At the WiValdi research wind farm operated by DLR in Krummendeich, we have installed two Doppler wind lidars. One lidar serves as a vertical profiler in the wind farm, providing information about wind and turbulence properties throughout the atmospheric boundary layer. The other lidar is mounted on the nacelle of a wind turbine (WT), which is located upstream of a second WT in the main wind direction. This nacelle lidar has been measuring the wind field behind the rotor that is influenced by the turbine wake since WT operations started in November 2023. The measurement strategy to capture long-term wake behavior involves horizontal plan position indicator scans with three elevation angles and an opening angle of 90°. In addition, an inertial measurement unit on the nacelle aids in determining the impact of WT movement on the nacelle lidar measurements. We will describe the methods used to detect and characterize wakes from nacelle lidar measurements, including data filtering and correction for turbine motion. A particular focus will be on wake decay, which is influenced by atmospheric stability and background turbulence, and can not only be obtained from in-situ observations on measurement masts at WiValdi, but also requires lidar data.
Menken et al. (2026) studied this question.