Collaborative Research: The Role of Coherent Structures in Scalar Transport over Heterogeneous Landscapes

合作研究：相干结构在异质景观标量传输中的作用

• 批准号: 1853050
• 负责人: Heping Liu
• 金额: $ 40.65万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1853050&HistoricalAwards=false
• 关键词: Collaborative; Research; Role; Coherent; Structures

Scalar fluxes including sensible heat, latent heat, and trace gases such as CO2, methane, ammonia fluxes, from or to land surfaces have direct impacts on weather and climate, air quality, agricultural management, and ecosystem services. A better understanding of turbulence in the lower atmosphere is the prerequisite for better quantification and modeling of these scalar fluxes. Over the past few decades, there has been active research on the topology and transporting capacity of coherent structures in canonical turbulent boundary layers and convective systems. However, problems of practical relevance in micrometeorology have not profited from these studies. This project aims to fill the research gap by investigating the role of coherent structures in scalar transport in atmospheric boundary layer flows over heterogeneous landscapes. The project focuses on the interactions between land surface heterogeneity and coherent structures at the point- and landscape- scales, and their implications for the breakdown of Monin-Obukhov Similarity Theory (MOST) in describing scalar fluxes. At the point-scale, the breakdown of MOST arises from advective terms communicating the signatures of land surface heterogeneity and vertical transport terms bearing the signatures of coherent structures. At the landscape-scale where a spatial averaging is conducted, dispersive fluxes arise from the interactions between land surface heterogeneity and coherent structures. This work combines field experiments and large-eddy simulations (LES) under a unifying framework via flux budget equations and their spatially-averaged version. The field experiment will be conducted over a relatively flat but heterogeneous terrain in Idaho Falls, Idaho, with a 62-m tower and several short towers to be equipped with eddy covariance systems, a sodar, a wind profiler with RASS, 35 mesonet stations, and other instruments. The field work will provide a unique characterization of coherent structures and scalar turbulence in three dimensions and at high resolutions. It will allow quantification of horizontal and vertical terms in the scalar flux budget simultaneously. A series of LES runs will be used to extend the insights afforded by the field experiment from point to landscape scales. A novel approach based on quadrant analysis in time and space will be employed to model dispersive fluxes. The new datasets generated by the field experiment will provide opportunities for exploring other topics related to atmospheric boundary layer and land surface processes. Beyond the tutoring of two graduate students and two undergraduate students, the project will involve several educational and outreach components. It will generate mini-projects for students in several graduate and undergraduate courses taught by the PIs on boundary layer meteorology, applied meteorology, and fluid dynamics. Short films and videos will be created to present the significance of the findings to researchers and the general public.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

标量通量包括感热、潜热和痕量气体（如CO2、甲烷、氨），来自或流向陆地表面，对天气和气候、空气质量、农业管理和生态系统服务有直接影响。更好地了解低层大气中的湍流是更好地量化和模拟这些标量通量的先决条件。在过去的几十年里，人们对典型湍流边界层和对流系统中相干结构的拓扑结构和输运能力进行了积极的研究。然而，在微气象学的实际相关问题并没有从这些研究中获益。本计画的目的在于探讨非均匀地形上大气边界层流动中，相干结构在标量输运中的角色，以填补研究空白。该项目的重点是陆面异质性和相干结构之间的相互作用，在点和景观尺度，以及它们的影响，莫宁-奥布霍夫相似性理论（MOST）的故障在描述标量通量。在点尺度上，MOST的分解来自于传达陆面异质性特征的平流项和承载相干结构特征的垂直输送项。在进行空间平均的尺度上，分散通量来自于陆面异质性和相干结构之间的相互作用。这项工作结合了现场实验和大涡模拟（LES）下的统一框架下，通过通量收支方程和空间平均版本。现场实验将在爱达荷州的爱达荷州福尔斯一个相对平坦但不均匀的地形上进行，有一个62米高的塔和几个短塔，配备涡度相关系统、一个声雷达、一个带有RASS的风廓线仪、35个中网站和其他仪器。实地工作将提供三维和高分辨率的相干结构和标量湍流的独特表征。它将允许同时量化标量通量预算中的水平和垂直项。一系列的LES运行将被用来扩展的现场实验提供的见解，从点到景观尺度。一种新的方法的基础上象限分析的时间和空间将被用来模拟色散通量。实地实验产生的新数据集将为探索与大气边界层和陆面过程有关的其他专题提供机会。除了两名研究生和两名本科生的辅导，该项目将涉及几个教育和推广部分。它将产生小型项目，为学生在几个研究生和本科生课程讲授的PI边界层气象学，应用气象学和流体动力学。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。