Abstract Near-surface soil hydro-thermodynamics plays an important role in heat and water transfer between land and atmosphere. However, it is difficult to quantify these processes in field campaigns, such as movement of liquid water and water vapor. This has affected determination of ground heat flux, a key component of surface energy budget. This study aims to quantify soil heat and water processes utilizing in situ measurements, and to improve ground heat flux estimation and surface energy imbalance. A new model has been proposed based on three main physical processes, including thermal conduction, convection of heat by moving water, and convection of latent heat. The model was tested at a grassland site in Colorado, USA. Results show that the model can capture high values of soil water content during rain events, low values under intense solar radiation, and high-frequency fluctuations under intermittent cloudy conditions. Also, the model produces reasonable vertical velocity and mass flux of water vapor. For the estimation of ground heat flux, the method that considers vertical variation of soil thermal conductivity and the contribution of water vapor gives better energy balance ratio than methods that ignore these conditions. In spite of this, the energy balance ratio is still low. Footprint analysis further shows the seasonal variation of ground cover is a potential reason responsible for this.

中文翻译：

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基于近地表土壤水热力学的地热通量测定

摘要 近地表土壤水热力学在陆地和大气之间的热量和水分传递中起着重要作用。然而，很难在现场活动中量化这些过程，例如液态水和水蒸气的运动。这影响了地热通量的确定，地热通量是地表能量收支的一个关键组成部分。本研究旨在利用原位测量量化土壤热和水过程，并改进地热通量估计和地表能量失衡。提出了一种基于三个主要物理过程的新模型，包括热传导、流动水的热量对流和潜热对流。该模型在美国科罗拉多州的草地现场进行了测试。结果表明，该模型可以在降雨事件期间捕获较高的土壤含水量值，在强烈的太阳辐射下较低的值，在间歇性多云条件下的高频波动。此外，该模型还产生了合理的水蒸气垂直速度和质量通量。对于地热通量的估算，考虑土壤热导率垂直变化和水汽贡献的方法比忽略这些条件的方法具有更好的能量平衡比。尽管如此，能量平衡比率仍然很低。足迹分析进一步表明，地面覆盖的季节性变化是造成这种情况的潜在原因。考虑土壤热导率垂直变化和水汽贡献的方法比忽略这些条件的方法提供更好的能量平衡比。尽管如此，能量平衡比率仍然很低。足迹分析进一步表明，地面覆盖的季节性变化是造成这种情况的潜在原因。考虑土壤热导率垂直变化和水汽贡献的方法比忽略这些条件的方法提供更好的能量平衡比。尽管如此，能量平衡比率仍然很低。足迹分析进一步表明，地面覆盖的季节性变化是造成这种情况的潜在原因。