Flow D istortion in N on-orthogonal 3-D Sonic Anemometers

1. T.W. Horst, S.P. Oncley, and S.R. Semmer Flow Distortion in Non-orthogonal 3-D Sonic Anemometers National Center for Atmospheric Research Boulder, CO

2. Flow Distortion in Non-orthogonal 3-D Sonic Anemometers • History of sonic development • Proposed flow distortion correction • Theoretical dependence on wind direction and • sonic geometry • Application to <w’w’> and <w’tc’>: CSAT vs ATI-K:

7. ChandranKaimal

8. Kaimal and Businger 1960 vertical-path sonic anemometer

9. 1973 EG&G 3-component sonic anemometer

10. Transducer Shadowing (Zhang et al, 1986)

11. Transducer shadowing depends on wind direction w.r.t. path and L/d (Kaimal, 1979)

12. Field demonstration of correction for path shadowing in K-probe sonic anemometer (Kaimal et al, 1990)

13. Kaimal, Gaynor, Zimmerman and Zimmerman, 1990

14. University of Washington non-orthogonal sonic anemometer, Businger and Oncley (1984)

15. Gill non-orthogonal sonic anemometer

16. Vertical velocity statistics, such as <w’w’> and <w’Ts’>, are measured to be less with a non-orthogonal sonic than with a vertical-path sonic.

17. CSAT Transducer Shadowing, L/d = 18, d/L = 0.056 18 +

19. u,v,w,tc from HATS data Sept 2, 2000

20. Simulation of transducer shadowing • Transform observed uvw data to path wind components abc • Apply transducer shadowing to abc, e.g. a_attenuated = a [0.84 + 0.16 sin(theta_a)] • Transform attenuated path components back to orthogonal coordinatesuvw_attenuated • Compare attenuated uvw statistics to original data

21. Simulation of transducer shadowing • Transform observed uvw data to path wind components abc • Apply transducer shadowing to each path, e.g. a_attenuated = a [0.84 + 0.16 sin(theta_a)] • Transform attenuated path components back to orthogonal coordinatesuvw_attenuated • Compare attenuated uvw statistics to original data

22. Simulation of transducer shadowing • Transform observed uvw data to path wind components abc • Apply transducer shadowing to each path, e.g. a_attenuated = a [0.84 + 0.16 sin(theta_a)] • Transform attenuated path components back to orthogonal coordinatesuvw_attenuated • Compare attenuated uvw statistics to original data

23. Simulation of transducer shadowing • Transform observed uvw data to path wind components abc • Apply transducer shadowing to each path, e.g. a_attenuated = a [0.84 + 0.16 sin(theta_a)] • Transform attenuated path components back to orthogonal coordinatesuvw_attenuated • Compare attenuated uvw statistics to original data

24. Simulation of transducer shadowing

25. Simulated attenuation by transducer shadowing

26. Marshall-2012 sonic anemometer field test 5 sonics at 3m height, 0.5 m spacing ATI-K.e (reference) CSAT.w (reference) CSAT.x (reference) CSAT.va (vertical a-path) ATI-K.w (reference)

29. Can coherent continuous-wave Doppler Lidars beutilized for in-situ instrument calibration?E. Dellwik, J. Mann, N. Angelou, E. Simley,M. Sjoholm & T. Mikkelsen, Technical University of DenmarkJanuary 2014 – ISARS, New Zealand

30. Can coherent continuous-wave Doppler lidars beutilized for in-situ instrument calibration?E. Dellwik, J. Mann et al., Technical University of DenmarkJanuary 2014 – ISARS, New Zealand

31. Lidar co-located with sonic u, v, w: fine lines, sonic; broad lines, Lidar (60 Hz data) Lidar 0.8 m ahead of sonic