ABSTRACT Wind energy has been growing steadily in the U.S. and worldwide in the past decades. As wind farms are projected to increase in size and number, however, concerns are rising about possible undesirable effects of wind turbines near the Earth's surface. The literature is highly divided about what these effects could be, including warming, cooling, both, or neither. Only one mechanism, however, has been widely accepted (but never tested) to explain how wind turbines affect the lower boundary layer, namely that turbulence generated in wind turbine wakes enhances vertical mixing near the ground. Wakes are plume-like volumes downwind of wind turbines that are characterised by lower wind speeds and higher turbulent kinetic energy (TKE) than the undisturbed upwind flow. The few observational campaigns that have measured changes in near-surface properties by wind turbines have not provided an answer with respect to vertical mixing near the ground. To fill this knowledge gap, the VERTEX (VERTical Enhanced miXing) measurement campaign was conducted in August-October 2016 near a large wind turbine in coastal Delaware, using 15 surface flux towers, a 50-m meteorological tower, a radiometer, and two scanning lidars. During VERTEX, lidar scans and a wake detection algorithm were used to detect wake events and identify which sites were affected by the wake of the wind turbine. TKE, momentum and heat fluxes near the ground were compared between the sites below the wake and those outside of it. Preliminary findings based on two case studies (30 August and 20 September 2016) suggest a lack of enhancement of vertical mixing near the ground.

中文翻译：

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VERTEX 现场活动：观察风力涡轮机尾流的近地效应

摘要 在过去的几十年里，风能在美国和世界范围内一直在稳步增长。然而，随着风力发电场的规模和数量预计会增加，人们越来越担心地球表面附近的风力涡轮机可能产生的不良影响。关于这些影响可能是什么，包括变暖、变冷、两者兼而有之，文献中存在高度分歧。然而，只有一种机制被广泛接受（但从未测试过）来解释风力涡轮机如何影响下边界层，即风力涡轮机尾流中产生的湍流增强了地面附近的垂直混合。尾流是风力涡轮机顺风的羽状体积，其特征是比未受干扰的逆风流动更低的风速和更高的湍流动能 (TKE)。少数通过风力涡轮机测量近地表特性变化的观测活动并没有提供关于地面附近垂直混合的答案。为了填补这一知识空白，VERTEX（垂直增强混合）测量活动于 2016 年 8 月至 10 月在特拉华州沿海的大型风力涡轮机附近进行，使用了 15 个表面通量塔、一个 50 米气象塔、一个辐射计和两个扫描激光雷达。在 VERTEX 期间，激光雷达扫描和尾流检测算法用于检测尾流事件并确定哪些站点受到风力涡轮机尾流的影响。对尾迹下方和尾迹外部的位置之间的地面附近的 TKE、动量和热通量进行了比较。