Forced and Natural Turbulence Allowing Studies of Turbulent anIsotropic Conditions (FaNTASTIC- 1)

大气边界层(ABL)的下部--距地球表面约300m的大气部分--经历了夜间冷却的快速转换，导致相干涡旋的时间和空间特性迅速演变。利用一个独特的、高度仪表化的观测区域，该项目将详细观测这些变化(漩涡)。一套现场和遥感仪器将安装在一个有200个涡轮机的风力发电场内(强制湍流)，另一套安装在大约22公里外的自然湍流景观中。研究小组将建立在先前的建模和测量经验的基础上，通过比较强迫湍流和自然湍流来对边界层产生新的理解。智力价值：这项研究的创新源于这样一个事实，即涡轮机或其他景观结构产生的湍流与自然景观(如玉米/大豆田)产生的湍流具有明显不同的光谱特征，并随后对大气交换过程产生明显的影响。莫宁-奥布霍夫相似理论(MOST)不能正确地描述作为大气边界层中心特征的相干涡旋。高分辨率的现场测量将为稳定条件下的MOST提供物理替代，这反过来又将提高天气预报和模拟的技能，特别是在稳定层结条件下。该项目有三个目标：目标1.利用高分辨率近地表湍流测量塔、战略性地放置两个高塔和声雷达来表征各向异性和大的相干湍流涡旋(自然和强迫)。它们是如何在傍晚过渡(EET)期间和之后启动的？当ABL在稳定层结条件下演变时，哪些因素有助于能量守恒？目的2.使用多分辨率分解(MRD)和小波变换方法来识别低频(例如，中尺度)相对于高频(局部湍流)对湍流协方差影响最小的相干结构事件。这些方法如何帮助改进对纯粹由局部湍流驱动的地表通量的描述，而不是受独特强迫(涡轮机)或中尺度(例如，重力波、地表不均匀和地形)影响的地表通量的描述？目标3.结合对目标1和目标2的测量和分析，以及使用WRF和其他模式的中尺度和大涡模拟，以发展对相干涡旋演变和近地面湍流势能(TPE)对ABL EET辐射变化的响应的新的理解。在不同的层结水平下，模式对TKE和TPE的相对大小的敏感性是什么？什么原则应该指导选择一致的涡长尺度来模拟稳定层结中的流动？更广泛的影响：1)这项研究提高了对科学的理解，将产生广泛的科学、社会和经济影响。研究结果将交叉许多STEM学科，并在国家重点研究领域提供新的基础性理解。2)学生学习和培训。这项研究的结果将加强各级学生的教育和经验，重点是培养具有学科深度和跨越学科边界、能够有效地在团队中工作的科学家。在研究生阶段，研究小组将利用爱荷华州立大学NSFIGERT奖的积极计划，从波多黎各大学招收学生。在本科一级，该小组将与IINSPIRE-LSAMP联盟合作，执行支助股是该联盟的伙伴机构。研究团队将与ISU新成立的风能学生组织(WESO)合作，该组织积极拓展到K-12和社区大学层面。5)双向指导体系。在EPSCoR、IGERT、MRI和REU下目前和最近由ISU NSF资助的风能项目的基础上，研究团队建立了近乎同行的导师关系，认识到性别、种族、个人兴趣和气质在成功配对中的作用。

The lower part of the atmospheric boundary layer (ABL) - the part of the atmosphere extending ~300 m from Earth's surface - undergoes rapid transitions with nocturnal cooling, resulting in rapidly evolving temporal and spatial properties of coherent eddies. Using a unique and highly instrumented observation region, this project will observe these variations (eddies) in detail. One set of in-situ and remote sensing instruments will be sited inside a 200-turbine wind farm (forced turbulence) and another set ~22 km away in a matched landscape of natural turbulence. The research team will build on prior modeling and measurement experience to produce new understanding of the boundary layer by comparing forced and natural turbulence.Intellectual Merit:The innovativeness of this study derives from the fact that turbulence generated by turbines or other landscape structures has a distinctly different spectral signature and subsequent distinct influence on atmospheric exchange processes than do natural landscapes, such as fields of corn/soybean. Coherent eddies, known to be the central feature of the ABL, are not represented correctly by Monin-Obukhov Similarity Theory (MOST). The high-resolution in situ measurements will provide a physical alternativeto MOST for stable conditions, which in turn will improve the skill of weather forecasts and simulations, particularly under stably stratified conditions. The project has three objectives: Objective 1. Characterize anisotropic and large coherent turbulence eddies (natural and forced) by use of a high-resolution near-surface turbulence-measurement tower, strategically placed two tall towers, and a sodar. How are they initiated during and after the early evening transition (EET)? What are the contributing factors to energy conservation as the ABL evolves under stably stratified conditions? Objective 2. Employ multi-resolution decomposition (MRD) and wavelet transform methods to identify events of coherent structures that show minimal low frequency (e.g., mesoscale) compared to high frequency (local turbulence) influences on turbulent covariances. How can these methods help refine descriptions of surface fluxes driven purely by local turbulence from those influenced by uniquely forced (turbines) or mesoscale (e.g., gravity waves, surface heterogeneities, and terrain) influences? Objective 3. Combine measurements and analyses of Objectives 1 and 2, together with mesoscale and LES simulations with WRF and other models, to develop new understanding of coherent eddy evolution and the role of turbulent potential energy (TPE) near the surface in response to radiative changes in the EET of the ABL. What is the model sensitivity to the relative magnitudes of TKE and TPE under various levels of stratification? What principles should guide the choice of coherent eddy length scales for simulating flow in stable stratification?Broader Impacts:1) Improved Scientific Understanding from this research will have broad scientific, societal and economic ramifications. The research results will cross-cut many STEM disciplines and provide new fundamental understanding in research areas of high national priority.2) Student Learning and Training. Results from the study will enhance the education and experience for students at all levels, with emphasis on developing scientists with disciplinary depth and ability to reach across disciplinary boundaries, capable of working effectively in teams.3) Outreach to Underserved Populations. At the graduate level the research team will take advantage of the Iowa State University's NSFIGERT award's aggressive plan for recruiting students from the University of Puerto Rico. At the undergraduate level, the team will collaborate with the IINSPIRE-LSAMP Alliance, of which ISU is a partner institution.4) K-14 Engagement. The research team will partner with ISU's new Wind Energy Student Organization (WESO) that has active outreach to both the K-12 and community college level.5) Bi-Directional Mentoring Hierarchy. Built on current and recent ISU NSF-funded wind energy projects under EPSCoR, IGERT, MRI, and REU, the research team has established near-peer mentorships recognizing roles of gender, ethnicity, personal interests, and temperament in pairing-for-success.