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Seasonal variability of stratospheric methane: implications for constraining tropospheric methane budgets using total column observations

Journal Article


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Abstract


  • Global and regional methane budgets are markedly uncertain. Conventionally, estimates of methane

    sources are derived by bridging emissions inventories with atmospheric observations employing chemical transport models. The accuracy of this approach requires correctly simulating advection and chemical loss such that modeled methane concentrations scale with surface fluxes. When total

    column measurements are assimilated into this framework, modeled stratospheric methane introduces additional potential for error. To evaluate the impact of such errors, we compare

    Total Carbon Column Observing Network (TCCON) and GEOS-Chem total and tropospheric column-averaged dry-air mole fractions of methane. We find that the model’s stratospheric contribution to the total column is insensitive to perturbations to the seasonality or distribution of tropospheric

    emissions or loss. In the Northern Hemisphere, we identify disagreement between the measured and modeled stratospheric contribution, which increases as the tropopause altitude decreases, and a temporal phase lag in the model’s tropospheric seasonality driven by transport errors. Within the context of GEOS-Chem, we find that the errors in tropospheric advection partially compensate for the stratospheric methane errors, masking inconsistencies between the modeled and measured tropospheric methane. These seasonally varying errors alias into source attributions resulting from

    model inversions. In particular, we suggest that the tropospheric phase lag error leads to large misdiagnoses of wetland emissions in the high latitudes of the Northern Hemisphere.

UOW Authors


  •   Saad, K M. (external author)
  •   Wunch, Debra (external author)
  •   Deutscher, Nicholas
  •   Griffith, David
  •   Hase, Frank (external author)
  •   de Maziere, Martine (external author)
  •   Notholt, Justus (external author)
  •   Pollard, David F. (external author)
  •   Roehl, Coleen M. (external author)
  •   Schneider, Matthias (external author)
  •   Sussmann, Ralf (external author)
  •   Warneke, Thorsten (external author)
  •   Wennberg, Paul O. (external author)

Publication Date


  • 2016

Citation


  • Saad, K. M., Wunch, D., Deutscher, N. M., Griffith, D. W. T.., Hase, F., de Maziere, M., Notholt, J., Pollard, D. F., Roehl, C. M., Schneider, M., Sussmann, R., Warneke, T. & Wennberg, P. O. (2016). Seasonal variability of stratospheric methane: implications for constraining tropospheric methane budgets using total column observations. Atmospheric Chemistry and Physics, 16 (21), 14003-14024.

Scopus Eid


  • 2-s2.0-84995476610

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=5236&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/4212

Number Of Pages


  • 21

Start Page


  • 14003

End Page


  • 14024

Volume


  • 16

Issue


  • 21

Place Of Publication


  • Germany

Abstract


  • Global and regional methane budgets are markedly uncertain. Conventionally, estimates of methane

    sources are derived by bridging emissions inventories with atmospheric observations employing chemical transport models. The accuracy of this approach requires correctly simulating advection and chemical loss such that modeled methane concentrations scale with surface fluxes. When total

    column measurements are assimilated into this framework, modeled stratospheric methane introduces additional potential for error. To evaluate the impact of such errors, we compare

    Total Carbon Column Observing Network (TCCON) and GEOS-Chem total and tropospheric column-averaged dry-air mole fractions of methane. We find that the model’s stratospheric contribution to the total column is insensitive to perturbations to the seasonality or distribution of tropospheric

    emissions or loss. In the Northern Hemisphere, we identify disagreement between the measured and modeled stratospheric contribution, which increases as the tropopause altitude decreases, and a temporal phase lag in the model’s tropospheric seasonality driven by transport errors. Within the context of GEOS-Chem, we find that the errors in tropospheric advection partially compensate for the stratospheric methane errors, masking inconsistencies between the modeled and measured tropospheric methane. These seasonally varying errors alias into source attributions resulting from

    model inversions. In particular, we suggest that the tropospheric phase lag error leads to large misdiagnoses of wetland emissions in the high latitudes of the Northern Hemisphere.

UOW Authors


  •   Saad, K M. (external author)
  •   Wunch, Debra (external author)
  •   Deutscher, Nicholas
  •   Griffith, David
  •   Hase, Frank (external author)
  •   de Maziere, Martine (external author)
  •   Notholt, Justus (external author)
  •   Pollard, David F. (external author)
  •   Roehl, Coleen M. (external author)
  •   Schneider, Matthias (external author)
  •   Sussmann, Ralf (external author)
  •   Warneke, Thorsten (external author)
  •   Wennberg, Paul O. (external author)

Publication Date


  • 2016

Citation


  • Saad, K. M., Wunch, D., Deutscher, N. M., Griffith, D. W. T.., Hase, F., de Maziere, M., Notholt, J., Pollard, D. F., Roehl, C. M., Schneider, M., Sussmann, R., Warneke, T. & Wennberg, P. O. (2016). Seasonal variability of stratospheric methane: implications for constraining tropospheric methane budgets using total column observations. Atmospheric Chemistry and Physics, 16 (21), 14003-14024.

Scopus Eid


  • 2-s2.0-84995476610

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=5236&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/4212

Number Of Pages


  • 21

Start Page


  • 14003

End Page


  • 14024

Volume


  • 16

Issue


  • 21

Place Of Publication


  • Germany