Collaborative Research: Understanding Interactions between Mesoscale and Microscale Flows in the Stable Boundary Layer over Shallow Terrain

合作研究：了解浅层稳定边界层中尺度流和微尺度流之间的相互作用

• 批准号: 2220664
• 负责人: Jielun Sun
• 金额: $ 14.41万
• 依托单位: NorthWest Research Associates, Incorporated
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2220664&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Interactions; between

Atmospheric flows under unstable conditions (e.g., sunny days) are better understood than that under stable conditions which often occur at night. If the terrain is not perfectly flat or the surface is vegetated, flows become even more difficult to understand. This uncertainty means nighttime weather forecasts can lack accuracy. This is particularly true in slightly sloping topography as seen through much of the central US. This project will answer fundamental physics questions that exist for stable conditions over much of the planet including: How do plant, terrain, and elevation changes impact atmospheric flows? How do the impacted atmospheric flows interact with flows from other regions? What special flows (like down gully cold air flow; flows colliding) exist in gently sloped areas? This project will use previously collected experimental data to deduce empirical relationships defining when, where, and why these phenomena are likely to occur. This improvement of current theoretical frameworks will further understanding of nighttime pollutant transport and transformation. Public health and safety can benefit from improved quantitative prediction of transport of chemical or biological hazardous pollution. The agricultural community will benefit from increased knowledge of physical processes controlling field-scale temperature, including those affecting crop health and those leading to patches of frost and subsequent crop loss, a major challenge in ensuring global food security. Using unique observations taken during the NSF funded Stable Atmospheric Variability ANd Transport (SAVANT) campaign, this work will lead to an improved understanding of impacts of shallow complex terrain on mechanical and thermodynamic properties of the stable boundary layer and to fill the knowledge gap in scale interactions between environmental and local flows, specifically with respect to flow patterns that occur in shallow topography. SAVANT collected concurrent in-situ and remote sensing observations during two intensive months in the fall of 2018. The field setup was designed to investigate causes and effects of cold air drainage (down gully) flow in a shallow gully. Tracer plume releases tracked with multiple lidar (Light Detection and Ranging) systems offer the unique opportunity to examine interacting flows at multiple spatial scales. Two critical factors for stable-layer turbulent mixing in complex terrain, wind shear and the stable stratification, will be used to stratify observations to describe the most energetic turbulence eddies using the tower data within and above the main gully, augmented by spatial shear observations from lidars. Vertical scaling factors for turbulent eddies and the influences of drainage flows will be investigated. Factors leading to non-uniform drainage flows (i.e., pulsing, meandering, and converging flows) will be detailed. The unique combination of tower and 3-D lidar observations will allow for improved parameterizations of energy and mass exchanges, which will improve predictive model capabilities.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.

在不稳定的条件下（例如，晴天）的大气流量比在晚上经常发生的稳定条件下更好地理解。如果地形不是完全平坦的，或者表面是植被，则流动变得更加难以理解。这种不确定性意味着夜间天气预报可能缺乏准确性。从美国中部大部分地区可以看出，在略微倾斜的地形中尤其如此。该项目将回答整个地球上稳定条件存在的基本物理问题，包括：植物，地形和高程如何影响大气流？受影响的大气流如何与其他地区的流相互作用？轻轻倾斜的区域中存在哪些特殊流动（例如向下沟渠冷空气流；流相撞）？该项目将使用先前收集的实验数据来推断经验关系，以定义何时，何时何地以及为什么可能发生这些现象。当前理论框架的这种改进将进一步了解夜间污染物的运输和转型。公共卫生和安全可以通过改进化学或生物危险污染的运输定量预测而受益。农业界将受益于对控制野外温度的物理过程的知识，包括影响农作物健康的温度以及导致霜冻堆积的那些温度和后来的作物损失，这是确保全球粮食安全的重大挑战。利用NSF资助的稳定大气变异性和运输（Savant）活动期间进行的独特观察，这项工作将提高人们对浅层复杂地形对稳定边界层机械和热力学特性影响的影响的了解，以填补环境和本地流之间的规模相互作用的知识差距，具体是针对出现在Shallow Possograph中的流动模式。 Savant在2018年秋天的两个密集一次内收集了同时的原位和遥感观测值。该田间设置旨在研究浅沟渠中冷空气排水（向下沟渠）流动的原因和影响。用多个LiDAR（光检测和范围）系统跟踪的示踪羽流释放提供了独特的机会，可以在多个空间尺度上检查相互作用的流量。在复杂的地形，风剪切和稳定分层中稳定湍流混合的两个关键因素将用于对观测值进行分层，以使用主要沟渠内外的塔数据来描述最有能力的湍流涡流，并由liDars的空间剪切量增强。将研究用于湍流涡流的垂直缩放因子和排水流的影响。将详细介绍导致不均匀排水流（即脉冲，弯曲和融合流）的因素。塔楼和3-D LIDAR观察的独特组合将允许改进能源和大规模交流的参数化，这将提高预测模型能力。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响审查标准通过评估来进行评估的。