Global methane budget and trend, 2010–2017: complementarity of inverse analyses using in situ (GLOBALVIEWplus CH<sub>4</sub> ObsPack) and satellite (GOSAT) observations

Lu, Xiao; Jacob, Daniel J.; Zhang, Yuzhong; Maasakkers, Joannes D.; Sulprizio, Melissa P.; Shen, Lu; Qu, Zhen; Scarpelli, Tia R.; Nesser, Hannah; Yantosca, Robert M.; Sheng, Jianxiong; Andrews, Arlyn; Parker, Robert J.; Boesch, Hartmut; Bloom, A. Anthony; Ma, Shuang

doi:https://doi.org/10.5194/acp-21-4637-2021

Articles | Volume 21, issue 6

https://doi.org/10.5194/acp-21-4637-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-21-4637-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 6

Research article

|

25 Mar 2021

Research article |

| 25 Mar 2021

Global methane budget and trend, 2010–2017: complementarity of inverse analyses using in situ (GLOBALVIEWplus CH₄ ObsPack) and satellite (GOSAT) observations

Xiao Lu, Daniel J. Jacob, Yuzhong Zhang, Joannes D. Maasakkers, Melissa P. Sulprizio, Lu Shen, Zhen Qu, Tia R. Scarpelli, Hannah Nesser, Robert M. Yantosca, Jianxiong Sheng, Arlyn Andrews, Robert J. Parker, Hartmut Boesch, A. Anthony Bloom, and Shuang Ma

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Final revised paper (published on 25 Mar 2021)
Supplement to the final revised paper
Preprint (discussion started on 17 Sep 2020)

Interactive discussion

Status: closed

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

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- Supplement

SC1: 'Short comment to Lu et al.:Global methane budget and trend, 2010–2017: complementarity of inverse analyses using in situ (GLOBALVIEWplus CH4ObsPack) and satellite (GOSAT) observation', Luke Western, 03 Nov 2020
- AC3: 'Response to SC1', Xiao Lu, 26 Dec 2020
RC1: 'Unsure if the results are really showing consistency of the measurements', Julia Marshall, 05 Nov 2020
- AC1: 'Response to RC1', Xiao Lu, 26 Dec 2020
RC2: 'Review to acp-2020-775', Anonymous Referee #3, 20 Nov 2020
- AC2: 'Response to RC2', Xiao Lu, 26 Dec 2020

Peer-review completion

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

AR by Xiao Lu on behalf of the Authors (26 Dec 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Jan 2021) by Patrick Jöckel

RR by Anonymous Referee #3 (19 Jan 2021)

RR by Julia Marshall (17 Feb 2021)

Suggestions for revision or reasons for rejection

The paper is much improved after revision! I have only a couple very minor comments about the new material that was added, which might clarify the interpretation. The following paragraph remains a sticking point for me:

In L575-L579 of the revised manuscript the author's state: "...in situ observations, in particular surface and tower measurements, are more effective than the satellite observations in independently constraining methane emissions independently from the sink by OH", but also that "the in-situ-only inversion yields a larger interannual variability of posterior OH concentrations and thus methane lifetime than the GOSAT only inversion (Fig.7b), due to the heterogeneous spatial and temporal distribution of the in situ observations."

Both of these things cannot be true. It cannot be that the in-situ measurements better constrain the emissions independently of the OH fields while simultaneously leading to more OH interannual variability. I think the latter finding (more interannual variability in OH in the surface-only inversion) is instead related to having only trends to optimize in anthropogenic emissions. If the model cannot allow emissions to e.g. first decrease and then increase, it can only match the data by adjusting the sink! But this does not necessarily make it a physically reasonable solution. I think this needs to be discussed in some more detail.

Then a comment to the added figures: Please replace figure 7b with the interhemispheric scaling factors (like Maassakkers et. al. 2019 Figure 7d, but with two values instead of one), so the size of the scaling is clear. It is not straightforward to deduce these (especially the interhemispheric ratio) based on the lifetime alone, which is why I requested this figure in the first review.

About Figure S2: Thank you for including this information! However the figure is quite difficult to see. The points are so tiny, I can hardly see the colours. Would it be possible to bin the data somewhat so that it's easier to interpret? A suggestion would be e.g. a few degrees of latitude, 1-km altitude bins, and then perhaps have slightly larger points. Perhaps the colour could show the mean value in the bin, and the size of the point the standard deviation within the bin? This way the noise in the NH mid-latitudes would be easier to interpret. This is just an example: I am sure there are different ways that the information could be plotted to make it clearer.

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ED: Publish subject to minor revisions (review by editor) (17 Feb 2021) by Patrick Jöckel

AR by Xiao Lu on behalf of the Authors (19 Feb 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (19 Feb 2021) by Patrick Jöckel

AR by Xiao Lu on behalf of the Authors (19 Feb 2021) Manuscript

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Short summary

We use an analytical solution to the Bayesian inverse problem to quantitatively compare and combine the information from satellite and in situ observations, and to estimate global methane budget and their trends over the 2010–2017 period. We find that satellite and in situ observations are to a large extent complementary in the inversion for estimating global methane budget, and reveal consistent corrections of regional anthropogenic and wetland methane emissions relative to the prior inventory.

Global methane budget and trend, 2010–2017: complementarity of inverse analyses using in situ (GLOBALVIEWplus CH4 ObsPack) and satellite (GOSAT) observations

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Interactive discussion

Peer-review completion

Global methane budget and trend, 2010–2017: complementarity of inverse analyses using in situ (GLOBALVIEWplus CH₄ ObsPack) and satellite (GOSAT) observations