Testing of the bandpass eddy covariance method for a long-term measurement of water vapour flux over a forest

Watanabe, Tsutomu; Yamanoi, Katsumi; Yasuda, Yukio

doi:10.1023/a:1002642028984

Cited by 34 publications

(32 citation statements)

References 10 publications

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“…of the cospectrum of the raw CO 2 flux to the sensible heat flux is similar (Watanabe et al, 2000). The sensor separation correction for CP was negligibly small because the CO 2 flux by CP was considerably small as shown in a later section.…”

Section: Eddy Covariance Techniquesupporting

confidence: 60%

Experimental validation of WPL correction for CO2 flux by eddy covariance technique over the asphalt surface

Kondo

Tsukamoto

2012

J. Agric. Meteorol.

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We experimentally validated the density correction (called WPL or Webb correction) over the dry asphalt surface by simultaneously measuring CO 2 fluxes by closed-path eddy covariance and closedchamber techniques, which is inescapable for evaluating the surface CO 2 flux by the open-path eddy covariance technique. The total CO 2 flux with WPL correction by the open-path eddy covariance technique was evaluated as a systematically small upward flux, which was consistent with that of our previous study. The instrumental error of the sonic anemometers and the additional heating correction for the open-path gas analyzer were not potential sources of total upward CO 2 fluxes. The CO 2 flux by the closed-chamber technique was also an upward flux; however, it was three orders of magnitude smaller than the total CO 2 flux by the open-path eddy covariance technique. The CO 2 flux calculated from the CO 2 mixing ratio by the closed-path eddy covariance technique was almost zero. Our results suggest the possible upward overestimation of the total CO 2 flux with the WPL correction by the open-path eddy covariance technique.

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Section: Eddy Covariance Techniquesupporting

confidence: 60%

Experimental validation of WPL correction for CO2 flux by eddy covariance technique over the asphalt surface

Kondo

Tsukamoto

2012

J. Agric. Meteorol.

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“…This procedure included 3-D rotation of the coordinate axis for the wind field (McMillen 1988), linear trend removal, correction for the effects of lateral wind and water vapor on sonic velocity (Kaimal et al 1968), a bandpass covariance method for high-frequency loss (Watanabe et al 2000), and WPL correction (Webb et al 1980). The effect of WPL correction on the CO 2 fluxes was small because of the dehumidification of the sample air and thermal mixing through the tubing (Yasuda et al 1998).…”

Section: Measurementsmentioning

confidence: 99%

Interannual variability of net ecosystem production for a broadleaf deciduous forest in Sapporo, northern Japan

Kitamura

Nakai

Suzuki

et al. 2012

Journal of Forest Research

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To estimate net ecosystem production (NEP), ecosystem respiration (R E ), and gross primary production (GPP), and to elucidate the interannual variability of NEP in a cool temperate broadleaf deciduous forest in Sapporo, northern Japan, we measured net ecosystem exchange (NEE) using an eddy covariance technique with a closedpath infrared gas analyzer from 2000 to 2003. NEP, R E , and GPP were derived from NEE, and data gaps were filled using empirical regression models with meteorological variables such as photosynthetic active radiation and soil temperature. In general, NEP was positive (CO 2 uptake) from May to September, either positive or negative in October, and negative (CO 2 release) from November to the following April. NEP rapidly increased during leaf expansion in May and reached its maximum in June or July. The four-year averages (± standard deviation) of annual NEP, GPP, and R E were 443 ± 45, 1,374 ± 39, and 931 ± 11 g C m -2 year -1 , respectively. The lower annual NEP and GPP in 2000 may have been caused by lower solar radiation in the foliated season. During the foliated season, monthly GPP varied from year to year more than monthly R E .

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“…An analysis of scalar similarity by spectral analysis on more extended time scales was reported by Watanabe et al (2000) for the assessment of the 'Bandpass Eddy Covariance method' (e.g., Hicks and McMillen, 1988;Horst and Oncley, 1995). While achieving relatively good latent heat flux results using fast temperature measurements for the spectral correction of a slow humidity sensor, flux errors became large during times with small sensible heat fluxes, which confirms our finding for Case 3.…”

Section: Spectral Analysismentioning

confidence: 99%

Scalar Similarity for Relaxed Eddy Accumulation Methods

Ruppert

Thomas

Foken

2006

Boundary-Layer Meteorol

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The relaxed eddy accumulation (REA) method allows the measurement of trace gas fluxes when no fast sensors are available for eddy covariance measurements. The flux parameterisation used in REA is based on the assumption of scalar similarity, i.e., similarity of the turbulent exchange of two scalar quantities. In this study changes in scalar similarity between carbon dioxide, sonic temperature and water vapour were assessed using scalar correlation coefficients and spectral analysis. The influence on REA measurements was assessed by simulation. The evaluation is based on observations over grassland, irrigated cotton plantation and spruce forest.Scalar similarity between carbon dioxide, sonic temperature and water vapour showed a distinct diurnal pattern and change within the day. Poor scalar similarity was found to be linked to dissimilarities in the energy contained in the low frequency part of the turbulent spectra (< 0.01 Hz).The simulations of REA showed significant change in b-factors throughout the diurnal course. The b-factor is part of the REA parameterisation scheme and describes a relation between the concentration difference and the vertical flux of a trace gas. The diurnal course of b-factors for carbon dioxide, sonic temperature and water vapour matched well. Relative flux errors induced in REA by varying scalar similarity were generally below ±10%. Systematic underestimation of the flux of up to −40% was found for the use of REA applying a hyperbolic deadband (HREA). This underestimation was related to poor scalar similarity between the scalar of interest and the scalar used as proxy for the deadband definition.

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Testing of the bandpass eddy covariance method for a long-term measurement of water vapour flux over a forest

Cited by 34 publications

References 10 publications

Experimental validation of WPL correction for CO2 flux by eddy covariance technique over the asphalt surface

Experimental validation of WPL correction for CO2 flux by eddy covariance technique over the asphalt surface

Interannual variability of net ecosystem production for a broadleaf deciduous forest in Sapporo, northern Japan

Scalar Similarity for Relaxed Eddy Accumulation Methods

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