Estimating surface carbon fluxes based on a local ensemble transform Kalman filter with a short assimilation window and a long observation window: an observing system simulation experiment test in GEOS-Chem 10.1

Liu, Yun; Kalnay, Eugenia; Zeng, Ning; Asrar, Ghassem; Chen, Zhaohui; Jia, Binghao

doi:https://doi.org/10.5194/gmd-12-2899-2019

Articles | Volume 12, issue 7

https://doi.org/10.5194/gmd-12-2899-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gmd-12-2899-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 12, issue 7

Development and technical paper

|

12 Jul 2019

Development and technical paper |

| 12 Jul 2019

Estimating surface carbon fluxes based on a local ensemble transform Kalman filter with a short assimilation window and a long observation window: an observing system simulation experiment test in GEOS-Chem 10.1

Yun Liu, Eugenia Kalnay, Ning Zeng, Ghassem Asrar, Zhaohui Chen, and Binghao Jia

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Final revised paper (published on 12 Jul 2019)
Preprint (discussion started on 13 Dec 2017)
Paper acquired from discussion forum ACPD

Interactive discussion

Status: closed

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

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- Supplement

SC1: 'Executive Editor comment on "Estimating Surface Carbon Fluxes Based on a Local Ensemble Transform Kalman Filter with a Short Assimilation Window and a Long Observation Window"', Astrid Kerkweg, 21 Dec 2017
- AC1: 'Answer to the comments', Yun Liu, 18 May 2018
RC1: 'Review of "Estimating Surface Carbon Fluxes..."', Anonymous Referee #1, 08 Aug 2018
- AC2: 'answer to the reviewer', Yun Liu, 31 Aug 2018
RC2: 'Review of “Estimating Surface Carbon Fluxes Based on a Local Ensemble Transform Kalman Filter with a Short Assimilation Window and a Long Observation Window” by Yun Liu et al.', Anonymous Referee #2, 23 Aug 2018
- AC3: 'Answer to reviewer', Yun Liu, 31 Aug 2018

Peer-review completion

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

AR by Yun Liu on behalf of the Authors (15 Oct 2018) Author's response

ED: Referee Nomination & Report Request started (19 Nov 2018) by Adrian Sandu

RR by Anonymous Referee #2 (26 Dec 2018)

Suggestions for revision or reasons for rejection

[General comments]
This reviewer doubts whether the manuscript is the final version that authors have revised, because the current manuscript has not been updated completely although authors replied that it was fixed or revised (For example, the localization scale is not fixed in the manuscript yet, and any additional brief description of OCO data aggregation cannot be found). This reviewer strongly suggests authors to check if the uploaded manuscript was the final one. If you add or modify some, it would be good to point out where you made changes (page and lines) in the author’s response. In addition, this reviewer mentioned that it needs to assimilate “additional” observation dataset such as GV+ and GOSAT to see whether long OW is necessary when there are “more” observations to constrain the surface carbon fluxes. However, authors seem to provide the results from the experiment assimilating only GV+. This is somewhat distant from what this reviewer asked authors to prove. More observational data, GV+ in addition to OCO, may give somewhat different sensitivity of the length of OW. If Figure 10 results from the experiment assimilating both GV+ and OCO, please revise the context appropriately. If Figure 10 results from the experiment assimilating only GV+, this reviewer strongly suggests authors to try the corresponding experiment again. This reviewer agrees that it is worth finding that assimilating each datasets required consistent length of OW (8d-15d) though. Before the publication, authors need to revise the manuscript carefully again.

[Specific comments]
1. p. 7, line 1: Why did the authors drop the citation of Liu et al. (2017) from the previous manuscript?
2. p. 10, line 22: Typo of localization scale (150km) has not been corrected yet, although it is important experimental setting.
3. Figures 3, 5, and 10: It needs to address what period authors made temporal average for. It seems to me that authors may drop the spinup period from Jan. to the end of Feb., 2015. Please clarify it.
4. p.13, lines 19-22: The statement leads to a question, what would happen if the experiments start from APR. It would be great to add discussion about it, although authors do not need to show those results.

[Technical corrections]
1. p. 7, line 1: unbalanced parenthesis.
2. p. 8, line 31: unbalanced parenthesis
3. p. 9, line 3: unbalanced parenthesis
4. p. 16, lines 4-7: Text miscalls experiment #. EXP7 should be changed to EXP6, and EXP8 should be changed to EXP7. Please check them carefully again.
5. Figure 7: Color bars need to be rescaled to analyze figures better. For example, authors need to include large concentration better for the first four figures. Current color bar does not show what is going on over 409 ppmv (authors should add the unit "ppmv" in the figure too) although Figure 7f shows a difference greater than 5 ppmv. Due to the current color bar, Figure 7a and Figure 7c look almost identical (Figure 7b and Figure 7d, too). Please rescale the color bar, or add more colors to specify more levels of CO2 concentration.
6. p. 16, line 31 – p. 17, lines 1-2: Please rephrase the sentence to clarify what authors would like to point out precisely.
7. p. 18, lines 5-6: Current sentence is not a grammatically complete. Please rephrase it. The sentence in the previous manuscript was better.
8. Figure 10: Resolution or shading style of the Figure 10 looks different from Figure 5. Is there any reason? If not, please be consistent.
9. p. 20, lines 4-5: Please clarify what you mean by “hybrid ensemble data assimilation system”, since there are so many similar systems recently.
10. p. 20, line 8: Could you please provide any examples?

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ED: Reconsider after major revisions (06 Feb 2019) by Adrian Sandu

AR by Yun Liu on behalf of the Authors (20 Mar 2019)

ED: Referee Nomination & Report Request started (11 Apr 2019) by Adrian Sandu

RR by Anonymous Referee #1 (18 Apr 2019)

RR by Anonymous Referee #3 (05 May 2019)

ED: Publish as is (16 May 2019) by Adrian Sandu

AR by Yun Liu on behalf of the Authors (25 May 2019) Manuscript

Short summary

We developed a new carbon data assimilation system to estimate the surface carbon fluxes using the LETKF and GEOS-Chem model, which uses a new scheme with a short assimilation window and a long observation window. The analysis is more accurate using the short assimilation window and is exposed to the future observations that accelerate the spin-up. In OSSE, the system reduces the analysis error significantly, suggesting that this method could be used for other data assimilation problems.