Comparison of turbulence measurements by a CSAT3B sonic anemometer and a high-resolution bistatic Doppler lidar

• Published in: Atmospheric measurement techniques Vol. 13; no. 2; pp. 969 - 983
• Main Authors: Mauder, Matthias, Eggert, Michael, Gutsmuths, Christian, Oertel, Stefan, Wilhelm, Paul, Voelksch, Ingo, Wanner, Luise, Tambke, Jens, Bogoev, Ivan
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 02.03.2020; Copernicus Publications
• Subjects: Anemometers; Atmospheric models; Atmospheric turbulence; Comparative analysis; Computational fluid dynamics; Covariance; Doppler lidar; Doppler sonar; Eddy covariance; Energy research; Flow distortion; Frequency ranges; Friction; High resolution; Instruments; Intercomparison; Lidar; Lidar measurements; Mathematical models; Mean winds; Novels; Numerical models; Optical radar; Prejudice; Remote sensing; Resolution; Sonic anemometers; Spectra; Standard deviation; Statistical analysis; Statistical methods; Transducers; Turbulence; Turbulence (Fluid dynamics); Turbulence measurement; Turbulence measurements; Turbulence spectra; Velocity; Vertical wind velocities; Wind measurement; Wind measuring instruments; Wind power; Wind power plants; Wind speed; Wind velocities
• ISSN: 1867-8548; 1867-1381; 1867-8548
• DOI: 10.5194/amt-13-969-2020

Accurate measurements of turbulence statistics in the atmosphere are important for eddy-covariance measurements, wind energy research, and the validation of atmospheric numerical models. Sonic anemometers are widely used for these applications. However, these instruments are prone to probe-induced flow distortion effects, and the magnitude of the resulting errors has been debated due to the lack of an absolute reference instrument under field conditions. Here, we present the results of an intercomparison experiment between a CSAT3B sonic anemometer and a high-resolution bistatic Doppler lidar, which is inherently free of any flow distortion. This novel remote sensing instrument has otherwise very similar spatial and temporal sampling characteristics to the sonic anemometer and hence served as a reference for this comparison. The presented measurements were carried out over flat homogeneous terrain at a measurement height of 30 m. We provide a comparative statistical analysis of the resulting mean wind velocities, the standard deviations of the vertical wind speed and the friction velocity and investigate the reasons for the observed deviations based on the turbulence spectra and co-spectra. Our results show an agreement of the mean wind velocity measurements and the standard deviations of the vertical wind speed with a comparability of 0.082 and 0.020 m s−1, respectively. Biases for these two quantities were 0.003 and 0.012 m s−1, respectively. Slightly larger differences were observed for friction velocity. Analysis of the corresponding co-spectra showed that the CSAT3B underestimates this quantity systematically by about 3 % on average as a result of co-spectral losses in the frequency range between 0.1 and 5 s−1. We also found that an angle-of-attack-dependent transducer-shadowing correction does not improve the agreement between the CSAT3B and the Physikalisch-Technische Bundesanstalt (PTB) lidar effectively.