Preprints
https://doi.org/10.5194/amt-2021-417
https://doi.org/10.5194/amt-2021-417

  13 Dec 2021

13 Dec 2021

Review status: this preprint is currently under review for the journal AMT.

Scan strategies for wind profiling with Doppler lidar – An LES-based evaluation

Charlotte Rahlves1, Frank Beyrich2, and Siegfried Raasch1 Charlotte Rahlves et al.
  • 1Leibniz University Hannover, Institute of Meteorology and Climatology, Hannover, Germany
  • 2Meteorological Observatory Lindenberg, Richard-Aßmann-Observatory, German Meteorological Service, Germany

Abstract. Lidar scan techniques for wind profiling rely on the assumption of a horizontally homogeneous wind field and stationarity for the duration of the scan. As this condition is mostly violated in reality, detailed knowledge of the resulting measurement error is required. The objective of this study is to quantify and compare the expected error associated with Doppler-lidar wind profiling for different scan strategies and meteorological conditions by performing virtual measurements implemented in a large-eddy simulation (LES) model. Various factors influencing the lidar retrieval error are analyzed through comparison of the wind measured by the virtual lidar with the ‘true’ value generated by the LES. These factors include averaging interval length, zenith angle configuration, scan technique and instrument orientation. For the first time, ensemble simulations are used to determine the statistically expected uncertainty of the lidar error. The analysis reveals a root-mean-square deviation (RMSD) of less than 1 m s−1 for 10 min averages of wind speed measurements in a moderately convective boundary layer, while RMSD exceeds 2 m s−1 in strongly convective conditions. Unlike instrument orientation and scanning scheme, the zenith angle configuration proved to have significant effect on the retrieval error. Horizontal wind speed error is reduced when a larger zenith angle configuration is used, but is increased for measurements of vertical wind. Results suggest that the scan strategy has a relevant effect on the lidar retrieval error and that instrument configuration should be chosen depending on the quantity of interest and the flow conditions in which the measurement is performed.

Charlotte Rahlves et al.

Status: open (until 18 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-417', Anonymous Referee #1, 03 Jan 2022 reply
  • RC2: 'Comment on amt-2021-417', Anonymous Referee #2, 12 Jan 2022 reply

Charlotte Rahlves et al.

Charlotte Rahlves et al.

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Short summary
Lidars can measure the wind profile in the lower part of the atmosphere provided that the wind field is horizontally uniform and does not change during the time of the measurement. These requirements are mostly not fulfilled in reality and the lidar wind measurement will thus hold a certain error. We investigate different strategies for lidar wind profiling using a lidar simulator implemented in a numerical simulation of the wind field. Our findings can help to improve wind measurements.