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Tytuł pozycji:

Air temperature equation derived from sonic temperature and water vapor mixing ratio for turbulent airflow sampled through closed-path eddy-covariance flux systems

Tytuł:
Air temperature equation derived from sonic temperature and water vapor mixing ratio for turbulent airflow sampled through closed-path eddy-covariance flux systems
Autorzy:
X. Zhou
T. Gao
E. S. Takle
X. Zhen
A. E. Suyker
T. Awada
J. Okalebo
J. Zhu
Temat:
Environmental engineering
TA170-171
Earthwork. Foundations
TA715-787
Źródło:
Atmospheric Measurement Techniques, Vol 15, Pp 95-115 (2022)
Wydawca:
Copernicus Publications, 2022.
Rok publikacji:
2022
Kolekcja:
LCC:Environmental engineering
LCC:Earthwork. Foundations
Typ dokumentu:
article
Opis pliku:
electronic resource
Język:
English
ISSN:
1867-1381
1867-8548
Relacje:
https://amt.copernicus.org/articles/15/95/2022/amt-15-95-2022.pdf; https://doaj.org/toc/1867-1381; https://doaj.org/toc/1867-8548
DOI:
10.5194/amt-15-95-2022
Dostęp URL:
https://doaj.org/article/d3974a559a4140d4ae61e86c40f1bba1  Link otwiera się w nowym oknie
Numer akcesji:
edsdoj.3974a559a4140d4ae61e86c40f1bba1
Czasopismo naukowe
Air temperature (T) plays a fundamental role in many aspects of the flux exchanges between the atmosphere and ecosystems. Additionally, knowing where (in relation to other essential measurements) and at what frequency T must be measured is critical to accurately describing such exchanges. In closed-path eddy-covariance (CPEC) flux systems, T can be computed from the sonic temperature (Ts) and water vapor mixing ratio that are measured by the fast-response sensors of a three-dimensional sonic anemometer and infrared CO2–H2O analyzer, respectively. T is then computed by use of either T=Ts1+0.51q-1, where q is specific humidity, or T=Ts1+0.32e/P-1, where e is water vapor pressure and P is atmospheric pressure. Converting q and e/P into the same water vapor mixing ratio analytically reveals the difference between these two equations. This difference in a CPEC system could reach ±0.18 K, bringing an uncertainty into the accuracy of T from both equations and raising the question of which equation is better. To clarify the uncertainty and to answer this question, the derivation of T equations in terms of Ts and H2O-related variables is thoroughly studied. The two equations above were developed with approximations; therefore, neither of their accuracies was evaluated, nor was the question answered. Based on first principles, this study derives the T equation in terms of Ts and the water vapor molar mixing ratio (χH2O) without any assumption and approximation. Thus, this equation inherently lacks error, and the accuracy in T from this equation (equation-computed T) depends solely on the measurement accuracies of Ts and χH2O. Based on current specifications for Ts and χH2O in the CPEC300 series, and given their maximized measurement uncertainties, the accuracy in equation-computed T is specified within ±1.01 K. This accuracy uncertainty is propagated mainly (±1.00 K) from the uncertainty in Ts measurements and a little (±0.02 K) from the uncertainty in χH2O measurements. An improvement in measurement technologies, particularly for Ts, would be a key to narrowing this accuracy range. Under normal sensor and weather conditions, the specified accuracy range is overestimated, and actual accuracy is better. Equation-computed T has a frequency response equivalent to high-frequency Ts and is insensitive to solar contamination during measurements. Synchronized at a temporal scale of the measurement frequency and matched at a spatial scale of measurement volume with all aerodynamic and thermodynamic variables, this T has advanced merits in boundary-layer meteorology and applied meteorology.
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