Method Development and Variability Class-Dependent Validation of the New CAMS Radiation Service V4.5

International audience The Copernicus Atmosphere Monitoring Service (CAMS) of the European Union provides open data access to solar irradiance data through its CAMS Radiation Service (CRS). In the CRS observations from the Meteosat Second Generation (MSG) meteorological satellites are combined with modeled data for aerosols, water vapor, and ozone data from the ECMWF CAMS Integrated Forecasting System (IFS) to derive irradiance at the Earth's surface. CRS data is provided from 2004 to the day before yesterday. Time series in 1 min, 15 min, hourly and daily temporal resolution are produced 'on-the-fly' on user request using the most recent method and input datasets at the desired location inside the domain of the MSG satellite view. In the expert mode, all input datasets e.g. on aerosols, water vapour, clouds, surface albedo can also be accessed as additional time series. In addition to the standard access as time series, a gridded dataset in 0.1° and 15 min for the years 2004-2022 has been created for land surfaces of Europe and Africa. A new version CRS v4.5 was released in 2022. It uses APOLLO Next Generation (APOLLO_NG) for deriving cloud information from weather satellites in the Heliosat-4 method (Qu et al., 2017; Schroedter-Homscheidt et al., 2022). APOLLO_NG is based on a probabilistic cloud detection (Klüser et al., 2015) and its usage in Heliosat-4 follows a detection approach that is highly optimized for solar energy needs. The method is operationally applied for Europe, Africa and the Middle East, but has also been tested for the Himawari-8 AHI and GOES-16 ABI instruments in Asia/Australia and North and South America, respectively. In addition, work is underway to deploy on APOLLO_NG the upcoming Meteosat Third Generation (MTG), which will provide higher spatial and temporal resolutions. There are quarterly validation reports of the service available, which now also routinely include quality information on the new CRS v4.5. Besides the data access via the CAMS web page, the CAMS Radiation Service data is also operationally accessible via the python package pvlib since v0.9.0 (released on the 1st September 2021).