CAREER: Departure from Monin-Obukhov Similarity Theory (MOST) using high-resolution turbulence models

湍流控制着热量、水分、空气和被动化学示踪剂(如二氧化碳)在陆地和大气之间流动的速度。准确的地表湍流通量的模型表示对于精确的水文、天气和气候预报是至关重要的。我们目前的湍流通量模式表示假定大多数涡旋输送可以由模式中的局部观测和参数来解释。然而，水平方向(例如，由于地表特征的变化)和垂直方向(由于横跨异常大的垂直延伸的涡流)的可变性可能会使这些假设失效。在这项提议中，我们将结合高分辨率湍流模型和观测来测试后一种效应。我们的主要目标是更好地占最大？最高效的？在我们对地表湍流交换的表述中出现了漩涡。这最终应该会改进我们测量地表通量并对其进行建模的方式。一个特别令人感兴趣的通量是蒸发量(湿气通量)，它影响水文预报(如径流)以及天气和气候预报。除了这项研究活动，这项提案的主要教育目标之一是提供科学接触，并通过科学示范和高中实习鼓励纽约州哈莱姆区未被充分代表的群体选择科学职业和教育。目前大多数地面湍流传输定律的表述基于Monin-Obukhov相似理论(MOST)，该理论基于局部表层尺度。近年来，这一理论已被证明是有缺陷的。造成这一缺陷的主要原因之一是由于相干湍流结构的存在，这种结构将湍流特性从边界层顶部向下传输到地面。这些结构不容易被时间平均涡旋协方差技术观测到，并且可能是用于验证我们的陆面模式的现场地表能量收支不闭合的主要原因之一。为了解决这些问题，本方案的研究目标是：i)利用直接数值模拟(DNS)和大涡模拟(LES)研究与边界层顶部卷吸有关的非局地输送的作用及其与地面湍流的相互作用；ii)推导考虑非局地输送影响的新的地表湍流定律和廓线相似性；iii)为地表湍流通量的涡动协方差观测定义大涡改正。与这项研究活动相一致，该计划的教育目标是：a)开发国际学生交换计划，b)鼓励和建议未被充分代表的群体参与STEM研究，c)开发针对该问题的具有广泛视野的课程(例如，陆地-大气相互作用和湍流)，以促进跨学科合作和工作。

Turbulence controls the rate at which heat, moisture, air, and passive chemical tracers such as CO2 flow between the land and the atmosphere. Accurate model representation of such turbulent fluxes from the surface is essential for precise hydrologic, weather, and climate predictions. Our current model representation of turbulent fluxes assumes that most eddies transport can be explained by local observations and parameters in models. Nonetheless variability in the horizontal (e.g. due to variability in the surface characteristics) and in the vertical (due to eddies that span an unusually large vertical extend) directions can invalidate these assumptions. In this proposal we will test the latter effect using a combination of high-resolution turbulence models and observations. Our main objective is to better account for the largest ? most efficient ? eddies in our representation of turbulent exchange at the surface. This should ultimately improve the way we measure surface fluxes and model them. One flux of special interest is evaporation (the flux of moisture), which impacts hydrological forecasts (such as streamflow) along with weather and climate predictions. Along with this research activity, one of the main educational objectives of this proposal is to provide science exposure and encourage under-represented groups in Harlem, NY to choose scientific careers and education through science demonstrations and high-school internships.Most current formulations of the surface turbulent transport laws are based on Monin-Obukhov Similarity Theory (MOST), which is based on local surface layer scaling. This theory has been shown to be deficient in recent years. One of the main causes of this deficiency is due to the presence of coherent turbulent structures, which transport turbulent properties over large distances from the top of the boundary layer down to the surface. These structures cannot readily be observed by time-averaging eddy-covariance technique and may be one of the main reasons of non-closure of the in situ surface energy budget, which are used to validate our land-surface models. To address these issues, the research objectives of this proposal are to: i) Investigate the role of non-local transport related to the entrainment at the boundary layer top and its interaction with surface turbulence using Direct Numerical Simulations (DNS) and Large-Eddy Simulations (LES),ii) Derive new surface turbulent laws and profile similarity accounting for the effect of non-local transport, iii) Define large-eddy corrections for eddy-covariance observations of surface turbulent fluxes. iv) Evaluate the impact of these new formulations in a coupled land-surface and weather model.Consistent with this research activity, the educational objectives of the proposal are to: a) develop international student exchange programs, b) encourage and advise under-represented groups to participate in STEM research and c) develop classes (e.g. land-atmosphere interactions and turbulence) with a broad vision of the problem geared toward multiple scientific communities to facilitate cross-disciplinary collaborations and work.