The Implications of Surface Heterogeneity and Mesoscale Variability on the Dynamics of Stable Atmospheric Boundary Layers

该奖项为稳定大气边界层（SABL）的研究提供资金，即在稳定分层抵抗垂直位移的情况下，目的是更深入地了解最接近地球表面的这一层内湍流和运输的动力学和结构。 研究人员计划通过探索SABL的基本动力学如何受到表面异质性和中尺度大气变化的影响来实现这一目标。 这项工作将基于大涡模拟（LES）类型的计算机建模，使用数值代码和亚网格尺度模型，已被验证为稳定的流动。 计划中的研究围绕着四个主要问题：（1）表面粗糙度和热不均匀性如何改变湍流动能（TKE）产生-耗散平衡？(2)在稳定性强的地区，TKE的水平输送能产生比静止局部条件下预期的高得多的地面通量吗？(3)中尺度变率如何影响SABL中的紊流结构、产生和输送？（4）地面非均匀性和/或中尺度变率是否显著增加SABL TKE水平，它们能否解释在粗网格（非LES）模式中实现闭合所需的额外湍流，以及如何将这些信息整合到这些模式中？ 为了追求这些主题，研究人员将模拟不同中尺度强迫和表面粗糙度特征条件下的流动，计算TKE预算的所有项，并对流场进行适当的正交分解。 分析的最后一步将是在这样的模拟中同时包括表面非均匀性和中尺度变率，以探索它们潜在的相互作用。这项工作的智力价值集中在改进计划的数值试验提供的理想化和受控SABL条件的表示，这反过来又使研究人员能够分别和同时研究表面异质性和中尺度变化的影响。 这种方法将允许定性和定量地了解与这两个构件相关的动态，并以数据驱动的实地实验研究极具挑战性的方式进行数值计算。研究的更广泛影响将包括博士后研究人员和研究生的教育和培训，以及本科生和/或高中生通过外部资助的项目参与这项研究。 这项工作将有利于那些致力于改善大气边界层和陆地-大气相互作用在大尺度大气模型中的表现的合作者，并可能与从污染扩散到风力发电等领域的研究人员有关。

This award provides funding for study of the stable atmospheric boundary layer (SABL), i.e. in situations of stable stratification resisting vertical displacement, with the goal of producing a deeper understanding of the dynamics and structure of turbulent flow and transport within this layer nearest the earth's surface. The researchers plan to accomplish this by exploring how the basic dynamics of the SABL are impacted by surface heterogeneity and mesoscale atmospheric variability. The work will be based on large eddy simulation (LES) type computer modeling using a numerical code and subgrid scale model that have been validated for stable flows. The planned research centers around obtaining answers to four main questions: (1) How is the turbulent kinetic energy (TKE) production-dissipation equilibrium altered by the roughness and thermal heterogeneities of the surface?; (2) Can horizontal transport of TKE produce much higher surface fluxes over areas with strong stability than would be expected under quiescent local conditions?; (3) How does mesoscale variability affect turbulence structure, production and transport in the SABL?; and (4) Do surface heterogeneity and/or mesoscale variability significantly increase SABL TKE levels, can they account for the extra turbulence needed to achieve closure in coarse-mesh (non-LES) models, and how can this information be integrated into such models? To pursue these topics, the researchers will simulate flows under conditions of varying mesoscale forcing and surface roughness characteristics, compute all terms of the TKE budget, and perform a proper orthogonal decomposition of the flow fields. The last step of the analysis will be to simultaneously include both surface heterogeneity and mesoscale variability in such simulations to explore their potential interactions.The intellectual merit of the work is centered on improved representation of idealized and controlled SABL conditions that the planned numerical experiments provide, which will in turn allow the researchers to study the effect of surface heterogeneity and mesoscale variability both separately and concurrently. This approach will allow a qualitative and quantitative understanding of the dynamics associated with these two building blocks on a numerical basis in ways that are extremely challenging to pursue from data-driven field experimental studies.The broader impacts of the research will include the education and training of a post-doctorate researcher and graduate student, as well as involvement of undergraduate and/or high school students in this research through an externally funded program. The work will benefit collaborators who are working to improve the representation of atmospheric boundary layers and land-atmosphere interactions in larger-scale atmospheric models, and potentially be relevant to researchers in fields from pollution dispersion to wind power generation.