Long-term solar-induced fluorescence data record from GOME-2A and GOME-2B (2007–2023) using the SIFTER v3 algorithm

Abstract. Design differences in sensors and retrieval algorithms complicate the harmonisation of space-based solar-induced fluorescence (SIF) observations. The GOME-2 series, with its identical sensor design, offers potential for constructing a long-term coherent record. However, instrumental artefacts, such as degradation, affect the sensors differently and diverge the intersensor SIF observations. Achieving internal consistency within each record is therefore a critical first step in harmonisation. We present a combined GOME-2 SIF dataset for 2007–2023 that consists of GOME-2A (Jan. 2007–Dec. 2017) and GOME-2B SIF (July 2013–Dec. 2023) data. Both individual records are retrieved using the previously developed SIFTER v3 algorithm, which applies time-, wavelength-, and scan-angle-dependent degradation corrections. Spatial agreement between GOME-2A and GOME-2B SIF during the overlapping period was strong (r ≥ 0.96), although viewing geometry differences caused substantial systematic biases, specifically over high activity regions; these were reduced to within 2 % by constraining to common viewing zenith angle ranges. In terms of temporal alignment, most analysed regions showed no significant step change at the July 2013 sensor transition, from full-swath GOME-2A to GOME-2B SIF. Small offsets in Eastern China and the Amazon were corrected for using a simple additive correction, which improved the coherence and agreement with independent GPP estimations from FluxSat. Finally, the GOME-2 records align closely with FluxSat GPP and TROPOMI SIF across various biomes, and support monitoring of vegetation activity over 17 years. Our work presents a framework for detecting and, when necessary, correcting intersensor offset biases, enabling the use of GOME-2A and GOME-2B SIF as a single record. Moreover, it offers guidance for harmonising multi-sensor datasets and for other causes of potential structural breaks in long-term observation records. The GOME-2A and GOME-2B SIF (obtained in this study) datasets are available at https://doi.org/10.21944/gome2a-sifter-v3-solar-induced-fluorescence and https://doi.org/10.21944/gome2b-sifter-v3-solar-induced-fluorescence, respectively.