accuracy of wind measurements on towers or stacks1,2

Gill, Gerald C.; Olsson, Lars E.; Sela, Josef; Suda, M.

doi:10.1175/1520-0477-48.9.665

Cited by 40 publications

(18 citation statements)

References 3 publications

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“…The wind field can be affected by the trailer up to 10 trailer heights downwind or 2 trailer heights upwind (Gill et al 1967), which translates to approximately 40 m for a 4-m trailer height and reduces the fetch along the vector to the trailer from the measurement point accordingly.…”

Section: Position Of the Tower Within The Fieldmentioning

confidence: 99%

Towards standards for measuring greenhouse gas fluxes from agricultural fields using instrumented towers

Pattey¹,

Edwards²,

Strachan³

et al. 2006

Can. J. Soil. Sci.

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Riddle, C. 2006. Towards standards for measuring greenhouse gas fluxes from agricultural fields using instrumented towers. Can. J. Soil Sci. Can. J. Soil Sci. 86: 373-400. This is a discussion of the available technology for measuring turbulent fluxes using instrumented towers. This review focuses on the flux measurements of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) for agricultural systems and the development of standards and protocols for measuring them. Agroecosystems present unique challenges because they undergo large leaf area index (LAI) and canopy architecture changes in a relatively short period of time (i.e., months) coupled with the fact that many of the greenhouse gas sources are diffuse. This review examines all aspects of the theory and application of the micrometeorological techniques, with focus on the flux gradient, eddy accumulation and eddy covariance techniques. Instrument placement, sensor response and noise characteristics are also explored. Innovative applications of micrometeorological methods are discussed for closed-and open-path trace gas sensors and commonly used meteorological instrumentation. The use of fastresponse single-pass optical tunable diode laser (i.e., CH 4 , N 2 O) and infrared gas analyzers (i.e., CO 2 , H 2 O) is described. Consideration is also taken of the trace gas sensors' flow system design, mixing ratio measurement, and data acquisition and reduction requirements for micrometeorological flux measurement. Procedures are outlined for the meteorological instrumentation necessary for eddy covariance-based energy budget measurement including ultrasonic anemometry. Les écosystèmes agricoles présentent des contraintes spécifiques du fait que l'indice foliaire et l'architecture du couvert végétal subissent d'importants changements durant la saison de croissance (quelques mois) et que la plupart des sources de gaz à effet de serre sont diffuses. Les auteurs examinent les principes et les applications de la micrométéorologie sous toutes leurs facettes, en insistant sur les techniques des gradients de flux, d'accumulation des tourbillons et la covariance des fluctuations. Ils abordent aussi l'installation des instruments, la sensibilité des capteurs et les caractéristiques du bruit de fond. Les auteurs présentent des applications novatrices de la micrométéorologie pour les capteurs de gaz à l'état de traces à parcours ouvert et fermé ainsi que des instruments employés couramment en météorologie. Ils décrivent l'utilisation de diode laser accordable à parcours optique unique et à réponse rapide (pour le CH 4 et le N 2 O) et d'analyseurs de gaz à infrarouge (pour le CO 2 et H 2 O). Enfin, ils tiennent compte de la conception du système captant les gaz à l'état de traces, des mesures du rapport de mélange ainsi que de l'acquisition des données et de leur réduction afin de mesurer les flux micrométéorologiques. Suit la description des méthodes servant aux instruments nécessaire à la mesure du bilan énergétique par la covariance des fluctuations, tels que...

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Section: Position Of the Tower Within The Fieldmentioning

confidence: 99%

Towards standards for measuring greenhouse gas fluxes from agricultural fields using instrumented towers

Pattey¹,

Edwards²,

Strachan³

et al. 2006

Can. J. Soil. Sci.

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“…In reality, an instrument mounted on a mast would also be affected by the flow distortion caused by the mast itself. The extent of this distortion depends primarily on the distance between the mast and the instrument (Gill et al, 1967). However, such information is not presently available, even in the VOSClim metadata.…”

Section: Generic Ship Modelsmentioning

confidence: 99%

An overview of the airflow distortion at anemometer sites on ships

Moat

Yelland

Pascal

et al. 2005

Intl Journal of Climatology

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Wind speed measurements obtained from ship-mounted anemometers are biased by the presence of the ship itself distorting the flow of air to the anemometer. Recent studies have used numerical models to simulate the flow around very detailed representations of individual research ships in order to quantify the effects of flow distortion at the anemometer locations. Such anemometers are generally in well-exposed positions, typically on a mast in the bows of the ship. In contrast, very little is known about the possible effects of airflow distortion on the wind speed measurements from fixed anemometers on Voluntary Observing Ships (VOS). This is because (1) the several thousand or so merchant vessels vary significantly in shape and size and it would be impractical to study each individual ship, and (2) the anemometer location is not usually known.This paper describes initial results from a study of flow distortion over 'typical' tankers and bulk carriers. A method to describe the shapes of these VOS and container ships is presented. The influence of distortion on the flow above the bridges of VOS is shown to be significant, with possible biases in the measured wind speed of between +11% and −100%, depending on the anemometer location. Recommendations for the siting of anemometers are made.

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“…Originally it was believed that this construction restricted the interference of the mast on the wind measurements within 1 y0 (Gill et al, 1967). However, a preliminary analysis shows that for some wind directions, the error due to obstruction by booms and tower is much larger (Wessels, 1983).…”

Section: Cabauw Data Basementioning

confidence: 99%

Estimates of diabatic wind speed profiles from near-surface weather observations

Holtslag

1984

Boundary-Layer Meteorol

135

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In this paper we analyse diabatic wind profiles observed at the 213 m meteorological tower at Cabauw, the Netherlands. It is shown that the wind speed profiles agree with the well-known similarity functions of the atmospheric surface layer, when we substitute an effective roughness length. For very unstable conditions, the agreement is good up to at least 200 m or z/L u -7 (z is height, L is Obukhov length scale). For stable conditions, the agreement is good up to z/L N 1. For stronger stability, a semi-empirical extension is given of the log-linear profile, which gives acceptable estimates up to u 100 m. A scheme is used for the derivation of the Obukhov length scale from single wind speed, total cloud cover and air temperature. With the latter scheme and the similarity functions, wind speed profiles can be estimated from near-surface weather data only. The results for wind speed depend on height and stability. Up to 80 m, the rms difference with observations u is on average u 1.1 m s -'. At 200 m, u = 0.8 m s -' for very unstable conditions increasing to c N 2.1 m s -i for very stable conditions. The proposed methods simulate the diurnal variation of the 80 m wind speed very well. Also the simulated frequency distribution of the 80 m wind speed agrees well with the observed one. It is concluded that the proposed methods are applicable up to at least 100 m in generally level terrain.

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accuracy of wind measurements on towers or stacks1,2

Cited by 40 publications

References 3 publications

Towards standards for measuring greenhouse gas fluxes from agricultural fields using instrumented towers

Towards standards for measuring greenhouse gas fluxes from agricultural fields using instrumented towers

An overview of the airflow distortion at anemometer sites on ships

Estimates of diabatic wind speed profiles from near-surface weather observations

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