Estimating global and North American methane emissions with high spatial resolution using GOSAT satellite data

Turner, A. J.; Jacob, D. J.; Wecht, K. J.; Maasakkers, J. D.; Lundgren, E.; Andrews, A. E.; Biraud, S. C.; Boesch, H.; Bowman, K. W.; Deutscher, N. M.; Dubey, M. K.; Griffith, D. W. T.; Hase, F.; Kuze, A.; Notholt, J.; Ohyama, H.; Parker, R.; Payne, V. H.; Sussmann, R.; Sweeney, C.; Velazco, V. A.; Warneke, T.; Wennberg, P. O.; Wunch, D.

doi:https://doi.org/10.5194/acp-15-7049-2015

Articles | Volume 15, issue 12

https://doi.org/10.5194/acp-15-7049-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-15-7049-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 15, issue 12

Research article

|

30 Jun 2015

Research article |

| 30 Jun 2015

Estimating global and North American methane emissions with high spatial resolution using GOSAT satellite data

A. J. Turner, D. J. Jacob, K. J. Wecht, J. D. Maasakkers, E. Lundgren, A. E. Andrews, S. C. Biraud, H. Boesch, K. W. Bowman, N. M. Deutscher, M. K. Dubey, D. W. T. Griffith, F. Hase, A. Kuze, J. Notholt, H. Ohyama, R. Parker, V. H. Payne, R. Sussmann, C. Sweeney, V. A. Velazco, T. Warneke, P. O. Wennberg, and D. Wunch

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Final revised paper (published on 30 Jun 2015)
Preprint (discussion started on 18 Feb 2015)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC C868: 'review of acp-2014-955', Anonymous Referee #2, 18 Mar 2015
RC C1188: 'Review', Anonymous Referee #1, 30 Mar 2015
AC C2997: 'Response to reviews.', Alexander Turner, 27 May 2015

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Alexander Turner on behalf of the Authors (27 May 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (31 May 2015) by Ilse Aben

RR by Anonymous Referee #1 (04 Jun 2015)

Suggestions for revision or reasons for rejection

The author's have addressed most of my concerns well. I am still looking for more to address the issues of representation and transport error. I give a couple suggestions for actions the authors can consider taking to attempt to more directly address these concerns.

Representation error:
The author’s have simulations at relatively high (50x50km) and low (4x5degree) resolution over North America. GOSAT footprints are about 10 km in diameter, but spaced by hundreds of km oftentimes. This means in the author’s inverse framework there is an assumption the 10km diameter footprint observation is representative of the 4x5 degree box. One could test this assumption using the ‘higher’ resolution simulation to see what the variance in XCH4 is in the simulations within 4x5 degree boxes. This is not perfect—50km is much coarser than 10km, and the model transport is assumed correct, but it gives some test. With intense point sources for methane, there may be many cases where the representation error becomes quite large, and, could be systematic since the GOSAT observing pattern will mean the same 10km diameter location will be assumed representative of a 4x5degree cell—and that location could be biased high or low depending on the location of intense sources in that region. As I say- this is not a perfect approach (nor the only way for the authors to address this question) but at least this directly would address the potential issue of systematic errors from representation error and would not require any new model runs, simply some analysis of data the author’s have in hand.

Transport error:
One approach the author’s could take is to consider the impact of using different version GEOS winds. The great concern is always that systematic transport errors will lead to biased inversions (for example, the transport model may ventilate the boundary layer too quickly systematically). Using a different version of GEOS winds for a short time window and comparing even just the forward model simulation with the same fluxes would be very informative of the potential magnitude of systematic transport errors and confidence that can be placed in the inverted fluxes. This could be done for a very short time window (and thus not be a large additional simulation task). This is not the only approach, but a suggestion that could be relatively straightforward.

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ED: Reconsider after minor revisions (Editor review) (10 Jun 2015) by Ilse Aben

AR by Alexander Turner on behalf of the Authors (15 Jun 2015) Author's response Manuscript

ED: Publish as is (17 Jun 2015) by Ilse Aben

AR by Alexander Turner on behalf of the Authors (17 Jun 2015)