Large-Eddy Simulation studies of Land-Atmosphere Interaction over Complex Terrain, Using New-Generation Dynamic Models

[909679]大气边界层近似理论（ABL）是水文学中获取区域尺度蒸发量的主要实用方法。该理论是基于均匀的陆地表面，但由于ABL中的湍流，它已经被发现在非均匀的自然陆地表面的实地研究中起作用，它有效地混合了景观中的各种来源和不均匀性。陆地表面不同斑块上形成的内部边界层如何在ABL中混合，以及哪些表面和边界层特征对控制ABL动力学和结构至关重要，目前还不清楚。本文将对非均质热源和水汽源进行ABL湍流流动和输运的大涡模拟（LESs），以确定不同分层条件下湍流混合的混合特性。非均质粗糙度也将被考虑。数值模拟将采用并适应新一代亚网格尺度模型，这些模型特别适合于捕捉复杂环境中未解决的小尺度湍流物理，其中湍流偏离了各向同性惯性范围行为的经典假设。这些模型是基于以下因素的组合：(a)动态过程，它消除了指定可调模型系数的需要；(b)动态模型的概化，以考虑湍流惯性范围以外应用（如ABL的近地动力学）系数的尺度依赖；(c)拉格朗日平均方法，允许将动态模型应用于空间非均匀流动条件。(d)混合相似或非线性模型，更真实地描述了亚网格尺度过程，包括动能和标量方差的反向级联，以及相干结构与亚网格尺度通量和耗散的关系。高分辨率LES将用于确定地表尺度对大气动力学和输送的作用。研究结果将首先与众所周知的在统计上均质陆地表面上的实地观测结果进行比较，然后扩展到更一般的陆地表面格局和稳定性条件。通过一系列的模拟，其中地表湿度、温度、粗糙度和几何排列是系统变化的，我们将量化那些在非均匀地形上驱动陆地-大气交换动力学的特征。最终，这些信息将用于获取复杂地形上区域尺度蒸发的新策略

9909679Parlange Similarity theory of the atmospheric boundary layer (ABL) is the main practical approach in hydrology to obtain regional-scale evaporation. The theory is based on a uniform land surface, yet it has been found to work in field studies over heterogeneous natural land surfaces due to the turbulent flow in the ABL, which efficiently blends the various sources and inhomogeneities across the landscape. It is not well understood how internal boundary layers formed over various patches on the land surface are blended in the ABL and what surface and boundary layer features are critical to controlling ABL dynamics and structure. Large eddy simulations (LESs) of turbulent flow and transport in the ABL will be conducted over heterogeneous sources of heat and water vapor to identify the blending properties of turbulent mixing under various conditions of stratification. Heterogeneous roughness properties will also be considered. Numerical simulations will employ and adapt new-generation subgrid-scale models that are particularly well suited to capture unresolved small-scale turbulence physics in complex environments in which turbulence deviates from the classical assumptions of isotropic inertial-range behavior. The models are based on a combination of (a) the dynamic procedure which eliminates the need to specify tunable model coefficients, (b) a generalization of the dynamic model to account for scale dependence of the coefficients for applications outside of the inertial range of turbulence such as the near-ground dynamics of the ABL, (c) the Lagrangian averaging method, which allows applications of the dynamic model to spatially non-homogeneous flow conditions, and (d) the mixed similarity or nonlinear model, which provides more realistic descriptions of subgrid-scale processes, including reverse cascade of kinetic energy and scalar variance, and the relationship between coherent structures and subgrid-scale fluxes and dissipation. High-resolution LES will be conducted to identify the role of land surface scale on atmospheric dynamics and transport. The results will first be compared with well-known field observations over statistically homogeneous land surfaces and extended to more general land surface patterns and stability conditions. Through a series of simulations, where surface humidity, temperature, roughness and geometric arrangements are varied systematically, we will quantify those features which drive the dynamics of land-atmosphere exchange over heterogeneous terrain. Ultimately, this information will be used in new strategies for obtaining regional-scale evaporation over complex terrain