Comment on egusphere-2022-1023

Abstract

Being itself part of the Copernicus Atmosphere Monitoring Service (CAMS), the McClear service provides estimates of the downwelling shortwave irradiance and its direct and diffuse components received at ground level in cloud-free conditions, with inputs on ozone, water vapor and aerosol properties from CAMS. McClear estimates have been validated over several parts of the world by various authors. This article makes a step forward by comparing McClear estimates to measurements performed at 44 ground-based stations located in the Sub-Saharan Africa and Maldives Archipelago in the Indian Ocean. The global irradiances G and its direct component at normal incidence BN from McClear-v3 were compared to 1 min measurements made in cloud-free conditions at the stations. The correlation coefficient is greater than 0.96 for G whereas it is greater than 0.70 at all stations but five for BN. The mean of G is correctly estimated at stations located in arid climates (BSh, BWh, BSk, BWk) and temperate climates without dry season and hot or warm summer (Cfa, Cfb) or with dry and hot summer (Csa) with a relative bias in the range [−1.5, 1.5] %. It is underestimated in tropical climate of monsoon type (Am) and overestimated in tropical climate of savannah type (Aw) and temperate climates with dry winter and hot (Cwa) or warm (Cwb) summer. McClear tends to overestimate the means of BN. The standard deviation of errors for G ranges between 13 W m−2 (1.3 %) and 31 W m−2 (3.7 %) and that for BN ranges between 31 W m−2 (3.0 %) and 70 W m−2 (7.9 %). Both offer small variations in time and space. A review of previous works reveals no significant difference between their results and ours. This work establishes a general overview of the performances of the McClear service.