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Estimating aerosol characteristics from solar irradiance measurements at an urban location in southeastern Spain
Author(s) -
FoyoMoreno I.,
Alados I.,
Antón M.,
FernándezGálvez J.,
Cazorla A.,
AladosArboledas L.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd020599
Subject(s) - aerosol , irradiance , environmental science , solar zenith angle , atmospheric sciences , zenith , radiative forcing , solar irradiance , meteorology , radiative transfer , remote sensing , geography , physics , optics
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 – G – and diffuse – D –) 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 D of 200 W/m 2 was used. The analysis was performed evaluating G , D , and I N (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 2 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 2 . Large dependency was shown of the ratios D / G and D / I N which increased with increasing AOD, while I N / G decreased. On the other hand, the ratio D / I N 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.