An Application of the Theory of Maximum Entropy Production in Modeling Evapotranspiration

最大熵产生理论在地表蒸散发模拟中的应用（NSF提案0943356）[ei]: Rafael L. Bras, wangjingfeng，加州大学欧文分校[ei] .摘要本项目旨在基于最大熵产生理论（MEP）——一个新兴的非平衡系统理论框架——建立一个创新的地表蒸散发（ET）模型。这项工作的指导方针是获得干燥陆地表面上地面和感热通量的表达式的有希望的初步结果。研究分为两个部分：(1)理论发展和(2)观测验证。理论发展的中心任务是根据我们对大气边界层（ABL）湍流输送的最佳理解，制定一个？传递潜热的热惯性？这是耗散函数的关键参数，耗散函数的极值可以得到潜热通量、感热通量和地热通量的MEP解。我们遵循三条线索来制定？潜热的热惯量？：(1)引起地表感热输送的湍流混合也引起了水汽的输送；(2)蒸发表面正上方的水汽与土壤水分处于平衡状态；(3)地表的温度和湿度变量（以及冠层上的气孔导度）足以确定蒸散发的能量学。因此，？传递潜热的热惯性？对于裸土（冠层），预计是地表温度和湿度（以及气孔导度）的函数。该项目的验证阶段有两个目标：(1)在局部尺度上验证裸地和冠层的MEP ET模型，(2)探索在局部尺度（定义为Monin-Obukhov湍流模型适用的尺度）上制定的MEP ET模型在区域尺度上的可能应用。在局部尺度上验证MEP模型将主要使用以前现场活动的存档数据集，并在需要时补充额外的现场测量。在区域尺度上对MEP蒸散发模式的测试将把MEP模式预测的潜热通量、感热通量和地热通量与使用其他蒸散发模式的再分析数据集进行比较。根据进展，理论发展可能扩大到包括水（海洋，湖泊等）和雪表面的情况。该项目如果成功实施，将为预测局部尺度的地表能量平衡提供一个新的建模框架，并有望产生具有全球覆盖范围的改进的地表热通量数据集。如果成功，这一努力的结果将提供一种计算陆地表面能量平衡的全新方法，这种方法将是简洁的，几乎不需要校准。该方法将在用于水文气候预测的现有陆地表面模型中实施。除了让博士生参与研究之外，该项目还将利用现有的本科生研究机会计划，让至少一名本科生（最好是来自弱势群体）参与到能源和水文平衡的学习中，通过进行实地实验来获得支持数据集。有一整套测量能量通量和温度、土壤湿度和其他所需水文变量的仪器。所有学生，研究生和本科生，将在适当的科学会议和期刊上展示他们的研究成果。这所大学为本科生出版一份研究期刊。这位高级研究员是加州大学欧文分校工程学院MESA和CAMP外展项目的领导者、主持人和参与者。这为初中和高中以及社区大学的贫困学生提供了机会。这种访问将用于吸引感兴趣的参与者参与与水文和地球科学有关的问题。机制包括访问学校，在大学接待学生，进行公开讲座以及赞助或监督项目工作。

An Application of the Theory of Maximum Entropy Production in ModelingEvapotranspiration(NSF Proposal 0943356)PIs: Rafael L. Bras and Jingfeng WangUniversity of California, IrvineAbstractThis project aims at developing an innovative model of evapotranspiration (ET) over land surfaces based on the theory of maximum entropy production (MEP), an emerging theoretical framework for non-equilibrium systems. The effort is guided by promising preliminary results that obtained expressions for ground and sensible heat fluxes over a dry land surface. The research is organized in: (1) theoretical development and (2) observational validation. The central task of the theoretical development is to formulate, based on our best understanding of the turbulent transport in the atmospheric boundary layer (ABL), an expression for the ?thermal inertia for transferring latent heat? that is the key parameter of the dissipation function whose extremization leads to the MEP solution of latent, sensible and ground heat fluxes. We follow three leads in formulating the ?thermal inertia for latent heat?: (1) the turbulent mixing responsible for the transport of sensible heat in the ABL is also responsible for the transport of water vapor, (2) water vapor right above the evaporating surface is in equilibrium with the soil water, and (3) the surface variables of temperature and humidity (as well as stomatal conductance over the canopy) are sufficient to determine the energetics of the evapotranspiration. As a result, the ?thermal inertia for transferring latent heat? is expected to be a function of surface temperature and humidity (and stomatal conductance) for the case of bare soil (canopy). The validation phase of the project has a two-fold objective: (1) validating the MEP model of ET for bare soil and canopy at local scales, and (2) exploring a possible application of the MEP model of ET formulated at local scale (defined as the scales at which the Monin-Obukhov turbulence model applies) to regional scales. Validation of the MEP model at local scales will mostly use archived datasets from previous field campaigns supplemented by additional field measurements whenever needed. Test of the MEP model of ET at regional scales will compare latent, sensible, and ground heat fluxes predicted by the MEP model with the reanalysis datasets using other ET models. Depending on progress, the theoretical development may expand to include the case of water (oceans, lakes, etc.) and snow surfaces. The project, if successfully carried out, will provide a new modeling framework for predicting the land surface energy balance at local scales and hopefully producing improved datasets of surface heat fluxes with global coverage.If successful the results of this effort will provide a completely new method to compute the land surface energy balance that would be parsimonious and require little calibration. The method will be implemented in existing land surface models that are used to make hydro-climatic predictions. Besides engaging doctoral students in the effort, the project will use an existing undergraduate research opportunities program to engage at least one undergraduate student, preferably from a disadvantaged group, in learning energy and hydrologic balances by performing field experiments that could yield supporting data sets. A complete set of instruments to measure energy fluxes and temperature, soil moisture and other hydrologic variables required are available. All students, graduate and undergraduate, will be engaged in presenting their results in appropriate scientific meetings and journals. The University publishes a research journal for undergraduates. The senior investigator is a leader, host and participant of the MESA and CAMP outreach programs housed at the school of engineering of the University of California, Irvine. This provides access to underprivileged students in middle and high schools as well as community colleges. This access will be used to engage interested participants in issues related to hydrology and earth sciences. Mechanisms include visits to schools, receiving students at the university, giving public lectures and sponsoring or supervising project work.