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

职业生涯：使用高分辨率湍流模型偏离 Monin-Obukhov 相似理论 (MOST)

• 批准号: 1552304
• 负责人: Pierre Gentine
• 金额: $ 43.54万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2022-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1552304&HistoricalAwards=false
• 关键词: CAREER; Departure; Monin; Obukhov; Similarity

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.

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率。这种地表湍流通量的精确模型表示对于精确的水文、天气和气候预测至关重要。我们目前紊流通量的模型表示假设大多数涡旋输运可以用模型中的局部观测和参数来解释。尽管如此，水平方向（例如，由于地表特征的变化）和垂直方向（由于跨越异常大的垂直延伸的涡流）的可变性可以使这些假设无效。在本提案中，我们将使用高分辨率湍流模型和观测相结合的方法来检验后一种效应。我们的主要目标是更好地占到最大的？效率最高？在我们的表面湍流交换代表的漩涡。这将最终改善我们测量地表通量和建模的方式。一种特别有趣的通量是蒸发（水分通量），它影响水文预报（如河流流量）以及天气和气候预测。除了这项研究活动，该提案的主要教育目标之一是提供科学接触，并鼓励纽约哈莱姆区代表性不足的群体通过科学示范和高中实习选择科学职业和教育。目前大多数地表湍流输运规律的表述都是基于基于局部地表尺度的Monin-Obukhov相似理论（Most）。近年来，这一理论已被证明是有缺陷的。造成这种缺陷的主要原因之一是由于相干湍流结构的存在，这些结构将湍流特性从边界层顶部传输到表面很远的距离。这些结构不容易被时间平均涡旋协方差技术观测到，这可能是原位地表能量收支不闭合的主要原因之一，而原位地表能量收支用于验证我们的陆面模型。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）研究边界层顶部卷带相关的非局部输运的作用及其与地表湍流的相互作用；ii)推导出考虑非局部输运影响的新的地表湍流规律和剖面相似性；iii)定义地表湍流通量涡旋协方差观测的大涡修正。iv)评估这些新公式在陆地表面和天气耦合模式中的影响。与这项研究活动相一致，该提案的教育目标是：a)发展国际学生交流项目；b)鼓励和建议代表性不足的群体参与STEM研究；c)开设课程（例如，陆地-大气相互作用和湍流），以面向多个科学社区的问题的广泛视野，促进跨学科合作和工作。