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Spectral solar irradiance before and during a Harmattan dust spell
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
1996 (English)In: Solar Energy, ISSN 0038-092X, Vol. 57, no 3, 195-203 p.195-203 p.Article in journal (Refereed) Published
Abstract [en]

Measurements of the ground-level spectral distributions of the direct, diffuse and global solar irradiance between 300 and 1100 nm were made at Akure (7.15°N, 5.5°E), Nigeria, in December 1991 before and during a Harmattan dust spell employing a spectroradiometer (LICOR LI-1800) with 6 nm resolution. The direct spectral solar irradiance which was initially reduced before the dust storm was further attenuated by about 50% after the spell. Estimated values of the Ångström turbidity coefficient β indicated an increase of about 146% of this parameter while the Ångström wavelength-exponent α decreased by about 65% within the 2-day study period. The spectral diffuse-to-direct and diffuse-to-global ratios suggest that the main cause of the significant reduction in solar irradiance at the surface was the scattering by the aerosol which led to an increase in the diffuse component. The global irradiance though reduced, was less sensitive to changing Harmattan conditions. It is recommended that solar energy devices that use radiation from Sun and sky be used under fluctuating Harmattan conditions. There are some deviations from the Ångström formula under very turbid Harmattan conditions which could be explained by the relative increase of the particle sizes.

Place, publisher, year, edition, pages
1996. Vol. 57, no 3, 195-203 p.195-203 p.
Keyword [en]
Saharan dust, Nigeria, model
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-28175DOI: 10.1016/S0038-092X(97)80003-EOAI: oai:DiVA.org:uu-28175DiVA: diva2:56071
Available from: 2008-10-17 Created: 2008-10-17 Last updated: 2013-10-04Bibliographically approved

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