09 Aug 2023
 | 09 Aug 2023
Status: this preprint is open for discussion.

Verifying triple and single Doppler lidar wind measurements with sonic anemometer data based on a new filter strategy for virtual tower measurements

Kevin Wolz, Christopher Holst, Frank Beyrich, Eileen Paeschke, and Matthias Mauder

Abstract. In this study, we compare the wind measurements of a virtual tower triple Doppler lidar setup to those of a sonic anemometer located at a height of 90 m above ground on an instrumented tower and with those of two single Doppler lidars to evaluate the effect of the horizontal homogeneity assumption used for single Doppler lidar applications on the measurement accuracy. The triple lidar setup was operated in a 90 m stare and a step/stare mode at six heights between 90 and 500 m above ground, while the single lidars were operated in a continuous scan Velocity-Azimuth-Display (VAD) mode where one of them had a zenith angle of 54.7 ° and the other one of 28.0 °. The instruments were set up at the boundary-layer field site of the German Meteorological Service (DWD) in July and August of 2020 during the FESST@MOL (Field Experiment on sub-mesoscale spatio-temporal variability at the Meteorological Observatory Lindenberg) 2020 campaign. Overall, we found good agreement of the lidar methods for the whole study period for different averaging times and scan modes compared to the sonic anemometer. For the step/stare mode wind speed measurements, the comparability between the triple lidar and the sonic anemometer was 0.47 m s-1 at an average time of 30 minutes with a bias value of -0.34 m s-1. For wind speed measured by one single lidar setup for the same period with an averaging time of 30 minutes, we found a comparability of 0.32 m s-1 at an averaging time of 30 minutes and a bias value of 0.07 m s-1 and values of 0.47 m s-1 and -0.34 m s-1 for the other one, respectively. We also compared the wind velocity measurements of the single and triple lidars at different heights and we found a decreasing agreement between them with increasing measurement height up to 495 m above ground for the single lidar systems. We found, that the single Doppler lidar with the increased zenith angle produced a poorer agreement with the triple Doppler lidar setup than the one with the lower zenith angle, especially at higher altitudes. At a height of 495 m above ground and with an averaging time of 30 minutes the comparability and bias for the larger zenith angle were 0.71 m s-1 and -0.50 m s-1, respectively, compared to values of 0.57 m s-1 and -0.28 m s-1 for the smaller zenith angle. Our results confirm that a single Doppler lidar provides reliable wind speed and direction data over heterogeneous but basically flat terrain in different scan configurations. For the virtual tower scanning strategies, we developed a new filtering approach based on a Median Absolute Deviation (MAD) filter combined with a relatively relaxed filtering criterion for the signal-to-noise-ratio output by the instrument.

Kevin Wolz et al.

Status: open (extended)

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Kevin Wolz et al.

Kevin Wolz et al.


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Short summary
We compared wind measurements using different lidar setups at various heights. The triple Doppler lidar, sonic anemometer, and two single Doppler lidars were tested. Overall, the lidar methods showed good agreement with the sonic anemometer. The triple Doppler lidar performed better than single Doppler lidars, especially at higher altitudes. We also developed a new filtering approach for virtual tower scanning strategies. Single Doppler lidars provide reliable wind data over flat terrain.