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International Journal of Photoenergy
Volume 2017 (2017), Article ID 8107435, 9 pages
Research Article

Enhancement of UV Radiation by Cloud Effect in NE of Brazil

1Nuclear Energy Department of the Federal University of Pernambuco (UFPE), Av. Prof. Luiz Freire, 1000-CDU, 50.740-540 Recife, PE, Brazil
2Federal Institute of Education, Science and Technology of Pernambuco (IFPE), São Paulo, SP, Brazil

Correspondence should be addressed to Chigueru Tiba

Received 27 April 2017; Accepted 21 June 2017; Published 24 July 2017

Academic Editor: Mark van Der Auweraer

Copyright © 2017 Chigueru Tiba and Sérgio da Silva Leal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This paper reports a detailed analysis of ground-based measurements of cloud-enhanced global solar and UV radiation in NE Brazil in the city of Recife. It was found that (a) the phenomenon of UV enhancement, above clear sky model, is not uncommon and that it occurs on at least eight months; (b) the cumulative duration can reach 13 minutes; (c) there is a clear seasonal effect, and the probability of occurrence on a monthly basis shows two peaks, one in March and another in October; and (d) the most extreme UV radiation was 70.4 W/m2, approximately 6 W/m2 higher than the clear sky UV radiation. The extreme values should be taken into account in the study of effects related to the UV index and biological effects. Two statistical models also were elaborated, to estimate the UV solar radiation, in which the first is for all sky conditions and the second exclusively for situations where the global solar radiation is equal to or higher than 1367 W/m2, resulting from the enhancement effect caused by a particular configuration of the clouds. The statistical indicatives for both models presented, respectively, MBE% of 3.09 and 0.48% and RMSE% of 15.80 and 3.90%.