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| Titel |
Using sonic anemometer temperature to measure sensible heat flux in strong winds |
| VerfasserIn |
S. P. Burns, T. W. Horst, L. Jacobsen, P. D. Blanken, R. K. Monson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 9 ; Nr. 5, no. 9 (2012-09-03), S.2095-2111 |
| Datensatznummer |
250003078
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| Publikation (Nr.) |
 copernicus.org/amt-5-2095-2012.pdf |
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| Zusammenfassung |
| Sonic anemometers simultaneously measure the turbulent fluctuations of
vertical wind (w') and sonic temperature (Ts'), and are
commonly used to measure sensible heat flux (H). Our study examines 30-min
heat fluxes measured with a Campbell Scientific CSAT3 sonic anemometer above
a subalpine forest. We compared H calculated with Ts 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 ≈ 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
Ts in high winds (due to a delayed detection of the sonic pulse),
which resulted in the large CSAT heat flux errors. Although this
Ts 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 Ts; however, a Ts
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 Ts 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. |
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