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STIR Proposal For Research Area 2.1.2 Surface Energy Balance: Transient Soil Density Impacts Land Surface Characteristics and Characterization

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Technical Report,01 Jan 2015,30 Sep 2015

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North Carolina State University Raleigh United States

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Soil density is commonly treated as static in studies on land surface property dynamics. Magnitudes of errors associated with this assumption are largely unknown. Objectives of this preliminary investigation were to i quantify effects of soil density variation on soil properties, and ii evaluate impact of changing soil density on surface energy balance and heat and water transfer. Six soil properties were evaluated over a range of soil densities, using a combination of ten modeling approaches. Thermal conductivity, water characteristics, hydraulic conductivity, and vapor diffusivity were most sensitive these properties changed by fractions greater than associated change in density i.e., 10 change in density led to 10 change in property. Subsequently, three field seasons were simulated with a numerical model HYDRUS-1D for arange of bulk densities. Among the surface energy balance terms, ground heat flux and latent heat flux were most sensitive to bulk density. Surface soil temperature variation increased in with low bulk densities but subsurface temperature variation decreased. Surface water content varied with bulk density but effects mostly disappeared in the subsurface. Results demonstrate significance of transient density on surface conditions and point to need for continued evaluation of impacts with improved measurements and modeling.

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