scholarly journals Tower and Aircraft Eddy Covariance Measurements of Water Vapor, Energy, and Carbon Dioxide Fluxes during SMACEX

2005 ◽  
Vol 6 (6) ◽  
pp. 954-960 ◽  
Author(s):  
J. H. Prueger ◽  
J. L. Hatfield ◽  
T. B. Parkin ◽  
W. P. Kustas ◽  
L. E. Hipps ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Water Vapor ◽  
Eddy Covariance ◽  
Spatial And Temporal Variability ◽  
Co2 Fluxes ◽  
Sensible Heat ◽  
Carbon Dioxide Fluxes ◽  
Crop Growth Stage ◽  
Aircraft Flux Measurements ◽  
Carbon Dioxide Co2

Abstract A network of eddy covariance (EC) and micrometeorological flux (METFLUX) stations over corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] canopies was established as part of the Soil Moisture–Atmosphere Coupling Experiment (SMACEX) in central Iowa during the summer of 2002 to measure fluxes of heat, water vapor, and carbon dioxide (CO2) during the growing season. Additionally, EC measurements of water vapor and CO2 fluxes from an aircraft platform complemented the tower-based measurements. Sensible heat, water vapor, and CO2 fluxes showed the greatest spatial and temporal variability during the early crop growth stage. Differences in all of the energy balance components were detectable between corn and soybean as well as within similar crops throughout the study period. Tower network–averaged fluxes of sensible heat, water vapor, and CO2 were observed to be in good agreement with area-averaged aircraft flux measurements.

scholarly journals Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK

2016 ◽  
Author(s):  
Carole Helfter ◽  
Anja H. Tremper ◽  
Christoforos H. Halios ◽  
Simone Kotthaus ◽  
Alex Bjorkegren ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Air Temperature ◽  
Combustion Efficiency ◽  
Spatial And Temporal Variability ◽  
Co2 Fluxes ◽  
Flux Footprint ◽  
Emissions Inventory ◽  
Carbon Dioxide Co2 ◽  
Cold Starts

Abstract. We report on more than three years of measurements of fluxes of methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2) taken by eddy-covariance in central London, UK. Inter-annual variability in the period 2012–2014 ranged from 36.3 to 40.7 ktons km−2 y−1 for CO2, and from 69 to 75 tons km−2 y−1 for CH4. Mean annual emissions of CO2 (39.1 ± 2.4 ktons km−2 y−1) and CO (89 ± 16 tons km−2 y−1) were consistent (within 1 % and 5 % respectively) with values from the London Atmospheric Emissions Inventory, but measured CH4 (72 ± 3 tons km−2 y−1) was over two-fold larger than the inventory value. Seasonal variability was large for CO with a winter to summer reduction of 69 %. Monthly fluxes of CO were strongly anti-correlated with mean air temperature, and the winter emissions accounted for 45 % of the annual budget. The winter increment in CO emissions was attributed mainly to vehicle cold starts and reduced fuel combustion efficiency. CO2 fluxes were 33 % higher in winter and anti-correlated with mean air temperature, albeit to a lesser extent than for CO. This was attributed to an increased demand for natural gas for heating during the winter. Seasonality in CH4 fluxes was moderate (21 % larger in winter) and linear correlation with air temperature was only statistically significant for certain wind sectors (N, NE, E and W), which was also the case for CO2. Differences in resident population within the flux footprint explained ca. 90 % variability by wind direction in annual CO2 fluxes and 99 % for CH4 (wind sectors excluded from linear regressions: S for CO2; S, SE and E for CH4). Seasonality and proportionality of emissions with respect to population in the outlying wind sectors (S, SE and E) might be masked by constant sources of CO2 and CH4, perhaps of industrial or biogenic origin. To our knowledge, this study is unique given the long-term, continuous dataset of urban CH4 fluxes analysed.

scholarly journals Low-level jets and above-canopy drainage as causes of turbulent exchange in the nocturnal boundary layer

2014 ◽  
Vol 11 (16) ◽  
pp. 4507-4519 ◽  
Author(s):  
T. S. El-Madany ◽  
H. F. Duarte ◽  
D. J. Durden ◽  
B. Paas ◽  
M. J. Deventer ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Wind Speed ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Heat Fluxes ◽  
Vertical Wind ◽  
Sensible Heat ◽  
Intermittent Turbulence ◽  
Low Level Jets ◽  
Vertical Wind Velocity

Abstract. Sodar (SOund Detection And Ranging), eddy-covariance, and tower profile measurements of wind speed and carbon dioxide were performed during 17 consecutive nights in complex terrain in northern Taiwan. The scope of the study was to identify the causes for intermittent turbulence events and to analyze their importance in nocturnal atmosphere–biosphere exchange as quantified with eddy-covariance measurements. If intermittency occurs frequently at a measurement site, then this process needs to be quantified in order to achieve reliable values for ecosystem characteristics such as net ecosystem exchange or net primary production. Fourteen events of intermittent turbulence were identified and classified into above-canopy drainage flows (ACDFs) and low-level jets (LLJs) according to the height of the wind speed maximum. Intermittent turbulence periods lasted between 30 and 110 min. Towards the end of LLJ or ACDF events, positive vertical wind velocities and, in some cases, upslope flows occurred, counteracting the general flow regime at nighttime. The observations suggest that the LLJs and ACDFs penetrate deep into the cold air pool in the valley, where they experience strong buoyancy due to density differences, resulting in either upslope flows or upward vertical winds. Turbulence was found to be stronger and better developed during LLJs and ACDFs, with eddy-covariance data presenting higher quality. This was particularly indicated by spectral analysis of the vertical wind velocity and the steady-state test for the time series of the vertical wind velocity in combination with the horizontal wind component, the temperature, and carbon dioxide. Significantly higher fluxes of sensible heat, latent heat, and shear stress occurred during these periods. During LLJs and ACDFs, fluxes of sensible heat, latent heat, and CO2 were mostly one-directional. For example, exclusively negative sensible heat fluxes occurred while intermittent turbulence was present. Latent heat fluxes were mostly positive during LLJs and ACDFs, with a median value of 34 W m−2, while outside these periods the median was 2 W m−2. In conclusion, intermittent turbulence periods exhibit a strong impact on nocturnal energy and mass fluxes.

scholarly journals Carbon Dioxide Fluxes and Carbon Stocks under Conservation Agricultural Practices in South Africa

Agriculture ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 374 ◽  
Author(s):  
Patrick Nyambo ◽  
Chiduza Cornelius ◽  
Tesfay Araya
Keyword(s):  
South Africa ◽  
Carbon Dioxide ◽  
Soil Moisture ◽  
Carbon Stock ◽  
Crop Residue ◽  
Agricultural Practices ◽  
Carbon Stocks ◽  
Residue Management ◽  
Co2 Fluxes ◽  
Carbon Dioxide Fluxes

Understanding the impacts of agricultural practices on carbon stocks and CO2 emission is imperative in order to recommend low emission strategies. The objective of this study was to investigate the effects of tillage, crop rotation, and residue management on soil CO2 fluxes, carbon stock, soil temperature, and moisture in the semi-arid conditions in the Eastern Cape of South Africa. The field trial was laid out as a split-split-plot design replicated three times. The main plots were tillage viz conventional tillage (CT) and no-till (NT). The sub-plots were allocated to crop rotations viz maize–fallow–maize (MFM), maize–oat–maize (MOM), and maize–vetch–maize (MVM). Crop residue management was in the sub-sub plots, viz retention (R+), removal (R−), and biochar (B). There were no significant interactions (p > 0.05) with respect to the cumulative CO2 fluxes, soil moisture, and soil temperature. Crop residue retention significantly increased the soil moisture content relative to residue removal, but was not different to biochar application. Soil tilling increased the CO2 fluxes by approximately 26.3% relative to the NT. The carbon dioxide fluxes were significantly lower in R− (2.04 µmoL m−2 s−1) relative to the R+ (2.32 µmoL m−2 s−1) and B treatments (2.36 µmoL m−2 s−1). The carbon dioxide fluxes were higher in the summer (October–February) months compared to the winter period (May–July), irrespective of treatment factors. No tillage had a significantly higher carbon stock at the 0-5 cm depth relative to CT. Amending the soils with biochar resulted in significantly lower total carbon stock relative to both R+ and R−. The results of the study show that NT can potentially reduce CO2 fluxes. In the short term, amending soils with biochar did not reduce the CO2 fluxes compared to R+, however the soil moisture increases were comparable.

scholarly journals Variability of dissolved CO<sub>2</sub> in the Pang and Lambourn Chalk rivers

2007 ◽  
Vol 11 (1) ◽  
pp. 328-339 ◽  
Author(s):  
J. Griffiths ◽  
J. Nutter ◽  
A. Binley ◽  
N. Crook ◽  
A. Young ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Seasonal Variation ◽  
Surface Waters ◽  
Temporal Variability ◽  
Stream Water ◽  
Spatial And Temporal Variability ◽  
Dissolved Carbon ◽  
Dissolved Carbon Dioxide ◽  
Borehole Water ◽  
Carbon Dioxide Co2

Abstract. This paper presents the results of a two-year field campaign to determine the spatial and temporal variability of groundwater interaction with surface waters in two Cretaceous Chalk catchments (the Pang and Lambourn) in the Upper Thames in Berkshire, UK, based on measurement of dissolved carbon dioxide (CO2). Average stream water concentrations of dissolved CO2 were up to 35 times the concentration at atmospheric equilibrium. Mean groundwater concentrations of 85 and 70 times the atmospheric equilibrium were determined from borehole water sampled in the Pang and Lambourn respectively. Diurnal and seasonal variation of in-stream concentration of dissolved CO2 is not significant enough to mask the signal from groundwater inputs.

scholarly journals Quantitative Fluxes of the Greenhouse Gases CH4 and CO2 from the Surfaces of Selected Polish Reservoirs

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 286
Author(s):  
Renata Gruca-Rokosz
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Gases ◽  
Water Column ◽  
Co2 Fluxes ◽  
Ch4 Flux ◽  
Chamber Method ◽  
Tropical Reservoirs ◽  
Se Poland ◽  
Carbon Dioxide Co2 ◽  
Eutrophic Reservoirs

Research carried out in the years 2009–2011 and 2018–2019 sought to determine the magnitudes of fluxes of methane (CH4) and carbon dioxide (CO2) from the surfaces of three eutrophic reservoirs in SE Poland. The “static chamber” method was deployed at five or six stations located along the reservoirs, where the water column at its deepest slightly exceeds 2 m. Obtained values for the fluxes of CH4 varied across a wide (0–2513.48 mmol·m−2·d−1) range, with many of these values therefore exceeding those characteristics for large tropical reservoirs. The reservoirs studied were not found to differ significantly in terms of average CH4 flux, however. Where obtained values for CO2 fluxes in the range from −10.96 to 621.69 mmol·m−2·d−1 were concerned, most fell within the range given for temperate-zone reservoirs, while differences between reservoirs were noted for average values in this case.

scholarly journals Carbon dioxide, water vapor and sensible heat fluxes over a tallgrass prairie

1989 ◽  
Vol 46 (1-2) ◽  
pp. 53-67 ◽  
Author(s):  
Shashi B. Verma ◽  
Joon Kim ◽  
Robert J. Clement
Keyword(s):  
Carbon Dioxide ◽  
Water Vapor ◽  
Tallgrass Prairie ◽  
Heat Fluxes ◽  
Sensible Heat

Effects of heat and water vapor transport on eddy covariance measurement of CO2 fluxes

1982 ◽  
Vol 23 (2) ◽  
pp. 209-222 ◽  
Author(s):  
R. Leuning ◽  
O. T. Denmead ◽  
A. R. G. Lang ◽  
E. Ohtaki
Keyword(s):  
Water Vapor ◽  
Eddy Covariance ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Co2 Fluxes ◽  
Eddy Covariance Measurement
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