ATMOSPHERIC TURBIDITY AND TRANSMITTANCE OF SOLAR-RADIATION IN RIYADH,SAUDI-ARABIA

During the last two decades, the urban areas in the city of Riyadh-the capital of Saudi Arabia-were increasing at an exceptionally high rate through a series of development plans. The major plans had been compl eted by the end of 1982. Some other big utility projects were started and completed during 1987. As a consequence, the air quality has deter iorated markedly and air pollution episodes recorded during these acti vities showed that particulates were present in the atmosphere at high concentrations. Later in January 1991 the Gulf war started and the fi ring of the oh fields in Kuwait soon followed. It was estimated that s oot particulates were emitted at a rate of 600 ton d(-1) along with hi gh rates of other gases. This event has led to significant air quality and visibility problems. Direct normal solar radiation has been measu red during the summer months of July and August which were characteriz ed by very dry and cloudless weather for the period between 1982 and 1 992 A year-to-year trend of the transmittance of direct normal solar i rradiance was then determined. The atmospheric fine aerosol (<2 mu m d iameter) loading data during the same period were used to establish a correlation between the aerosol concentration and the extinction coeff icient. The total horizontal and direct normal solar radiation measure ments during some days when the dark smoke emitted from the oil field fires in Kuwait were passing over Riyadh are presented. The solar irra diation reflects the intensity of dark smoke at a distance of 500 km f rom Kuwait.