Articles | Volume 14, issue 24
Research article
19 Dec 2014
Research article |  | 19 Dec 2014

Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula

D. Mateos, M. Antón, C. Toledano, V. E. Cachorro, L. Alados-Arboledas, M. Sorribas, M. J. Costa, and J. M. Baldasano

Abstract. A better understanding of aerosol radiative properties is a crucial challenge for climate change studies. This study aims at providing a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW) solar spectrum. For this purpose, long-term data sets of aerosol properties from six AERONET stations located in the Iberian Peninsula (southwestern Europe) have been analyzed in terms of climatological characterization and inter-annual changes. Aerosol information was used as input for the libRadtran model in order to determine the aerosol radiative effect (ARE) at the surface in the ultraviolet (AREUV), visible (AREVIS), near-infrared (ARENIR), and the entire SW range (ARESW) under cloud-free conditions. Over the whole Iberian Peninsula, yearly aerosol radiative effects in the different spectral ranges were found to be −1.1 < AREUV < −0.7, −5.7 < AREVIS < −3.5, −2.6 < ARENIR < −1.6, and −8.8 < ARESW < −5.7 (in W m−2). Monthly means of ARE showed a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE), ARE per unit of aerosol optical depth, has also been evaluated in the four spectral ranges. AFE exhibited a dependence on single scattering albedo as well as a weaker one on the Ångström exponent. AFE is larger (in absolute value) for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency varied with the aerosol types. The predominant aerosol size determined the fractions AFEVIS/AFESW and AFENIR/AFESW. The AFEVIS was the dominant contributor for all aerosol types, although non-absorbing large particles caused more even contribution of VIS and NIR intervals. The AFEUV / AFESW ratio showed a higher value in the case of absorbing fine particles.

Short summary
A long-term analysis of aerosol radiative effects over the Iberian Peninsula is carried out. A reduction of aerosol effects on solar radiation at the surface is observed in the 2000s. Aerosol forcing efficiency is stronger for small and absorbing particles. The contributions of the ultraviolet, visible, and near-infrared spectral intervals to the total shortwave efficiency vary with the aerosol types, producing the visible range the dominant contribution for all aerosol types.
Final-revised paper