Effects of Near Surface Soil Moisture Profiles During Evaporation on Far‐Field Ground‐Penetrating Radar Data: A Numerical Study
Effects of Near Surface Soil Moisture Profiles During Evaporation on Far‐Field Ground‐Penetrating Radar Data: A Numerical Study
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DOI：
10.2136/vzj2012.0138
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发表时间：
2013-05
影响因子：
2.8
通讯作者：
D. Moghadas;K. Jadoon;J. Vanderborght;S. Lambot;H. Vereecken
中科院分区：
文献类型：
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作者：
D. Moghadas;K. Jadoon;J. Vanderborght;S. Lambot;H. Vereecken
我们研究了出现在蒸发土壤表面下方的干燥锋对远场探地雷达（GPR）数据的影响。首先，我们进行了12种不同质地的土壤干燥锋的宽度的分析，通过使用一个分析模型。然后，我们数值模拟了垂直土壤水分剖面蒸发过程中发展的土壤质地。我们使用仅考虑液态水流动的理查兹流动模型和考虑耦合水、蒸汽和热流的模型进行了模拟。然后从模拟的土壤含水量分布考虑到视电导率和介电常数的频率依赖性产生的GPR信号。分析结果表明，在第一阶段蒸发结束时，粉质土的干燥锋宽度大于其它质地的土壤，而桑迪的干燥锋宽度小于其它质地的土壤。我们还证明，干燥锋宽度的分析估计值可以被视为干燥锋对远场GPR数据的影响的代理。数值模拟得出的结论是，土壤中的蒸汽传输导致S形土壤水分剖面，这显然影响了GPR数据。因此，在耦合反演方法中解释GPR数据时，需要考虑蒸汽流。此外，蒸汽流对GPR数据的影响是更大的粉土比桑迪。这些对探地雷达数据的影响为利用雷达监测蒸发提供了有希望的前景。
We investigated the effects of a drying front that emerges below an evaporating soil surface on the far‐field ground‐penetrating radar (GPR) data. First, we performed an analysis of the width of the drying front in soils with 12 different textures by using an analytical model. Then, we numerically simulated vertical soil moisture profiles that develop during evaporation for the soil textures. We performed the simulations using a Richards flow model that considers only liquid water flow and a model that considers coupled water, vapor, and heat flows. The GPR signals were then generated from the simulated soil water content profiles taking into account the frequency dependency of apparent electrical conductivity and dielectric permittivity. The analytical approach indicated that the width of the drying front at the end of Stage I of the evaporation was larger in silty soils than in other soil textures and smaller in sandy soils. We also demonstrated that the analytical estimate of the width of the drying front can be considered as a proxy for the impact that a drying front could have on far‐field GPR data. The numerical simulations led to the conclusion that vapor transport in soil resulted in S‐shaped soil moisture profiles, which clearly influenced the GPR data. As a result, vapor flow needs to be considered when GPR data are interpreted in a coupled inversion approach. Moreover, the impact of vapor flow on the GPR data was larger for silty than for sandy soils. These effects on the GPR data provide promising perspectives regarding the use of radars for evaporation monitoring.