Estimation of the near surface soil water content during evaporation using air-launched ground-penetrating radar
Estimation of the near surface soil water content during evaporation using air-launched ground-penetrating radar
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DOI：
10.3997/1873-0604.2014017
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发表时间：
2014-10
影响因子：
1.6
通讯作者：
D. Moghadas;K. Jadoon;J. Vanderborght;Sebastian Lambot;H. Vereecken
中科院分区：
文献类型：
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作者：
D. Moghadas;K. Jadoon;J. Vanderborght;Sebastian Lambot;H. Vereecken
蒸发是全球水循环中的重要过程，其变化影响近地表土壤含水量，这对地表水文和气候模拟至关重要。土壤蒸发速率通常具有两个明显的阶段，即能量限制阶段（阶段I）和土壤水力限制阶段（阶段II）。在室内进行了23天的细砂蒸发试验。该装置配备有称重系统，以恒定的时间步长自动记录砂箱的重量。此外，时间推移的空中发射的地面穿透雷达（GPR）测量进行监测蒸发过程。探地雷达模型涉及三维多层介质中波传播的麦克斯韦方程的全波形频域解。对三种不同岩石物理模型的全波形探地雷达正演模拟的精度进行了研究。此外，全波形反演的探地雷达数据被用来估计定量信息，如近地表土壤含水量。雷达图中可以清楚地观察到蒸发的两个阶段，定性地表明雷达数据中包含了足够的信息。考虑到探地雷达的宽频率范围（0.8-5.0 GHz）时，全波形探地雷达反演允许在扩展蒸发阶段精确估计近地表土壤含水量。此外，研究结果表明，CRIM模型可能构成一个相关的替代方案，在解决全波形GPR建模的频率依赖性问题。
Evaporation is an important process in the global water cycle and its variation affects the near surface soil water content, which is crucial for surface hydrology and climate modelling. Soil evaporation rate is often characterized by two distinct phases, namely, the energy limited phase (stage-I) and the soil hydraulic limited period (stage-II). In this paper, a laboratory experiment was conducted using a sand box filled with fine sand, which was subject to evaporation for a period of twenty three days. The setup was equipped with a weighting system to record automatically the weight of the sand box with a constant time-step. Furthermore, time-lapse air-launched ground penetrating radar (GPR) measurements were performed to monitor the evaporation process. The GPR model involves a full-waveform frequency-domain solution of Maxwell’s equations for wave propagation in three-dimensional multilayered media. The accuracy of the full-waveform GPR forward modelling with respect to three different petrophysical models was investigated. Moreover, full-waveform inversion of the GPR data was used to estimate the quantitative information, such as near surface soil water content. The two stages of evaporation can be clearly observed in the radargram, which indicates qualitatively that enough information is contained in the GPR data. The fullwaveform GPR inversion allows for accurate estimation of the near surface soil water content during extended evaporation phases, when a wide frequency range of GPR (0.8–5.0 GHz) is taken into account. In addition, the results indicate that the CRIM model may constitute a relevant alternative in solving the frequency-dependency issue for full waveform GPR modelling.