Influence of soil heterogeneity on evapotranspiration under shallow water table conditions: transient, stochastic simulations

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Title:Main Title: Influence of soil heterogeneity on evapotranspiration under shallow water table conditions: transient, stochastic simulations
Description:Abstract: Ensembles of soil column numerical experiments were performed to study the influence of heterogeneity in the saturated hydraulic conductivity on the evapotranspiration or latent heat, LE, under varying water table conditions. In the numerical experiments, a variably saturated groundwater flow model coupled with a land surface model (ParFlow[CLM]) was used. The model was forced at the top with an atmospheric time series from Oklahoma, USA. The heterogeneity was simulated for two different soils (clay and sand) using uncorrelated Gaussian random fields with different variances. Soil heterogeneity has a strong influence on LE during the dry months of the year and negligible influence during months with sufficient moisture availability. The influence is stronger for unstructured soils, such as sand. An increase in shallow water table depth collapses the ensemble onto a single curve, i.e., heterogeneity plays a minor role and LE is limited by the increasing redistribution distance from the water table to the land surface. Accounting for correlations between the hydraulic conductivity and the shape factor in the pressure–saturation function increases the variability in LE. In the case of laterally interconnected soil columns, 3D hydrodynamics homogenize LE fluxes by establishing additional flow paths toward the land surface. Comparison with geometric mean simulations shows good agreement over many time periods for weekly and monthly averaged LE fluxes. Instantaneous daily and hourly differences sometimes exhibit values on the order of 100–101 Wm−2 (10−2–10−1 mm d−1) and white noise behavior over extended time periods. In the simulations, perhaps the strongest limitation is the application of a constant atmospheric time series at the top of the simulation domain. In order to assess the impact of this limitation in simulations of subsurface–land surface–atmosphere interactions, it would be necessary to allow for two-way feedbacks with the lower atmosphere. This will require resolving the boundary layer immediately adjacent to the land surface, including the lateral exchange of mass, energy, and momentum.
Identifier:10.1088/1748-9326/4/3/035007 (DOI)
Responsible Party
Creator:Stefan Kollet (Author)
Publisher:IOP Publishing Ltd
Publication Year:2013
Topic
TR32 Topic:Soil
Related Subproject:D7
Subjects:Keywords: soil Heterogeneity, Evapotranspiration, Coupled Modeling, Stochastic Simulations
File Details
Filename:2009_Kollet_EnvironResLet.pdf
Data Type:Text - Article
Size:9 Pages
File Size:1.5 MB
Date:Issued: 07.09.2009
Mime Type:application/pdf
Data Format:PDF
Language:English
Status:Completed
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Download Permission:Only Project Members
General Access and Use Conditions:For internal use only
Access Limitations:For internal use only
Licence:[TR32DB] Data policy agreement
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Publication Status:Published
Review Status:Peer reviewed
Publication Type:Article
Article Type:Journal
Source:Environmental Research Letters
Issue:3
Volume:4
Number of Pages:9 (1 - 9)
Metadata Details
Metadata Creator:Stefan Kollet
Metadata Created:03.12.2013
Metadata Last Updated:03.12.2013
Subproject:D7
Funding Phase:2
Metadata Language:English
Metadata Version:V50
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