Abstract The process of evaporation interacts with the soil, which has various comprehensive mechanisms. Multiphase flow models solve air, vapour, water, and heat transport equations to simulate non-isothermal soil moisture transport of both liquid water and vapor flow, but are only applied in non-vegetated soils. For (sparsely) vegetated soils often energy balance models are used, however these lack the detailed information on non-isothermal soil moisture transport. In this study we coupled a multiphase flow model with a two-layer energy balance model to study the impact of non-isothermal soil moisture transport on evaporation fluxes (i.e., interception, transpiration, and soil evaporation) for vegetated soils. The proposed model was implemented at an experimental agricultural site in Florida, US, covering an entire maize-growing season (67 days). As the crops grew, transpiration and interception became gradually dominated, while the fraction of soil evaporation dropped from 100% to less than 20%. The mechanisms of soil evaporation vary depending on the soil moisture content. After precipitation the soil moisture content increased, exfiltration of the liquid water flow could transport sufficient water to sustain evaporation from soil, and the soil vapor transport was not significant. However, after a sufficient dry-down period, the soil moisture content significantly reduced, and the soil vapour flow significantly contributed to the upward moisture transport in topmost soil. A sensitivity analysis found that the simulations of moisture content and temperature at the soil surface varied substantially when including the advective (i.e., advection and mechanical dispersion) vapour transport in simulation, including the mechanism of advective vapour transport decreased soil evaporation rate under wet condition, while vice versa under dry condition. The results showed that the formulation of advective soil vapor transport in a soil-vegetation-atmosphere transfer continuum can affect the simulated evaporation fluxes, especially under dry condition.

中文翻译：

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非等温土壤水分输送对玉米农田蒸发通量的影响

摘要 蒸发过程与土壤相互作用，具有多种综合机制。多相流模型求解空气、蒸汽、水和热传输方程，以模拟液态水和蒸汽流的非等温土壤水分传输，但仅适用于非植被土壤。对于（稀疏）植被土壤，通常使用能量平衡模型，但是这些模型缺乏关于非等温土壤水分输送的详细信息。在本研究中，我们将多相流模型与两层能量平衡模型相结合，研究非等温土壤水分输送对植被土壤蒸发通量（即截留、蒸腾和土壤蒸发）的影响。提议的模型在美国佛罗里达州的一个农业试验场实施，覆盖了整个玉米生长季节（67 天）。随着作物的生长，蒸腾作用和截留作用逐渐成为主导，而土壤蒸发量从100%下降到20%以下。土壤蒸发的机制因土壤水分含量而异。降水后土壤含水量增加，液态水流的渗出可以输送足够的水分来维持土壤蒸发，而土壤蒸汽输送不显着。然而，经过足够的干涸期后，土壤含水量显着降低，土壤蒸汽流动显着促进了最表层土壤的向上水分输送。敏感性分析发现，当包括平流（即，平流和机械弥散) 模拟中的蒸汽输运，包括在潮湿条件下平流蒸汽输运降低土壤蒸发率的机制，而在干燥条件下反之亦然。结果表明，土壤-植被-大气转移连续体中的对流土壤蒸汽传输的公式可以影响模拟的蒸发通量，尤其是在干燥条件下。