Correlation between sunshine duration and global solar radiation in south-eastern Romania
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Fruit Research Institute, 0312 Pitesti-Maracineni, Romania
Ovidius University, Constanta, B-dul Mamaia, No. 124, 8700 Constanta, Romania
Acceptance date: 2002-02-28
Int. Agrophys. 2002, 16(2): 139–145
This paper deals with the correlation between global solar radiation and sunshine duration for the south-eastern part of Romania. Daily data on sunshine duration (n) and global solar radiation (Rs) from the Constanta weather station were used for a period of 30 years, between 1971 and 2000. Coefficients a and b from Angström’s equation calculated for the Constanţa location were very close to those recommended worldwide. About 24% of extra-terrestrial radiation penetrates the atmosphere on a fully- clouded (n = 0) day, and about 74-75% on a clear-sky day, respec- tively. The coefficients computed from the mean monthly data did not practically differ from those computed using the mean daily data. Both data pairs can be used in estimating global solar ra- diation for the Black Sea coastal area of Romania. The direct cor- relation equations between Rs and n can be also used in estimating global solar radiation. Similarly, the regression equation between Rs and temperature could be utilized too. However, they do not present the same consistency or physical significance as Ang- ström’s equation type.