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

最大熵产生理论在蒸发蒸腾模拟中的应用(美国国家科学基金会提案0943356)PI：Rafael L.Bras和加州大学欧文分校王景峰摘要这个项目旨在发展一个基于最大熵产生理论的陆地表面蒸发蒸散的创新模式，这是一个新兴的非平衡系统理论框架。这项工作是由有希望的初步结果指导的，这些结果获得了干燥陆地表面上的地面和感热通量的表达式。本研究分为两部分：(1)理论发展和(2)观测验证。理论发展的中心任务是，基于我们对大气边界层(ABL)中湍流输送的最佳理解，推导出传递潜热的热惯量的表达式。这是耗散函数的关键参数，它的极值化导致了潜热、感热和地热通量的MEP解。我们遵循三条线索来建立潜热的热惯量：(1)负责ABL中感热输送的湍流混合也负责水汽的输送，(2)蒸发面正上方的水汽与土壤水分是平衡的，(3)地表温度和湿度(以及冠层上的气孔导度)变量足以确定蒸发蒸腾的能量。结果表明，潜热传递的热惯量？在裸土(树冠)的情况下，预计是表面温度和湿度(以及气孔导度)的函数。该项目的验证阶段有两个目标：(1)验证在局部尺度上裸露土壤和冠层的ETMEP模型，以及(2)探索在局部尺度(定义为Monin-Obukhov湍流模型应用的尺度)建立的ETMEP模型应用于区域尺度的可能性。在地方尺度上验证MEP模型将主要使用以前实地活动的存档数据集，并在需要时辅之以额外的实地测量。在区域尺度上对ET的MEP模式进行检验，将MEP模式预测的潜热、感热和地面热通量与使用其他ET模式的再分析数据集进行比较。根据进展情况，理论发展可能会扩展到包括水(海洋、湖泊等)的情况。和雪面。如果该项目成功实施，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，这项工作的结果将提供一种全新的方法来计算陆地表面能量平衡，该方法将是一种简单易行且几乎不需要校准的方法。该方法将在现有的陆地表面模型中实施，这些模型用于进行水文气候预测。除了让博士生参与到这项工作中来，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)通过进行实地实验来学习能量和水文平衡，这些实验可能会产生支持的数据集。可提供一整套仪器来测量所需的能量通量和温度、土壤湿度和其他水文变量。所有学生，无论是研究生还是本科生，都将在适当的科学会议和期刊上展示他们的成果。这所大学出版了一本面向本科生的研究期刊。这位高级研究员是加州大学欧文分校工程学院梅萨和营地外展项目的负责人、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。这一途径将被用来使感兴趣的参与者参与与水文学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.