Preprints
https://doi.org/10.5194/amt-2022-138
https://doi.org/10.5194/amt-2022-138
 
02 May 2022
02 May 2022
Status: this preprint is currently under review for the journal AMT.

Quantification of Motion-Induced Measurement Error on Floating Lidar Systems

Felix Kelberlau1 and Jakob Mann2 Felix Kelberlau and Jakob Mann
  • 1Fugro Norway AS, Havnegata 9, 7462 Trondheim, Norway
  • 2DTU Wind, Technical University of Denmark, 4000 Roskilde, Denmark

Abstract. Floating lidar systems (FLS) are widely used for offshore wind site assessment and their measurements show good agreement when compared to trusted reference sources. Though, some influence of motion on mean wind speed data from FLS has to be assumed but could not have been quantified with experimental methods yet because the involved uncertainties are larger than the expected impact of motion. This study describes the motion-induced bias on horizontal mean wind speed estimates from FLS with the help of simulations of the lidar sampling pattern of a continuous-wave (CW) velocity-azimuth display (VAD) scanning wind lidar. Analytic modelling is used to validate the simulations. It is found that the error depends on amplitude and frequency of tilt motion, the relative angle between wind direction and tilt motion, and the strength of wind shear. The results are used to quantify the measurement deviation that is caused by motion for the example of the Fugro SEAWATCH Wind LiDAR Buoy (SWLB) carrying a ZX 300M lidar. For the test case of "normal" wave conditions, the bias is as low as 0.04 % and for "strong" waves the estimated error is -0.14 % of the measurement value. The reason for these low errors lies in a fortunate combination of the frequencies of lidar prism rotation and tilt motion.

Felix Kelberlau and Jakob Mann

Status: open (until 22 Jun 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-138', Anonymous Referee #1, 24 May 2022 reply

Felix Kelberlau and Jakob Mann

Felix Kelberlau and Jakob Mann

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Short summary
Floating lidar systems are used for measuring wind speeds offshore and their motion influences the measurements. This study describes the motion-induced bias on mean wind speed estimates by simulating the lidar sampling pattern of a moving lidar. An analytic model is used to validate the simulations. The bias depends on amplitude and frequency of motion as well as wind shear. For the example of the Fugro SEAWATCH Wind LiDAR Buoy carrying a ZX 300M lidar the bias is normally as low as 0.04 %.