Estimate of Aerosol Optical Depth Using Broadband Direct Normal Observations at Highest Polluted Area in the World

Problem statement: The measurement of different components of direct solar radiation for this research has been carried out in Helwan, Egypt. Helwan (Latitude 29°52 N, Longitude 31°20 E). This is a considered as the largest polluted region in the world. The level of pollution in Helwan region is higher, compared to the international limit by about 7 or 10 times in industrial and populated region respectively. Approach: The daily variation for different components of solar radiation bands as global, direct (total, yellow, red and infrared) and diffuse solar radiation had been studied and discussed. The data measurements have been taken for nine years (1991-2000). Hourly data of solar irradiance on a horizontal plane had also been recorded simultaneously together with relative humidity and wind speed along with some traditional techniques for selecting the clear sky days of the period examined. Results: The results clearly showed seasonal dynamics in aerosol loading, type and perceptible water. Conclusion: Background levels of aerosols, which we defined as yellow color less than 0.10, had observed at almost all sites but varying frequencies.