Geographical distribution of the angle of incidence uncertainty on the measurement of global horizontal irradiance

Abstract

One of the main contributing factors to uncertainty for ground-based global irradiance measurements is the angular response of the pyranometer. Since it depends on the angle of incidence, the measurement uncertainty will depend on the time of day and time of the year, as well as the site latitude and local climate. This work explores the geographical and seasonal distribution of the angle of incidence impact on the measurement accuracy of the global horizontal irradiance. Based on direct irradiance estimates from the ERA5 reanalysis, a model for the angle of incidence uncertainty, based on latitude and the fraction of diffuse irradiation, is proposed and validated, considering empirical estimates of the GHI component closure from the Baseline Surface Radiation Network. Results show that the model is accurately estimating the angle of incidence uncertainty at mid and high latitudes.