Partitioning global land evapotranspiration using CMIP5 models constrained by observations

Lian, Xu; Piao, Shilong; Huntingford, Chris; Li, Yue; Zeng, Zhenzhong; Wang, Xuhui; Ciais, Philippe; McVicar, Tim R.; Peng, Shushi; Ottlé, Catherine; Yang, Hui; Yang, Yuting; Zhang, Yongqiang; Wang, Tao

doi:10.1038/s41558-018-0207-9

Cited by 285 publications

(233 citation statements)

References 57 publications

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“…For open canopy towers, the changes in T/ET associated with our new calibration are minor. Our calibration results are therefore consistent with efforts to increase the T/ET ratio in ESMs (Lian et al, ).…”

Section: Discussionsupporting

confidence: 89%

“…ET parameterization plays an important role in climate and ESMs. However, ESMs have large uncertainties in simulating ET, particularly in partitioning ET into its components (e.g., soil evaporation, canopy evaporation, transpiration, and open water body evaporation; Lian et al, 2018;Zeng et al, 2017). Several previous studies proposed to improve soil evaporation estimates in CLM by adding a surface litter layer (Sakaguchi & Zeng, 2009), introducing a new bare-soil evaporation formulation (Tang & Riley, 2013), or replacing the empirical soil resistance parameterization with a dry surface layer (Swenson & Lawrence, 2014).…”

Section: Et Parameterizations In Esmsmentioning

confidence: 99%

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Improving Representation of Deforestation Effects on Evapotranspiration in the E3SM Land Model

Cai

Riley

Zhu

et al. 2019

J Adv Model Earth Syst

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Evapotranspiration (ET) plays an important role in land‐atmosphere coupling of energy, water, and carbon cycles. Following deforestation, ET is typically observed to decrease substantially as a consequence of decreases in leaf area and roots and increases in runoff. Changes in ET (latent heat flux) revise the surface energy and water budgets, which further affects large‐scale atmospheric dynamics and feeds back positively or negatively to long‐term forest sustainability. In this study, we used observations from a recent synthesis of 29 pairs of adjacent intact and deforested FLUXNET sites to improve model parameterization of stomatal characteristics, photosynthesis, and soil water dynamics in version 1 of the Energy Exascale Earth System Model (E3SM) Land Model (ELMv1). We found that default ELMv1 predicts an increase in ET after deforestation, likely leading to incorrect estimates of the effects of deforestation on land‐atmosphere coupling. The calibrated model accurately represented the FLUXNET observed deforestation effects on ET. Importantly, the search for global optimal parameters converged at values consistent with recent observational syntheses, confirming the reliability of the calibrated physical parameters. Applying this improved model parameterization to the globe scale reduced the bias of annual ET simulation by up to ~600 mm/year. Analysis on the roles of parameters suggested that future model development to improve ET simulation should focus on stomatal resistance and soil water‐related parameterizations. Finally, our predicted differences in seasonal ET changes from deforestation are large enough to substantially affect land‐atmosphere coupling and should be considered in such studies.

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Section: Discussionsupporting

confidence: 89%

Section: Et Parameterizations In Esmsmentioning

confidence: 99%

Improving Representation of Deforestation Effects on Evapotranspiration in the E3SM Land Model

Cai

Riley

Zhu

et al. 2019

J Adv Model Earth Syst

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“…Our analysis confirms the important role of LAI in regulating Ω (Figure Column d). LAI is one of the most important variables in simulating AET processes and AET partitioning in climate models and Earth System models (Lian et al, ; Zeng, Peng, & Piao, ). At a given g a and temperature, g s increases with LAI, enhancing Ω and the coupling between atmosphere and canopy (Figure b).…”

Section: Discussionmentioning

confidence: 99%

Determinants of the ratio of actual to potential evapotranspiration

Peng

Zeng

Wei

et al. 2019

Global Change Biology

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A widely used approach for estimating actual evapotranspiration (AET) in hydrological and earth system models is to constrain potential evapotranspiration (PET) with a single empirical stress factor (Ω = AET/PET). Ω represents the water availability and is fundamentally linked to canopy–atmosphere coupling. However, the mean and seasonal variability of Ω in the models have rarely been evaluated against observations, and the model performances for different climates and biomes remain unclear. In this study, we first derived the observed Ω from 28 FLUXNET sites over North America during 2000–2007, which was then used to evaluate Ω in six large‐scale model‐based datasets. Our results confirm the importance of incorporating canopy height in the formulation of aerodynamic conductance in the case of forests. Furthermore, leaf area index (LAI) is central to the prediction of Ω and can be quantitatively linked to the partitioning between transpiration and soil evaporation (R2 = 0.43). The substantial differences between observed and model‐based Ω in forests (range: 0.2~0.9) are highly related to the way these models estimated PET and the way they represented the responses of Ω to the environmental drivers, especially wind speed and LAI. This is the first assessment of Ω in models based on in situ observations. Our findings demonstrate that the observed Ω is useful for evaluating, validating, and optimizing the modeling of AET and thus of water and energy balances.

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“…The transpiration fraction (T/ET), as an indicator of ET partition, plays an important role in qualifying vegetation‐climate feedback and improving future hydrological prediction (Jasechko et al, ; Maxwell & Condon, ; Wang et al, ; Zhu et al, ). Globally, transpiration accounts for 64 ± 13% of ET by global isotope‐budget (Good et al, ) and 62 ± 6% of ET by Coupled Model Intercomparison Project Phase 5 (CMIP5; Lian et al, ). Transpiration represents the largest loss of water from ecosystems (Berkelhammer et al, ; Sun et al, ), and the quantification of T/ET still faces many uncertainties.…”

Section: Introductionmentioning

confidence: 99%

Seasonality of the Transpiration Fraction and Its Controls Across Typical Ecosystems Within the Heihe River Basin

Tong

Wang

et al. 2019

JGR Atmospheres

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Understanding the seasonality of the transpiration fraction (T/ET) of total terrestrial evapotranspiration (ET) is vital for coupling ecological and hydrological systems and quantifying the heterogeneity among various ecosystems. In this study, a two‐source model was used to estimate T/ET in five ecosystems over the Heihe River Basin. In situ measurements of daily energy flux, sap flow, and surface soil temperature were compared with model outputs for 2014 and 2015. Agreement between model predictions and observations demonstrates good performance in capturing the ecosystem seasonality of T/ET. In addition, sensitivity analysis indicated that the model is insensitive to errors in measured input variables and parameters. T/ET among the five sites showed only slight interannual fluctuations while exhibited significant seasonality. All the ecosystems presented a single‐peak trend, reaching the maximum value in July and fluctuating day to day. During the growing season, average T/ET was the highest for the cropland ecosystem (0.80 ± 0.13), followed by the alpine meadow ecosystem (0.79 ± 0.12), the desert riparian forest Populus euphratica (0.67 ± 0.07), the Tamarix ramosissima Ledeb desert riparian shrub ecosystem (0.67 ± 0.06), and the alpine swamp meadow (0.55 ± 0.23). Leaf area index exerted a first‐order control on T/ET and showed divergence among the five ecosystems because of different vegetation dynamics and environmental conditions (e.g., water availability or vapor pressure deficits). This study quantified transpiration fraction across diverse ecosystems within the same water basin and emphasized the biotic controls on the seasonality of the transpiration fraction.

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Partitioning global land evapotranspiration using CMIP5 models constrained by observations

Cited by 285 publications

References 57 publications

Improving Representation of Deforestation Effects on Evapotranspiration in the E3SM Land Model

Improving Representation of Deforestation Effects on Evapotranspiration in the E3SM Land Model

Determinants of the ratio of actual to potential evapotranspiration

Seasonality of the Transpiration Fraction and Its Controls Across Typical Ecosystems Within the Heihe River Basin

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