A Novel Approach for Retrieving Water Use Efficiency and Gross Primary Production from the “analytical triangle” technique: extending the Ts/VI feature space properties

Monitoring and quantifying the carbon-water exchange under climate change is a key indicator for the study of interactions between carbon and water cycles in terrestrial ecosystems. To support the growing need for monitoring surface–atmosphere exchange processes, the present study proposes a novel methodological framework for deriving carbon components from the Ts/VI feature space, coupled with land process-based modelling, which can be applied across local, regional, and large spatial scales using EO data. The current framework, introduces a proof-of-concept for a new scheme that extends the application of the “analytical” triangle, by producing spatially explicit, instantaneous maps of ambient gross primary productivity, carbon concentration, and water use efficiency. An initial evaluation of the proof-of-concept methodological framework was tested in 6 sites belong to the global network of ground measurements FLUXNET, across 5 different ecosystem types, for a total of 35 days, using the Landsat-8 EO data coupled with the SimSphere model. Results of GPP and WUE produced a small bias of -0.103 μmol CO 2 m −2 s −1 and RMSD of 7.66 μmol CO 2 m −2 s −1 and also a bias of 2.216 kg m −3 and RMSD of 4.54 kg m −3 , respectively. The predicted [CO 2 ] showed high deviation (bias of -18.24 μmol mol −1 ), and a moderate overall agreement (R = 0.52). The predictions have shown a reasonable level of agreement with FLUXNET observations, providing a preliminary proof of concept for the proposed method, with potential for future applications at regional to large scales. Yet, further investigation is ongoing to confirm its to access the method’s generality and its ability to represent physical processes across various ecosystems.