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The Scientific World Journal
Volume 2012, Article ID 768530, 10 pages
Research Article

Improving the S-Shape Solar Radiation Estimation Method for Supporting Crop Models

Crop Modeling research group, Department of Environmental Informatics, Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó út 15, H-1022 Budapest, Hungary

Received 20 October 2011; Accepted 27 December 2011

Academic Editor: Antonio Ferrante

Copyright © 2012 Nándor Fodor. 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.


In line with the critical comments formulated in relation to the S-shape global solar radiation estimation method, the original formula was improved via a 5-step procedure. The improved method was compared to four-reference methods on a large North-American database. According to the investigated error indicators, the final 7-parameter S-shape method has the same or even better estimation efficiency than the original formula. The improved formula is able to provide radiation estimates with a particularly low error pattern index ( P I d o y ) which is especially important concerning the usability of the estimated radiation values in crop models. Using site-specific calibration, the radiation estimates of the improved S-shape method caused an average of 2 . 7 2 ± 1 . 0 2 ( 𝛼 = 0 . 0 5 ) relative error in the calculated biomass. Using only readily available site specific metadata the radiation estimates caused less than 5% relative error in the crop model calculations when they were used for locations in the middle, plain territories of the USA.