SOFTWARE
Correction of ultrasonic anemometer angle of attack errors
under turbulent conditions
Preface
Source code of the correction of Gill ultrasonic anemometer angle of attack errors under turbulent conditions (Nakai and Shimoyama, 2012) is released here.
This software provides newly derived calibration functions obtained by field experiments under turbulent conditions (Nakai and Shimoyama, 2012), with corrections using the method by Nakai et al. (2006).
Important notice
Recently (July 8th, 2016), the Gill's staff announced the important bug information on WindMaster and WindMaster Pro.
http://gillinstruments.com/data/manuals/KN1509-WM-WMPro-W-Bug-Info-Sheet.pdf
In short,
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They found the internal (firmware) bug, which significantly underestimates ‘w’ wind component.
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In the latest firmware, this bug has already been fixed, which is a simple multiplication scaling factor.
Most importantly, according to Gill, all other Gill anemometer products such as R3, HS, R3-50 and HS-50 do not have the ‘w’ bug, and thus the correction by Nakai and Shimoyama (2012) is NOT applicable to these anemometers. Besides, the WindMaster and WindMaster Pro with the serial number starts with X or W also do not have the bug.
Therefore, the software provided here is only applicable to WindMaster and WindMaster Pro (from 2006 to October 2015; firmware version# up to 2329 v 601).
Please DO NOT apply our software to the WindMaster/WindMaster Pro using the latest firmware, because this firmware works similar to our software, otherwise the w component will be overestimated and erroneous.
License
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
For more information about licensing the software commercially, please contact me (Taro Nakai).
Downloads
Original code: C/C++
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File: aoa2012.h
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Author: Taro Nakai
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Last updated: 4/20/2012
Translated version: Fortran
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Translator: Gerardo Fratini
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Last updated: 4/17/2013
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The Fortran version is a package including a stand-alone program together with the translated source code.
Translated version: MATLAB
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File: aoa2012.m
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Translator: Hiroki Ikawa
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Last updated: 3/1/2013
Sample data
For checking whether the program works properly, I prepared the sample data. If the correction is made correctly, the results will be identical to my results until the 5th or 6th decimal digit.
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Data file: sample_data.zip
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sample.csv : u, v, w (observed wind data)
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sample_aoa.csv : ua, va, wa, aoa (corrected wind data and angle of attack)
Applications
The following universal flux calculation apps incorporate this correction.
References
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Nakai, T., Iwata, H., Harazono, Y., Ueyama, M. An inter-comparison between Gill and Campbell sonic anemometers. Agric. For. Meteorol., 195–196, 123–131, 2014.
[doi: 10.1016/j.agrformet.2014.05.005]
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Nakai, T., Shimoyama, K. Ultrasonic anemometer angle of attack errors under turbulent conditions. Agric. For. Meteorol., 162–163, 14–26, 2012.
[doi: 10.1016/j.agrformet.2012.04.004] Open Access
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Nakai, T., van der Molen, M.K., Gash, J.H.C., Kodama, Y. Correction of sonic anemometer angle of attack errors. Agric. For. Meteorol., 136, 19–30, 2006.
[doi: 10.1016/j.agrformet.2006.01.006] [HUSCAP]
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van der Molen, M.K., Gash, J.H.C., Elbers, J.A. Sonic anemometer (co)sine response and flux measurement. II. The effect of introducing an angle of attack dependent calibration. Agric. For. Meteorol., 122, 95-109, 2004.
[doi: 10.1016/j.agrformet.2003.09.003]
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Gash, J.H.C., Dolman, A.J. Sonic anemometer (co)sine response and flux measurement. I. The potential for (co)sine error to affect sonic anemometer-based flux measurements. Agric. For. Meteorol., 119, 195-207, 2003.
[doi: 10.1016/S0168-1923(03)00137-0]