Effect of pollutant aerosols on spectral atmospheric transmissivity in Cairo

Spectral atmospheric transmissivity has been greatly affected by air pollutants in Cairo atmosphere. This has been studied by measuring the energy of solar radiation, selecting four bands at different wave-lenghts. Three selected bands are in the visible (blue 440 nm., green 500 nm., and red 640 nm.), while the fourth band is in the infrared region (880 nm.). The Cairo atmosphere was found to be greatly polluted by fine particulates, which were held in suspension for a longer time than coarse pollutants. The transmissivity of the spectral radiation showed a clear wavelength dependence comparable to particulate sizes found in different concentrations. The transmissivity was found to be highest for the infrared band, followed by the red and then the green bands, and the lowest was for the blue band.