Long-term monitoring and analysis of hourly solar UV radiation in the 290-380 nm range in the middle region of Saudi Arabia.

The UV and global solar radiation on a horizontal surface at ground level in Riyadh City (latitude 24 degrees 34' N, longitude 46 degrees 43' E) have been measured and analyzed. Measurements of UV radiation (295-385 nm) were recorded every 10 min for five years (January 1983-December 1987). The maximum recorded hourly mean irradiance UV radiation was 28 W/m2 and occurred in July, while the minimum was 14 W/m2 in December. A steady monthly value of [formula: see text] was obtained and equaled 2.9%. A similar trend was found for the monthly variation of [formula: see text] and [formula: see text]. Maximum values of 90% and 2.6% were recorded in June for Kt and Kv, respectively, while minimum values of 35% and 1%, respectively, were obtained in December. A linear correlation was obtained between Kv and Kt. These findings were discussed and connected to the meteorological events. The results were compared with the regions of Kuwait, Bahrain, Dhahran, and Makkah.