A Simple Formula for Attenuation of Eddy Fluxes Measured With First-Order-Response Scalar Sensors

Horst, Thomas

doi:10.1023/a:1000229130034

Cited by 322 publications

(306 citation statements)

References 14 publications

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“…Covariances among u, v, and w and with T s , ρ v , and ρ c were calculated every half hour from the time series data, rotated into the long-term planar fit coordinate [Lee et al, 2004a], and time-lag adjusted with the IRGA (half-hour time lags long-term modeled from wind speed and direction [Horst and Lenschow, 2009] with an offset optimized to maximize the absolute covariance within ±1 s lag). The covariances between w and u, T s , ρ v , and ρ c were spectrally corrected (half-hour corrections [Massman, 2000;Massman and Clement, 2004] based on long-term modeled peak frequency [Horst, 1997] determined from median-pooled normalized cospectra). Sensible heat (H), water vapor (F v ), and CO 2 (F c ) ecosystem fluxes were calculated from the vertical wind covariances using the WebbPearman-Leuning (WPL) corrections [Gu et al, 2012;Massman and Lee, 2002;Webb et al, 1980] and Massman, 2011].…”

Section: Eddy Covariance Measurementsmentioning

confidence: 99%

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

et al. 2014

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Disturbances are increasing globally due to anthropogenic changes in land use and climate. This study determines whether a disturbance that affects the physiology of individual trees can be used to predict the response of the ecosystem by weighing two competing hypothesis at annual time scales: (a) changes in ecosystem fluxes are proportional to observable patterns of mortality or (b) to explain ecosystem fluxes the physiology of dying trees must also be incorporated. We evaluate these hypotheses by analyzing 6 years of eddy covariance flux data collected throughout the progression of a spruce beetle (Dendroctonus rufipennis) epidemic in a Wyoming Engelmann spruce (Picea engelmannii)-subalpine fir (Abies lasiocarpa) forest and testing for changes in canopy conductance (g c ), evapotranspiration (ET), and net ecosystem exchange (NEE) of CO 2 . We predict from these hypotheses that (a) g c , ET, and NEE all diminish (decrease in absolute magnitude) as trees die or (b) that (1) g c and ET decline as trees are attacked (hydraulic failure from beetle-associated blue-stain fungi) and (2) NEE diminishes both as trees are attacked (restricted gas exchange) and when they die. Ecosystem fluxes declined as the outbreak progressed and the epidemic was best described as two phases: (I) hydraulic failure caused restricted g c , ET (28 ± 4% decline, Bayesian posterior mean ± standard deviation), and gas exchange (NEE diminished 13 ± 6%) and (II) trees died (NEE diminished 51 ± 3% with minimal further change in ET to 36 ± 4%). These results support hypothesis b and suggest that model predictions of ecosystem fluxes following massive disturbances must be modified to account for changes in tree physiological controls and not simply observed mortality.

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Section: Eddy Covariance Measurementsmentioning

confidence: 99%

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

et al. 2014

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“…an equation that is widely used, for example by Horst (1997), Su et al (2004), Ibrom et al (2007), Hiller et al (2008) and Mammarella et al (2009).…”

Section: Eddy-covariance Spectral Analysismentioning

confidence: 99%

New Transfer Functions for Correcting Turbulent Water Vapour Fluxes

Ligne

Heinesch

Aubinet

2010

Boundary-Layer Meteorol

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We address the problem of the high-frequency correction of water vapour fluxes measured by eddy covariance with a closed-path infrared gas analyser (IRGA). Different transfer functions are compared and evaluated at a forested (Vielsalm, Belgium) and an agricultural (Lonzée, Belgium) site. Classical functions, usually applied to correct CO 2 fluxes (Gaussian, Lorentzian), are found to be unsuited to water vapour cospectral corrections, being characterised by too sharp a decrease at high frequency. Two other functions characterised by a lower decreasing slope are found to better fit experimental transfer functions. They were calibrated and validated on experimental transfer functions and their dependency on air humidity is parameterised. On this basis, new correction coefficients are estimated. The coefficients are found to be larger than those based on the classical functions, even when the dependency of the latter on air humidity is taken into account. The difference amounts to 10% at the forested site and to 5% larger at the crop site. The study highlights the necessity of characterising the water transfer function shape and taking it into account in the correction factor at each site equipped with a closed path IRGA.

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“…The data also confirm that measurements with characteristic time constants significantly shorter than the maximum 0.6 s TD-LIF time constant would have been of limited additional benefit. Loss of flux signal from the instrument time constant can be approximated as: where F m is the observed flux, F t is the true flux, f m is the frequency at which the frequency-multiplied cospectrum maximizes, and τ is the first-order response time of the sensor (Horst, 1997). For f m of 0.01 Hz and τ of 0.6 s, the underestimation is 3.6% for the HNO 3 flux.…”

Section: Spectral Analysismentioning

confidence: 99%

Application of thermal-dissociation laser induced fluorescence (TD-LIF) to measurement of HNO<sub>3</sub>, Σalkyl nitrates, Σperoxy nitrates, and NO<sub>2</sub> fluxes using eddy covariance

2006

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Abstract. Nitrogen exchange between the atmosphere and biosphere directly influences atmospheric composition. While much is known about mechanisms of NO and N 2 O emissions, instrumentation for the study of mechanisms contributing to exchange of other major nitrogen species is quite limited. Here we describe the application of a new technique, thermal dissociation-laser induced fluorescence (TD-LIF), to eddy covariance measurements of the fluxes of NO 2 , total peroxy acyl and peroxy nitrates, total alkyl and multifunctional alkyl nitrates, and nitric acid. The technique offers the potential for investigating mechanisms of exchange of these species at the canopy scale over timescales from days to years. Examples of flux measurements at a ponderosa pine plantation in the mid-elevation Sierra Nevada Mountains in California are reported and used to evaluate instrument performance.

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A Simple Formula for Attenuation of Eddy Fluxes Measured With First-Order-Response Scalar Sensors

Cited by 322 publications

References 14 publications

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

New Transfer Functions for Correcting Turbulent Water Vapour Fluxes

Application of thermal-dissociation laser induced fluorescence (TD-LIF) to measurement of HNO<sub>3</sub>, Σalkyl nitrates, Σperoxy nitrates, and NO<sub>2</sub> fluxes using eddy covariance

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A Simple Formula for Attenuation of Eddy Fluxes Measured With First-Order-Response Scalar Sensors

Cited by 322 publications

References 14 publications

Ecosystem CO2/H2O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Ecosystem CO2/H2O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

New Transfer Functions for Correcting Turbulent Water Vapour Fluxes

Application of thermal-dissociation laser induced fluorescence (TD-LIF) to measurement of HNO&lt;sub&gt;3&lt;/sub&gt;, Σalkyl nitrates, Σperoxy nitrates, and NO&lt;sub&gt;2&lt;/sub&gt; fluxes using eddy covariance

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Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Application of thermal-dissociation laser induced fluorescence (TD-LIF) to measurement of HNO<sub>3</sub>, Σalkyl nitrates, Σperoxy nitrates, and NO<sub>2</sub> fluxes using eddy covariance