Bulk density effects on soil hydrologic and thermal characteristics: A numerical investigation
Bulk density effects on soil hydrologic and thermal characteristics: A numerical investigation
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DOI：
10.1002/hyp.13152
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发表时间：
2018-06
影响因子：
3.2
通讯作者：
Yuki Kojima;J. Heitman;M. Sakai;C. Kato;R. Horton
中科院分区：
文献类型：
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作者：
Yuki Kojima;J. Heitman;M. Sakai;C. Kato;R. Horton
在地表动力学研究中，土壤容重 (ρb) 通常被视为静态。与这一假设相关的误差大小在很大程度上是未知的。我们的目标是 (a) 量化 ρb 对土壤水文和热性质的影响，以及 (b) 评估 ρb 对表面能量平衡以及热量和水传递的影响。我们使用 6 个模型的组合，在 ρb 范围内评估了 6 种土壤特性、体积热容、导热系数、土壤热扩散率、保水特性、导水率和蒸汽扩散率。热导率、保水性、导水率和蒸汽扩散率对 ρb 最敏感，每项变化的分数都大于 ρb 的相关分数变化。 ρb 变化 10%，导致热导率变化 10-11%，饱和水和残余水含量变化 6-11%，饱和导水率变化 49-54%，蒸汽扩散率变化 80%。随后，使用数值模型 (HYDRUS-1D) 对一系列 ρb 值模拟了 3 个野外季节。当ρb增加25%（从1.2到1.5 Mg m−3）时，浅层土壤温度变化减少2.1°C，地下层增加1°C。在干燥过程中，不同 ρb 值的地表水含量相差 0.02 m3 m−3，但差异在地下基本消失。基质势随水深 >100 m 的变化而变化。表面能量平衡随 ρb 显示出明显的趋势。潜热通量减少 6%，感热通量增加 9%，地热通量大小变化 18%（ρb 增加 25%）。瞬态 ρb 影响表面条件和通量，显然，它值得在现场和建模研究中考虑。
Soil bulk density (ρb) is commonly treated as static in studies of land surface dynamics. Magnitudes of errors associated with this assumption are largely unknown. Our objectives were to (a) quantify ρb effects on soil hydrologic and thermal properties and (b) evaluate effects of ρb on surface energy balance and heat and water transfer. We evaluated 6 soil properties, volumetric heat capacity, thermal conductivity, soil thermal diffusivity, water retention characteristics, hydraulic conductivity, and vapour diffusivity, over a range of ρb, using a combination of 6 models. Thermal conductivity, water retention, hydraulic conductivity, and vapour diffusivity were most sensitive to ρb, each changing by fractions greater than the associated fractional changes in ρb. A 10% change in ρb led to 10–11% change in thermal conductivity, 6–11% change in saturated and residual water content, 49–54% change in saturated hydraulic conductivity, and 80% change in vapour diffusivity. Subsequently, 3 field seasons were simulated with a numerical model (HYDRUS‐1D) for a range of ρb values. When ρb increased 25% (from 1.2 to 1.5 Mg m−3), soil temperature variation decreased by 2.1 °C in shallow layers and increased by 1 °C in subsurface layers. Surface water content differed by 0.02 m3 m−3 for various ρb values during drying events but differences mostly disappeared in the subsurface. Matric potential varied by >100 m of water. Surface energy balance showed clear trends with ρb. Latent heat flux decreased 6%, sensible heat flux increased 9%, and magnitude of ground heat flux varied by 18% (with a 25% ρb increase). Transient ρb impacted surface conditions and fluxes, and clearly, it warrants consideration in field and modelling investigations.