Using sonic anemometer temperature to measure sensible heat flux in strong winds

S. P. Burns, T. W. Horst, L. Jacobsen, P. D. Blanken, Russell Monson

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Sonic anemometers simultaneously measure the turbulent fluctuations of vertical wind ( w ') and sonic temperature (T '), and are commonly used to measure sensible heat flux (<i>H</i>). Our study examines 30-min heat fluxes measured with a Campbell Scientific CSAT3 sonic anemometer above a subalpine forest. We compared H calculated with T to H calculated with a co-located thermocouple and found that, for horizontal wind speed ( U ) less than 8 m s-1, the agreement was around ±30 W m-2. However, for U &asymp; 8 m s-1, the CSAT H had a generally positive deviation from H calculated with the thermocouple, reaching a maximum difference of ≈250 W m-2 at U ≈ 18 m s-1. With version 4 of the CSAT firmware, we found significant underestimation of the speed of sound and thus T in high winds (due to a delayed detection of the sonic pulse), which resulted in the large CSAT heat flux errors. Although this T error is qualitatively similar to the well-known fundamental correction for the crosswind component, it is quantitatively different and directly related to the firmware estimation of the pulse arrival time. For a CSAT running version 3 of the firmware, there does not appear to be a significant underestimation of T ; however, a T error similar to that of version 4 may occur if the CSAT is sufficiently out of calibration. An empirical correction to the CSAT heat flux that is consistent with our conceptual understanding of the T error is presented. Within a broader context, the surface energy balance is used to evaluate the heat flux measurements, and the usefulness of side-by-side instrument comparisons is discussed.

Original languageEnglish (US)
Pages (from-to)2095-2111
Number of pages17
JournalAtmospheric Measurement Techniques
Volume5
Issue number9
DOIs
StatePublished - 2012

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anemometer
sensible heat flux
heat flux
temperature
flux measurement
arrival time
surface energy
energy balance
wind velocity
calibration

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Using sonic anemometer temperature to measure sensible heat flux in strong winds. / Burns, S. P.; Horst, T. W.; Jacobsen, L.; Blanken, P. D.; Monson, Russell.

In: Atmospheric Measurement Techniques, Vol. 5, No. 9, 2012, p. 2095-2111.

Research output: Contribution to journalArticle

Burns, S. P. ; Horst, T. W. ; Jacobsen, L. ; Blanken, P. D. ; Monson, Russell. / Using sonic anemometer temperature to measure sensible heat flux in strong winds. In: Atmospheric Measurement Techniques. 2012 ; Vol. 5, No. 9. pp. 2095-2111.
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