Ground-based validation of aerosol optical depth from CAMS reanalysis project: An uncertainty input on direct normal irradiance under cloud-free conditions

Abstract Under cloud-free skies, aerosols are mainly responsible for controlling the observed Direct Normal Irradiance (DNI) variability for studying and designing Solar Concentrating Technologies. In this study, the induced uncertainties on cloud-free DNI due to the use of aerosol optical properties from the CAMS reanalysis project (AODCAMS) are investigated. DNI is calculated using a radiative transfer model while a pre-comparison and calibration of aerosol reanalysis products are performed using as skill reference the observations from AERONET. The site-specific validation showed an overestimation of the AOD in locations affected by volcanic eruptions while underestimation and higher dispersion metrics are revealed in regions dominated by coarse aerosols from mineral dust and biomass burning. A pre-calibration process of AODCAMS significantly improved the error metrics in all AERONET locations providing significant reductions in all ‘hot-spot error’ regions. In terms of DNI, using the initial AODCAMS, rMBE extends between –28% to 30%, exhibiting higher magnitudes in South and South-Eastern Asia. Using the calibrated AODCAMS, the pre-described error metrics are significantly improved in site-specific and regional scales.