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An Improved Outdoor Calibration Procedure for Broadband Ultraviolet Radiometers

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  • Posted on the website on 5 May 2005

*To whom correspondence should be addressed: Departamento de Física, Universidad de Extremadura, 06071 Badajoz, Spain. Fax: +34 924 289651; e-mail: mcf@unex.es

ABSTRACT

This article aims at improving the broadband ultraviolet radiometer's calibration methodology. For this goal, three broadband radiometers are calibrated against a spectrophotometer of reference. Three different one-step calibration models are tested: ratio, first order and second order. The latter is proposed in order to adequately reproduce the high dependence on the solar zenith angle shown by the other two models and, therefore, to improve the calibration performance at high solar elevations. The proposed new second-order model requires no additional information and, thus, keeps the operational character of the one-step methodology. The models are compared in terms of their root mean square error and the most qualified is subsequently validated by comparing its predictions with the spectrophotometer measurements within an independent validation data subset. Results show that the best calibration is achieved by the second-order model, with a mean bias error and mean absolute bias error lower than 2.2 and 6.7%, respectively.

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