Ultraviolet solar radiation at Dhahran, Saudi Arabia

Measurements of ultraviolet solar radiation for the period January 1985 to December 1987 at Dhahran (26°32′N, 50°13′E), Saudi Arabia, are analyzed. Dependence of ultraviolet radiation on the atmospheric clearness index is investigated. For a clearness index above 0.65, the ratio of ultraviolet radiation to total horizontal radiation is a constant value of 3.45%. For a clearness index below 0.65, the ratio was found to vary significantly with clearness index but it was also a strong function of the meteorological events (i.e., rainfall, clouds and suspended dust) bringing about the clearness index change. A ratio of ultraviolet to total horizontal radiation as high as 4.6% was reached on a rainy day, while a ratio as low as 2.1% was obtained for a dusty day.