Abstract
The increasing number of wind farms installed in the North Sea has an impact on the downstream wind speed. This has been hypothesized as well for sea state properties. Wave effects can be expected in particular in fetch-limited conditions with offshore wind directions. With systematic flights deploying an airborne laser scanner, these impacts are shown directly for the first time. The flights were conducted perpendicular to the main wind direction upstream and downstream of the cluster of the offshore wind parks Amrumbank West, Nordsee Ost, and Meerwind Süd/Ost. The flight legs covered the area potentially influenced by the wind parks and the undisturbed area next to the wind parks. The analysis of the spectral energy distribution shows a re-distribution of the wave energy in the downstream area with enhanced energy at smaller wavelengths. The effect is still clearly visible at a distance of 55 km. As the sea surface constitutes the link between the atmosphere and the ocean, it is very likely that wind parks modify the properties of the water column as well.
Highlights
E.g., a temperature inversion induced by the flow of warm air masses from land above colder air masses influenced by the water surface, reduced wind speed in the downstream area has been reported to an extent of several 10 km [5]
As more k-vectors are present for the convolution into an omnidirectional spectrum toward higher frequencies, the relative estimation error of the variance density estimate is reduced toward high frequencies according to [30] with σ = 100 % · N −0.5 (7)
Where N denotes the number of k-vectors for a specific omnidirectional wavenumber
Summary
The waves observed in this study are so-called surface gravity waves. These waves are generated by the wind and can have wavelengths of up to several hundred meters with periods up to about 20 s. The nonlinear interaction component is the only part of the model that can be derived from first-order physics principles far Both dissipation and wind generation source functions contain empirical components, which were tuned to observations. In fetch-limited conditions as present during the observations discussed in this study, most of the energy input from the wind is absorbed by the spectral region around the peak of the wave spectrum. This energy is moved by nonlinear processes both to longer and shorter waves.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
