Eddy covariance methane measurements at a Ponderosa pine plantation in California

Smeets, C. J. P. P.; Holzinger, Rupert; Vigano, I.; Goldstein, Allen H.; Röckmann, T.

doi:10.5194/acp-9-8365-2009

Cited by 60 publications

(45 citation statements)

References 43 publications

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“…If noise is truly random, there should not be significant covariance with fluctuations in vertical wind; however this has been observed in other situations (e.g. methane fluxes reported in Querino et al (2011) and Smeets et al (2009)). In the case of PROPHET, we see a less marked increase in cospectral power at the high frequencies, indicating that perhaps noise was less of an issue during this campaign.…”

Section: Cospectral Analysismentioning

confidence: 95%

Observations of reactive nitrogen oxide fluxes by eddy covariance above two midlatitude North American mixed hardwood forests

Geddes

Murphy

2014

Atmos. Chem. Phys.

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Abstract. Significant knowledge gaps persist in the understanding of forest-atmosphere exchange of reactive nitrogen oxides, partly due to a lack of direct observations. Chemical transport models require representations of dry deposition over a variety of land surface types, and the role of canopy exchange of NO x (= NO + NO 2 ) is highly uncertain. Biosphere-atmosphere exchange of NO x and NO y (= NO x + HNO 3 + PANs + RONO 2 + pNO − 3 + . . . ) was measured by eddy covariance above a mixed hardwood forest in central Ontario (Haliburton Forest and Wildlife Reserve, or HFWR), and a mixed hardwood forest in northern lower Michigan (Program for Research on Oxidants: Photochemistry, Emissions and Transport, or PROPHET) during the summers of 2011 and 2012 respectively. NO x and NO y mixing ratios were measured by a custom-built two-channel analyser based on chemiluminescence, with selective NO 2 conversion via LED photolysis and NO y conversion via a hot molybdenum converter. Consideration of interferences from water vapour and O 3 , and random uncertainty of the calculated fluxes are discussed. NO y flux observations were predominantly of deposition at both locations. In general, the magnitude of deposition scaled with NO y mixing ratios. Average midday (12:00-16:00) deposition velocities at HFWR and PROPHET were 0.20 ± 0.25 and 0.67 ± 1.24 cm s −1 respectively. Average nighttime (00:00-04:00) deposition velocities were 0.09 ± 0.25 cm s −1 and 0.08 ± 0.16 cm s −1 respectively. At HFWR, a period of highly polluted conditions (NO y concentrations up to 18 ppb) showed distinctly different flux characteristics than the rest of the campaign. Integrated daily average NO y flux was −0.14 mg (N) m −2 day −1 and −0.34 mg (N) m −2 day −1 (net deposition) at HFWR and PROPHET respectively. Concurrent wet deposition measurements were used to estimate the contributions of dry deposition to total reactive nitrogen oxide inputs, found to be 22 and 40 % at HFWR and PROPHET respectively.

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Section: Cospectral Analysismentioning

confidence: 95%

Observations of reactive nitrogen oxide fluxes by eddy covariance above two midlatitude North American mixed hardwood forests

Geddes

Murphy

2014

Atmos. Chem. Phys.

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“…In such conditions, the corrections are large relative to the real flux (cf. Smeets et al, 2009). This problem is relevant for all analysers, but especially open-path instruments and those closed-path devices that do not measure H 2 O simultaneously.…”

Section: Discussionmentioning

confidence: 99%

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

et al. 2014

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Abstract. The performance of eight fast-response methane (CH 4 ) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimise the effect of varying turbulent conditions. The moderate CH 4 fluxes observed at the location, of the order of 25 nmol m −2 s −1 , provided a suitable signal for testing the instruments' performance.Generally, all analysers tested were able to quantify the concentration fluctuations at the frequency range relevant for turbulent exchange and were able to deliver high-quality data. The tested cavity ringdown spectrometer (CRDS) instruments from Picarro, models G2311-f and G1301-f, were superior to other CH 4 analysers with respect to instrumental noise. As an open-path instrument susceptible to the effects of rain, the LI-COR LI-7700 achieved lower data coverage and also required larger density corrections; however, the system is especially useful for remote sites that are restricted in power availability. In this study the open-path LI-7700 results were compromised due to a data acquisition problem in our data-logging setup. Some of the older closed-path analysers tested do not measure H 2 O concentrations alongside CH 4 (i.e. FMA1 and DLT-100 by Los Gatos Research) and this complicates data processing since the required corrections for dilution and spectroscopic interactions have to be based on external information. To overcome this issue, we used H 2 O mole fractions measured by other gas analysers, adjusted them with different methods and then applied them to correct the CH 4 fluxes. Following this procedure we estimated a bias of the order of 0.1 g (CH 4 ) m −2 (8 % of the measured mean flux) in the processed and corrected CH 4 fluxes on a monthly scale due to missing H 2 O concentration measurements. Finally, cumulative CH 4 fluxes over 14 days from three closed-path gas analysers, G2311-f (Picarro Inc.), FGGA (Los Gatos Research) and FMA2 (Los Gatos Research), which were measuring H 2 O concentrations in addition to CH 4 , agreed within 3 % (355-367 mg (CH 4 ) m −2 ) and were not clearly different from each other, whereas the other instruments derived total fluxes which showed small but distinct differences (±10 %, 330-399 mg (CH 4 ) m −2 ).Published by Copernicus Publications on behalf of the European Geosciences Union. 3164O. Peltola et al.: Evaluating the performance of gas analysers for CH 4 EC flux measurements

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“…Disturbed ecosystems cover a variable, small, but unknown fractional area of the land, and are intense sources of CO 2 to the atmosphere until plant production recovers, leading to a gradual change in activity towards a carbon sink. In recent years, there have been developments in the use of the eddy covariance measurement technique for measuring CH 4 and N 2 O fluxes (Hargreaves et al, 2001;Rinne et al, 2007;Smeets et al, 2009;Kroon et al, 2010) but no global product exists to our knowledge.…”

Section: Eddy Covariance Flux Tower Networkmentioning

confidence: 99%

Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system

Dolman²,

et al. 2014

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Abstract.A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observation system requires transformational advances from the existing sparse, exploratory framework towards a dense, robust, and sustained system in all components: anthropogenic emissions, the atmosphere, the ocean, and the terrestrial biosphere. The paper is addressed to scientists, policymakers, and funding agencies who need to have a global picture of the current state of the (diverse) carbon observations. We identify the current state of carbon observations, and the needs and notional requirements for a global integrated carbon observation system that can be built in the next decade. A key conclusion is the substantial expansion of the ground-based observation networks required to reach the high spatial resolution for CO 2 and CH 4 fluxes, and for carbon stocks for addressing policy-relevant objectives, and attributing flux changes to underlying processes in each region. In order to establish flux and stock diagnostics over areas such as the southern oceans, tropical forests, and the Arctic, in situ observations will have to be complemented with remote-sensing measurements. Remote sensing offers the advantage of dense spatial coverage and frequent revisit. A key challenge is to bring remote-sensing measurements to a level of long-term consistency and accuracy so that they can be efficiently combined in models to reduce uncertainties, in synergy with groundbased data. Bringing tight observational constraints on fossil fuel and land use change emissions will be the biggest challenge for deployment of a policy-relevant integrated carbon observation system. This will require in situ and remotely sensed data at much higher resolution and density than currently achieved for natural fluxes, although over a small land area (cities, industrial sites, power plants), as well as the inclusion of fossil fuel CO 2 proxy measurements such as radiocarbon in CO 2 and carbon-fuel combustion tracers. Additionally, a policy-relevant carbon monitoring system should also provide mechanisms for reconciling regional top-down (atmosphere-based) and bottom-up (surface-based) flux estimates across the range of spatial and temporal scales relevant to mitigation policies. In addition, uncertainties for each observation data-stream should be assessed. The success of the system will rely on long-term commitments to monitoring, on improved international collaboration to fill gaps in the current observations, on sustained efforts to improve access to the different data streams and make databases interoperable, and on the calibration of each component of the system to agreed-upon international scales.

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Eddy covariance methane measurements at a Ponderosa pine plantation in California

Cited by 60 publications

References 43 publications

Observations of reactive nitrogen oxide fluxes by eddy covariance above two midlatitude North American mixed hardwood forests

Observations of reactive nitrogen oxide fluxes by eddy covariance above two midlatitude North American mixed hardwood forests

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system

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