Building global and diffuse solar radiation series and assessing decadal trends in Girona (NE Iberian Peninsula)

Abstract

Measurement of solar radiation was initiated in Girona, northeast of the Iberian Peninsula, in the late 1980s. Initially, two pyranometers were installed, one of them equipped with a shadowband for measuring the diffuse component. Two other pyranometers currently exist, both ventilated and one of them shadowed, with a sphere, and a pyrheliometer for measuring direct radiation. Additional instruments for other shortwave and longwave components, clouds, and atmospheric aerosols have been installed in recent years. The station is subject to daily inspection, data are saved at high temporal resolution, and instruments are periodically calibrated, all in accordance with the directions of the Baseline Surface Radiation Network. The present paper describes how the entire series of global solar radiation (1987–2014) and diffuse radiation (1994–2014) were built, including the quality control process. Appropriate corrections to the diffuse component were made when a shadowband was employed to make measurements. Analysis of the series reveals that annual mean global irradiance presents a statistically significant increase of 2.5 W m−2 (1.4 %) decade−1 (1988–2014 period), mainly due to what occurs in summer (5.6 W m−2 decade−1). These results constitute the first assessment of solar radiation trends for the northeastern region of the Iberian Peninsula and are consistent with trends observed in the regional surroundings and also by satellite platforms, in agreement with the global brightening phenomenon. Diffuse radiation has decreased at −1.3 W m−2 (−2 %) decade−1 (1994–2014 period), which is a further indication of the reduced cloudiness and/or aerosol load causing the changesWe wish to thank the Spanish Ministry of Economy and Competitiveness, whose funding, through project NUCLIERSOL (CGL2010-18546-CLI), made the records from the radiometric station in Girona freely available on the station’s webpage (http://nuclierdata.udg.edu/). The instrumentation used in this research was acquired and has been maintained over the years thanks to the support of several institutions, mainly the Spanish Ministry of Science, the Catalan Directorate for Research, and the University of Girona. The present paper was supported by the Spanish Ministry of Economy and Competitiveness, through project NUBESOL (CGL2014-55976-R

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“…Calbo et al . () also observed a significant upward trend in the mean annual R S records of 1987–2014 in Girona (Spain). Rahimzadeh et al .…”

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