An international turbulence comparison experiment (ITCE 1976)

Dyer, A. J.; Garratt, J. R.; Francey, R. J.; McIlroy, I. C.; Bacon, Nicole; Hyson, P.; Bradley, E. F.; Denmead, O. T.; Tsvang, L. R.; Volkov, Yu. A.; Koprov, B. M.; Elagina, L. G.; Sahashi, Ken; Monji, Nobutaka; Hanafusa, Tadashi; Tsukamoto, Osamu; Frenzen, Paul D.; Hicks, B. B.; Wesely, M. L.; Miyake, M.; Shaw, W. J.

doi:10.1007/bf00121667

Cited by 58 publications

(26 citation statements)

References 16 publications

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“…Comparisons between eddy-covariance measurements have been presented in the literature before, albeit with different motivations and foci (Dyer et al, 1982;Tsvang et al, 1985;Fritschen et al, 1992;Christen et al, 2000;Mauder and Foken, 2001;Wieser et al, 2001;Mauder et al, 2008). In these studies an attempt was generally made either to study turbulence structures (using identical instrumentation and analysis approaches), to compare anemometers and latent heat flux instrumentation (using identical analysis packages) or to compare analysis approaches (using the same input data).…”

Section: Sources Of Discrepancy In the Estimatesmentioning

confidence: 99%

“…Pure instrument comparisons have been presented elsewhere (e.g. Dyer et al, 1982;Tsvang et al, 1985;Fritschen et al, 1992;Christen et al, 2000;Mauder and Foken, 2001;Mauder et al, , 2008. Instead, this paper focuses on the differences that may be expected to be introduced by a combination of differences in instrumentation, chosen measurement height and analysis protocols, as they would be applied by individual groups in real applications.…”

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Intercomparison and assessment of turbulent and physiological exchange parameters of grassland

et al. 2009

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Abstract. Commonly, the micrometeorological parameters that underline the calculations of surface atmosphere exchange fluxes (e.g. friction velocity and sensible heat flux) and parameters used to model exchange fluxes with SVATtype parameterisations (e.g. latent heat flux and canopy temperature) are measured with a single set of instrumentation and are analysed with a single methodology. This paper evaluates uncertainties in these measurements with a single instrument, by comparing the independent results from nine different institutes during the international GRAMINAE integrated field experiment over agricultural grassland near Braunschweig, Lower Saxony, Germany. The paper discusses uncertainties in measuring friction velocity, sensible and latent heat fluxes, canopy temperature and investigates the energy balance closure at this site. Although individual 15-min flux calculations show a large variability between the instruments, when averaged over the campaign, fluxes agree within 2% for momentum and 11% for sensible heat. However, the spread in estimates of latent heat flux (λE) is Correspondence to: E. Nemitz (en@ceh.ac.uk) larger, with standard deviations of averages of 18%. The dataset averaged over the different instruments fails to close the energy budget by 20%, significantly larger than the uncertainties in the individual flux corrections. However, if the largest individual turbulent flux estimates are considered, energy closure can be achieved, indicating that the closure gap is within the spread of the measurements. The uncertainty in λE feeds results in an uncertainty in the bulk stomatal resistance, which further adds to the uncertainties in the estimation of the canopy temperature that controls the exchange. The paper demonstrated how a consensus dataset was derived, which is used by the individual investigators to calculate fluxes and drive their models.

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Section: Sources Of Discrepancy In the Estimatesmentioning

confidence: 99%

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confidence: 99%

Intercomparison and assessment of turbulent and physiological exchange parameters of grassland

et al. 2009

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“…Previous experience with the psychrometric method in turbulence measurements has not been entirely successful. Thus Dyer et al (1982) show a 40% loss in measurements of the covariance of the vertical velocity and the wet bulb temperature at heights of 2.8 and 4 m above the ground. This is due to the relatively long time constant of the wet bulb sensor.…”

Section: Turbulenceinstrumentationmentioning

confidence: 99%

Turbulent exchange above a pine forest, I: Fluxes and gradients

Högström¹,

Bergström²,

Smedman³

et al. 1989

Boundary-Layer Meteorol

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Measurements of gradients of wind, temperature and humidity and of the corresponding turbulent fluxes have been carried out over a sparse pine forest at Jiidra&s in Sweden. In order to ascertain that correct gradient estimates were obtained, two independent measuring systems were employed: one system with sensors at 10 fixed levels on a 51 m tower and another with reversing sensors for temperature and humidity, covering the height interval 23 to 32 m. Turbulent fluxes were measured at three levels simultaneously. Data from three field campaigns: in June 1985, June 1987 and September 1987 have been analyzed. The momentum flux is found on the average to be virtually constant from tree top level, at 20 to 50 m. The average fluxes of sensible and latent heat are not so well behaved. The ratio of the non-dimensional gradients of wind and temperature to their corresponding values under 'ideal conditions' (low vegetation) are both found to be small immediately above the canopy (about 0.3 for temperature and 0.4 for wind). With increasing height, the ratios increase, but the values vary substantially with wind direction. The ratios are not found to vary systematically with stability (unstable stratification only studied). The ratio of the non-dimensional humidity gradient to the corresponding nondimensional potential temperature gradient (equivalent to KH/KW) is found to be unity for (I -d)/L, less than about -0.1 and about 1.4 for near neutral stratification, but the scatter of the data is very large.

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“…The first experiment was carried out in 1968 near Vancouver, Canada, over the ocean (Miyake et al 1971), followed by one over steppe country at Tsimlyansk, Russia in 1970 (Tsvang et al 1973). Additional experiments were carried out in 1976 in Conargo, Australia (Dyer 1981;Dyer et al 1982) and in 1981 again in Tsimlyansk (Tsvang et al 1985). In these early intercomparison experiments mostly prototype instrumentation was tested.…”

Section: Introductionmentioning

confidence: 99%

The energy balance experiment EBEX-2000. Part II: Intercomparison of eddy-covariance sensors and post-field data processing methods

Mauder

Oncley

Vogt

et al. 2006

Boundary-Layer Meteorol

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166

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The eddy-covariance method is the primary way of measuring turbulent fluxes directly. Many investigators have found that these flux measurements oftenThe National Center for Atmospheric Research is supported by the National Science Foundation. do not satisfy a fundamental criterion-closure of the surface energy balance. This study investigates to what extent the eddy-covariance measurement technology can be made responsible for this deficiency, in particular the effects of instrumentation or of the post-field data processing. Therefore, current eddy-covariance sensors and several post-field data processing methods were compared. The differences in methodology resulted in deviations of 10% for the sensible heat flux and of 15% for the latent heat flux for an averaging time of 30 min. These disparities were mostly due to different sensor separation corrections and a linear detrending of the data. The impact of different instrumentation on the resulting heat flux estimates was significantly higher. Large deviations from the reference system of up to 50% were found for some sensor combinations. However, very good measurement quality was found for a CSAT3 sonic together with a KH20 krypton hygrometer and also for a UW sonic together with a KH20. If these systems are well calibrated and maintained, an accuracy of better than 5% can be achieved for 30-min values of sensible and latent heat flux measurements. The results from the sonic anemometers Gill Solent-HS, ATI-K, Metek USA-1, and R.M. Young 81000 showed more or less larger deviations from the reference system. The LI-COR LI-7500 open-path H 2 O/CO 2 gas analyser in the test was one of the first serial numbers of this sensor type and had technical problems regarding direct solar radiation sensitivity and signal delay. These problems are known by the manufacturer and improvements of the sensor have since been made.

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An international turbulence comparison experiment (ITCE 1976)

Cited by 58 publications

References 16 publications

Intercomparison and assessment of turbulent and physiological exchange parameters of grassland

Intercomparison and assessment of turbulent and physiological exchange parameters of grassland

Turbulent exchange above a pine forest, I: Fluxes and gradients

The energy balance experiment EBEX-2000. Part II: Intercomparison of eddy-covariance sensors and post-field data processing methods

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