The AWAKEN wind farm benchmark – Part 1: Observed conditions

Wind turbine wakes significantly reduce downstream performance, yet accurately modeling their sensitivity to atmospheric stability and terrain remains a challenge. To address this, the International Energy Agency Wind Technology Collaboration Programme Task 57 launched a new wind farm wake benchmark leveraging high-resolution observations from the American WAKE experimeNt (AWAKEN). This paper, Part 1 of a two-part series, details the observational dataset and the selection of 24 August 2023 as the case study for the benchmark. This date was selected for its canonical diurnal cycle, which features a low-level jet with strong nocturnal stratification and high turbulence during the daytime. Analysis of the observational data reveals that despite the relatively simple terrain, interactions between the low-level jet and topography drove significant spatial variability in wind flow, leading to turbine power differences of up to 80 % across the considered wind farm. These findings demonstrate that a single vertical profile is insufficient to characterize wind plant inflow even in moderately complex terrain and that terrain-induced flow modifications can outweigh wake losses under stable stratification. The observed conditions documented here, together with the openly released dataset, constitute a unique multi-scale reference case for wake model validation at a large operating wind plant and provide the foundation for the modeling performance evaluation presented in the companion Part 2 paper.