This study presents the comparison of the EUMETSAT CM SAF SARAH version 3 climate data record of global Photosynthetically Active Radiation (PAR) with ground-based measurements collected at the ENEA Climate Observatory on the island of Lampedusa, in the Central Mediterranean. The analysis is carried out with daily averages in the period 2006-2018 and takes into account all-sky and cloud-free conditions, allowing to assess the role of the aerosol optical depth (AOD) on the observed differences among the two datasets. SARAH-3 PAR under all-sky conditions show a very good agreement with ground-based measurements, with a mean bias and one standard deviation of (1.0±24.7) μmol m−2s−1 or (1.1±8.1)%. Under cloud-free conditions, the results show an overall underestimation of SARAH-3 PAR data, with a mean bias and one standard deviation of (-9.1±26.8) μmol m−2s−1 or (-1.6±4.3)%. The differences may be explained with the AOD climatological values assumed in the SARAH-3 retrieval, which in most cases overestimate the ground-based AOD measurements. The outcomes of this study confirm the reliability of SARAH-3 daily PAR estimates and the importance of the validation process in order to assess the impact of the AOD used in the satellite retrieval.

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