Collaborative Research: Perdigao--The Stable Boundary Layer over Complex Terrain

大气的最底层，即边界层，其特征从白天频繁的空气运动混合到夜间的稳定和分层状态。然而，尽管夜间边界层整体稳定，但仍有间歇性的湍流空气运动。这项研究将利用葡萄牙Perdigao的一项大型野外活动，研究复杂地形下的稳定边界层。更好地了解复杂地形中的湍流和风流将改进数值天气模型，并支持诸如空气质量、航空、风能、交通和气候模型等关键应用。该项目还将有助于下一代科学家的教育和培训，研究人员将通过各种外联努力为公众科学素养做出贡献。Perdigao的现场试验是欧洲提高风能生产效率的大型运动的一部分。该奖项将带来一个基础研究组成部分，重点研究复杂地形中稳定边界层中控制湍流间歇性的机制。这将是观测和建模工作的结合，额外的观测数据将由科罗拉多大学博尔德分校的系留提升系统（TLS）和三个剖面激光雷达提供。建模组件将使用带有浸入边界方法（IBM）的WRF模型，以便在陡峭的地形表面上进行模拟，并且模型模拟将能够在水平方向上嵌入5米，在垂直方向上嵌入0.5米。研究人员计划解决以下问题：(i)湍流预算的结构是什么，特别是湍流耗散率，在山谷内部和之上？它是如何随着稳定性的演变而变化的，特别是在稳定的条件下？（ii）湍流的间歇性是由什么机制产生的？在大涡模拟中，山谷内部和山谷上方的间歇性湍流是如何表现的？（iii）相干结构如何受到风力涡轮机尾流的影响？这对间歇性有什么影响？需要什么样的物理参数化和数值技术才能在复杂地形中适当地综合中尺度和微尺度模式？

The lowest part of the atmosphere, known as the boundary layer, changes character from being well-mixed with frequent air movement during the day to a nocturnal state of stability and stratification. However, despite the overall stability of the nocturnal boundary layer, there is still intermittent turbulent air movement. This study will leverage a large field campaign effort in Portugal, known as Perdigao, to study the stable boundary layer in complex topography. Better understanding of turbulence and wind flow in complex terrain will improve numerical weather models and support critical applications such as air quality, aviation, wind energy, transportation, and climate modeling. The project will also contribute to the education and training of the next generation of scientists and the researchers will contribute to public literacy of science through various outreach efforts.The Perdigao field experiment is part of a large European campaign to improve the efficiency of wind energy production. This award will bring in a basic research component with a focus on studying the mechanisms controlling turbulence intermittency in stable boundary layers in complex terrain. This will be a combined observational and modeling effort, with additional observational data provided by the Univ. of Colorado at Boulder's Tethered Lifting System (TLS) and three profiling Lidars. The modeling component will make use of the WRF model with an immersed boundary method (IBM) implemented in order to enable simulation over steep terrain surfaces, and the model simulations will be able to nest down to 5m in the horizontal and 0.5m in the vertical. The researchers plan to address the following questions: (i) What is the structure of turbulence budgets, especially turbulence dissipation rate, within and above the valley? How does it change with the evolution of stability, particularly under stable conditions? (ii) What mechanisms generate intermittency of the turbulence? How is the intermittent turbulence within and above the valley represented in large-eddy simulations? (iii) How are coherent structures affected by the wind turbine wake? How does this influence intermittency? (iv) What physical parameterizations and numerical techniques are needed to appropriately integrate mesoscale and microscale models in complex terrain?