Global Methane Emissions Through an Isotopic Lens

2020 ◽  
Author(s):  
Alice Drinkwater ◽  
Tim Arnold ◽  
Paul Palmer
Keyword(s):  
Transport Model ◽  
Global Climate ◽  
Agricultural Practices ◽  
Isotope Ratios ◽  
Atmospheric Methane ◽  
Source Attribution ◽  
Chemical Transport Model ◽  
Magnitude Distribution ◽  
In Situ Data

<p>Changes in atmospheric methane (CH<sub>4</sub>) are mainly driven by natural, anthropogenic and pyrogenic emissions and oxidation by OH.</p><p>There is no consensus about the underlying explanations about hemispheric-scale changes in atmospheric methane (CH<sub>4</sub>). This is partly due to sparse data that do not exclusively identify individual changes in surface emissions and surface and atmospheric losses of CH<sub>4</sub>. This challenge represents a major scientific weakness in our understanding of this potent greenhouse gas, with implications for meeting global climate policy obligations.  A confounding challenge is that the regional importance of individual emission sources change with time due to, for example, innovations in agricultural practices, climate-sensitive wetlands, and political decisions associated with climate friendlier transitional fuels.  </p><p><br>Here we use bulk isotope ratios δ<sup>13</sup>C and δD of CH<sub>4</sub> that have been previously shown to provide effective constraints on source apportionment: different CH<sub>4</sub> sources have characteristic isotope ratios. One of the key challenges associated with using these data is that region-specific isotope ratios change with time due to varying source prevalance, in addition to source signatures having inherent uncertainties. We use the GEOS-Chem global 3-D chemical transport model to describe the spatial and temporal isotopic behaviour of atmospheric CH<sub>4</sub>. We develop a Maximum A-Posteriori inverse method to simultaneously infer time dependent CH<sub>4</sub> emissions and isotope ratios from in situ data. </p><p>We will report the magnitude, distribution and source attribution of CH<sub>4</sub> emissions from 2004 to 2017, inferred from in situ measurements of total atmospheric CH<sub>4</sub> mole fraction and the corresponding measurements of δ<sup>13</sup>C and δD. We will compare our results with previous studies.</p>

scholarly journals Ten years of atmospheric methane from ground-based NDACC FTIR observations

2016 ◽  
Author(s):  
Whitney Bader ◽  
Benoît Bovy ◽  
Stephanie Conway ◽  
Kimberly Strong ◽  
Dan Smale ◽  
...  
Keyword(s):  
Transport Model ◽  
Atmospheric Composition ◽  
Atmospheric Methane ◽  
Chemical Transport Model ◽  
Oil Transport ◽  
Sigma Level ◽  
Solar Observations ◽  
Time Period ◽  
Emissions Inventories

Abstract. Changes of atmospheric methane (CH4) since 2005 have been evaluated using Fourier Transform Infrared (FTIR) solar observations performed at ten ground-based sites, all members of the Network for Detection of Atmospheric Composition Change (NDACC). From this, we find an increase of atmospheric methane total columns that amounts to 0.31 ± 0.03 % year−1 (2-sigma level of uncertainty) for the 2005–2014 period. Comparisons with in situ methane measurements at both local and global scales show good agreement. We used the GEOS-Chem Chemical Transport Model tagged simulation that accounts for the contribution of each emission source and one sink in the total methane, simulated over the 2005–2012 time period and based on emissions inventories and transport. After regridding according to NDACC vertical layering using a conservative regridding scheme and smoothing by convolving with respective FTIR seasonal averaging kernels, the GEOS-Chem simulation shows an increase of atmospheric methane of 0.35 ± 0.03 % year−1 between 2005 and 2012, which is in agreement with NDACC measurements over the same time period (0.30 ± 0.04 % year−1, averaged over ten stations). Analysis of the GEOS-Chem tagged simulation allows us to quantify the contribution of each tracer to the global methane change since 2005. We find that natural sources such as wetlands and biomass burning contribute to the inter-annual variability of methane. However, anthropogenic emissions such as coal mining, and gas and oil transport and exploration, which are mainly emitted in the Northern Hemisphere and act as secondary contributors to the global budget of methane, have played a major role in the increase of atmospheric methane observed since 2005. Based on the GEOS-Chem tagged simulation, we discuss possible cause(s) for the increase of methane since 2005, which is still unexplained.

scholarly journals Intercomparison methods for satellite measurements of atmospheric composition: application to tropospheric ozone from TES and OMI

2010 ◽  
Vol 10 (1) ◽  
pp. 1417-1456 ◽  
Author(s):  
L. Zhang ◽  
D. J. Jacob ◽  
X. Liu ◽  
J. A. Logan ◽  
K. Chance ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Kernel Smoothing ◽  
Transport Model ◽  
Atmospheric Composition ◽  
Chemical Transport Model ◽  
Ozone Monitoring Instrument ◽  
Satellite Measurements ◽  
In Situ Data ◽  
In Situ Method

Abstract. We analyze three different methods to validate and intercompare satellite measurements of atmospheric composition, and apply them to tropospheric ozone retrievals from the Tropospheric Emission Spectrometer (TES) and the Ozone Monitoring Instrument (OMI). The first method (in situ method) uses in situ vertical profiles for absolute instrument validation; it is limited by the sparseness of in situ data. The second method (CTM method) uses a chemical transport model (CTM) as an intercomparison platform; it provides a globally complete intercomparison with relatively small noise added by model error. The third method (averaging kernel smoothing method) involves smoothing the retrieved profile from one instrument with the averaging kernel matrix of the other; it also provides a global intercomparison but dampens the actual difference between instruments and adds noise from the a priori. Application to a full year (2006) of TES and OMI data shows mean positive biases of 5.3 parts per billion volume (ppbv) (10%) for TES and 2.8 ppbv (5%) for OMI at 500 hPa relative to in situ data from ozonesondes. We show that the CTM method (using the GEOS-Chem CTM) closely approximates results from the in situ method while providing global coverage. It reveals that differences between TES and OMI are generally less than 10 ppbv (18%), except at northern mid-latitudes in summer and over tropical continents. The CTM method allows for well-constrained CTM evaluation in places where the satellite observations are consistent. We thus find that GEOS-Chem underestimates tropospheric ozone in the tropics, reflecting a combination of possible factors, and overestimates ozone in the northern subtropics and southern mid-latitudes, likely because of excessive stratospheric influx.

scholarly journals The recent increase of atmospheric methane from 10 years of ground-based NDACC FTIR observations since 2005

2017 ◽  
Vol 17 (3) ◽  
pp. 2255-2277 ◽  
Author(s):  
Whitney Bader ◽  
Benoît Bovy ◽  
Stephanie Conway ◽  
Kimberly Strong ◽  
Dan Smale ◽  
...  
Keyword(s):  
Transport Model ◽  
Atmospheric Composition ◽  
Atmospheric Methane ◽  
Chemical Transport Model ◽  
Oil Transport ◽  
Solar Observations ◽  
Time Period ◽  
Possible Cause ◽  
Good Agreement

Abstract. Changes of atmospheric methane total columns (CH4) since 2005 have been evaluated using Fourier transform infrared (FTIR) solar observations carried out at 10 ground-based sites, affiliated to the Network for Detection of Atmospheric Composition Change (NDACC). From this, we find an increase of atmospheric methane total columns of 0.31 ± 0.03 % year−1 (2σ level of uncertainty) for the 2005–2014 period. Comparisons with in situ methane measurements at both local and global scales show good agreement. We used the GEOS-Chem chemical transport model tagged simulation, which accounts for the contribution of each emission source and one sink in the total methane, simulated over 2005–2012. After regridding according to NDACC vertical layering using a conservative regridding scheme and smoothing by convolving with respective FTIR seasonal averaging kernels, the GEOS-Chem simulation shows an increase of atmospheric methane total columns of 0.35 ± 0.03 % year−1 between 2005 and 2012, which is in agreement with NDACC measurements over the same time period (0.30 ± 0.04 % year−1, averaged over 10 stations). Analysis of the GEOS-Chem-tagged simulation allows us to quantify the contribution of each tracer to the global methane change since 2005. We find that natural sources such as wetlands and biomass burning contribute to the interannual variability of methane. However, anthropogenic emissions, such as coal mining, and gas and oil transport and exploration, which are mainly emitted in the Northern Hemisphere and act as secondary contributors to the global budget of methane, have played a major role in the increase of atmospheric methane observed since 2005. Based on the GEOS-Chem-tagged simulation, we discuss possible cause(s) for the increase of methane since 2005, which is still unexplained.

scholarly journals Intercomparison methods for satellite measurements of atmospheric composition: application to tropospheric ozone from TES and OMI

2010 ◽  
Vol 10 (10) ◽  
pp. 4725-4739 ◽  
Author(s):  
L. Zhang ◽  
D. J. Jacob ◽  
X. Liu ◽  
J. A. Logan ◽  
K. Chance ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Kernel Smoothing ◽  
Transport Model ◽  
Atmospheric Composition ◽  
Chemical Transport Model ◽  
Ozone Monitoring Instrument ◽  
Satellite Measurements ◽  
In Situ Data ◽  
In Situ Method

Abstract. We analyze the theoretical basis of three different methods to validate and intercompare satellite measurements of atmospheric composition, and apply them to tropospheric ozone retrievals from the Tropospheric Emission Spectrometer (TES) and the Ozone Monitoring Instrument (OMI). The first method (in situ method) uses in situ vertical profiles for absolute instrument validation; it is limited by the sparseness of in situ data. The second method (CTM method) uses a chemical transport model (CTM) as an intercomparison platform; it provides a globally complete intercomparison with relatively small noise from model error. The third method (averaging kernel smoothing method) involves smoothing the retrieved profile from one instrument with the averaging kernel matrix of the other; it also provides a global intercomparison but dampens the actual difference between instruments and adds noise from the a priori. We apply the three methods to a full year (2006) of TES and OMI data. Comparison with in situ data from ozonesondes shows mean positive biases of 5.3 parts per billion volume (ppbv) (10%) for TES and 2.8 ppbv (5%) for OMI at 500 hPa. We show that the CTM method (using the GEOS-Chem CTM) closely approximates results from the in situ method while providing global coverage. It reveals that differences between TES and OMI are generally less than 10 ppbv (18%), except at northern mid-latitudes in summer and over tropical continents. The CTM method further allows for CTM evaluation using both satellite observations. We thus find that GEOS-Chem underestimates tropospheric ozone in the tropics due to possible underestimates of biomass burning, soil, and lightning emissions. It overestimates ozone in the northern subtropics and southern mid-latitudes, likely because of excessive stratospheric influx of ozone.

scholarly journals MIPAS observations of volcanic sulfate aerosol and sulfur dioxide in the stratosphere

2018 ◽  
Vol 18 (2) ◽  
pp. 1217-1239 ◽  
Author(s):  
Annika Günther ◽  
Michael Höpfner ◽  
Björn-Martin Sinnhuber ◽  
Sabine Griessbach ◽  
Terry Deshler ◽  
...  
Keyword(s):  
Transport Model ◽  
Michelson Interferometer ◽  
Background Level ◽  
Volcanic Eruptions ◽  
Sulfate Aerosol ◽  
Boreal Summer ◽  
Chemical Transport Model ◽  
In Situ Data

Abstract. Volcanic eruptions can increase the stratospheric sulfur loading by orders of magnitude above the background level and are the most important source of variability in stratospheric sulfur. We present a set of vertical profiles of sulfate aerosol volume densities and derived liquid-phase H2SO4 (sulfuric acid) mole fractions for 2005–2012, retrieved from infrared limb emission measurements performed with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board of the Environmental Satellite (Envisat). Relative to balloon-borne in situ measurements of aerosol at Laramie, Wyoming, the MIPAS aerosol data have a positive bias that has been corrected, based on the observed differences to the in situ data. We investigate the production of stratospheric sulfate aerosol from volcanically emitted SO2 for two case studies: the eruptions of Kasatochi in 2008 and Sarychev in 2009, which both occurred in the Northern Hemisphere midlatitudes during boreal summer. With the help of chemical transport model (CTM) simulations for the two volcanic eruptions we show that the MIPAS sulfate aerosol and SO2 data are qualitatively and quantitatively consistent with each other. Further, we demonstrate that the lifetime of SO2 is explained well by its oxidation by hydroxyl radicals (OH). While the sedimentation of sulfate aerosol plays a role, we find that the long-term decay of stratospheric sulfur after these volcanic eruptions in midlatitudes is mainly controlled by transport via the Brewer–Dobson circulation. Sulfur emitted by the two midlatitude volcanoes resides mostly north of 30∘ N at altitudes of ∼ 10–16 km, while at higher altitudes (∼ 18–22 km) part of the volcanic sulfur is transported towards the Equator where it is lifted into the stratospheric “overworld” and can further be transported into both hemispheres.

scholarly journals Global estimates of CO sources with high resolution by adjoint inversion of multiple satellite datasets (MOPITT, AIRS, SCIAMACHY, TES)

2009 ◽  
Vol 9 (5) ◽  
pp. 19967-20018 ◽  
Author(s):  
M. Kopacz ◽  
D. J. Jacob ◽  
J. A. Fisher ◽  
J. A. Logan ◽  
L. Zhang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Transport Model ◽  
Large Fraction ◽  
A Priori ◽  
A Posteriori ◽  
Chemical Transport Model ◽  
In Situ Data ◽  
Global Emission ◽  
Cold Starts

Abstract. We combine CO column measurements from the MOPITT, AIRS, SCIAMACHY, and TES satellite instruments in a full-year (May 2004–April 2005) global inversion of CO sources at 4°×5° spatial resolution and monthly temporal resolution. The inversion uses the GEOS-Chem chemical transport model (CTM) and its adjoint applied to MOPITT, AIRS, and SCIAMACHY. Observations from TES, surface sites (NOAA/GMD), and aircraft (MOZAIC) are used for evaluation of the a posteriori solution. Global intercomparison of the different satellite datasets using GEOS-Chem as a common intercomparison platform shows consistency between the satellite datasets and with the in situ data. The majority of the differences between the datasets can be explained by different averaging kernels and a priori information. The global CO emission from combustion as constrained in the inversion is 1350 Tg a−1, with an additional 217 Tg a−1 from oxidation of co-emitted VOCs. This is much higher than current bottom-up emission inventories. Consistent with both the satellite and in situ data, a large fraction of the correction results from a seasonal underestimate of CO sources at northern mid-latitudes and suggests a larger-than-expected CO source from vehicle cold starts and residential heating. A posteriori emissions also indicate a general underestimation of biomass burning relative to the GFED2 inventory. However, the tropical biomass burning constraints are not consistent across the different datasets. Although the datasets reveal regional inconsistencies over tropical biomass burning regions, we find the global emission estimates to be a balance of information from all three instruments.

scholarly journals Ozone source apportionment during peak summer events over southwestern Europe

2018 ◽  
Author(s):  
Maria Teresa Pay ◽  
Gotzon Gangoiti ◽  
Marc Guevara ◽  
Sergey Napelenok ◽  
Xavier Querol ◽  
...  
Keyword(s):  
Iberian Peninsula ◽  
Source Apportionment ◽  
Ad Hoc ◽  
Transport Model ◽  
Vertical Mixing ◽  
Ground Level ◽  
Source Attribution ◽  
Chemical Transport Model ◽  
Target Value ◽  
Mediterranean Countries

Abstract. It is well established that in Europe, high O3 concentrations are most pronounced in southern/Mediterranean countries due to the more favorable climatological conditions for its formation. However, the contribution of the different sources of precursors to O3 formation within each country relative to the imported (regional and hemispheric) O3 is poorly quantified. This lack of quantitative knowledge prevents local authorities from effectively designing plans that reduce the exceedances of the O3 Target Value set by the European Air Quality Directive. O3 source attribution is a challenge because the concentration at each location and time results not only from local biogenic and anthropogenic precursors, but also from the transport of O3 and precursors from neighbouring regions, O3 regional and hemispheric transport and stratospheric O3 injections. Our study applies and thoroughly evaluates a countrywide O3 source apportionment method implemented in a Chemical Transport Model (CTM) at high resolution (4 × 4 km) over the Iberian Peninsula (IP) to understand and quantify the origin of peak O3 events over a 10-day period covering the most frequent synoptic summer conditions in the IP. The method tags both O3 and its gas precursor emissions from source sectors within one simulation and each tagged species is subject to the typical physical processes (advection, vertical mixing, deposition, emission and chemistry) as the actual conditions remain unperturbed. We quantify the individual contributions of the largest NOx local sources to high O3 concentrations compared to the contribution of imported O3. We show for the first time that imported O3 is the largest input to the ground-level O3 concentration in the IP, accounting for 46 % to 68 % of the daily mean O3 concentration during exceedances of the European Target Value. The hourly imported O3 increases during typical northwestern advections (70–90 %, 60–80 µg/m3), and decreases during typical stagnant conditions (30–40 %, 30–60 µg/m3) due to the local NO titration effect. During stagnant conditions, the anthropogenic precursors control the O3 peaks in areas downwind of the main urban and industrial regions (up to 40 % in hourly peaks). We also show that ground-level O3 concentrations are strongly affected by vertical mixing of O3-rich layers present in the free troposphere, which result from local/regional layering and accumulation, and continental/hemispheric transport. Indeed, vertical mixing largely explains the presence of imported O3 at ground level in the Iberian Peninsula. Our results demonstrate the need for detailed quantification of the local and remote contributions to high O3 concentrations for local O3 management, being the O3 source apportionment an essential analysis prior to the design of O3 mitigation plans in any non-attainment area. To achieve the European O3 objectives in southern Europe, ad hoc local actions should be complemented by decided national and European-wide strategies.

scholarly journals Attribution of recent increases in atmospheric methane through 3-D inverse modelling

2018 ◽  
Author(s):  
Joe McNorton ◽  
Chris Wilson ◽  
Manuel Gloor ◽  
Rob Parker ◽  
Hartmut Boesch ◽  
...  
Keyword(s):  
Growth Rate ◽  
Transport Model ◽  
Energy Sector ◽  
Total Carbon ◽  
Sensitivity Analyses ◽  
Northern Eurasia ◽  
Atmospheric Methane ◽  
Chemical Transport Model ◽  
Bottom Up ◽  
Source And Sink

Abstract. The atmospheric methane (CH4) growth rate has varied considerably in recent decades. Unexplained renewed growth after 2006 followed seven years of stagnation and coincided with an isotopic trend toward CH4 more depleted in 13C, suggesting changes in sources and/or sinks. Using surface observations of both CH4 and the isotopologue ratio value (δ13CH4) to constrain a global 3D chemical transport model (CTM), we have performed a synthesis inversion for source and sink attribution. Our method extends on previous studies by providing monthly and regional attribution of emissions from 6 different sectors and changes in atmospheric sinks for the extended 2003–2015 period. Regional evaluation of the model CH4 tracer with independent column observations from the Greenhouse gases Observing SATellite (GOSAT) shows improved performance when using posterior fluxes (R = 0.94–0.96, RMSE = 8.3–16.5 ppb), relative to prior fluxes (R = 0.60–0.92, RMSE = 48.6–64.6 ppb). Further independent validation with data from the Total Carbon Column Observing Network (TCCON) shows a similar improvement in the posterior fluxes (R = 0.90, RMSE = 21.4 ppb) compared to the prior (R = 0.71, RMSE = 55.3 ppb). Based on these improved posterior fluxes, the inversion results suggest the most likely cause of the renewed methane growth is a post-2006 1.8 ± 0.4 % decrease in mean OH, a 12.9 ± 2.7 % increase in energy sector emissions, mainly from Africa/Middle East and Southern Asia/Oceania, and a 2.6 ± 1.8 % increase in wetland emissions, mainly from Northern Eurasia. The posterior wetland increases are in general agreement with bottom-up estimates, but the energy sector growth is greater than estimated by bottom-up methods. The model results are consistent across a range of sensitivity analyses performed. When forced to assume a constant (annually repeating) OH distribution, the inversion requires a greater increase in energy sector (13.6 ± 2.7 %) and wetland (3.6 ± 1.8 %) emissions but also introduces an 11.5 ± 3.8 % decrease in biomass burning emissions. Assuming no prior trend in sources and sinks slightly reduces the posterior growth rate in energy sector and wetland emissions and further increases the amplitude of the negative OH trend. We find that possible tropospheric Cl variations do not to influence δ13CH4 and CH4 trends, although we suggest further work on Cl variability is required to fully diagnose this contribution. While the study provides quantitative insight into possible emissions variations which may explain the observed trends, uncertainty in prior source and sink estimates and a paucity of δ13CH4 observations limit the accuracy of the posterior estimates.

scholarly journals Retrieval of total column and surface NO<sub>2</sub> from Pandora zenith-sky measurements

2019 ◽  
Author(s):  
Xiaoyi Zhao ◽  
Debora Griffin ◽  
Vitali Fioletov ◽  
Chris McLinden ◽  
Jonathan Davies ◽  
...  
Keyword(s):  
Transport Model ◽  
Surface Concentration ◽  
In Situ Measurements ◽  
Radiative Transfer Model ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Chemical Transport Model ◽  
High Quality ◽  
Vertical Column

Abstract. Pandora spectrometers can retrieve nitrogen dioxide (NO2) vertical column densities (VCDs) via two viewing geometries: direct-sun and zenith-sky. The direct-sun NO2 VCD measurements have high quality (0.1 DU accuracy in clear-sky conditions) and do not rely on any radiative transfer model to calculate air mass factors (AMFs); however, they are not available when the sun is obscured by clouds. To perform NO2 measurements in cloudy conditions, a simple but robust NO2 retrieval algorithm is developed for Pandora zenith-sky measurements. This algorithm derives empirical zenith-sky NO2 AMFs from coincident high-quality direct-sun NO2 observations. Moreover, the retrieved Pandora zenith-sky NO2 VCD data are converted to surface NO2 concentrations with a scaling algorithm that uses chemical-transport-model predictions and satellite measurements as inputs. NO2 VCDs and surface concentrations are retrieved from Pandora zenith-sky measurements made in Toronto, Canada, from 2015 to 2017. The retrieved Pandora zenith-sky NO2 data (VCD and surface concentration) show good agreement with both satellite and in situ measurements. The diurnal and seasonal variations of derived Pandora zenith-sky surface NO2 data also agree well with in situ measurements (diurnal difference within ±2 ppbv). Overall, this work shows that the new Pandora zenith-sky NO2 products have the potential to be used in various applications such as future satellite validation in moderate cloudy scenes and air quality monitoring.

scholarly journals Atmospheric peroxyacetyl nitrate (PAN): a global budget and source attribution

2014 ◽  
Vol 14 (5) ◽  
pp. 2679-2698 ◽  
Author(s):  
E. V. Fischer ◽  
D. J. Jacob ◽  
R. M. Yantosca ◽  
M. P. Sulprizio ◽  
D. B. Millet ◽  
...  
Keyword(s):  
Transport Model ◽  
Oxidation Products ◽  
Anthropogenic Sources ◽  
Source Attribution ◽  
Chemical Transport Model ◽  
Peroxyacetyl Nitrate ◽  
Northern Latitudes ◽  
Remote Troposphere ◽  
Terpene Oxidation ◽  
Lightning Nox

Abstract. Peroxyacetyl nitrate (PAN) formed in the atmospheric oxidation of non-methane volatile organic compounds (NMVOCs) is the principal tropospheric reservoir for nitrogen oxide radicals (NOx = NO + NO2). PAN enables the transport and release of NOx to the remote troposphere with major implications for the global distributions of ozone and OH, the main tropospheric oxidants. Simulation of PAN is a challenge for global models because of the dependence of PAN on vertical transport as well as complex and uncertain NMVOC sources and chemistry. Here we use an improved representation of NMVOCs in a global 3-D chemical transport model (GEOS-Chem) and show that it can simulate PAN observations from aircraft campaigns worldwide. The immediate carbonyl precursors for PAN formation include acetaldehyde (44% of the global source), methylglyoxal (30%), acetone (7%), and a suite of other isoprene and terpene oxidation products (19%). A diversity of NMVOC emissions is responsible for PAN formation globally including isoprene (37%) and alkanes (14%). Anthropogenic sources are dominant in the extratropical Northern Hemisphere outside the growing season. Open fires appear to play little role except at high northern latitudes in spring, although results are very sensitive to plume chemistry and plume rise. Lightning NOx is the dominant contributor to the observed PAN maximum in the free troposphere over the South Atlantic.

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