Validation of the McClear clear-sky model in desert conditions with three stations in Israel

Abstract. The new McClear clear-sky model, a fast model based on a radiative transfer solver, exploits the atmospheric properties provided by the EU-funded Copernicus Atmosphere Monitoring Service (CAMS) to estimate the solar direct and global irradiances received at ground level in cloud-free conditions at any place any time. The work presented here focuses on desert conditions and compares the McClear irradiances to coincident 1 min measurements made in clear-sky conditions at three stations in Israel which are distant from less than 100 km. The bias for global irradiance is comprised between 2 and 32 W m⁻², i.e. between 0 and 4 % of the mean observed irradiance (approximately 830 W m⁻²). The RMSE ranges from 30 to 41 W m⁻² (4 %) and the squared correlation coefficient is greater than 0.976. The bias for the direct irradiance at normal incidence (DNI) is comprised between −68 and +13 W m⁻², i.e. between −8 and 2 % of the mean observed DNI (approximately 840 W m⁻²). The RMSE ranges from 53 (7 %) to 83 W m⁻² (10 %). The squared correlation coefficient is close to 0.6. The performances are similar for the three sites for the global irradiance and for the DNI to a lesser extent, demonstrating the robustness of the McClear model combined with CAMS products. These results are discussed in the light of those obtained by McClear for other desert areas in Egypt and United Arab Emirates.