A method to assess the accuracy of sonic anemometer measurements
Abstract. We propose a method to assess the accuracy of atmospheric turbulence
measurements performed by sonic anemometers and test it by analysis of
measurements from two commonly used sonic anemometers, a Metek USA-1 and a
Campbell CSAT3, at two locations in Denmark. The method relies on the
estimation of the ratio of the vertical to the along-wind velocity power
spectrum within the inertial subrange and does not require the use of another
measurement as reference. When we correct the USA-1 to account for
three-dimensional flow-distortion effects, as recommended by Metek GmbH, the
ratio is very close to 4∕3 as expected from Kolmogorov's hypothesis, whereas
non-corrected data show a ratio close to 1. For the CSAT3, non-corrected data
show a ratio close to 1.1 for the two sites and for wind directions where the
instrument is not directly affected by the mast. After applying a previously
suggested flow-distortion correction, the ratio increases up to ≈1.2 ,
implying that the effect of flow distortion in this instrument is still not
properly accounted for.