Estimating aerosol characteristics from solar irradiance measurements at an urban location in southeastern Spain. Issue 4 (25th February 2014)

• Record Type: Journal Article
• Authors: Foyo‐Moreno, I.; Alados, I.; Antón, M.; Fernández‐Gálvez, J.; Cazorla, A.; Alados‐Arboledas, L.
• Is Part Of: Journal of geophysical research. Volume 119:Issue 4(2014:Apr.)
• Page Start: 1845
• Page End: 1859
• Publication Date: 2014-02-25
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2013JD020599
• Languages: English
• ISSNs: 2169-897X

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Under cloudless conditions aerosols are the main atmospheric components responsible for direct effects on solar radiation. Measurements of aerosol optical properties along with simultaneous measurements of solar irradiances (global –<italic>G</italic>– and diffuse –<italic>D</italic>–) were recorded at an urban site (Granada, Spain) to characterize the radiative effect of atmospheric aerosols from 2006 to 2008. The selection of cloudless conditions was made considering cases with 0 oktas. To avoid cloud contamination, a restricted data set with clearness index larger than 0.65 and maximum <italic>D</italic> of 200 W/m<sup>2</sup> was used. The analysis was performed evaluating <italic>G</italic>, <italic>D</italic>, and <italic>I</italic><sub>N</sub> (direct normal irradiance) and the ratios between them in association with aerosol optical depth (AOD) at 675 nm. Results show an aerosol forcing efficiency of −279 ± 21 W/m<sup>2</sup> per unit of AOD at 675 nm at 15° solar zenith angle and a maximum value in June for monthly mean aerosol radiative forcing of −23 ± 7 W/m<sup>2</sup>. Large dependency was shown of the ratios <italic>D</italic>/<italic>G</italic> and <italic>D</italic>/<italic>I</italic><sub>N</sub> which increased with increasing AOD, while <italic>I</italic><sub>N</sub>/<italic>G</italic> decreased. On the other hand, the ratio <italic>D</italic>/<italic>I</italic><sub>N</sub> was the most reliable parameter to estimate AOD with a coefficient of determination of 0.94; the empirical relationship obtained was validated using an independent data set obtaining 2.5% mean bias deviation and 13.5% root‐mean‐square deviation. This relationship constitutes an alternative tool for estimating AOD from routine irradiance measurements available from numerous radiometric stations worldwide.</p> </abstract>