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How Well Can We Measure the Vertical Wind Speed? Implications for Fluxes of Energy and Mass.
- Source :
-
Boundary-Layer Meteorology . Nov2012, Vol. 145 Issue 2, p383-398. 16p. 1 Color Photograph, 1 Black and White Photograph, 3 Charts, 7 Graphs. - Publication Year :
- 2012
-
Abstract
- Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10-50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a non-orthogonal transducer orientation were estimated for over 100 combinations of angle-of-attack and wind direction using a novel technique to measure the true angle-of-attack and wind speed within the turbulent atmospheric surface layer. Corrections to the vertical wind speed varied from −5 to 37% for all angles-of-attack and wind directions examined. When applied to eddy-covariance data from three NOAA flux sites, the wind-velocity corrections increased the magnitude of CO fluxes, sensible heat fluxes, and latent heat fluxes by ≈11%, with the actual magnitude of flux corrections dependent upon sonic anemometer, surface type, and scalar. A sonic anemometer that uses vertically aligned transducers to measure the vertical wind speed was also tested at four angles-of-attack, and corrections to the vertical wind speed measured using this anemometer were within ±1% of zero. Sensible heat fluxes over a forest canopy measured using this anemometer were 15% greater than sensible heat fluxes measured using a sonic anemometer with a non-orthogonal transducer orientation. These results indicate that sensors with a non-orthogonal transducer orientation, which includes the majority of the research-grade three-dimensional sonic anemometers currently in use, should be redesigned to minimize sine errors by measuring the vertical wind speed using one pair of vertically aligned transducers. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00068314
- Volume :
- 145
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Boundary-Layer Meteorology
- Publication Type :
- Academic Journal
- Accession number :
- 82179550
- Full Text :
- https://doi.org/10.1007/s10546-012-9738-1