American WAKE Experiment (AWAKEN) Field Campaign Report: U.S. Department of Energy (DOE), Office of Science

The American WAKE experimeNt (AWAKEN) was a large-scale, international collaborative field campaign funded primarily by the U.S. Department of Energy (DOE) Wind Energy Technologies Office. Its main purpose was to gather detailed observations of wind farm-atmosphere interactions to improve understanding of wind farm physics, validate and improve simulation tools, lower uncertainties in wind farm modeling, understand environmental impacts, and ultimately reduce the cost and increase the reliability of wind energy systems. The campaign specifically focused on seven testable hypotheses that include characterizing wind turbine and wind farm wake effects, wind farm blockage, turbulent mixing, structural loading impacts, local environmental impacts, and testing wind farm control technologies. AWAKEN was a highly collaborative effort involving numerous agencies, including: DOE, through the Wind Energy Technologies Office and the Office of Science Atmospheric Radiation Measurement (ARM) User Facility, the U.S. Department of Commerce through the National Oceanic and Atmospheric Administration, many American universities, and internationally funded collaborators from Germany and Brazil. The campaign was located in northern Oklahoma, specifically in a region near DOE's ARM Southern Great Plains (SGP) long-term atmospheric observatory. The campaign leveraged the extensive existing ARM infrastructure, historical data, and ongoing measurements, particularly from the ARM SGP Central Facility. Additional AWAKEN-specific instrument sites were deployed around five wind farms in the area, several kilometers south of the ARM facility. The ARM Mobile Facility, AMF3, was also used at these sites. The AWAKEN field campaign began instrument deployment in September 2022 and ran through July 2025. Specific intensive operating campaigns, such as the mobile lidar and aircraft measurements, were conducted in August and September 2023, and tethersonde measurements occurred during October 2024. Key observations and initial results from AWAKEN provide critical insights into wind farm physics and environmental impacts. The campaign saw the first land-based, long-duration use of X-band dual-Doppler radar systems for wind energy applications, capable of reconstructing wind fields over an approximate 35x35-km domain, which documented various wind phenomena including a tornadic event and thunderstorm outflows. These radar observations also showed that the wake of one wind farm can extend at least 15 km downstream under specific stable atmospheric conditions. Preliminary analyses of atmospheric boundary-layer interactions identified a pattern of stronger lower-atmospheric mixing at near-farm sites compared to far-field locations. Initial observations from sonic anemometers indicated that near-surface turbulence kinetic energy within the wind farm was significantly modified, being more than 50% larger at an in-farm site compared to an upwind site in stable conditions. Furthermore, observations of nocturnal low-level jets revealed key findings about how low-level jet height impacts wake recovery, with faster recovery largely occurring due to enhanced entrainment of vertical momentum flux. AWAKEN was also notable for the first large-scale deployment of thermodynamic profilers around wind farms, the temperature profiles of which substantiated the theory of nighttime warming of the surface layer in turbine wakes by correlating with the mixing of warm air aloft enabled by wake-added turbulence. Lidar measurements were used to characterize the variability of wake mean velocity and turbulence intensity under different atmospheric stability regimes, showing significant variability in the downstream evolution of wind farm wakes depending on incoming wind shear. Dual-Doppler lidar measurements also suggested that wind farm blockage can cause standard ground-based lidar wind profiling methods to underestimate inflow wind speed, particularly under stable conditions, due to persistent horizontal gradients in the flow upwind of the wind farm. Finally, analysis indicated that even in regions with relatively simple topography, local terrain features can induce significant spatial variability and flow acceleration, especially under certain atmospheric conditions, adding complexity and challenging the observation of wind farm-specific phenomena. This extensive data set is now being used for validating and improving various simulation tools, including through international benchmark studies. The data is publicly available at the DOE Wind Data Hub and the authors encourage usage by the atmospheric science and wind energy community for further study.