Posters

Abstract

Low-Level Jets (LLJs) represent a critical underrepresented atmospheric phenomenon for near-shore and offshore wind farms, as they are intersecting with turbine’s rotor heights and generate strong vertical wind shear that can influence both energy production and the structural loads of a turbine. This study investigates the characteristics and impacts of LLJs in the Marmara Sea using floating LiDAR observations from two different near-shore locations. High-resolution vertical wind profiles were obtained from floating LiDAR systems installed close to the coastline, while atmospheric stability was independently derived from meteorological mast measurements at nearby coastal sites. Futhermore, a comparison with land-based LiDAR measurements was conducted to isolate the influence of the marine boundary layer on jet evolution. The stability information was used to assess the role of stratification in controlling LLJ formation and persistence in the near-shore marine boundary layer. The results quantify the LLJ as a systematic feature of the offshore wind climate, occurring with a frequency of approximately 2.9% at the offshore location, significantly outperforming the coastal reference site which registered an occurrence rate of only 0.45%. While the onshore jets remained fragmented and lower, typically at heights lower than 100 meters, the offshore jets formed a high-frequency regime with core heights ranged between 120 and 140 meters, which creates a high-shear zone directly across the rotor plane. A distinct spatial evolution was observed; unlike terrestrial jets which dissipated by sunrise, the offshore regime maintained strong activity into the late morning (06:00–09:00 UTC), suggesting that the stable marine surface effectively decouples the flow, allowing the jet to carry on longer. Atmospheric stability was analysed using the vertical gradient of potential virtual temperature (dθv/dz) derived from the near-cost mast measurements. The analysis identifies a strict thermodynamic control mechanism, where the transition to stable stratification (θv/dz > 0) decouples the flow from surface friction, directly driving the acceleration of the nocturnal jet core. LiDAR wind profiles reveal strong vertical wind shear during LLJ events, leading to non-uniform inflow conditions across the rotor. Furthermore, the analysis extends to high-frequency (1-second resolution) measurements to characterize turbulence intensity profiles within the jet core versus the shear layers. In contrast to the increased turbulent kinetic energy at the rotor tips, preliminary results showed a decoupling of shear and turbulence, where the jet core displays laminar flow with low TI. These results imply that the complex fatigue environment in the Sea of Marmara may be underestimated by standard design assumptions. We conclude that capturing these stability-driven shear events requires pairing floating LiDARs with coastal masts, providing a necessary upgrade over conventional observation methods that often miss these transient dynamics.