Heat and water transport in soils and across the soil‐atmosphere interface: 2. Numerical analysis

Fetzer, Thomas; Vanderborght, Jan; Mosthaf, Klaus; Smits, Kathleen M.; Helmig, Rainer

doi:10.1002/2016wr019983

Cited by 41 publications

(47 citation statements)

References 34 publications

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“…Although the Richards equation models are mostly employed in a form that only considers isothermal liquid water flow, it should be noted that the heat transfer is coupled with water flow in all these three models in this study to provide a consistent comparison. In addition, even though lateral water flow has been ignored in some models, it has been indicated that the lateral flow has an effect on the fluxes within the soil profiles and also at the soil-atmosphere interface (Fetzer et al 2017) and therefore is considered in all the three models.…”

Section: Numerical Modelsmentioning

confidence: 99%

“…Defining the thickness of the top surface layer is a problem as the soil resistance parameter is highly dependent on the chosen thickness. Interested readers can refer to Fetzer et al (2017) for more discussions on the effect of the chosen top layer thickness on the simulation results. Equations 9 and 14 are referred to as Top Boundary Condition 1 and 2 (TBC 1 and TBC 2) in the following analysis.…”

Section: Top Boundary Conditions (Tbcs)mentioning

confidence: 99%

“…In theory, it should correspond to a small hydraulic conductivity and capacity (dθ w /dp w ) so the simulation results remain relatively constant when the water pressure continues to decrease (Vanderborght et al 2017). In practice, different values varying from (−1E5 to −1E7 Pa) are used in the literature (e.g., Bechtold et al 2012;Assouline et al 2014;Fetzer et al 2017).…”

Section: Evaluation Of Tbcmentioning

confidence: 99%

“…How these values are selected is oftentimes unclear. The influence of the selection of critical water pressure is numerically analyzed using a Richards equation-based model in Fetzer et al (2017), demonstrating the sensitivity of the numerical model to the critical water pressure varies with soil hydraulic properties. However, there is no comparison with experimental data in the study.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Model Concepts to Describe Water Transport in Shallow Subsurface Soil and Across the Soil–Air Interface

Vanderborght

Smits

2018

Transp Porous Med

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Soil water evaporation plays a critical role in mass and energy exchanges across the landatmosphere interface. Although much is known about this process, there is no agreement on the best modeling approaches to determine soil water evaporation due to the complexity of the numerical modeling scenarios and lack of experimental data available to validate such models. Existing studies show numerical and experimental discrepancies in the evaporation behavior and soil water distribution in soils at various scales, driving us to revisit the key process representation in subsurface soil. Therefore, the goal of this work is to test different mathematical formulations used to estimate evaporation from bare soils to critically evaluate the model formulations, assumptions and surface boundary conditions. This comparison required the development of three numerical models at the REV scale that vary in their complexity in characterizing water flow and evaporation, using the same modeling platform. The performance of the models was evaluated by comparing with experimental data generated from a soil tank/boundary layer wind tunnel experimental apparatus equipped with a sensor network to continuously monitor water-temperature-humidity variables. A series of experiments were performed in which the soil tank was packed with different soil types. Results demonstrate that the approaches vary in their ability to capture different stages of evaporation and no one approach can be deemed most appropriate for every scenario. When a proper top boundary condition and space discretization are defined, the Richards equation-based models (Richards model and Richards vapor model) can generally capture the evaporation behaviors across the entire range of soil saturations, comparing well with the experimental data. The simulation results of the non-equilibrium two-component two-phase model which considers vapor transport as an independent process generally agree well with the observations in terms of evaporation behavior and soil water dynamics. Certain differences in simulation results can be observed between equilibrium and non-equilibrium approaches. Comparisons of the models and the boundary layer formulations highlight the need to revisit key assumptions that influence evaporation behavior, highlighting the need to further understand water and vapor transport processes in soil to improve model accuracy.

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Section: Numerical Modelsmentioning

confidence: 99%

Section: Top Boundary Conditions (Tbcs)mentioning

confidence: 99%

Section: Evaluation Of Tbcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation of Model Concepts to Describe Water Transport in Shallow Subsurface Soil and Across the Soil–Air Interface

Vanderborght

Smits

2018

Transp Porous Med

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“…A state‐of‐the‐art review by Vanderborght et al () suggests further that the coupled water and heat transport processes in the soil remains local (for homogeneous medium) and one‐dimensional. In a complementary effort, Fetzer et al () provided numerical analysis showcasing the variations in lateral and vertical water and heat fluxes for simplified heterogeneous (two‐soil) systems. In this paper we revisited some of these available modeling concepts (Vanderborght et al, ) and propose a new and more general multiphysics multidimensional model accounting for soil heterogeneity in water as well as in vapor flows.…”

Section: Introductionmentioning

confidence: 99%

Upscaling the Coupled Water and Heat Transport in the Shallow Subsurface

Sviercoski¹,

Efendiev²,

Mohanty³

2018

Water Resources Research

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Predicting simultaneous movement of liquid water, water vapor, and heat in the shallow subsurface has many practical interests. The demand for multidimensional multiscale models for this region is important given: (a) the critical role that these processes play in the global water and energy balances, (b) that more data from air‐borne and space‐borne sensors are becoming available for parameterizations of modeling efforts. On the other hand, numerical models that consider spatial variations of the soil properties, termed here as multiscale, are prohibitively expensive. Thus, there is a need for upscaled models that take into consideration these features, and be computationally affordable. In this paper, a multidimensional multiscale model coupling the water flow and heat transfer and its respective upscaled version are proposed. The formulation is novel as it describes the multidimensional and multiscale tensorial versions of the hydraulic conductivity and the vapor diffusivity, taking into account the tortuosity and porosity properties of the medium. It also includes the coupling with the energy balance equation as a boundary describing atmospheric influences at the shallow subsurface. To demonstrate the accuracy of both models, comparisons were made between simulation and field experiments for soil moisture and temperature at 2, 7, and 12 cm deep, during 11 days. The root‐mean‐square errors showed that the upscaled version of the system captured the multiscale features with similar accuracy. Given the good matching between simulated and field data for near‐surface soil temperature, the results suggest that it can be regarded as a 1‐D variable.

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Prediction of soil evaporation measured with weighable lysimeters using the FAO Penman–Monteith method in combination with Richards’ equation

Schneider

Groh

Pütz

et al. 2021

Vadose Zone Journal

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Multiannual data (2016-2018) from 12 weighed lysimeters (four soil types with textures ranging from sandy loam to silt loam, three replicates) of the TERENO SOIL-Can network were used to evaluate if evaporation (E) rates could be predicted from weather data using the FAO Penman-Monteith (PM) method combined with soil water flow simulations using the Richards equation. Soil hydraulic properties (SHPs) were estimated either from soil texture using the ROSETTA pedotransfer functions, from in situ measured water retention curves, or from soil surface water contents using inverse modeling. In all years, E was water limited and the measured evaporation rates (E m) surprisingly did not vary significantly among the four different soil types. When SHPs derived from pedotransfer functions were used, simulated evaporation rates of the finer textured soils overestimated the measured ones considerably. Better agreement was obtained when simulations were based on in situ measured or inversely estimated SHPs. The SHPs estimated from pedotransfer functions represented unrealistically large characteristic lengths of evaporation (L c), and L c was found to be a useful characteristic to constrain estimates of SHPs. Also, when soil evaporation was water limited and E m rates were below E pot (PM evaporation scaled by an empirical coefficient), the diurnal dynamics of E m followed those of E pot. The Richards equation that considers only isothermal liquid water flow did not reproduce these dynamics caused by temperature dependent vapor transport in the soil.

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Heat and water transport in soils and across the soil‐atmosphere interface: 2. Numerical analysis

Cited by 41 publications

References 34 publications

Evaluation of Model Concepts to Describe Water Transport in Shallow Subsurface Soil and Across the Soil–Air Interface

Evaluation of Model Concepts to Describe Water Transport in Shallow Subsurface Soil and Across the Soil–Air Interface

Upscaling the Coupled Water and Heat Transport in the Shallow Subsurface

Prediction of soil evaporation measured with weighable lysimeters using the FAO Penman–Monteith method in combination with Richards’ equation

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