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

Saad, Katherine M. and Wunch, Debra and Deutscher, Nicholas M. and Griffith, David W. T. and Hase, Frank and De Mazière, Martine and Notholt, Justus and Pollard, David F. and Roehl, Coleen M. and Schneider, Matthias and Sussmann, Ralf and Warneke, Thorsten and Wennberg, Paul O. (2016) Seasonal variability of stratospheric methane: implications for constraining tropospheric methane budgets using total column observations. Atmospheric Chemistry and Physics, 16 (21). pp. 14003-14024. ISSN 1680-7324.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wunch, Debra0000-0002-4924-0377
Deutscher, Nicholas M.0000-0002-2906-2577
Griffith, David W. T.0000-0002-7986-1924
Pollard, David F.0000-0001-9923-2984
Roehl, Coleen M.0000-0001-5383-8462
Warneke, Thorsten0000-0001-5185-3415
Wennberg, Paul O.0000-0002-6126-3854
Additional Information:© 2016 Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 07 Apr 2016 – Published in Atmos. Chem. Phys. Discuss.: 10 May 2016. Revised: 24 Oct 2016 – Accepted: 25 Oct 2016 – Published: 11 Nov 2016. This work was supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program grant NNX14AL30H and NASA’s Carbon Cycle Science program. Park Falls, Lamont, and JPL are funded by NASA grants NNX14AI60G, NNX11AG01G, NAG5-12247, NNG05-GD07G, and NASA Orbiting Carbon Observatory Program; we are grateful to the DOE ARM program and Jeff Ayers for their technical support in Lamont and Park Falls, respectively. Darwin and Wollongong are funded by NASA grants NAG5-12247 and NNG05-GD07G and the Australian Research Council grants DP140101552, DP110103118, DP0879468, and LP0562346, and Nicholas Deutscher is supported by an Australian Research Council Fellowship, DE140100178; we are grateful to the DOE ARM program for technical support in Darwin. Bremen, Bialystok, and Orleans are funded by the EU projects InGOS and ICOS-INWIRE and by the Senate of Bremen. Réunion Island is funded by the EU FP7 project ICOS-INWIRE, the national Belgian support to ICOS and the AGACC-II project (Science for Sustainable Development Program), the Université de la Réunion, and the French regional and national organizations (INSU, CNRS). From 2004 to 2011 the Lauder TCCON program was funded by the New Zealand Foundation of Research Science and Technology contracts CO1X0204, CO1X0703, and CO1X0406. We thank Shuji Kawakami for his technical support in Saga. We thank Peter Bernath, Kaley Walker, and Chris Boone for their guidance using the ACE-FTS data, which were obtained through the Atmospheric Chemistry Experiment (ACE) mission, primarily funded by the Canadian Space Agency. We are grateful to Geoff Toon for his continuous efforts developing the GGG software, for providing the MkIV data, and his input on the manuscript. We thank Arlyn Andrews for providing the LEF surface flask data, which were generated by NOAA-ESRL, Carbon Cycle Greenhouse Gases Group. Baring Head NIWA surface data were provided courtesy of Gordon Brailsford, Dave Lowe, and Ross Martin. We also acknowledge the contributions of in situ vertical profiles from the AirCore, HIPPO, IMECC, INTEX, Learjet, and START08 campaigns. We are grateful to Kelvin Bates for providing monthly OH fields for the GEOS-Chem Updated OH sensitivity experiments. Lastly, we thank the three anonymous reviewers who provided feedback and suggestions.
Funding AgencyGrant Number
Australian Research CouncilDP140101552
Australian Research CouncilDP110103118
Australian Research CouncilDP0879468
Australian Research CouncilLP0562346
Australian Research CouncilDE140100178
European UnionInGOS
European UnionICOS-INWIRE
Senate of BremenUNSPECIFIED
Université de la RéunionUNSPECIFIED
Institut national des sciences de l'Univers (INSU)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
New Zealand Foundation of Research Science and TechnologyCO1X0204
New Zealand Foundation of Research Science and TechnologyCO1X0703
New Zealand Foundation of Research Science and TechnologyCO1X0406
Canadian Space Agency (CSA)UNSPECIFIED
Issue or Number:21
Record Number:CaltechAUTHORS:20161206-132313816
Persistent URL:
Official Citation:Saad, K. M., Wunch, D., Deutscher, N. M., Griffith, D. W. T., Hase, F., De Mazière, M., Notholt, J., Pollard, D. F., Roehl, C. M., Schneider, M., Sussmann, R., Warneke, T., and Wennberg, P. O.: Seasonal variability of stratospheric methane: implications for constraining tropospheric methane budgets using total column observations, Atmos. Chem. Phys., 16, 14003-14024, doi:10.5194/acp-16-14003-2016, 2016
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72599
Deposited By: Tony Diaz
Deposited On:06 Dec 2016 21:47
Last Modified:09 Mar 2020 13:19

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