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Land Surface Energy Partitioning Dominates Dry-Season Water Availability Uncertainties in Earth System Models

Dong, Jianzhi ; Gao, Man ; Zhou, Jianhong ; Wei, Lingna ; Zhou, Haoran ; Zhang, Yongqiang ; Gao, Hongkai ; Duan, Zheng LU and Crow, Wade T. (2025) In Water Resources Research 61(5).
Abstract

Accurately characterizing dry-season water availability (Wd) is critical for projecting terrestrial carbon exchange and global water security. Wd is commonly calculated as the minimum value of precipitation minus evapotranspiration within each calendar year. However, Earth System Model (ESM) projected Wd contains substantial uncertainties and can disagree on even the sign. Based on a newly proposed framework, we disentangle the uncertainty sources in ESM-based Wd projections. Results demonstrate that ESM-based Wd uncertainties are dominated by land surface energy partitioning (summarized by evaporation fraction, denoted as EF) instead of precipitation or available energy. As such,... (More)

Accurately characterizing dry-season water availability (Wd) is critical for projecting terrestrial carbon exchange and global water security. Wd is commonly calculated as the minimum value of precipitation minus evapotranspiration within each calendar year. However, Earth System Model (ESM) projected Wd contains substantial uncertainties and can disagree on even the sign. Based on a newly proposed framework, we disentangle the uncertainty sources in ESM-based Wd projections. Results demonstrate that ESM-based Wd uncertainties are dominated by land surface energy partitioning (summarized by evaporation fraction, denoted as EF) instead of precipitation or available energy. As such, EF alone can explain more than 83% of inter-ESM variability in historical and future Wd projections. Compared against data-driven benchmarks, ESMs tend to overestimate dry-season EF—suggesting that Wd is likely to be underestimated in ESMs. Our analysis indicates that the ET resistance parameterization is the central error source in ESM-based EF, which should be constrained to enhance the reliability of EF, and by extension, Wd projections.

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author
; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
earth system modeling, evaporation fraction, evapotranspiration, uncertainty, water availability
in
Water Resources Research
volume
61
issue
5
article number
e2024WR038000
publisher
Wiley-Blackwell
external identifiers
  • scopus:105004187056
ISSN
0043-1397
DOI
10.1029/2024WR038000
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025. The Author(s).
id
cfcdeea4-34b4-42bf-9317-36647978fd41
date added to LUP
2025-08-06 12:33:02
date last changed
2025-08-06 12:33:32
@article{cfcdeea4-34b4-42bf-9317-36647978fd41,
  abstract     = {{<p>Accurately characterizing dry-season water availability (W<sub>d</sub>) is critical for projecting terrestrial carbon exchange and global water security. W<sub>d</sub> is commonly calculated as the minimum value of precipitation minus evapotranspiration within each calendar year. However, Earth System Model (ESM) projected W<sub>d</sub> contains substantial uncertainties and can disagree on even the sign. Based on a newly proposed framework, we disentangle the uncertainty sources in ESM-based W<sub>d</sub> projections. Results demonstrate that ESM-based W<sub>d</sub> uncertainties are dominated by land surface energy partitioning (summarized by evaporation fraction, denoted as EF) instead of precipitation or available energy. As such, EF alone can explain more than 83% of inter-ESM variability in historical and future W<sub>d</sub> projections. Compared against data-driven benchmarks, ESMs tend to overestimate dry-season EF—suggesting that W<sub>d</sub> is likely to be underestimated in ESMs. Our analysis indicates that the ET resistance parameterization is the central error source in ESM-based EF, which should be constrained to enhance the reliability of EF, and by extension, W<sub>d</sub> projections.</p>}},
  author       = {{Dong, Jianzhi and Gao, Man and Zhou, Jianhong and Wei, Lingna and Zhou, Haoran and Zhang, Yongqiang and Gao, Hongkai and Duan, Zheng and Crow, Wade T.}},
  issn         = {{0043-1397}},
  keywords     = {{earth system modeling; evaporation fraction; evapotranspiration; uncertainty; water availability}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Water Resources Research}},
  title        = {{Land Surface Energy Partitioning Dominates Dry-Season Water Availability Uncertainties in Earth System Models}},
  url          = {{http://dx.doi.org/10.1029/2024WR038000}},
  doi          = {{10.1029/2024WR038000}},
  volume       = {{61}},
  year         = {{2025}},
}