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Effects of Sound Speed Fluctuations on Sonic Anemometer Measurements

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  • 1 Department of Applied Mechanics and Engineering Sciences, University of California, San Diego, La Jolla, Calif. 92093
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Abstract

The effects of sound speed fluctuations on various measurements made with sonic anemometers are derived. Corrections due to temperature-generated sound speed fluctuations on measured statistics are estimated from the 1968 AFCRL Kansas data for different stability conditions. For most statistics, the corrections were not large: the maxima were −3.5% to the measured horizontal velocity, vertical velocity covariance (uw, proportional to the Reynolds stress) and −8.2% to the measured horizontal velocity, temperature covariance (, proportional to the horizontal heat flux) for unstable conditions. It is also shown that the measured cospectrum of uw is contaminated by the cospectrum of ; in the inertial subrange of frequencies, the measured uw cospectra for the AFCRL data for unstable conditions were calculated to be high by 5–11%.

Abstract

The effects of sound speed fluctuations on various measurements made with sonic anemometers are derived. Corrections due to temperature-generated sound speed fluctuations on measured statistics are estimated from the 1968 AFCRL Kansas data for different stability conditions. For most statistics, the corrections were not large: the maxima were −3.5% to the measured horizontal velocity, vertical velocity covariance (uw, proportional to the Reynolds stress) and −8.2% to the measured horizontal velocity, temperature covariance (, proportional to the horizontal heat flux) for unstable conditions. It is also shown that the measured cospectrum of uw is contaminated by the cospectrum of ; in the inertial subrange of frequencies, the measured uw cospectra for the AFCRL data for unstable conditions were calculated to be high by 5–11%.

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