scholarly journals A Primer on Gas Phase CO2 Production and Transport in Peatland Soils

Land Science ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. p45
Author(s):  
Stephen Barry ◽  
Alan Gilmer ◽  
John Cassidy ◽  
Eugene McGovern ◽  
Vivienne Byers
Keyword(s):  
Vegetation Type ◽  
Emission Factors ◽  
Surface Fluxes ◽  
Co2 Production ◽  
Co2 Efflux ◽  
Diffusive Transport ◽  
Landuse Change ◽  
Tier 1 ◽  
Modelling Studies ◽  
Short Time

CO2 sequestered by peatlands is accounted for and offset against national emissions. Observational and modelling studies are used to estimate emission factors that dictate the rate of CO2 emissions or removals from peatlands accounted for within the Landuse and landuse change including forestry (LULUCF) sector and often use simple Tier 1 emission factors found in the IPCC (1996) guidebook. However, the current estimates are predominately based off peatland surface fluxes measured using either chamber methods or eddy covariance techniques. These methods do not focus on sub-surface conditions while this information may prove useful in understanding efflux rates and conditions that influence them. To help assess the potential significance of subsurface dynamics in overall CO2 efflux rates from peatlands this study proposes to review the literature dealing with subsurface conditions. The review found that the production of CO2 in the sub-surface layers was often uncoupled from emissions and that on short time-scales the storage of CO2 in soil pores and dissolved in soil water may account for this. The rate of production was found to be influenced by decomposition rate, vegetation type, nutrient availability and peat depth. The review also found that the mechanism of transport of CO2 within the sub-surface was important in accounting for efflux rates. While diffusion is often assumed the most significant form of transport, the quantification and dynamics of other non-diffusive transport methods were found to also be important and further research is required to ascertain the drivers of both diffusive and non-diffusive transport.

Peering into the internal structure of cold pools and their interactions with a dense observational network

2021 ◽  
Author(s):  
Cathy Hohenegger ◽  
Jaemyeong Seo ◽  
Hannes Nevermann ◽  
Bastian Kirsch ◽  
Nima Shokri ◽  
...  
Keyword(s):  
Internal Structure ◽  
Land Surface ◽  
Surface Fluxes ◽  
Cold Pool ◽  
Convective Clouds ◽  
Cold Pools ◽  
Soil Sensors ◽  
Modelling Studies ◽  
Surface Network ◽  
Shed Light

<p>Melting and evaporation of hydrometeors in and below convective clouds generates cold, dense air that falls through the atmospheric column and spreads at the surface like a density current, the cold pool. In modelling studies, the importance of cold pools in controlling the lifecycle of convection has often been emphasized, being through their organization of the cloud field or through their sheer deepening of the convection. Larger, longer-lived cold pools benefit convection, but little is actually known on the size and internal structure of cold pools from observations as the majority of cold pools are too small to be captured by the operational surface network.  One aim of the field campaign FESSTVaL was to peer into the internal structure of cold pools and their interactions with the underlying land surface by deploying a dense network of surface observations. This network consisted of 80 self-designed cold pool loggers, 19 weather stations and 83 soil sensors deployed in an area of 15 km around Lindenberg. FESSTVaL took place from 17 May to 27 August 2021.</p> <p>In principle, cold pool characteristics are affected both by the atmospheric state, which fuels cold pools through melting and evaporation of hydrometeors, and the land surface, which acts to destroy cold pools through friction and warming by surface fluxes. In this talk, the measurements collected during FESSTVaL will be used to shed light on these interactions.  We are particularly interested to assess how homogeneous the internal structure of cold pools is and whether heterogeneities of the land surface imprint themselves on this internal structure. The results will be compared to available model simulations.</p>

scholarly journals Laboratory measurements of trace gas emissions from biomass burning of fuel types from the Southeastern and Southwestern United States

2010 ◽  
Vol 10 (7) ◽  
pp. 16425-16473 ◽  
Author(s):  
I. R. Burling ◽  
R. J. Yokelson ◽  
D. W. T. Griffith ◽  
T. J. Johnson ◽  
P. Veres ◽  
...  
Keyword(s):  
Gas Phase ◽  
Prescribed Burning ◽  
Vegetation Type ◽  
Emission Factors ◽  
Military Bases ◽  
Coastal Regions ◽  
Trace Gas Emissions ◽  
Us Military ◽  
Flaming Combustion ◽  
Us Forest Service

Abstract. Vegetation commonly managed by prescribed burning was collected from five southeastern and southwestern US military bases and burned under controlled conditions at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. The smoke emissions were measured with a large suite of state-of-the-art instrumentation including an open-path Fourier transform infrared (OP-FTIR) spectrometer for measurement of gas-phase species. The OP-FTIR detected and quantified 19 gas-phase species in these fires: CO2, CO, CH4, C2H2, C2H4, C3H6, HCHO, HCOOH, CH3OH, CH3COOH, furan, H2O, NO, NO2, HONO, NH3, HCN, HCl, and SO2. Emission factors for these species are presented for each vegetation type burned. Gas-phase nitrous acid (HONO), an important OH precursor, was detected in the smoke from all fires. The HONO emission factors ranged from 0.15 to 0.60 g kg−1 and were higher for the southeastern fuels. The fire-integrated molar emission ratios of HONO (relative to NOx) ranged from approximately 0.03 to 0.20, with higher values also observed for the southeastern fuels. The majority of non-methane organic compound (NMOC) emissions detected by OP-FTIR were oxygenated volatile organic compounds (OVOCs) with the total identified OVOC emissions constituting 61±12% of the total measured NMOC on a molar basis. These OVOC may undergo photolysis or further oxidation contributing to ozone formation. Elevated amounts of gas-phase HCl and SO2 were also detected during flaming combustion, with the amounts varying greatly depending on location and vegetation type. The fuels with the highest HCl emission factors were all located in the coastal regions, although HCl was also observed from fuels farther inland. Emission factors for HCl were generally higher for the southwestern fuels, particularly those found in the chaparral biome in the coastal regions of California.

scholarly journals Examining the link between vegetation leaf area and land-atmosphere exchange of water, energy, and carbon fluxes using FLUXNET data

2020 ◽  
Author(s):  
Anne J. Hoek van Dijke ◽  
Kaniska Mallick ◽  
Martin Schlerf ◽  
Miriam Machwitz ◽  
Martin Herold ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Primary Productivity ◽  
Large Scale ◽  
Vegetation Type ◽  
Carbon Fluxes ◽  
Surface Fluxes ◽  
Energy Fluxes ◽  
Area Index ◽  
Vegetation Control

Abstract. Vegetation regulates the exchange of water, energy, and carbon fluxes between the land and the atmosphere. This regulation of surface fluxes differs with vegetation type and climate, but the effect of vegetation on surface fluxes is not well understood. A better knowledge of how and when vegetation influences surface fluxes could improve climate models and the extrapolation of ground-based water, energy, and carbon fluxes. We aim to study the large-scale link between vegetation and surface fluxes by combining MODIS leaf area index with flux tower measurements of water (latent heat), energy (sensible heat), and carbon (gross primary productivity and net ecosystem exchange). We show that the correlation between leaf area index and water and energy fluxes depends on vegetation and aridity. In water-limited conditions, the link between vegetation and water and energy fluxes is strong, which is in line with a strong stomatal or vegetation control found in earlier studies. In energy-limited forest we found no vegetation control on water and energy fluxes. In contrast to water and energy fluxes, we found a strong correlation between leaf area index and gross primary productivity that was independent of vegetation type and aridity index. This study provides insight in the large-scale link between vegetation and surface fluxes. The study indicates that for modelling or extrapolating large-scale surface fluxes, LAI can be useful in savanna and grassland, but only of limited use in deciduous broadleaf forest and evergreen needleleaf forest.

Assessment of shipping emission factors through monitoring and modelling studies

2020 ◽  
Vol 743 ◽  
pp. 140742 ◽  
Author(s):  
Araks Ekmekçioğlu ◽  
S. Levent Kuzu ◽  
Kaan Ünlügençoğlu ◽  
Uğur Buğra Çelebi
Keyword(s):  
Emission Factors ◽  
Modelling Studies

scholarly journals Near-field emission profiling of Rainforest and Cerrado fires in Brazil during SAMBBA 2012

2017 ◽  
Author(s):  
Amy K. Hodgson ◽  
William T. Morgan ◽  
Sebastian O'Shea ◽  
Stéphane Bauguitte ◽  
James D. Allan ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Near Field ◽  
Emission Factors ◽  
Fuel Combustion ◽  
Trace Gas ◽  
Particulate Emissions ◽  
Particulate Emission ◽  
Airborne Measurements ◽  
Modelling Studies ◽  
Fire Conditions

Abstract. We profile trace gas and particulate emissions from near-field airborne measurements of discrete smoke plumes in Brazil during the 2012 biomass burning season. The South American Biomass Burning Analysis (SAMBBA) Project conducted during September and October 2012 sampled across two distinct fire regimes prevalent in the Amazon Basin. Combined measurements from a Compact Time Of Flight Aerosol Mass Spectrometer (C-ToF-AMS) and a Single Particle Soot Photometer (SP2) are reported for the first time in a tropical biomass burning environment. Emissions from a mostly-smouldering rainforest wildfire in Rondonia state and numerous smaller flaming Cerrado fires in Tocantins state are presented. While the Cerrado fires appear to be representative of typical fire conditions in the existing literature, the rainforest wildfire likely represents a more extreme example of biomass burning with a bias towards mostly-smouldering emissions. We determined fire integrated modified combustion efficiencies, emission ratios and emission factors for trace gas and particulate components for these two fire types, alongside aerosol microphysical properties. Seven times more black carbon was emitted from the Cerrado fires per unit of fuel combustion (EFBC of 0.13 ± 0.04 g kg−1) compared to the rainforest fire (EFBC of 0.019 ± 0.006 g kg−1) and more than six times the amount of organic aerosol was emitted from the rainforest fire per unit of fuel combustion (EFOC of 5.00 ± 1.58 g kg−1) compared to the Cerrado fires (EFOC of 0.82 ± 0.26 g kg−1). Particulate phase species emitted from the fires sampled are generally lower than those reported in previous studies and in emission inventories, which is likely a combination of differences in fire combustion efficiency and fuel content, along with different measurement techniques. Previous modelling studies focussed on the biomass burning season in tropical South America have required significant scaling of emissions to reproduce in-situ and satellite aerosol concentrations over the region. Our results do not indicate that emission factors used in inventories are biased low, which could be one potential cause of the reported underestimates in modelling studies. This study supplements and updates trace gas and particulate emission factors for fire type specific biomass burning in Brazil for use in weather and climate models. The study illustrates that initial fire conditions can result in substantial differences in terms of their emitted chemical components, which can potentially perturb the Earth system.

scholarly journals Modelling the diurnal and seasonal dynamics of soil CO<sub>2</sub> exchange in a semiarid ecosystem with high plant–interspace heterogeneity

2018 ◽  
Vol 15 (1) ◽  
pp. 115-136 ◽  
Author(s):  
Jinnan Gong ◽  
Ben Wang ◽  
Xin Jia ◽  
Wei Feng ◽  
Tianshan Zha ◽  
...  
Keyword(s):  
Seasonal Dynamics ◽  
Root Zone ◽  
Model Simulation ◽  
Plant Cover ◽  
C Sequestration ◽  
Co2 Production ◽  
Co2 Efflux ◽  
Soil Co2 ◽  
Soil C ◽  
Water Flows

Abstract. We used process-based modelling to investigate the roles of carbon-flux (C-flux) components and plant–interspace heterogeneities in regulating soil CO2 exchanges (FS) in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of FS, the modelling considered simultaneously the CO2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation). The model was parameterized and validated with multivariate data measured during the years 2013–2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO2 dissolution and delay the emission of CO2 produced from rooting zone. In addition, an ineligible fraction of respired CO2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO2 source to sink due to the activated photosynthesis of biocrust but the restricted CO2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant–interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO2 efflux dynamics in dryland ecosystems.

scholarly journals Simulating the IHOP_2002 Fair-Weather CBL with the WRF-ARW–Noah Modeling System. Part I: Surface Fluxes and CBL Structure and Evolution along the Eastern Track

2010 ◽  
Vol 138 (3) ◽  
pp. 722-744 ◽  
Author(s):  
Margaret A. LeMone ◽  
Fei Chen ◽  
Mukul Tewari ◽  
Jimy Dudhia ◽  
Bart Geerts ◽  
...  
Keyword(s):  
Heat Flux ◽  
Land Surface ◽  
Roughness Length ◽  
Vegetation Type ◽  
Sensible Heat Flux ◽  
Surface Fluxes ◽  
Weather Data ◽  
Surface Model ◽  
Fair Weather ◽  
Convective Boundary

Abstract Fair-weather data from the May–June 2002 International H2O Project (IHOP_2002) 46-km eastern flight track in southeast Kansas are compared to simulations using the advanced research version of the Weather Research and Forecasting model coupled to the Noah land surface model (LSM), to gain insight into how the surface influences convective boundary layer (CBL) fluxes and structure, and to evaluate the success of the modeling system in representing CBL structure and evolution. This offers a unique look at the capability of the model on scales the length of the flight track (46 km) and smaller under relatively uncomplicated meteorological conditions. It is found that the modeled sensible heat flux H is significantly larger than observed, while the latent heat flux (LE) is much closer to observations. The slope of the best-fit line ΔLE/ΔH to a plot of LE as a function of H, an indicator of horizontal variation in available energy H + LE, for the data along the flight track, was shallower than observed. In a previous study of the IHOP_2002 western track, similar results were explained by too small a value of the parameter C in the Zilitinkevich equation used in the Noah LSM to compute the roughness length for heat and moisture flux from the roughness length for momentum, which is supplied in an input table; evidence is presented that this is true for the eastern track as well. The horizontal variability in modeled fluxes follows the soil moisture pattern rather than vegetation type, as is observed; because the input land use map does not capture the observed variation in vegetation. The observed westward rise in CBL depth is successfully modeled for 3 of the 4 days, but the actual depths are too high, largely because modeled H is too high. The model reproduces the timing of observed cumulus cloudiness for 3 of the 4 days. Modeled clouds lead to departures from the typical clear-sky straight line relating surface H to LE for a given model time, making them easy to detect. With spatial filtering, a straight slope line can be recovered. Similarly, larger filter lengths are needed to produce a stable slope for observed fluxes when there are clouds than for clear skies.

Legacy effects of multiyear summer drought on soil CO2 production, transport and efflux in a sub-alpine grassland

2021 ◽  
Author(s):  
Carmen Telser ◽  
Eliza Harris ◽  
David Reinthaler ◽  
Michael Bahn
Keyword(s):  
Soil Respiration ◽  
Soil Profile ◽  
Abiotic Factors ◽  
Co2 Production ◽  
Summer Drought ◽  
Diffusive Transport ◽  
Transport Mechanisms ◽  
Drought Treatment ◽  
Flux Gradient ◽  
Gradient Approach

&lt;p&gt;Climate change is expected to lead to an increase in frequency and severity of extreme climatic events like summer drought. Drought and rewetting have strong impacts on soil respiration, which constitutes the largest flux of CO&lt;sub&gt;2&lt;/sub&gt; from terrestrial ecosystems to the atmosphere. However, little is known about the role of biotic and abiotic factors in driving CO&lt;sub&gt;2&lt;/sub&gt; production and transport across the soil profile and how these processes are affected by repeated drought events. Soil CO&lt;sub&gt;2&lt;/sub&gt; transport can be assessed using the flux-gradient approach, a method which assumes that diffusion is the only transport mechanism for CO&lt;sub&gt;2&lt;/sub&gt; through soil, with diffusion rates primarily dependent on air-filled pore space. It is therefore generally assumed that the calculated soil CO&lt;sub&gt;2&lt;/sub&gt; concentration gradient translates directly into soil CO&lt;sub&gt;2&lt;/sub&gt; efflux, however, a discrepancy between measured soil CO&lt;sub&gt;2&lt;/sub&gt; efflux and modeled soil CO&lt;sub&gt;2&lt;/sub&gt; concentration gradients can indicate presence of non-diffusive transport mechanisms.&lt;/p&gt;&lt;p&gt;In a multiyear drought and rewetting experiment at a mountain meadow in the Austrian Alps, we compared soil CO&lt;sub&gt;2&lt;/sub&gt; production, transport and efflux for plots which were exposed to two and twelve subsequent years of experimental summer drought, respectively, versus plots with ambient precipitation and soil moisture. We measured soil respiration using automated chambers and assessed the production and transport of CO&lt;sub&gt;2&lt;/sub&gt; using the flux-gradient approach on data obtained with solid-state sensors in three soil depths through the soil profile. We tested the hypothesis that drought-driven reduction in soil respiration will be more intense for the 12-year drought treatment, but the CO&lt;sub&gt;2&lt;/sub&gt; pulse induced by rewetting will be higher. We furthermore expected that non-diffusive transport mechanisms would play a crucial role during drought and would be more pronounced in the 12-year drought treatment compared to the 2-year drought treatment. Data analysis is currently in progress, the findings will be presented at the conference.&lt;/p&gt;

scholarly journals What is the Mechanism for the Modification of Convective Cloud Distributions by Land Surface–Induced Flows?

2011 ◽  
Vol 68 (3) ◽  
pp. 619-634 ◽  
Author(s):  
Luis Garcia-Carreras ◽  
Douglas J. Parker ◽  
John H. Marsham
Keyword(s):  
Land Surface ◽  
Vegetation Type ◽  
Potential Temperature ◽  
Convective Cloud ◽  
Bowen Ratio ◽  
Surface Fluxes ◽  
Synoptic Conditions ◽  
Thermodynamic Conditions ◽  
Wind Velocities ◽  
Convergence Zones

Abstract The aim of this study is to determine the mechanism that modulates the initiation of convection within convergence zones caused by land surface–induced mesoscale flows. An idealized modeling approach linked quantitatively to observations of vegetation breezes over tropical Benin was used. A large-eddy model was used with a prescribed land surface describing heterogeneities between crop and forest over which vegetation breezes have been observed. The total surface fluxes were constant but the Bowen ratio varied with vegetation type. The heterogeneous land surface created temperature differences consistent with observations, which in turn forced mesoscale winds and convection at the convergence zones over the crop boundaries. At these convergence zones optimum conditions for the initiation of convection were found in the afternoon; the equivalent potential temperature was higher in the convergence zones than over anywhere else in the domain, due to reduced entrainment, and the mesoscale convergence produced a persistent increase in vertical wind velocities of up to 0.5 m s−1 over a 5–10-km region. The relative importance of these two mechanisms depended on the synoptic conditions. When convective inhibition was weak, the thermodynamic conditions at the convergence zone were most important, as the triggering of convection was easily accomplished. However, when the thermodynamic profile inhibited convection, the mesoscale updrafts became essential for triggering in order to break through the inhibiting barrier. At the same time, subsidence over the forest produced a warm capping layer over the boundary layer top that suppressed convection over the forest throughout the afternoon.

scholarly journals Does predictability of fluxes vary between FLUXNET sites?

2018 ◽  
Vol 15 (14) ◽  
pp. 4495-4513 ◽  
Author(s):  
Ned Haughton ◽  
Gab Abramowitz ◽  
Martin G. De Kauwe ◽  
Andy J. Pitman
Keyword(s):  
Land Surface ◽  
Vegetation Type ◽  
Individual Site ◽  
Site Characteristics ◽  
Tier 1 ◽  
Eddy Covariance Measurements ◽  
The Mean ◽  
Type Data ◽  
Definition Of ◽  
Data Length

Abstract. The FLUXNET dataset contains eddy covariance measurements from across the globe and represents an invaluable estimate of the fluxes of energy, water, and carbon between the land surface and the atmosphere. While there is an expectation that the broad range of site characteristics in FLUXNET result in a diversity of flux behaviour, there has been little exploration of how predictable site behaviour is across the network. Here, 155 datasets with 30 min temporal resolution from the Tier 1 of FLUXNET 2015 were analysed in a first attempt to assess individual site predictability. We defined site uniqueness as the disparity in performance between multiple empirical models trained globally and locally for each site and used this along with the mean performance as measures of predictability. We then tested how strongly uniqueness was determined by various site characteristics, including climatology, vegetation type, and data quality. The strongest determinant of predictability appeared to be that drier sites tended to be more unique. We found very few other clear predictors of uniqueness across different sites, in particular little evidence that flux behaviour was well discretised by vegetation type. Data length and quality also appeared to have little impact on uniqueness. While this result might relate to our definition of uniqueness, we argue that our approach provides a useful basis for site selection in LSM evaluation, and we invite critique and development of the methodology.

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