A Coupled CH4, CO and CO2 Simulation for Improved Chemical Source Modeling
Round 1
Reviewer 1 Report
No comments
Author Response
We thank Reviewer #1 for the rating of our paper.
Reviewer 2 Report
Please find the attachment for the review.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments:
It is unarguably important to understand the transition of greenhouse gases in their atmospheric abundances in order to understand climate change. This manuscript described a new coupled GEOS-Chem carbon gas simulation method to calculate CO2, CO, CH4 simultaneously. It is of great significance to eliminate the previous offline handling of the chemical production terms and OH inconsistency between the three species. The manuscript is well organized except for some minor unclearness. After a review of its coherence and the logic, this paper is eligible to be published. Following are the detailed comments:
1) The term “OH” should be given a definition before used.
2) The content of the article is a bit confusing. Generally, a paper is divided into introduction, methods, results and discussion, and conclusion. There may be appropriate additions, deletions and modifications. It is recommended that the authors readjust the table of contents. What’s more, title 7 (line 440) meaning should be specific.
3) In the discussion, the explanation of the reasons for the deviation of the model results is weak, and there is a lack of references.
4) To my knowledge, some coupled models are also new and applicable to simulate GH emissions. I give limited examples and the authors can considering finding more and citing them to frame the manuscript:
SWAT-DayCent coupled model: Zhao et al., Toward Sustainable Revegetation in the Loess Plateau Using Coupled Water and Carbon Management. Engineering, 2022. 15: p. 143-153.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
This manuscript reports research results of simulating the main anthropogenic greenhouse gases: CO2 and CH4. Due to the interconnection of these gases in the atmosphere through chemical/photochemical and transport processes, it is desirable to simulate these gas species in a holistic model system as described in this research compared to the previous uncoupled model studies. This is rather an extensive and comprehensive study involving model to model, and model to measurement comparisons. The manuscript is well written and clearly presented, and it can be published in Atmosphere with minor revisions.
Some minor observations:
1. On line 234, "the inclusion of a diurnal scaling to the OH field used for CH4 oxidation in the troposphere". Why is it only used for CH4 oxidation? Doesn't CO also react with OH as shown in Equation (3). Since it is the online coupled system, all reactions involved OH should be subject to this scaled OH field.
2. In Figure 2, the P(CO2) values in the coupled simulation for the years of 2008, 2012, 2016 are greater than the adjacent years, and the authors attributed it to the leap years that lead to larger total annual production. The leap years only have one more day than non-leap years, i.e., it is only 1/365 = 0.0027, or 0.27% more. But the differences in the figure seem much larger, especially in 2008 and 2012.
3. NH (North Hemisphere) isn't defined and SH should be defined earlier before Table 2 (or define in the table captions).
4. Line 589 and other places, "The modelled CO values also underestimate the measurements". It should say that the model underestimated CO values compared to measurements. "Measurements" are the objective values that can't be underestimated.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
