## 3 Results
### Average Wake Profiles
[27] from scanning LiDAR wake measurements downstream of a single Enercon 2-MW wind turbine, performed in Switzerland. They reported a steep increase of the wake region right behind the turbine, reaching 0.8 D above the hub height at a distance of 1 D downstream. With increasing distance downstream, the vertical wake extension decreases to about 0.5 D above hub height at a downstream distance of 3.5 D, which is in excellent agreement with our measurements. The lower panels in Figure 5 show expected upstream turbulence intensity (TI) profiles with values increasing towards the ground, which are in accordance with measurements from the German Research Platform FINO1 presented by [PERSON] [28]. Also in agreement with [PERSON] [28], the overall TI values are lowest in stable stratification. At hub height, the average TI values reach 0.08 for stable, 0.10 for neutral and 0.12 for unstable stratification. The profile for stable conditions shows a more or less linear decrease with height, while both neutral and unstable conditions indicate distinctly enhanced TI values for the lowest measurement heights. This could be associated with additional production of turbulence towards the ground, caused mainly by shear for the neutral atmosphere and by buoyancy effects in unstable conditions. The LiDARs situated in the wake of WT6 exhibit a large increase in turbulent activity, with maximum values of TI at hub height and below. The increase of TI is a combined effect created by the turbine structure, the rotating blades and the reduction in average wind speed in the wake. As for the average wind speed profiles, the wake effect on TI is also most pronounced for stable conditions, increasing upstream TI levels at hub height from 0.08 to 0.20 and 0.18 at 1.8 and 3.5 D downstream, respectively. The lowest average TI values in the wake are observed during neutral conditions with 0.17 and 0.15 at 1.8 D and 3.5 D downstream, respectively. Determining the vertical wake expansion by the TI profiles leads for the 1.8 D downstream distance of the wls67 to a similar result as using wind speed deficits (160 m). The TI data from the wls65, measuring further downstream in the wake at 3.5 D, show in contrast a larger vertical wake extension from the TI estimate, reaching altitudes closer to 150 m rather than the 120 m resulting from the wind speed profiles. The higher wake extension in TI goes along with the above-mentioned shear line that entrains ambient air from aloft into the wake, leading to enhanced mixing and with that, higher TI values in this region. In general, the location of the shear line between blade tip height and undisturbed air aloft can introduce measurements errors in the collocated ranged gate, due to probe volume averaging. Similar to the standard deviation of the wind profiles, unstable conditions show the largest standard deviations in the TI profiles. The relative increase from standard deviations up- and down-stream of the wind turbine is larger than for the wind profiles. A way to possibly reduce the enhanced turbulence in wakes is by the intentional increase of blade pitch angles; especially in stable cases, where TI values are highest and wind speeds are mostly below rated wind speed with non-active blade pitching. An earlier pitch control could potentially improve the wake recovery as illustrated for normalized wind and turbulence profiles under different blade pitch angles in Figures 6 and 7. Figures 6 and 7 show that even very small changes in the blade pitch angle have large effects both on the average wind speed and TI profiles. The largest wind speed deficits reduce from 40% to 20% for blade pitch angles greater than 3\({}^{\circ}\). Similarly, the largest TI values reduce from 24% to 15%. The effect seems to be consistent over all measurement heights. This information could in the future be beneficially applied to develop stability and wind speed-dependent wind farm control strategies.