TY - JOUR
T1 - The divergence of energy- and water-balance evapotranspiration estimates in humid regions
AU - Zhang, Lilin
AU - Marshall, M.
AU - Vrieling, A.
AU - Nelson, A.
N1 - Funding Information:
This study was supported by the China Scholarship Council (CSC) under Grant 201806040218 . Thanks to Dr. Joy Burrough-Boenisch, who was the language editor of a near-final draft of the paper. The authors also would like to express their gratitude to the researchers and their teams for providing all of the data used in this study and the last gratitude to Xiangyi Bei for the assistance in writing the paper.
Publisher Copyright:
© 2023 The Author(s)
PY - 2023/9
Y1 - 2023/9
N2 - Evapotranspiration (ET) calculated as the residual of catchment water balance (ET
WB) has often been used as a benchmark to evaluate satellite-based ET retrievals that use the energy-balance approach (ET
EB). However, errors from water balance components will accrue in ET
WB, leading to considerable disparities with ET
EB. In this study, we set out to investigate whether ET
EB from multiple sources (MOD16, GLEAM, PT-JPL, and PT-hybrid) can capture the spatiotemporal variability of ET
WB across 53 catchments in central-western Europe with a humid climate. Using ET retrievals from the Budyko framework that accounts for the control of energy demand on water supply and upscaled ET from FLUXCOM as references, we explored the causes of discrepancies between ET
WB and ET
EB at long-term, annual, and monthly scales. We found that (1) ET
EB significantly diverged from ET
WB at the mean annual scale (r = 0.35), particularly for energy-limited catchments, but Budyko-simulated ET considering energy limit correlated well with ET
EB (r > 0.86); (2) neither ET
EB nor upscaled ET can reproduce annual ET
WB time series (r < 0.40), and the closure errors in water budgets closely follow excess precipitation beyond energy demand; (3) monthly ET
WB exhibited better correspondences with ET
EB (r = 0.73), presumably because of similarity in seasonal patterns. Our results demonstrate that errors from precipitation and terrestrial water storage anomalies introduce large uncertainties in ET
WB, thereby complicating water balance validation in humid regions across multiple timesteps. To improve the application of ET
WB for benchmarking ET
EB in humid regions, high-quality input data should be used or – like the Budyko framework – energy constraints should be considered.
AB - Evapotranspiration (ET) calculated as the residual of catchment water balance (ET
WB) has often been used as a benchmark to evaluate satellite-based ET retrievals that use the energy-balance approach (ET
EB). However, errors from water balance components will accrue in ET
WB, leading to considerable disparities with ET
EB. In this study, we set out to investigate whether ET
EB from multiple sources (MOD16, GLEAM, PT-JPL, and PT-hybrid) can capture the spatiotemporal variability of ET
WB across 53 catchments in central-western Europe with a humid climate. Using ET retrievals from the Budyko framework that accounts for the control of energy demand on water supply and upscaled ET from FLUXCOM as references, we explored the causes of discrepancies between ET
WB and ET
EB at long-term, annual, and monthly scales. We found that (1) ET
EB significantly diverged from ET
WB at the mean annual scale (r = 0.35), particularly for energy-limited catchments, but Budyko-simulated ET considering energy limit correlated well with ET
EB (r > 0.86); (2) neither ET
EB nor upscaled ET can reproduce annual ET
WB time series (r < 0.40), and the closure errors in water budgets closely follow excess precipitation beyond energy demand; (3) monthly ET
WB exhibited better correspondences with ET
EB (r = 0.73), presumably because of similarity in seasonal patterns. Our results demonstrate that errors from precipitation and terrestrial water storage anomalies introduce large uncertainties in ET
WB, thereby complicating water balance validation in humid regions across multiple timesteps. To improve the application of ET
WB for benchmarking ET
EB in humid regions, high-quality input data should be used or – like the Budyko framework – energy constraints should be considered.
KW - ITC-ISI-JOURNAL-ARTICLE
KW - ITC-HYBRID
KW - UT-Hybrid-D
U2 - 10.1016/j.jhydrol.2023.129971
DO - 10.1016/j.jhydrol.2023.129971
M3 - Article
SN - 0022-1694
VL - 624
JO - Journal of hydrology
JF - Journal of hydrology
M1 - 129971
ER -