In most land-surface models, the evolution of soil moisture is governed by soil-hydraulic processes. In hyper-arid soils, these processes break down, but soil moisture continues to show clear temporal variations, suggesting that other processes may be at work. We hypothesize that moisture in such soils varies due to evaporation in the soil and to vapour fluxes at the air–soil interface. To test this, we include vapour exchange between the air and soil in a land-surface model, apply the model to a desert site, and compare the simulated and observed soil moisture. The good agreement between the simulations and observations confirms our hypothesis. Using the model results, we examine the interactions between the soil-moisture and soil-vapour phases and influences of the soil-vapour phase on the surface energy balance.

中文翻译：

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模拟超干旱条件下的土壤水分

在大多数地表模型中，土壤水分的演变受土壤水力过程的控制。在超干旱土壤中，这些过程会中断，但土壤水分继续显示出明显的时间变化，这表明其他过程可能在起作用。我们假设这些土壤中的水分因土壤蒸发和空气-土壤界面的蒸汽通量而变化。为了测试这一点，我们在地表模型中加入了空气和土壤之间的蒸汽交换，将该模型应用于沙漠场地，并比较模拟和观察到的土壤湿度。模拟和观察之间的良好一致性证实了我们的假设。使用模型结果，我们检查了土壤-水分和土壤-蒸气相之间的相互作用以及土壤-蒸气相对表面能量平衡的影响。