Microfronts and Other Nocturnal Submeso Motions over Microtopography

微地形上的微锋和其他夜间亚细观运动

• 批准号: 2309208
• 负责人: Larry Mahrt
• 金额: $ 47.3万
• 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: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309208&HistoricalAwards=false
• 关键词: Microfronts; Other; Nocturnal; Submeso; Motions

This award examines the boundary layer of air adjacent to the ground surface that cools at night. Strongest cooling occurs with clear skies and low wind speeds. This situation is poorly understood compared to other boundary layers with more significant winds or daytime heating. The strong cooling leads to practical issues including freezing street surfaces and frost damage to sensitive crops. The strong surface cooling also reduces vertical mixing and thus increases the probability of high concentrations of pollutants. The weak winds correspond to large variability of wind direction that spreads the pollutants over a variety of wind directions. This process is currently hard to predict. Formation of dense fog is another outcome of the strong cooling and weak vertical mixing. Local spatial variation of the surface cooling is an important feature requiring more attention. This project will increase understanding through analysis of intense measurements from different sites. Each site contains a network of clustered stations. The above analyses will improve the boundary-layer part of forecast computer models. The general analysis of different subclasses of very stable nocturnal boundary layers, and the relation of submeso motions to these subclasses, will be investigated. Very stable nocturnal boundary layers most often occur with strong stability associated with low wind speeds and clear skies. Submeso motions occur on scales just larger than the largest turbulent eddies but smaller than the mesoscale motions. Submeso motions include microfronts, wave motions, meandering motions, and more complex structures. These motions densely populate the very stable boundary layer. The analyses will be based on time series, spatial information across networks, and combined time-space domains from different datasets. The analysis will first concentrate on microfronts. The first stage focusses on increasing horizontal gradients of temperature. The second stage includes horizontal convergence that concentrates horizontal gradients into microfronts. Analysis of other submeso motions will follow with both individual analyses of each type of submeso motion and collective analysis of all submeso motions. Examination of the large wind-direction variability caused by submeso motions will be examined in detail. Additional data sets will be evaluated with possible recommendation of a new tailored field program.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.

该奖项研究了与夜间冷却的地面相邻的空气边界层。 晴朗的天空和低风速会发生最强的冷却。 与其他有明显的风或白天加热的边界层相比，这种情况知之甚少。强烈的冷却导致实际问题，包括冻结街道表面和对敏感农作物的霜冻损害。 强表面冷却还会减少垂直混合，从而增加高浓度污染物的可能性。弱的风对应于风向的巨大变化，将污染物传播到各种风向。目前很难预测此过程。密集雾的形成是强烈冷却和弱垂直混合的另一个结果。 表面冷却的局部空间变化是需要更多关注的重要特征。 该项目将通过分析来自不同站点的强烈测量来提高理解。 每个站点都包含一个集群站网络。 上述分析将改善预测计算机模型的边界层部分。对非常稳定的夜间边界层的不同亚类的一般分析以及对这些亚类的关系的关系。 非常稳定的夜间边界层最常发生与低风速和晴朗的天空相关的强稳定性。 尺度上的尺度比最大的湍流涡流发生，但比中尺度运动小。 群体运动包括微梯，波动运动，蜿蜒的运动和更复杂的结构。 这些运动密集地填充了非常稳定的边界层。 分析将基于时间序列，跨网络的空间信息以及来自不同数据集的时间间隔域的组合。 该分析将首先集中在微铁上。第一阶段的重点是增加温度的水平梯度。 第二阶段包括将水平梯度集中到微梯的水平收敛。 对其他子索动作的分析将遵循每种类型的集合运动的单个分析以及对所有子动议的集体分析。 将详细检查由子动议引起的大风向变异性的检查。 将在新的量身定制的现场计划的建议下评估其他数据集。该奖项反映了NSF的法定任务，并且使用基金会的知识分子优点和更广泛的影响审查标准，认为值得通过评估值得支持。