Simulation of Mountain Forced Turbulence and Boundary Layer Interactions

这项研究涉及一个数值模拟研究，重点是了解山脉如何通过内波破碎，尾流效应以及与大气边界层的相互作用来迫使湍流。 中心目标是确定湍流在地形强迫流中的作用，重点是（i）内波破裂，（ii）边界层相互作用，以及（iii）地形特征对湍流涡旋的直接局部强迫。 研究计划，扩大以前的努力，并侧重于上游边界层的作用和形成湍流与山区被迫流动。这项研究的主要目的是更好地了解湍流和边界层动力学如何修改地形引起的环流。 主要研究者（PI）将针对一系列山脉尺度、水流条件和底部边界条件，模拟理想化二维山脉上的水流。 具体目标是：1）确定上游边界层深度对山波结构的作用; 2）检查波反射层处的解析湍流如何与山波动力学相互作用; 3）评估表面对流加热和阻力对山波特性的作用; 4）检查湍流在背风侧风暴形成中的作用以及陡峭地形对气流分离和转子形成的影响; 5）评估山波阻力的参数化。将通过应用一个既能模拟地形特征又能模拟完全湍流边界层的大涡模拟模型来实现目标。 将对一系列流动条件进行模拟，包括低水平波浪破碎、临界层、转子形成以及表面粗糙度和表面加热的影响。 从这项研究的结果将有助于改进山阻力参数化的发展，通过提供动量通量和流动参数（如弗劳德数），表面边界强迫和边界层深度之间的定量关系。智力优势：这项研究的智力价值是基于山强迫湍流在航空，天气预报和大气环流准确预测方面的重大影响。 这项研究应有助于更好地了解山脉如何在整个对流层中产生湍流，以及表面边界层作用力如何影响山脉引起的内波和湍流。更广泛的影响：这项研究有可能通过提高对山区强迫风暴和当地湍流的预测能力产生广泛的影响，这对飞机运营至关重要。 在较长的时间尺度上，了解山脉如何迫使混合和传输动量将导致在气候预测模型中更好地代表山脉动态。 计划在项目期间由一名研究生参与，结果将发表在公认的同行评审期刊上。 这项研究的内容将纳入研究生课程以及公共学习工作。

This research involves a numerical modeling study centered on understanding how mountains force turbulence through internal wave breaking, wake effects, and interaction with the atmospheric boundary layer. The central goal is to determine the role of turbulence in terrain forced flows with an emphasis on (i) internal wave breakdown, (ii) boundary layer interaction, and (iii) the direct, local forcing of turbulent eddies by terrain features. Research is planned that expands on previous efforts and focuses on the role of the upstream boundary layer and formation of turbulence associated with mountain-forced flows. The main objective of this study is to better understand how turbulence and boundary layer dynamics modify terrain-induced circulations. The Principal Investigator (PI) will simulate flow over an idealized two-dimensional mountain for a range of mountain scales, flow conditions, and bottom boundary conditions. Specific objectives are to: 1) Determine the role of upstream boundary layer depth on mountain wave structure; 2) Examine how resolved turbulence at the wave reflection layer interacts with mountain wave dynamics; 3) Assess the role of surface convective heating and drag on mountain wave characteristics; 4) Examine the role of turbulence in the formation of lee side wind storms and the effects of steep terrain on flow separation and rotor formation; 5) Evaluate parameterizations of mountain wave drag.Objectives will be achieved by applying a large-eddy simulation model that can simulate both terrain features and a fully turbulent boundary layer. Simulations will be conducted for a range of flow conditions that include low level wave breaking, critical layers, rotor formation, and the effects of surface roughness and surface heating. Results from this study will aid in the development of improved mountain drag parameterizations by providing quantitative relationships between momentum flux and flow parameters (e.g. Froude numbers), surface boundary forcing, and boundary layer depth. Intellectual Merit: The intellectual merit of this research is based on the significant impact mountain-forced turbulence has in aviation, weather forecasting, and accurate prediction of the atmospheric general circulation. The research should lead to an improved understanding of how mountains force turbulence throughout the troposphere and how surface boundary layer forcing affects mountain-induced internal waves and turbulence. Broader Impacts: This study has potential for broad impacts by improving predictive capability for mountain forced windstorms and local turbulence that is of importance for aircraft operations. On longer time scales, understanding how mountains force mixing and transport momentum will lead to better representation of mountain dynamics in climate prediction models. Participation by a graduate student for the duration of the project is planned and results will be published in recognized peer-reviewed journals. Elements of this research will be incorporated into the graduate curriculum as well as in public learning efforts.