Variability class dependent validation of recent improvements in the CAMS Radiation Service

Abstract

The Copernicus Atmosphere Monitoring Service (CAMS) provides a surface solar irradiance (SSI) service which is currently derived from Meteosat Second Generation (MSG). The service combines satellite data products with numerical model output from CAMS on aerosols, water vapour and ozone in order to provide both clear-sky radiation and all-sky radiation time series. Both clear-sky and all-sky data products are available from 2004 until yesterday. A regular quality control of input parameters, quarterly benchmarking against ground measurements and automatic consistency checks ensure the service quality. The recent development focuses on the application of the APOLLO Next Generation (APOLLO_NG) cloud retrieval for the calculation of MSG SEVIRI based irradiances and - in preparation for MTG - for HIMAWARI-8 AHI and GOES-16 ABI instruments. A parameterization for the circumsolar radiation as seen by the pyrheliometer-based ground observations is applied and improves direct irradiances significantly. The validation is carried out base on different variability classes being defined in collaboration with experts from the solar energy sector where ground observations of direct normal irradiation are used to classify atmospheric situations into eight variability classes (Schroedter-Homscheidt et al., 2018). Such cloud situations may be better described with the help of spatially higher resolved visible channels in future. The relationship of observed spatial variability of HIMAWARI-8 visible channels to the variability classes will be presented.