Improving direct normal irradiance retrieval in cloud-free, but high aerosol load conditions by using aerosol optical depth

摘要: Measurements of the global surface solar irradiation and its direct diffuse components performed at three Egyptian sites (Aswan, Cairo, Port Said) are used to test ability two published decomposition models estimate hourly normal irradiance from measured horizontal one in cloud-free conditions. The tested failed reproduce temporal variability measurements, which we show be partly induced by large atmospheric content aerosols. We propose a revised formulation that takes into account aerosol optical depth (AOD) 1000 nm derived onsite measurements. It leads significant reduction bias root mean square deviation original this sites. However, because AOD is rarely meteorological stations, also quantify performance when either MODIS observations or obtained products Copernicus Atmospheric Monitoring Service (CAMS). Probably their finer resolution makes them more apt rapid variations AOD, best results with CAMS products. Therefore, recommend using combination these areas such as Egypt where aerosols ubiquitous. Note improved generally applicable all-sky conditions, although benefit has been demonstrated significant, probably limited to,