Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

    We have a manual that explains all the features 

    Records 1 - 16 / 16

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    Influence of Atmospheric Transport on Estimates of Variability in the Global Methane Burden
    Pandey, Sudhanshu ; Houweling, Sander ; Krol, Maarten ; Aben, Ilse ; Nechita-Banda, Narcisa ; Thoning, Kirk ; Röckmann, Thomas ; Yin, Yi ; Segers, Arjo ; Dlugokencky, Edward J. - \ 2019
    Geophysical Research Letters 46 (2019)4. - ISSN 0094-8276 - p. 2302 - 2311.
    atmospheric burden - atmospheric transport - CH emissions - interhemispheric difference - methane - TM5

    We quantify the impact of atmospheric transport and limited marine boundary layer sampling on changes in global and regional methane burdens estimate using tracer transport model simulations with annually repeating methane emissions and sinks but varying atmospheric transport patterns. We find the 1σ error due to this transport and sampling effect on annual global methane increases to be 1.11 ppb/year and on zonal growth rates to be 3.8 ppb/year, indicating that it becomes more critical at smaller spatiotemporal scales. We also find that the trends in inter-hemispheric and inter-polar difference of methane are significantly influenced by the effect. Contrary to a negligible trend in the inter-hemispheric difference of measurements, we find, after adjusting for the transport and sampling, a trend of 0.37 ± 0.06 ppb/year. This is consistent with the emission trend from a 3-D inversion of the measurements, suggesting a faster increase in emissions in the Northern Hemisphere than in the Southern Hemisphere.

    Methane budget estimates in Finland from the CarbonTracker Europe-CH4 data assimilation system
    Tsuruta, Aki ; Aalto, Tuula ; Backman, Leif ; Krol, Maarten C. ; Peters, Wouter ; Lienert, Sebastian ; Joos, Fortunat ; Miller, Paul A. ; Zhang, Wenxin ; Laurila, Tuomas ; Hatakka, Juha ; Leskinen, Ari ; Lehtinen, Kari E.J. ; Peltola, Olli ; Vesala, Timo ; Levula, Janne ; Dlugokencky, Ed ; Heimann, Martin ; Kozlova, Elena ; Aurela, Mika ; Lohila, Annalea ; Kauhaniemi, Mari ; Gomez-Pelaez, Angel J. - \ 2019
    Tellus Series B: Chemical and Physical Meteorology 71 (2019)1. - ISSN 0280-6509 - p. 1 - 20.
    atmospheric CH - CH flux - data assimilation - Finland - flux estimation

    We estimated the CH4 budget in Finland for 2004–2014 using the CTE-CH4 data assimilation system with an extended atmospheric CH4 observation network of seven sites from Finland to surrounding regions (Hyytiälä, Kjølnes, Kumpula, Pallas, Puijo, Sodankylä, and Utö). The estimated average annual total emission for Finland is 0.6 ± 0.5 Tg CH4 yr−1. Sensitivity experiments show that the posterior biospheric emission estimates for Finland are between 0.3 and 0.9 Tg CH4 yr−1, which lies between the LPX-Bern-DYPTOP (0.2 Tg CH4 yr−1) and LPJG-WHyMe (2.2 Tg CH4 yr−1) process-based model estimates. For anthropogenic emissions, we found that the EDGAR v4.2 FT2010 inventory (0.4 Tg CH4 yr−1) is likely to overestimate emissions in southernmost Finland, but the extent of overestimation and possible relocation of emissions are difficult to derive from the current observation network. The posterior emission estimates were especially reliant on prior information in central Finland. However, based on analysis of posterior atmospheric CH4, we found that the anthropogenic emission distribution based on a national inventory is more reliable than the one based on EDGAR v4.2 FT2010. The contribution of total emissions in Finland to global total emissions is only about 0.13%, and the derived total emissions in Finland showed no trend during 2004–2014. The model using optimized emissions was able to reproduce observed atmospheric CH4 at the sites in Finland and surrounding regions fairly well (correlation > 0.75, bias < ± ppb), supporting adequacy of the observations to be used in atmospheric inversion studies. In addition to global budget estimates, we found that CTE-CH4 is also applicable for regional budget estimates, where small scale (1x1 in this case) optimization is possible with a dense observation network.

    Constraints and biases in a tropospheric two-box model of OH
    Naus, Stijn ; Montzka, Stephen A. ; Pandey, Sudhanshu ; Basu, Sourish ; Dlugokencky, Ed J. ; Krol, Maarten - \ 2019
    Atmospheric Chemistry and Physics 19 (2019)1. - ISSN 1680-7316 - p. 407 - 424.

    The hydroxyl radical (OH) is the main atmospheric oxidant and the primary sink of the greenhouse gas CH4. In an attempt to constrain atmospheric levels of OH, two recent studies combined a tropospheric two-box model with hemispheric-mean observations of methyl chloroform (MCF) and CH4. These studies reached different conclusions concerning the most likely explanation of the renewed CH4 growth rate, which reflects the uncertain and underdetermined nature of the problem. Here, we investigated how the use of a tropospheric two-box model can affect the derived constraints on OH due to simplifying assumptions inherent to a two-box model. To this end, we derived species- A nd timedependent quantities from a full 3-D transport model to drive two-box model simulations. Furthermore, we quantified differences between the 3-D simulated tropospheric burden and the burden seen by the surface measurement network of the National Oceanic and Atmospheric Administration (NOAA). Compared to commonly used parameters in two-box models, we found significant deviations in the magnitude and timedependence of the interhemispheric exchange rate, exposure to OH, and stratospheric loss rate. For MCF these deviations can be large due to changes in the balance of its sources and sinks over time. We also found that changes in the yearly averaged tropospheric burden of CH4 and MCF can be obtained within 0.96 ppb yr-1 and 0.14%yr-1 by the NOAA surface network, but that substantial systematic biases exist in the interhemispheric mixing ratio gradients that are input to two-box model inversions. To investigate the impact of the identified biases on constraints on OH, we accounted for these biases in a two-box model inversion of MCF and CH4. We found that the sensitivity of interannual OH anomalies to the biases is modest (1 %-2 %), relative to the uncertainties on derived OH (3 %-4 %). However, in an inversion where we implemented all four bias corrections simultaneously, we found a shift to a positive trend in OH concentrations over the 1994-2015 period, compared to the standard inversion. Moreover, the absolute magnitude of derived global mean OH, and by extent, that of global CH4 emissions, was affected much more strongly by the bias corrections than their anomalies (∼ 10 %). Through our analysis, we identified and quantified limitations in the two-box model approach as well as an opportunity for full 3-D simulations to address these limitations. However, we also found that this derivation is an extensive and species-dependent exercise and that the biases were not always entirely resolvable. In future attempts to improve constraints on the atmospheric oxidative capacity through the use of simple models, a crucial first step is to consider and account for biases similar to those we have identified for the two-box model.

    Enhanced methane emissions from tropical wetlands during the 2011 la Niña
    Pandey, Sudhanshu ; Houweling, Sander ; Krol, Maarten ; Aben, Ilse ; Monteil, Guillaume ; Nechita-Banda, Narcisa ; Dlugokencky, Edward J. ; Detmers, Rob ; Hasekamp, Otto ; Xu, Xiyan ; Riley, William J. ; Poulter, Benjamin ; Zhang, Zhen ; McDonald, Kyle C. ; White, James W.C. ; Bousquet, Philippe ; Röckmann, Thomas - \ 2017
    Scientific Reports 7 (2017). - ISSN 2045-2322
    Year-to-year variations in the atmospheric methane (CH4) growth rate show significant correlation with climatic drivers. The second half of 2010 and the first half of 2011 experienced the strongest La Niña since the early 1980s, when global surface networks started monitoring atmospheric CH4 mole fractions. We use these surface measurements, retrievals of column-averaged CH4 mole fractions from GOSAT, new wetland inundation estimates, and atmospheric δ13C-CH4 measurements to estimate the impact of this strong La Niña on the global atmospheric CH4 budget. By performing atmospheric inversions, we find evidence of an increase in tropical CH4 emissions of ∼6-9 TgCH4 yr-1 during this event. Stable isotope data suggest that biogenic sources are the cause of this emission increase. We find a simultaneous expansion of wetland area, driven by the excess precipitation over the Tropical continents during the La Niña. Two process-based wetland models predict increases in wetland area consistent with observationally-constrained values, but substantially smaller per-area CH4 emissions, highlighting the need for improvements in such models. Overall, tropical wetland emissions during the strong La Niña were at least by 5% larger than the long-term mean.
    Global methane emission estimates for 2000-2012 from CarbonTracker Europe-CH4 v1.0
    Tsuruta, Aki ; Aalto, Tuula ; Backman, Leif ; Hakkarainen, Janne ; Laan-Luijkx, Ingrid T. Van Der; Krol, Maarten C. ; Spahni, Renato ; Houweling, Sander ; Laine, Marko ; Dlugokencky, Ed ; Gomez-Pelaez, Angel J. ; Schoot, Marcel Van Der; Langenfelds, Ray ; Ellul, Raymond ; Arduini, Jgor ; Apadula, Francesco ; Gerbig, Christoph ; Feist, D.G. ; Kivi, Rigel ; Yoshida, Yukio ; Peters, Wouter - \ 2017
    Geoscientific Model Development 10 (2017)3. - ISSN 1991-959X - p. 1261 - 1289.

    We present a global distribution of surface methane (CH4) emission estimates for 2000-2012 derived using the CarbonTracker Europe-CH4 (CTE-CH4) data assimilation system. In CTE-CH4, anthropogenic and biospheric CH4 emissions are simultaneously estimated based on constraints of global atmospheric in situ CH4 observations. The system was configured to either estimate only anthropogenic or biospheric sources per region, or to estimate both categories simultaneously. The latter increased the number of optimizable parameters from 62 to 78. In addition, the differences between two numerical schemes available to perform turbulent vertical mixing in the atmospheric transport model TM5 were examined. Together, the system configurations encompass important axes of uncertainty in inversions and allow us to examine the robustness of the flux estimates. The posterior emission estimates are further evaluated by comparing simulated atmospheric CH4 to surface in situ observations, vertical profiles of CH4 made by aircraft, remotely sensed dry-air total column-averaged mole fraction (XCH4) from the Total Carbon Column Observing Network (TCCON), and XCH4 from the Greenhouse gases Observing Satellite (GOSAT). The evaluation with non-assimilated observations shows that posterior XCH4 is better matched with the retrievals when the vertical mixing scheme with faster interhemispheric exchange is used. Estimated posterior mean total global emissions during 2000-2012 are 516 ± 51 Tg CH4 yr-1, with an increase of 18 Tg CH4 yr-1 from 2000-2006 to 2007-2012. The increase is mainly driven by an increase in emissions from South American temperate, Asian temperate and Asian tropical TransCom regions. In addition, the increase is hardly sensitive to different model configurations ( < 2 Tg CH4 yr-1 difference), and much smaller than suggested by EDGAR v4.2 FT2010 inventory (33 Tg CH4 yr-1), which was used for prior anthropogenic emission estimates. The result is in good agreement with other published estimates from inverse modelling studies (16-20 Tg CH4 yr-1). However, this study could not conclusively separate a small trend in biospheric emissions (-5 to +6.9 Tg CH4 yr-1) from the much larger trend in anthropogenic emissions (15-27 Tg CH4 yr-1). Finally, we find that the global and North American CH4 balance could be closed over this time period without the previously suggested need to strongly increase anthropogenic CH4 emissions in the United States. With further developments, especially on the treatment of the atmospheric CH4 sink, we expect the data assimilation system presented here will be able to contribute to the ongoing interpretation of changes in this important greenhouse gas budget.

    Inverse modeling of GOSAT-retrieved ratios of total column CH4 and CO2 for 2009 and 2010
    Pandey, Sudhanshu ; Houweling, Sander ; Krol, Maarten ; Aben, Ilse ; Chevallier, Frédéric ; Dlugokencky, Edward J. ; Gatti, Luciana V. ; Gloor, Emanuel ; Miller, John B. ; Detmers, Rob ; Machida, Toshinobu ; Röckmann, Thomas - \ 2016
    Atmospheric Chemistry and Physics 16 (2016)8. - ISSN 1680-7316 - p. 5043 - 5062.

    This study investigates the constraint provided by greenhouse gas measurements from space on surface fluxes. Imperfect knowledge of the light path through the atmosphere, arising from scattering by clouds and aerosols, can create biases in column measurements retrieved from space. To minimize the impact of such biases, ratios of total column retrieved CH4 and CO2 (Xratio) have been used. We apply the ratio inversion method described in Pandey et al. (2015) to retrievals from the Greenhouse Gases Observing SATellite (GOSAT). The ratio inversion method uses the measured Xratio as a weak constraint on CO2 fluxes. In contrast, the more common approach of inverting proxy CH4 retrievals (Frankenberg et al., 2005) prescribes atmospheric CO2 fields and optimizes only CH4 fluxes. The TM5-4DVAR (Tracer Transport Model version 5-variational data assimilation system) inverse modeling system is used to simultaneously optimize the fluxes of CH4 and CO2 for 2009 and 2010. The results are compared to proxy inversions using model-derived CO2 mixing ratios (XCO2model) from CarbonTracker and the Monitoring Atmospheric Composition and Climate (MACC) Reanalysis CO2 product. The performance of the inverse models is evaluated using measurements from three aircraft measurement projects. Xratio and XCO2model are compared with TCCON retrievals to quantify the relative importance of errors in these components of the proxy XCH4 retrieval (XCH4proxy). We find that the retrieval errors in Xratio (mean Combining double low line 0.61%) are generally larger than the errors in XCO2model (mean Combining double low line 0.24 and 0.01% for CarbonTracker and MACC, respectively). On the annual timescale, the CH4 fluxes from the different satellite inversions are generally in agreement with each other, suggesting that errors in XCO2model do not limit the overall accuracy of the CH4 flux estimates. On the seasonal timescale, however, larger differences are found due to uncertainties in XCO2model, particularly over Australia and in the tropics. The ratio method stays closer to the a priori CH4 flux in these regions, because it is capable of simultaneously adjusting the CO2 fluxes. Over tropical South America, comparison to independent measurements shows that CO2 fields derived from the ratio method are less realistic than those used in the proxy method. However, the CH4 fluxes are more realistic, because the impact of unaccounted systematic uncertainties is more evenly distributed between CO2 and CH4. The ratio inversion estimates an enhanced CO2 release from tropical South America during the dry season of 2010, which is in accordance with the findings of Gatti et al. (2014) and Van der Laan et al. (2015). The performance of the ratio method is encouraging, because despite the added nonlinearity due to the assimilation of Xratio and the significant increase in the degree of freedom by optimizing CO2 fluxes, still consistent results are obtained with respect to other CH4 inversions.

    Evaluating atmospheric methane inversion model results for Pallas, northern Finland
    Tsuruta, A. ; Aalto, T. ; Backman, L. ; Peters, W. ; Krol, M.C. ; Laan-Luijkx, I.T. van der; Hatakka, J. ; Heikkinen, P. ; Dlugokencky, E.J. ; Spahni, R. ; Paramonova, N.N. - \ 2015
    Boreal environment research 20 (2015)4. - ISSN 1239-6095 - p. 506 - 525.
    A state-of-the-art inverse model, CarbonTracker Data Assimilation Shell (CTDAS), was used to optimize estimates of methane (CH4) surface fluxes using atmospheric observations of CH4 as a constraint. The model consists of the latest version of the TM5 atmospheric chemistry-transport model and an ensemble Kalman filter based data assimilation system. The model was constrained by atmospheric methane surface concentrations, obtained from the World Data Centre for Greenhouse Gases (WDCGG). Prior methane emissions were specified for five sources: biosphere, anthropogenic, fire, termites and ocean, of which biosphere and anthropogenic emissions were optimized. Atmospheric CH4 mole fractions for 2007 from northern Finland calculated from prior and optimized emissions were compared with observations. It was found that the root mean squared errors of the posterior estimates were more than halved. Furthermore, inclusion of NOAA observations of CH4 from weekly discrete air samples collected at Pallas improved agreement between posterior CH4 mole fraction estimates and continuous observations, and resulted in reducing optimized biosphere emissions and their uncertainties in northern Finland.
    Erratum: A multi-year methane inversion using SCIAMACHY, accounting for systematic errors using TCCON measurements
    Houweling, S. ; Krol, M. ; Bergamaschi, P. ; Frankenberg, C. ; Dlugokencky, E.J. ; Morino, I. ; Notholt, J. ; Sherlock, V. ; Wunch, D. ; Beck, V. ; Gerbig, C. ; Chen, H. ; Kort, E.A. ; Röckmann, T. ; Aben, I. - \ 2014
    Atmospheric Chemistry and Physics 14 (2014)20. - ISSN 1680-7316 - p. 10961 - 10962.
    A multi-year methane inversion using SCIAMACHY, accounting for systematic errors using TCCON measurements
    Houweling, S. ; Krol, M.C. ; Bergamaschi, P. ; Frankenberg, C. ; Dlugokencky, E.J. ; Morino, I. - \ 2014
    Atmospheric Chemistry and Physics 14 (2014). - ISSN 1680-7316 - p. 3991 - 4012.
    column observing network - atmospheric methane - carbon-dioxide - tropospheric methane - lower stratosphere - data assimilation - transport model - emissions - ch4 - gosat
    This study investigates the use of total column CH4 (XCH4) retrievals from the SCIAMACHY satellite instrument for quantifying large-scale emissions of methane. A unique data set from SCIAMACHY is available spanning almost a decade of measurements, covering a period when the global CH4 growth rate showed a marked transition from stable to increasing mixing ratios. The TM5 4DVAR inverse modelling system has been used to infer CH4 emissions from a combination of satellite and surface measurements for the period 2003–2010. In contrast to earlier inverse modelling studies, the SCIAMACHY retrievals have been corrected for systematic errors using the TCCON network of ground-based Fourier transform spectrometers. The aim is to further investigate the role of bias correction of satellite data in inversions. Methods for bias correction are discussed, and the sensitivity of the optimized emissions to alternative bias correction functions is quantified. It is found that the use of SCIAMACHY retrievals in TM5 4DVAR increases the estimated inter-annual variability of large-scale fluxes by 22% compared with the use of only surface observations. The difference in global methane emissions between 2-year periods before and after July 2006 is estimated at 27–35 Tg yr-1. The use of SCIAMACHY retrievals causes a shift in the emissions from the extra-tropics to the tropics of 50 ± 25 Tg yr-1. The large uncertainty in this value arises from the uncertainty in the bias correction functions. Using measurements from the HIPPO and BARCA aircraft campaigns, we show that systematic errors in the SCIAMACHY measurements are a main factor limiting the performance of the inversions. To further constrain tropical emissions of methane using current and future satellite missions, extended validation capabilities in the tropics are of critical importance.
    Atmospheric CH4 in the first decade of the 21st century: Inverse modeling analysis using SCIAMACHY satellite retrievals and NOAA surface measurements
    Bergamaschi, P. ; Houweling, S. ; Segers, A. ; Krol, M.C. ; Frankenberg, C. ; Scheepmaker, R.A. ; Dlugokencky, E. ; Wofsy, S.C. ; Kort, E.A. ; Sweeney, C. ; Schuck, T. ; Brenninkmeijer, C. ; Chen, H. ; Beck, V. ; Gerbig, C. - \ 2013
    Journal of Geophysical Research: Atmospheres 118 (2013)13. - ISSN 2169-897X - p. 7350 - 7369.
    growth-rate - methane emissions - carbon-dioxide - northern-hemisphere - data assimilation - transport model - variability - chemistry - climate - troposphere
    The causes of renewed growth in the atmospheric CH4 burden since 2007 are still poorly understood and subject of intensive scientific discussion. We present a reanalysis of global CH4 emissions during the 2000s, based on the TM5-4DVAR inverse modeling system. The model is optimized using high-accuracy surface observations from NOAA ESRL's global air sampling network for 2000-2010 combined with retrievals of column-averaged CH4 mole fractions from SCIAMACHY onboard ENVISAT (starting 2003). Using climatological OH fields, derived global total emissions for 2007-2010 are 16-20 Tg CH4/yr higher compared to 2003-2005. Most of the inferred emission increase was located in the tropics (9-14 Tg CH4/yr) and mid- latitudes of the northern hemisphere (6-8 Tg CH4/yr), while no significant trend was derived for Arctic latitudes. The atmospheric increase can be attributed mainly to increased anthropogenic emissions, but the derived trend is significantly smaller than estimated in the EDGARv4.2 emission inventory. Superimposed on the increasing trend in anthropogenic CH4 emissions are significant inter-annual variations (IAV) of emissions from wetlands (up to +/- 10 Tg CH4/yr), and biomass burning (up to +/- 7 Tg CH4/yr). Sensitivity experiments, which investigated the impact of the SCIAMACHY observations (versus inversions using only surface observations), of the OH fields used, and of a priori emission inventories, resulted in differences in the detailed latitudinal attribution of CH4 emissions, but the IAV and trends aggregated over larger latitude bands were reasonably robust. All sensitivity experiments show similar performance against independent shipboard and airborne observations used for validation, except over Amazonia where satellite retrievals improved agreement with observations in the free troposphere.
    Small Interannual Variability of Global Atmospheric Hydroxyl
    Montzka, S.A. ; Krol, M.C. ; Dlugokencky, E. ; Hall, B. ; Jöckel, P. ; Lelieveld, J. - \ 2011
    Science 331 (2011)6013. - ISSN 0036-8075 - p. 67 - 69.
    methyl chloroform - carbon-monoxide - tropospheric oh - (co)-c-14 - chemistry - emissions - abundance - capacity - radicals - ozone
    The oxidizing capacity of the global atmosphere is largely determined by hydroxyl (OH) radicals and is diagnosed by analyzing methyl chloroform (CH3CCl3) measurements. Previously, large year-to-year changes in global mean OH concentrations have been inferred from such measurements, suggesting that the atmospheric oxidizing capacity is sensitive to perturbations by widespread air pollution and natural influences. We show how the interannual variability in OH has been more precisely estimated from CH3CCl3 measurements since 1998, when atmospheric gradients of CH3CCl3 had diminished as a result of the Montreal Protocol. We infer a small interannual OH variability as a result, indicating that global OH is generally well buffered against perturbations. This small variability is consistent with measurements of methane and other trace gases oxidized primarily by OH, as well as global photochemical model calculations.
    Satellite chartography of atmospheric methane from SCIAMACHY onboard ENVISAT: 2. Evaluation based on inverse model simulations
    Bergamaschi, P. ; Frankenberg, C. ; Meirink, J.F. ; Krol, M.C. ; Dentener, F. ; Wagner, T. ; Platt, U. ; Kaplan, J.O. ; Körner, S. ; Heimann, M. ; Dlugokencky, E.J. ; Goede, A. - \ 2007
    Journal of Geophysical Research: Atmospheres 112 (2007). - ISSN 2169-897X
    natural wetlands - carbon-dioxide - data set - tropospheric methane - transport models - seasonal cycles - nitrous-oxide - wfm-doas - ice core - emissions
    We extend the analysis of a global CH4 data set retrieved from SCIAMACHY (Frankenberg et al., 2006) by making a detailed comparison with inverse TM5 model simulations for 2003 that are optimized versus high accuracy CH4 surface measurements from the NOAA ESRL network. The comparison of column averaged mixing ratios over remote continental and oceanic regions shows that major features of the atmospheric CH4 distribution are consistent between SCIAMACHY observations and model simulations. However, the analysis suggests that SCIAMACHY CH4 retrievals may have some bias that depends on latitude and season (up to ~30 ppb). Large enhancements of column averaged CH4 mixing ratios (~50¿100 ppb) are observed and modeled over India, Southeast Asia, and the tropical regions of South America, and Africa. We present a detailed comparison of observed spatial patterns and their seasonal evolution with TM5 1° × 1° zoom simulations over these regions. Application of a new wetland inventory leads to a significant improvement in the agreement between SCIAMACHY retrievals and model simulations over the Amazon basin during the first half of the year. Furthermore, we present an initial coupled inversion that simultaneously uses the surface and satellite observations and that allows the inverse system to compensate for the potential systematic bias. The results suggest significantly greater tropical emissions compared to either the a priori estimates or the inversion based on the surface measurements only. Emissions from rice paddies in India and Southeast Asia are relatively well constrained by the SCIAMACHY data and are slightly reduced by the inversion
    Inverse Modeling Estimates of the Global Nitrous Oxide Surface Flux from 1998-2001
    Hirsch, A. ; Michalak, A. ; Bruhwiler, L. ; Peters, W. ; Dlugokencky, E. ; Tans, P.P. - \ 2006
    Global Biogeochemical Cycles 20 (2006)1. - ISSN 0886-6236 - 17 p.
    atmospheric transport models - trace-gas emissions - european emissions - seasonal-variation - n2o emissions - co2 sources - costa-rica - sinks - exchange - soils
    Measurements of nitrous oxide in air samples from 48 sites in the Cooperative Global Air Sampling Network made by NOAA/ESRL GMD CCGG (the Carbon Cycle Greenhouse Gases group in the Global Monitoring Division at the NOAA Earth System Research Laboratory in Boulder, Colorado) and the three-dimensional chemical transport model TM3 were used to infer global nitrous oxide fluxes and their uncertainties from 1998–2001. Results are presented for four semihemispherical regions (90°S–30°S, 30°S to equator, equator to 30°N, 30°N–90°N) and six broad “super regions” (Southern Land, Southern Oceans, Tropical Land, Tropical Oceans, Northern Land, and Northern Oceans). We found that compared to our a priori estimate (from the International Geosphere-Biosphere Programme's Global Emissions Inventory Activity), the a posteriori flux was much lower from 90°S–30°S and substantially higher from equator to 30°N. Consistent with these results, the a posteriori flux from the Southern Oceans region was lower than the a priori estimate, while Tropical Land and Tropical Ocean estimates were higher. The ratio of Northern Hemisphere to Southern Hemisphere fluxes was found to range from 1.9 to 5.2 (depending on the model setup), which is higher than the a priori ratio (1.5) and at the high end of previous estimates. Globally, ocean emissions contributed 26–36% of the total flux (again depending on the model setup), consistent with the a priori estimate (29%), though somewhat higher than some other previous estimates
    New directions : watching over tropospheric hydroxyl (OH)
    Lelieveld, J. ; Brenninkmeijer, C.A.M. ; Joeckel, P. ; Isaksen, I.S.A. ; Krol, M.C. ; Mak, J.E. ; Dlugokencky, E. ; Montzka, S.A. ; Novelli, P.C. ; Peters, W. ; Tans, P.P. - \ 2006
    Atmospheric Environment 40 (2006)29. - ISSN 1352-2310 - p. 5741 - 5743.
    Atmospheric constraints on global emissions of methane from plants
    Houweling, S. ; Rockmann, T. ; Aben, I. ; Keppler, F. ; Krol, M.C. ; Meirink, J.F. ; Dlugokencky, E.J. ; Frankenberg, C. - \ 2006
    Geophysical Research Letters 33 (2006). - ISSN 0094-8276 - 5 p.
    natural wetlands - model - ch4
    We investigate whether a recently proposed large source of CH4 from vegetation can be reconciled with atmospheric measurements. Atmospheric transport model simulations with and without vegetation emissions are compared with background CH4, d13C-CH4 and satellite measurements. For present–day CH4 we derive an upper limit to the newly discovered source of 125 Tg CH4 yr-1. Analysis of preindustrial CH4, however, points to 85 Tg CH4 yr-1 as a more plausible limit. Model calculations with and without vegetation emissions show strikingly similar results at background surface monitoring sites, indicating that these measurements are rather insensitive to CH4 from plants. Simulations with 125 Tg CH4 yr-1 vegetation emissions can explain up to 50% of the previously reported unexpectedly high CH4 column abundances over tropical forests observed by SCIAMACHY. Our results confirm the potential importance of vegetation emissions, and call for further research.
    Inverse modelling of national and European CH4 emissions using the atmospheric zoom model TM5
    Bergamaschi, P. ; Krol, M.C. ; Dentener, F. ; Vermeulen, A. ; Meinhardt, F. ; Graul, R. ; Ramonet, M. ; Peters, W. ; Dlugokencky, E.J. - \ 2005
    Atmospheric Chemistry and Physics 5 (2005)9. - ISSN 1680-7316 - p. 2431 - 2460.
    modern methane emissions - natural wetlands - co2 sources - interannual variability - transport - gases - sensitivity - lifetime - history - climate
    A synthesis inversion based on the atmospheric zoom model TM5 is used to derive top-down estimates of CH4 emissions from individual European countries for the year 2001. We employ a model zoom over Europe with 1° × 1° resolution that is two-way nested into the global model domain (with resolution of 6° × 4°. This approach ensures consistent boundary conditions for the zoom domain and thus European top-down estimates consistent with global CH4 observations. The TM5 model, driven by ECMWF analyses, simulates synoptic scale events at most European and global sites fairly well, and the use of high-frequency observations allows exploiting the information content of individual synoptic events. A detailed source attribution is presented for a comprehensive set of 56 monitoring sites, assigning the atmospheric signal to the emissions of individual European countries and larger global regions. The available observational data put significant constraints on emissions from different regions. Within Europe, in particular several Western European countries are well constrained. The inversion results suggest up to 50-90% higher anthropogenic CH4 emissions in 2001 for Germany, France and UK compared to reported UNFCCC values (EEA, 2003). A recent revision of the German inventory, however, resulted in an increase of reported CH4 emissions by 68.5% (EEA, 2004), being now in very good agreement with our top-down estimate. The top-down estimate for Finland is distinctly smaller than the a priori estimate, suggesting much smaller CH4 emissions from Finnish wetlands than derived from the bottom-up inventory. The EU-15 totals are relatively close to UNFCCC values (within 4-30%) and appear very robust for different inversion scenarios.
    Check title to add to marked list

    Show 20 50 100 records per page

     
    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.