Validation of the CLARA-A3 Top-of-Atmosphere Radiative Fluxes Climate Data Record

The third edition of the CM SAF Cloud, Albedo and Surface Radiation dataset from AVHRR data (CLARA-A3) contains for the first time the top-of-atmosphere products reflected solar flux (RSF) and outgoing longwave radiation (OLR), which are presented and validated using CERES, HIRS, and ERA5 reference data. The products feature an unprecedented resolution (0.25 degrees) and time span (4 decades) and offer synergy and compatibility with other CLARA-A3 products. The RSF is relatively stable; its bias with respect to (w.r.t.) ERA5 remains mostly within +/- 2 W m-2. Deviations are predominantly caused by absence of either morning or afternoon satellite, mostly during the first decade. The radiative impact of the Pinatubo volcanic eruption is estimated at 3 W m-2. The OLR is stable w.r.t. ERA5 and HIRS, except during 1979-80. OLR regional uncertainty w.r.t. HIRS is quantified by the mean absolute bias (MAB) and correlates with obser-vation density and time (satellite orbital configuration), which is optimal during 2002-16, with monthly and daily MAB of approximately 1.5 and 3.5 W m-2, respectively. Daily OLR uncertainty is higher (MAB +40%) during periods with only morning or only afternoon observations (1979-87). During the CERES era (2000-20), the OLR uncertainties w.r.t. CERES-EBAF, CERES-SYN, and HIRS are very similar. The RSF uncertainty achieves optimal results during 2002-16 with a monthly MAB w.r.t. CERES-EBAF of -2 W m-2 and a daily MAB w.r.t. CERES-SYN of -5 W m-2, and it more sensitive to orbital configuration than is OLR. Overall, validation results are satisfactory for this first release of TOA flux in the CLARA-A3