From site-scale land-atmsophere water fluxes to globally gridded products: Advances with the FLUXCOM-X framework

While eddy covariance (EC) is a standard for measuring total ecosystem evaporation (evapotranspiration, ET), upscaling from the tower to the regional and global scales is still marred with uncertainties. Here, we explore this scale translation via the FLUXCOM-X framework, which links data from EC measurements and remote sensing to machine learning techniques to produce models for generating globally gridded products. In particular, we explore potential sources of uncertainty inherent to this pipeline and how these influence the resulting gridded products: training data quality including site-selection and coverage of in-situ data, and modelling distinct water flux components (i.e., transpiration (T) and abiotic evaporation) individually compared to total evapotranspiration.

Overall, changes in the FLUXCOM-X framework compared to previous versions (Jung et al. 2019) results in tangible improvements to the spatial and temporal patterns of the global evapotranspiration products. Furthermore, the predictions of a corresponding transpiration product provide an empirical estimate of plant controlled water fluxes. The resulting global T/ET ratios are consistent with current estimates from isotopic analyses, but with the advantage of high spatio-temporal coverage. Lessons learned from this analysis provide a more targeted line of inquiry into potential avenues for further improvements in global evapotranspiration modeling.

Jung, M., Koirala, S., Weber, U. et al. The FLUXCOM ensemble of global land-atmosphere energy fluxes. Sci Data 6, 74 (2019). https://doi.org/10.1038/s41597-019-0076-8