CO2 transport over complex terrain

Sun, Jielun; Burns, Sean P.; Delany, A. C.; Oncley, Steven; Turnipseed, Andrew A.; Stephens, Britton B.; Lenschow, Donald H.; LeMone, Margaret A.; Monson, Russell K.; Anderson, Dean E.

doi:10.1016/j.agrformet.2007.02.007

Cited by 102 publications

(108 citation statements)

References 72 publications

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“…It is difficult to explore these processes via single tower measurements, though some theoretical and experimental attempts are presented in Assouline et al (2008) for heat and water vapour above small reservoirs. Recent studies (Feigenwinter et al 2004;Aubinet et al 2005;Sun et al 2007) found that advection may be significant even during daytime especially with low intensity turbulence. However, the main concern refers to nocturnal conditions when an underestimation of CO 2 fluxes using the eddy-covariance technique frequently occurs because non-turbulent transport processes, not taken into account by the eddy-covariance system, become significant.…”

Section: Discussionmentioning

confidence: 99%

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On the Anomalous Behaviour of Scalar Flux–Variance Similarity Functions Within the Canopy Sub-layer of a Dense Alpine Forest

Cava

Katul

Sempreviva

et al. 2008

Boundary-Layer Meteorol

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Within the canopy sub-layer (CSL), variability in scalar sources and sinks are known to affect flux-variance (FV) similarity relationships for water vapour (q) and carbon dioxide (C) concentrations, yet large-scale processes may continue to play a significant role. High frequency time series data for temperature (T ), q and C, collected within the CSL of an uneven-aged mixed coniferous forest in Lavarone, Italy, are used to investigate these processes within the context of FV similarity. This dataset suggests that MOST scaling describes the FV similarity function of T even though the observations are collected in the CSL, consistent with other studies. However, the measured FV similarity functions for q and C appear to have higher values than their temperature counterpart. Two hypotheses are proposed to explain the measured anomalous behaviour in the FV similarity functions for q and C when referenced to T . Respired CO 2 from the forest floor leads to large positive excursions in the C time series at the canopy top thereby contributing significantly to both C variance increase and C vertical flux decrease-both leading to an anomalous increase in the FV similarity function. For q, transport of dry air from the outer-layer significantly increases both the variance and the water vapour flux. However, the expected flux increase is much smaller than the variance increase so that the net effect remains an increase in the measured FV similarity function for water vapour above its T counterpart. The hypothesis here is that identifying these events in the temporal and/or in the frequency domain and filtering them from the C and q time series partially recovers a scalar flow field that appears to follow FV similarity theory scaling. Methods for identifying both types of events in the time and frequency domains and their subsequent effects on the FV similarity functions and corollary flow variables, such as the relative transport efficiencies, are also explored.

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Section: Discussionmentioning

confidence: 99%

“…It is possible that departures from MOST scaling for FV may provide additional clues as to when CO 2 advection is important. However, Feigenwinter et al 2004, Aubinet et al 2005, Sun et al 2007 do not discuss the role of advection on FV similarity functions (only on CO 2 fluxes via the mean scalar continuity).…”

Section: Discussionmentioning

confidence: 99%

On the Anomalous Behaviour of Scalar Flux–Variance Similarity Functions Within the Canopy Sub-layer of a Dense Alpine Forest

Cava

Katul

Sempreviva

et al. 2008

Boundary-Layer Meteorol

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“…Goulden et al, 1996;Suyker et al, 2005;Moureaux et al, 2006;Zhao et al, 2006); and (ii) the "correction approach", based on a direct estimation of all the CO 2 balance terms, including the advection terms (e.g. Aubinet et al, 2003Aubinet et al, , 2005Feigenwinter et al, 2004;Staebler and Fitzjarrald, 2004;Marcolla et al, 2005;Sun et al, 2007;Yi et al, 2008;Montagnani et al, 2009). …”

Section: Introductionmentioning

confidence: 99%

Application of a mass consistent flow model to study the CO2 mass balance of forests

Canepa

Georgieva

Manca

et al. 2010

Agricultural and Forest Meteorology

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The reconstruction of the wind field is one of the main issues in the mass conservation approach for calculation of CO 2 advection in forest ecosystems and still remains a challenging problem. In the current study, we present an advancement of this approach: the use of a mass consistent flow model (WINDS) which takes into account measured wind data and simulates the 3-D flow field, while imposing air mass conservation in the control volume. We apply the WINDS model to calculate half hourly mean total advective flux terms at the arboEurope-IP site of Renon (Bozen/Bolzano Autonomous Province), in Northern Italy. The data used refer to six time periods of one day representing three different meteorological conditions observed during the ADVEX campaign from April to September 2005. Current results are compared with results obtained in two other studies for the same time periods. One of these studies is based on the mass conservation approach as well, but applies only interpolations to reconstruct the wind field; the other study makes use of tilt correction (sectorwise planar fit method) for the vertical wind component. In the present study, the effect of the wind field reconstruction method on the estimation of the advective fluxes is discussed. The possibility of using reduced input wind data (i.e. number of towers) for WINDS is also investigated. The results suggest that the representativeness of wind tower measurements is of primary importance for estimating CO 2 advection terms and their uncertainty in complex terrain.

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“…Siebicke et al (2012) found an additional second maximum for stable stratification and low air temperature due to radiative cooling at the end of the night. Sun et al (2007) also reported significant horizontal CO 2 advection during transition periods in the early evening and early morning when turbulence intensity is low.…”

Section: Introductionmentioning

confidence: 99%

Line-averaging measurement methods to estimate the gap in the CO<sub>2</sub> balance closure – possibilities, challenges, and uncertainties

2017

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Abstract. An imbalance of surface energy fluxes using the eddy covariance (EC) method is observed in global measurement networks although all necessary corrections and conversions are applied to the raw data. Mainly during nighttime, advection can occur, resulting in a closing gap that consequently should also affect the CO 2 balances. There is the crucial need for representative concentration and wind data to measure advective fluxes. Ground-based remote sensing techniques are an ideal tool as they provide the spatially representative CO 2 concentration together with wind components within the same voxel structure. For this purpose, the presented SQuAd (Spatially resolved Quantification of the Advection influence on the balance closure of greenhouse gases) approach applies an integrated method combination of acoustic and optical remote sensing. The innovative combination of acoustic travel-time tomography (A-TOM) and open-path Fourier-transform infrared spectroscopy (OP-FTIR) will enable an upscaling and enhancement of EC measurements. OP-FTIR instrumentation offers the significant advantage of real-time simultaneous measurements of lineaveraged concentrations for CO 2 and other greenhouse gases (GHGs). A-TOM is a scalable method to remotely resolve 3-D wind and temperature fields. The paper will give an overview about the proposed SQuAd approach and first results of experimental tests at the FLUXNET site Grillenburg in Germany.Preliminary results of the comprehensive experiments reveal a mean nighttime horizontal advection of CO 2 of about 10 µmol m −2 s −1 estimated by the spatially integrating and representative SQuAd method. Additionally, uncertainties in determining CO 2 concentrations using passive OP-FTIR and wind speed applying A-TOM are systematically quantified. The maximum uncertainty for CO 2 concentration was estimated due to environmental parameters, instrumental characteristics, and retrieval procedure with a total amount of approximately 30 % for a single measurement. Instantaneous wind components can be derived with a maximum uncertainty of 0.3 m s −1 depending on sampling, signal analysis, and environmental influences on sound propagation. Averaging over a period of 30 min, the standard error of the mean values can be decreased by a factor of at least 0.5 for OP-FTIR and 0.1 for A-TOM depending on the required spatial resolution. The presented validation of the joint application of the two independent, nonintrusive methods is in the focus of attention concerning their ability to quantify advective fluxes.

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CO2 transport over complex terrain

Cited by 102 publications

References 72 publications

On the Anomalous Behaviour of Scalar Flux–Variance Similarity Functions Within the Canopy Sub-layer of a Dense Alpine Forest

On the Anomalous Behaviour of Scalar Flux–Variance Similarity Functions Within the Canopy Sub-layer of a Dense Alpine Forest

Application of a mass consistent flow model to study the CO2 mass balance of forests

Line-averaging measurement methods to estimate the gap in the CO<sub>2</sub> balance closure – possibilities, challenges, and uncertainties

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CO2 transport over complex terrain

Cited by 102 publications

References 72 publications

On the Anomalous Behaviour of Scalar Flux–Variance Similarity Functions Within the Canopy Sub-layer of a Dense Alpine Forest

On the Anomalous Behaviour of Scalar Flux–Variance Similarity Functions Within the Canopy Sub-layer of a Dense Alpine Forest

Application of a mass consistent flow model to study the CO2 mass balance of forests

Line-averaging measurement methods to estimate the gap in the CO&lt;sub&gt;2&lt;/sub&gt; balance closure – possibilities, challenges, and uncertainties

Contact Info

Product

Resources

About

Line-averaging measurement methods to estimate the gap in the CO<sub>2</sub> balance closure – possibilities, challenges, and uncertainties