Airborne LiDAR Measurements of Sea Surface Properties in the German Bight

Abstract

Sea surface measurements are mainly gathered using satellite altimeter, buoy, and platform measurements. Satellite measurements typically have a coarse spatial resolution and need recalibration in coastal regions, whereas point measurements of buoys only represent limited areas around the measurement point because of the complex coastal bathymetry. Wave models (WAM) are used to expand the sparse observations in space and time. As a part of the project WIndPArk far-field (WIPAFF), which focused on wakes behind offshore wind farms, extensive airborne light detection and ranging (LiDAR) measurements of ocean waves in the German Bight were performed for more than 90 h. The LiDAR data processed for significant wave height can be used to validate and improve WAM models for complex areas and fill the observation gap between satellite altimeter and point measurements. This creates a detailed picture of the sea surface for coastal engineering and environmental applications. After introducing the measurement techniques and the data situation, intercomparisons between the available airborne measurements, buoy data, and WAM model output are presented to provide an insight into the potential of airborne LiDAR measurements for wave characterization and wave model validation.

The Impact of Offshore Wind Farms on Sea State Demonstrated by Airborne LiDAR Measurements

“…The WIPAFF data set of an airborne laser scanner was used to derive the significant wave height for all flights. Very good agreement was found for the comparison with buoy data during overpasses [13]. The significant wave height was further compared to the results of a wave model (WAM).…”

“…Good agreement was found for large water depths. However, in particular in coastal areas with shallow bathymetry, the WAM underestimated the significant wave height [13].…”

“…The system and its measurements are introduced in Bärfuss et al [13] and Lampert et al [7], whereas datasets preprocessed for sea surface elevation variance are available in Bärfuss et al [6]. In addition to processing the variance of the surface elevation measurements η to estimate the significant waveheight H s ≈ 4 var(η) = H m0 , the observed surface can be transformed into the spectral domain and, subsequently, into the directional sea surface variance density spectrum.…”

In situ airborne measurements of atmospheric parameters and airborne sea surface properties related to offshore wind parks in the German Bight during the project X-Wakes

“…The laser scanner VZ-1000 (Riegl, Austria) is included onboard the Dornier 128 to measure sea state properties through an opening in the fuselage. With this setup it is possible to measure the significant wave height (Bärfuss et al, 2020) and derive wave spectra (Bärfuss et al, 2021) along the flight path. The laser scanner covers a line of sight range of up to 450 m.…”

Fit-for-Purpose Information for Offshore Wind Farming Applications—Part-II: Gap Analysis and Recommendations

“…Regular measurement campaigns are performed with ships (e.g., Ludwig Prandtl), e.g., including scanfish measurements. Dedicated airborne campaigns to analyze the OWF impacts on sea state were conducted by the University of Braunschweig [37,38].…”