Seasonal variation of solar irradiance and sunshine duration in Saudi Arabia

Saudi Arabia is a huge area with diverse climatic and topographical features. This diversity in climate is augmented by seasonal weather variations. The study discusses solar irradiance and sunshine duration in terms of seasonal weather systems. Sunshine duration and solar irradiance maps show that the East Mediterranean weather systems (such as Cyprus low) in winter affect the majority of the geographical regions in Saudi Arabia. In spring and autumn, Sudan low becomes more active than Cyprus low, especially in the west and central regions. Sunshine duration in April is 47% compared to 50% in January. Sunshine duration in the southwest region is affected by the rainy and wet summer monsoon which reduces sunshine duration to 33% in summer (July), while it is 43% in winter (January). In addition, the study uses the Angstrom equation to estimate solar irradiance. The absolute relative error between estimated and observed solar irradiance ranges between 2 and 10% in the majority of cases, with a few cases exceeding 13%.