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.

湍流控制热量、湿气、空气和二氧化碳等被动化学示踪剂在陆地和大气之间流动的速率。准确的模型表示来自地表的此类湍流对于精确的水文、天气和气候预测至关重要。我们当前的湍流通量模型表示假设大多数涡流传输可以通过模型中的局部观测和参数来解释。尽管如此，水平方向（例如由于表面特征的变化）和垂直方向（由于跨越异常大的垂直延伸的涡流）方向的变化可能使这些假设无效。在本提案中，我们将结合使用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？最有效率？涡流是我们对表面湍流交换的表示。这最终将改善我们测量表面通量和建模的方式。一种特别令人感兴趣的通量是蒸发（水分通量），它会影响水文预报（例如水流）以及天气和气候预测。除了这项研究活动之外，该提案的主要教育目标之一是提供科学接触，并鼓励纽约州哈莱姆区的代表性不足的群体通过科学演示和高中实习选择科学职业和教育。目前大多数表面湍流传输定律的表述都是基于莫宁-奥布霍夫相似理论 (MOST)，该理论基于局部表面层缩放。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相干湍流结构的存在，该结构将湍流特性从边界层顶部长距离传输到表面。这些结构不容易通过时间平均涡度协方差技术观察到，可能是原位表面能量预算不闭合的主要原因之一，该预算用于验证我们的陆地表面模型。为了解决这些问题，本提案的研究目标是：i）使用直接数值模拟（DNS）和大涡模拟（LES）研究与边界层顶部夹带相关的非局域传输的作用及其与表面湍流的相互作用，ii）推导新的表面湍流定律和剖面相似性来解释非局域传输的影响，iii）定义涡流协方差观测的大涡校正 表面湍流。 iv) 评估这些新公式在陆地-表面和天气耦合模型中的影响。与本研究活动一致，该提案的教育目标是：a) 制定国际学生交流计划，b) 鼓励和建议代表性不足的群体参与 STEM 研究，c) 开发针对多个科学界问题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 跨学科的合作和工作。