Quantifying gross primary production (GPP) remains a major challenge in global carbon cycle research. Spaceborne monitoring of solar-induced chlorophyll fluorescence (SIF), an integrative photosynthetic signal of molecular origin, can assist in terrestrial GPP monitoring. However, the extent to which SIF tracks spatiotemporal variations in GPP remains unresolved. Orbiting Carbon Observatory-2 (OCO-2)’s SIF data acquisition and fine spatial resolution permit direct validation against ground and airborne observations. Empirical orthogonal function analysis shows consistent spatiotemporal correspondence between OCO-2 SIF and GPP globally. A linear SIF-GPP relationship is also obtained at eddy-flux sites covering diverse biomes, setting the stage for future investigations of the robustness of such a relationship across more biomes. Our findings support the central importance of high-quality satellite SIF for studying terrestrial carbon cycle dynamics.
Bibliographical noteFunding Information:
A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. A.P.-C. is funded by the Academy of Finland (Research Fellow grant 1288039). L. Gu and J.D.W. are supported by the U.S. Department of Energy Biological and Environmental Research program through Oak Ridge National Laboratory’s Terrestrial Ecosystem Science (TES) Science Focus Area (SFA). M.J. acknowledges support from the European Union H2020 Biosphere Atmosphere Change Index project (grant 640176). We thank the data providers of FLUXCOM and MODIS for their contribution. The OCO-2 SIF data set is publicly available at https://co2.jpl.nasa.gov. The CFIS SIF retrieval and GPP inferred at flux towers are available upon request.