Cloudiness and estimation of incoming solar radiation in Iraq

Summary

Monthly and seasonal variations of cloudiness have been studied for different zones of Iraq. It was found to be very low over the entire country and descends as we proceed southwards, except in summer, when it was found to be higher in the south than in the north. From the daily records of the Campbell-Stokes sunshine recorders at Mosul, Baghdad and Basrah, during a period of 10 years from 1961 to 1970, the actual hours and the percentage of possible hours of sunshine duration have been studied in detail and the results obtained are presented in a practical form. It has also been found that the pyrheliometric conditions for Baghdad could be considered representative of the entire country.

Taking the incoming solar radiation for clear days during different months of the year, and radiation received on a horizontal surface at Baghdad into consideration, and applying Ångström empirical formulae, it was possible to estimate graphically the amount of solar radiation received at any location in Iraq at any time of the year when the cloudiness or the percentage of possible hours of sunshine is known.