral global solar radiation is very influenced by an increment or decrement of cloudless sky parameters except the wavelength exponent α.