Validation of surface solar irradiances estimates and forecast under clear-sky conditions from the CAMS McClear model in Benguerir, Morocco

Abstract

McClear is a fast model of surface solar irradiance under cloudless condition (clear-sky), based on the radiative transfer model libRadtran that exploits the clear sky atmospheric optical properties (notably partial and total aerosol optical depths —AOD— at different wavelengths, total contents of water vapor and ozone) provided by the EU-funded Copernicus Atmospheric Monitoring Service (CAMS). This model provides global, diffuse horizontal irradiances and direct normal irradiance at any place and any time since 2004 onwards, with 2 days of delay, with temporal resolution up to 1 min (interpolation). In this paper, we present a first validation of the McClear clear sky irradiance model for the specific climate of Benguerir, Morocco. McClear’s validation was performed by comparing the 1 min average clear sky irradiance data (GHI: Global Horizontal Irradiance and DNI: Direct Normal Irradiance) from a high precision thermopile-based pyranometric station installed in Benguerir at Green Energy Park, and the values estimated by McClear for the same instants. The bias for global horizontal irradiance is 5 W m-2 (0.6 % of the mean observed irradiance). The root means square error (RMSE) is 17 W m-2 (2.2 %) and the correlation coefficient (CC) is 0.996. The bias for the direct normal irradiance is -17 W m-2 (-1.9 %). The RMSE is 58 W m-2 (6.7 %) and the correlation coefficient (CC) is 0.845. The same types of comparison have been done to assess the ability of McClear to forecast clear-sky GHI and DNI one day-ahead, using the provided forecasts of the state of the clear atmosphere by CAMS. The Bias, RMSE, STDE and correlation coefficient of such comparisons on the average 1-min profile of GHI and DNI from McClear are respectively for GHI - 0.8%, 3.3%, 3.3% and 0.991. For DNI -2.8%, 9.9%, 9.5% and 0.779.McClear is a fast model of surface solar irradiance under cloudless condition (clear-sky), based on the radiative transfer model libRadtran that exploits the clear sky atmospheric optical properties (notably partial and total aerosol optical depths —AOD— at different wavelengths, total contents of water vapor and ozone) provided by the EU-funded Copernicus Atmospheric Monitoring Service (CAMS). This model provides global, diffuse horizontal irradiances and direct normal irradiance at any place and any time since 2004 onwards, with 2 days of delay, with temporal resolution up to 1 min (interpolation). In this paper, we present a first validation of the McClear clear sky irradiance model for the specific climate of Benguerir, Morocco. McClear’s validation was performed by comparing the 1 min average clear sky irradiance data (GHI: Global Horizontal Irradiance and DNI: Direct Normal Irradiance) from a high precision thermopile-based pyranometric station installed in Benguerir at Green Energy Park, and the va...