Academic literature on the topic 'Airborne Eddy Covariance'
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Journal articles on the topic "Airborne Eddy Covariance"
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Lloyd, J., O. Kolle, H. Fritsch, S. R. de Freitas, M. A. F. Silva Dias, P. Artaxo, A. D. Nobre, et al. "An airborne regional carbon balance for Central Amazonia." Biogeosciences 4, no. 5 (September 14, 2007): 759–68. http://dx.doi.org/10.5194/bg-4-759-2007.
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Abstract. We obtained regional estimates of surface CO2 exchange rates using atmospheric boundary layer budgeting techniques above tropical forest near Manaus, Brazil. Comparisons were made with simultaneous measurements from two eddy covariance towers below. Although there was good agreement for daytime measurements, large differences emerged for integrating periods dominated by the night-time fluxes. These results suggest that a systematic underestimation of night time respiratory effluxes may be responsible for the high Amazonian carbon sink suggested by several previous eddy covariance studies. Large CO2 fluxes from riverine sources or high respiratory losses from recently disturbed forests do not need to be invoked in order to balance the carbon budget of the Amazon. Our results do not, however, discount some contribution of these processes to the overall Amazon carbon budget.
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Lloyd, J., O. Kolle, H. Fritsch, S. R. de Freitas, M. A. F. Silva Dias, P. Artaxo, A. D. Nobre, et al. "An airborne regional carbon balance for Central Amazonia." Biogeosciences Discussions 4, no. 1 (January 24, 2007): 99–123. http://dx.doi.org/10.5194/bgd-4-99-2007.
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Abstract. We obtained regional estimates of surface CO2 exchange rates using atmospheric boundary layer budgeting techniques above tropical forest near Manaus, Brazil. Comparisons were made with simultaneous measurements from two eddy covariance towers below. Although there was good agreement for daytime measurements, large differences emerged for integrating periods dominated by the night-time fluxes. These results suggest that a systematic underestimation of night time respiratory effluxes may be responsible for the high Amazonian carbon sink suggested by several previous eddy covariance studies. Large CO2 fluxes from riverine sources or high respiratory losses from recently disturbed forests do not need to be invoked in order to balance the carbon budget of the Amazon. Our results do not, however, discount some contribution of these processes to the overall Amazon carbon budget.
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Ellsäßer, Florian, Christian Stiegler, Alexander Röll, Tania June, Alexander Knohl, and Dirk Hölscher. "Predicting evapotranspiration from drone-based thermography – a method comparison in a tropical oil palm plantation." Biogeosciences 18, no. 3 (February 5, 2021): 861–72. http://dx.doi.org/10.5194/bg-18-861-2021.
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Abstract. For the assessment of evapotranspiration, near-surface airborne thermography offers new opportunities for studies with high numbers of spatial replicates and in a fine spatial resolution. We tested drone-based thermography and the subsequent application of the DATTUTDUT energy balance model using the widely accepted eddy covariance technique as a reference method. The study site was a mature oil palm plantation in lowland Sumatra, Indonesia. For the 61 flight missions, latent heat flux estimates of the DATTUTDUT (Deriving Atmosphere Turbulent Transport Useful To Dummies Using Temperature) model with measured net radiation agreed well with eddy covariance measurements (r2 = 0.85; MAE = 47; RMSE = 60) across variable weather conditions and times of day. Confidence intervals for slope and intercept of a model II Deming regression suggest no difference between drone-based and eddy covariance methods, thus indicating interchangeability. The DATTUTDUT model is sensitive to the configuration of the net radiation assessment. Overall, we conclude that drone-based thermography with energy balance modeling is a reliable method complementing available methods for evapotranspiration studies. It offers promising, additional opportunities for fine grain and spatially explicit studies.
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Karl, T., P. K. Misztal, H. H. Jonsson, S. Shertz, A. H. Goldstein, and A. B. Guenther. "Airborne Flux Measurements of BVOCs above Californian Oak Forests: Experimental Investigation of Surface and Entrainment Fluxes, OH Densities, and Damköhler Numbers." Journal of the Atmospheric Sciences 70, no. 10 (October 1, 2013): 3277–87. http://dx.doi.org/10.1175/jas-d-13-054.1.
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Abstract Airborne flux measurements of isoprene were performed over the Californian oak belts surrounding the Central Valley. The authors demonstrate for the first time 1) the feasibility of airborne eddy covariance measurements of reactive biogenic volatile organic compounds; 2) the effect of chemistry on the vertical transport of reactive species, such as isoprene; and 3) the applicability of wavelet analysis to estimate regional fluxes of biogenic volatile organic compounds. These flux measurements demonstrate that instrumentation operating at slower response times (e.g., 1–5 s) can still be used to determine eddy covariance fluxes in the mixed layer above land, where typical length scales of 0.5–3 km were observed. Flux divergence of isoprene measured in the planetary boundary layer (PBL) is indicative of OH densities in the range of 4–7 × 106 molecules per cubic centimeter and allows extrapolation of airborne fluxes to the surface with Damköhler numbers (ratio between the mixing time scale and the chemical time scale) in the range of 0.3–0.9. Most of the isoprene is oxidized in the PBL with entrainment fluxes of about 10% compared to the corresponding surface fluxes. Entrainment velocities of 1–10 cm s−1 were measured. The authors present implications for parameterizing PBL schemes of reactive species in regional and global models.
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Witt, Felix, Javis Nwaboh, Henning Bohlius, Astrid Lampert, and Volker Ebert. "Towards a Fast, Open-Path Laser Hygrometer for Airborne Eddy Covariance Measurements." Applied Sciences 11, no. 11 (June 3, 2021): 5189. http://dx.doi.org/10.3390/app11115189.
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Water vapor fluxes play a key role in the energy budget of the atmosphere, and better flux measurements are needed to improve our understanding of the formation of clouds and storms. Large-scale measurements of these fluxes are possible by employing the eddy correlation (EC) method from an aircraft. A hygrometer used for such measurements needs to deliver a temporal resolution of at least 10 Hz while reliably operating in the harsh conditions on the exterior of an aircraft. Here, we present a design concept for a calibration-free, first-principles, open-path dTDLAS hygrometer with a planar, circular and rotationally symmetric multipass cell with new, angled coupling optics. From our measurements, the uncertainty of the instrument is estimated to be below 4.5% (coverage factor k = 1). A static intercomparison between a dTDLAS prototype of the new optics setup and a traceable dew point mirror hygrometer was conducted and showed a systematic relative deviation of 2.6% with a maximal relative error of 2.2%. Combined with a precision of around 1 ppm H2O at tropospheric conditions, the newly designed setup fulfills the static precision and accuracy requirements of the proposed airborne EC hygrometer.
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Miglietta, F., B. Gioli, Y. Brunet, R. W. A. Hutjes, A. Matese, C. Sarrat, and A. Zaldei. "Sensible and latent heat flux from radiometric surface temperatures at the regional scale: methodology and validation." Biogeosciences Discussions 6, no. 1 (February 10, 2009): 1945–78. http://dx.doi.org/10.5194/bgd-6-1945-2009.
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Abstract. The CarboEurope Regional Experiment Strategy (CERES) was designed to develop and test a range of methodologies to assess regional surface energy and mass exchange of a large study area in the south-western part of France. This paper describes a methodology to estimate sensible and latent heat fluxes on the basis of net radiation, surface radiometric temperature measurements and information obtained from available products derived from the Meteosat Second Generation (MSG) geostationary meteorological satellite, weather stations and ground-based eddy covariance towers. It is based on a simplified bulk formulation of sensible heat flux that considers the degree of coupling between the vegetation and the atmosphere and estimates latent heat as the residual term of net radiation. Estimates of regional energy fluxes obtained in this way are validated at the regional scale by means of a comparison with direct flux measurements made by airborne eddy-covariance. The results show an overall good matching between airborne fluxes and estimates of sensible and latent heat flux obtained from radiometric surface temperatures that holds for different weather conditions and different land use types. The overall applicability of the proposed methodology to regional studies is discussed.
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Miglietta, F., B. Gioli, Y. Brunet, R. W. A. Hutjes, A. Matese, C. Sarrat, and A. Zaldei. "Sensible and latent heat flux from radiometric surface temperatures at the regional scale: methodology and evaluation." Biogeosciences 6, no. 10 (October 2, 2009): 1975–86. http://dx.doi.org/10.5194/bg-6-1975-2009.
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Abstract. The CarboEurope Regional Experiment Strategy (CERES) was designed to develop and test a range of methodologies to assess regional surface energy and mass exchange of a large study area in the South-Western part of France. This paper describes a methodology to estimate sensible and latent heat fluxes on the basis of net radiation, surface radiometric temperature measurements and information obtained from available products derived from the Meteosat Second Generation (MSG) geostationary meteorological satellite, weather stations and ground-based eddy covariance towers. It is based on a simplified bulk formulation of sensible heat flux that considers the degree of coupling between the vegetation and the atmosphere and estimates latent heat as the residual term of net radiation. Estimates of regional energy fluxes obtained in this way are validated at the regional scale by means of a comparison with direct flux measurements made by airborne eddy-covariance. The results show an overall good matching between airborne fluxes and estimates of sensible and latent heat flux obtained from radiometric surface temperatures that holds for different weather conditions and different land use types. The overall applicability of the proposed methodology to regional studies is discussed.
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Ammann, C., V. Wolff, O. Marx, C. Brümmer, and A. Neftel. "Measuring the biosphere-atmosphere exchange of total reactive nitrogen by eddy covariance." Biogeosciences Discussions 9, no. 6 (June 13, 2012): 6857–98. http://dx.doi.org/10.5194/bgd-9-6857-2012.
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Abstract. The (net) exchange of reactive nitrogen (Nr) with the atmosphere is an important driver for ecosystem productivity and greenhouse gas exchange. The exchange of airborne Nr includes various trace compounds that usually require different specific measurement techniques, and up to now fast response instruments suitable for eddy covariance measurements are only available for few of these compounds. Here we present eddy covariance flux measurements with a recently introduced converter (TRANC) for the sum of all Nr compounds (∑Nr). Measurements were performed over a managed grassland field with phases of net emission and net deposition of ∑Nr and alternating dominance of oxidized (NOx) and reduced species (NH3). Spectral analysis of the eddy covariance data exhibited the existence of covariance function peaks at a reasonable time lag related to the sampling tube residence time under stationary conditions. Using ogive analysis, the high-frequency damping was quantified to 19–26% for a low measurement height of 1.2 m and to about 10% for 4.8 m measurement height. ∑Nr concentrations and fluxes were compared to parallel NO and NO2 measurements by dynamic chambers and NH3 measurements by the aerodynamic gradient technique. The average concentration results indicate that close-to-full conversion of the main compounds NO2 and NH3 was generally obtained by the TRANC system. With an optimised sample inlet also the fluxes of these compounds were recovered fairly including net deposition and net emission phases. The study shows that the TRANC system is suitable for fast response measurements of oxidized and reduced nitrogen compounds and can be used for continuous eddy covariance flux measurements of total reactive nitrogen.
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Ammann, C., V. Wolff, O. Marx, C. Brümmer, and A. Neftel. "Measuring the biosphere-atmosphere exchange of total reactive nitrogen by eddy covariance." Biogeosciences 9, no. 11 (November 2, 2012): 4247–61. http://dx.doi.org/10.5194/bg-9-4247-2012.
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Abstract. The (net) exchange of reactive nitrogen (Nr) with the atmosphere is an important driver for ecosystem productivity and greenhouse gas exchange. The exchange of airborne Nr includes various trace compounds that usually require different specific measurement techniques, and up to now fast response instruments suitable for eddy covariance measurements are only available for few of these compounds. Here we present eddy covariance flux measurements with a recently introduced converter (TRANC) for the sum of all Nr compounds (∑Nr). Measurements were performed over a managed grassland field with phases of net emission and net deposition of ∑Nr and alternating dominance of oxidized (NOX) and reduced species (NH3). Spectral analysis of the eddy covariance data exhibited the existence of covariance function peaks at a reasonable time lag related to the sampling tube residence time under stationary conditions. Using ogive analysis, the high-frequency damping was quantified to 19%–26% for a low measurement height of 1.2 m and to about 10% for 4.8 m measurement height. ∑Nr concentrations and fluxes were compared to parallel NO and NO2 measurements by dynamic chambers and NH3 measurements by the aerodynamic gradient technique. The average concentration results indicate that the main compounds NO2 and NH3 were converted by the TRANC system with an efficiency of near 100%. With an optimised sample inlet also the fluxes of these compounds were recovered reasonably well including net deposition and net emission phases. The study shows that the TRANC system is suitable for fast response measurements of oxidized and reduced nitrogen compounds and can be used for continuous eddy covariance flux measurements of total reactive nitrogen.
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Serafimovich, Andrei, Stefan Metzger, Jörg Hartmann, Katrin Kohnert, Donatella Zona, and Torsten Sachs. "Upscaling surface energy fluxes over the North Slope of Alaska using airborne eddy-covariance measurements and environmental response functions." Atmospheric Chemistry and Physics 18, no. 13 (July 13, 2018): 10007–23. http://dx.doi.org/10.5194/acp-18-10007-2018.
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Abstract. The objective of this study was to upscale airborne flux measurements of sensible heat and latent heat and to develop high-resolution flux maps. In order to support the evaluation of coupled atmospheric–land-surface models we investigated spatial patterns of energy fluxes in relation to land-surface properties. We used airborne eddy-covariance measurements acquired by the Polar 5 research aircraft in June–July 2012 to analyze surface fluxes. Footprint-weighted surface properties were then related to 21 529 sensible heat flux observations and 25 608 latent heat flux observations using both remote sensing and modeled data. A boosted regression tree technique was used to estimate environmental response functions between spatially and temporally resolved flux observations and corresponding biophysical and meteorological drivers. In order to improve the spatial coverage and spatial representativeness of energy fluxes we used relationships extracted across heterogeneous Arctic landscapes to infer high-resolution surface energy flux maps, thus directly upscaling the observational data. These maps of projected sensible heat and latent heat fluxes were used to assess energy partitioning in northern ecosystems and to determine the dominant energy exchange processes in permafrost areas. This allowed us to estimate energy fluxes for specific types of land cover, taking into account meteorological conditions. Airborne and modeled fluxes were then compared with measurements from an eddy-covariance tower near Atqasuk. Our results are an important contribution for the advanced, scale-dependent quantification of surface energy fluxes and they provide new insights into the processes affecting these fluxes for the main vegetation types in high-latitude permafrost areas.
Dissertations / Theses on the topic "Airborne Eddy Covariance"
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Vaughan, Adam Robert. "Measurement and understanding of emissions over London and Southern England by airborne eddy-covariance." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18146/.
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High anthropogenic emissions are a global problem with clear links existing between poor air quality and premature mortality, which is of great alarm to organisations such as the World Health Organisation (WHO). In Europe, high emissions of nitrogen oxides (NOx) are a concern with concentrations plateauing over the last 15 years. Emission assessment is a key part of the UK’s air quality strategy; this is done so by using tools such as the National Atmospheric Emissions Inventory (NAEI), to report annual emissions to the EU to meet strict air quality regulations. Due to the high importance placed on inventories such as the NAEI, their accuracy is vital. This thesis details the development and implementation of an airborne eddy−covariance (AEC) strategy to measure anthropogenic fluxes over highly polluted areas, and compare these findings to UK emission inventories. The Ozone Precursor Fluxes in an Urban Environment (OPFUE) campaign was run over two consecutive years, aiming at evaluating emissions from London and Southern England. NOx emissions were evaluated over London showing high emissions coming from central areas. Comparison to the NAEI found NOx emissions were being underestimation by up to a factor of 2. Refinement using the NAEI + road transport estimates scaled via road side measurements showed good improvement, suggesting the need to refine road transport estimates used in the NAEI. A variety of VOC emissions were also measured over London and Southern England. Measured VOCs over London showed good agreement to the NAEI, and highlighted the successful reduction of VOC emissions through air quality strategies. Measured biogenic emissions of isoprene were found to be higher than air quality model estimates, which could have implications towards regional air quality due to ground level ozone formation. Overall, the described methodology allows for real-time assessment of emission inventories which is key if the UK is to see improvements in its air quality.
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Bleyl, Matthias. "Experimentelle Bestimmung der Depositionsgeschwindigkeit luftgetragener Partikel mit Hilfe der Eddy-Kovarianzmethode über einem Fichtenaltbestand im Solling." Doctoral thesis, 2001. http://hdl.handle.net/11858/00-1735-0000-0006-B25A-0.
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