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

基本信息

批准号：
1853354
负责人：
Dan Li
金额：
$ 30.62万
依托单位：
Trustees of Boston 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 2024-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1853354&HistoricalAwards=false
关键词：
Collaborative Research Role Coherent Structures

项目摘要

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.

进出地表的标量通量，包括显热、潜热和微量气体（例如二氧化碳、甲烷、氨通量），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建模这些标量通量的先决条件。在过去的几十年里，人们对规范湍流边界层和对流系统中相干结构的拓扑和传输能力进行了积极的研究。然而，微气象学中的实际相关问题并未从这些研究中受益。该项目旨在通过研究相干结构在异质景观上大气边界层流标量传输中的作用来填补研究空白。该项目重点研究点和景观尺度上地表异质性和相干结构之间的相互作用，以及它们对描述标量通量的莫宁-奥布霍夫相似理论（MOST）的崩溃的影响。在点尺度上，MOST 的分解源于传达地表异质性特征的平流项和承载相干结构特征的垂直传输项。在进行空间平均的景观尺度上，色散通量是由地表异质性和相干结构之间的相互作用产生的。这项工作通过通量预算方程及其空间平均版本将现场实验和大涡模拟（LES）结合在统一的框架下。现场实验将在爱达荷州爱达荷福尔斯相对平坦但不均匀的地形上进行，其中有一座 62 米高的塔和几个短塔，配备涡流协方差系统、声雷达、带有 RASS 的风廓线仪、35 个中视网站、和其他仪器。现场工作将以三维和高分辨率提供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 LES 运行将用于将现场实验提供的见解从点扩展到景观尺度。将采用基于时间和空间象限分析的新颖方法来模拟色散通量。现场实验生成的新数据集将为探索与大气边界层和陆地表面过程相关的其他主题提供机会。除了辅导两名研究生和两名本科生外，该项目还将涉及多个教育和外展部分。它将为 PI 教授的边界层气象学、应用气象学和流体动力学几门研究生和本科课程的学生生成小型项目。将制作短片和视频，向研究人员和公众展示研究结果的重要性。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。