SARAH-3 – satellite-based climate data records of surface solar radiation

Abstract

The amount of energy reaching Earth's surface from the Sun is a quantity of high importance for the climate system and for renewable energy applications. SARAH-3 (SurfAce Radiation DAtaset Heliosat, https://doi.org/10.5676/EUM_SAF_CM/SARAH/V003, Pfeifroth et al., 2023) is a new version of a satellite-based climate data record of surface solar radiation parameters, generated and distributed by the European Organisation of Meteorological Satellites (EUMETSAT) Climate Monitoring Satellite Application Facility (CM SAF). SARAH-3 provides data from 1983 onwards, i.e. more than 4 decades of data, and has a spatial resolution of 0.05° × 0.05°, a temporal resolution of 30 min and daily and monthly means for the region covered by the Meteosat field of view (65° W to 65° E and 65° S to 65° N). SARAH-3 consists of seven parameters: surface irradiance, direct irradiance, direct normal irradiance, sunshine duration, daylight, photosynthetically active radiation and effective cloud albedo. SARAH-3 data between 1983 and 2020 have been generated with stable input data (i.e. satellite and auxiliary data) to ensure a high temporal stability; these data are temporally extended by operational near-real-time processing – the so-called Interim Climate Data Record. The data record is suitable for various applications, from climate monitoring to renewable energy. The validation of SARAH-3 shows good accuracy (deviations of ∼ 5 W m−2 from surface reference measurements for monthly surface irradiance), stability of the data record and further improvements over its predecessor SARAH-2.1. One reason for this improved quality is the new treatment of snow-covered surfaces in the algorithm, reducing the misclassification of snow as clouds. The SARAH-3 data record reveals an increase in the surface irradiance (∼ +3 W m−2 per decade) during recent decades in Europe, in line with surface observations.