Motion compensation and sensor time synchronization for Doppler wind LIDAR on an uncrewed lightship

Abstract. Platform motion can distort the beam geometry and introduce errors into radial velocity measurements from floating Doppler wind LIDAR (Light Detection and Ranging) systems. Building on an earlier assessment of lightship-based wind measurements, this study investigates retrospective time synchronization between sensors and motion compensation for a wind LIDAR installed on an uncrewed lightship in the German Bight. Global Positioning System (GPS) and attitude and heading reference system (AHRS) measurements are combined with LIDAR radial velocities to correct for platform motion, interpolate observations to nominal heights, and reconstruct wind vectors using a least-squares solution based on five lines of sight (LOS). A time-shift optimization based on the mean sum of squared residuals (SSR) estimates hourly time offsets between the LIDAR and motion-data data, providing a post-processing synchronization approach that could be applied to other Doppler wind LIDAR systems equipped with suitable motion-sensors. Post-processing reduced the variability of high-frequency wind speed estimates, while its effect on the 10-minute mean horizontal wind speed remained small: mean corrected-minus-raw differences ranged from −0.037 m s⁻¹ to −0.028 ⁻¹ in three evaluated heights. The small effect on the mean wind speed is consistent with the finding of Cañadillas et al. (2026), who analysed measurements over a longer period. LIDAR-derived turbulence intensity decreased by approximately 0.03 to 0.04 in absolute terms, although the contributions of motion compensation and wind-vector-reconstruction choices were not isolated. A simple correction based on the 10-minute mean platform heading yielded 10-minute wind directions close to those obtained with full motion compensation, with standard deviation differences below 0.71°. These findings support the practical use of this heading-based correction to obtain geographically referenced mean wind directions under the investigated conditions. Onboard meteorological observations provide a plausibility check for the corrected winds, but the absence of independent reference measurements at comparable heights prevents a full assessment of their accuracy. Together with the earlier assessment, this study provides a practical basis for refining the processing of lightship-based wind measurements and helps future users of the planned open-access dataset select correction methods suited to their temporal scales and applications.