Large Divergence of Satellite Monitoring of Diffuse Radiation Effect on Ecosystem Water-Use Efficiency

Water-use efficiency (WUE), defined as the ratio of gross primary productivity (GPP) and evapotranspiration (ET), is a key indicator of the coupling of carbon and water cycles in terrestrial ecosystems. Diffuse radiation significantly affects WUE as diffuse radiation has stronger fertilization effects on GPP than ET. Remote sensing data-driven (RS) models were widely used to estimate WUE. However, the performance of RS models in simulating diffuse radiation effect on WUE is poorly understood. We used GPP and ET products from MODIS, PML, BESS, and GLASS to explore the response of WUE to diffuse radiation across different vegetation types. We found that there was a large divergence among the RS models in estimating the response of WUE to FDP. PML model performed better than other RS models in simulating diffuse radiation effect on WUE. This research has significant implications for improving model simulations and understanding global carbon and water cycles. Water-use efficiency (WUE) defined as the ratio of gross primary productivity (GPP) and evapotranspiration (ET). It tells us how well plants balance their growth and water loss. Diffuse radiation can help plants use water more efficiently. Remote sensing data-driven models were widely used to estimate the WUE across different vegetation types. However, there are still no studies examining the performance of RS models in simulating the diffuse radiation effects on ecosystem WUE. In this study, we compared four satellite-based models with ground measurements of WUE and its components across different vegetation types. We found that there was a large divergence among the RS models in estimating the response of WUE to fraction of diffuse PAR (FDP). PML performed better than others, depending on the model structure, parameters, and input data. Our study shows the ability of RS models to capture the effect of diffuse radiation on WUE. This research is important for understanding how plants respond to changes in light availability under different climate scenarios. Four remote sensing data-driven (RS) models in simulating diffuse radiation effect on water-use efficiency (WUE) were evaluatedThere was a large divergence among RS models in estimating the response of WUE to fraction of diffuse PAR (fraction of diffuse PAR)PML model performed better than other RS models in simulating diffuse radiation effect on WUE