Coupled Heat and Water Transfer in Soil

0337553霍顿热量和水分在土壤表面的运动在很大程度上驱动了大气层和陆地水圈。 在近地表土壤中，水热耦合传递是普遍现象，但人们对耦合过程的认识却很少。 事实上，使用事实上的标准菲利普和德弗里斯型耦合传输模型所做的预测可能会大幅度偏离。 目前的模型，因为它们是基于数据集，只涵盖了一个狭窄的范围内的条件，忽略了至少两个重要的考虑因素：热驱动的平流（“土壤呼吸”），其中每天在土壤表面加热周期性地改变气相的密度，从而驱动土壤空气的平流，和润湿性，控制毛细管上升的高度和空气-水界面的面积。我们建议进行详细的实验测量热和水在密封和开放的土柱。 我们的实验将使用新的热TDR探头，能够测量温度，热特性和含水量，使我们能够对每个单独的土柱进行几个月的实验。 这使我们能够对每个土柱进行广泛的边界条件，从而从每个土柱中收集数据进行校准和验证。 我们将研究土壤质地和润湿性，含水量，平均温度，热梯度的方向，以及波动的边界条件对密封土柱中的耦合热和水运动的影响。 然后，我们将研究土壤质地和润湿性，平均温度，上边界条件，和对流水汽屏障从开放的土壤柱蒸发的影响。在室内实验的同时，我们将开发一个网络模型耦合的热量和水分在土壤中的传输。 一个网络模型从第一原则，和（与传统的连续模型相比）的属性，如不饱和水力传导率，空气/水界面面积，土壤呼吸出现的网络，而不是被明确编程。 这一基本方法将使我们能够研究哪些性质和过程在哪些条件下是重要的，从而进一步加深我们的理解，并在未来集中开发改进的连续模型。本项目将开发和推广实验和建模方面的新模型和方法。 这些想法，数据和模型将在同行教育文献，会议和小组网站上提供。 此外，研究将被纳入更广泛的计划和国家利益的活动，如自然资源管理和气候变化。

0337553HortonMovement of heat and water across the soil surface largely drives both the atmosphere and the terrestrial hydrosphere. In near-surface soil, coupled transfer of heat and water is the rule rather than the exception, yet the coupling process is poorly understood. In fact, predictions made using the de facto standard Philip and de Vries type coupled transfer model can be substantially off. Current models, based as they are on data sets covering only a narrow range of conditions, ignore at least two important considerations: thermally-driven advection ('soil breathing'), in which daily heating at the soil surface cyclically alters the density of the gas phase and so drives advection of soil air, and wettability, which controls both the height of capillary rise and the area of the air-water interface. We propose to conduct detailed experiments measuring heat and water in both sealed and open soil columns. Our experiments will use the new thermo-TDR probe, capable of measuring temperature, thermal properties, and water content, allowing us to conduct several months of experiments on each individual soil column. This permits us to subject each soil column to a wide range of boundary conditions, and so to collect data for both calibration and validation from each soil column. We will examine effects of soil texture and wettability, water content, mean temperature, direction of thermal gradient, and influence of fluctuating boundary conditions on coupled heat and water movement in sealed soil columns. We will then study effects of soil texture and wettability, mean temperature, upper boundary condition, and advective vapor barrier on evaporation from open soil columns. In parallel with the laboratory experiments, we will develop a network model of coupled heat and water transfer in soils. A network model operates from first principles, and (in contrast with conventional continuum models) properties such as unsaturated hydraulic conductivity, air/water interfacial area, and soil breathing emerge from the network rather than being explicitly programmed in. This fundamental approach will allow us to examine which properties and processes are important under which conditions, furthering our understanding and focusing the development of improved continuum models in the future.This project will develop and disseminate new models and approaches in both experiment and modeling. These ideas, data, and models will be made available in the peer-ed literature, at conferences, and on a group website. Additionally, the research will be integrated into broader programs and activities of national interest, such as natural resource management and climate change.