Using atmospheric trace gas vertical profiles to evaluate model fluxes: a case study of Arctic-CAP observations and GEOS simulations for the ABoVE domain

Sweeney, Colm; Chatterjee, Abhishek; Wolter, Sonja; McKain, Kathryn; Bogue, Robert; Conley, Stephen; Newberger, Tim; Hu, Lei; Ott, Lesley; Poulter, Benjamin; Schiferl, Luke; Weir, Brad; Zhang, Zhen; Miller, Charles E.

doi:https://doi.org/10.5194/acp-22-6347-2022

Articles | Volume 22, issue 9

https://doi.org/10.5194/acp-22-6347-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-22-6347-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 22, issue 9

Research article

|

17 May 2022

Research article |

| 17 May 2022

Using atmospheric trace gas vertical profiles to evaluate model fluxes: a case study of Arctic-CAP observations and GEOS simulations for the ABoVE domain

Colm Sweeney, Abhishek Chatterjee, Sonja Wolter, Kathryn McKain, Robert Bogue, Stephen Conley, Tim Newberger, Lei Hu, Lesley Ott, Benjamin Poulter, Luke Schiferl, Brad Weir, Zhen Zhang, and Charles E. Miller

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Final revised paper (published on 17 May 2022)
Preprint (discussion started on 11 Sep 2020)

Interactive discussion

Status: closed

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

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RC1: 'Review of Sweeney et al.', Anonymous Referee #1, 28 Sep 2020
AC1: 'Reply to review 1', Colm Sweeney, 30 Sep 2020
RC2: 'Referee#2', Thomas Lauvaux, 18 Dec 2020

Peer-review completion

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

AR by Colm Sweeney on behalf of the Authors (24 Jun 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (30 Jun 2021) by Christoph Gerbig

RR by Anonymous Referee #1 (09 Jul 2021)

RR by Anonymous Referee #3 (09 Sep 2021)

Suggestions for revision or reasons for rejection

General comments

Authors use the airborne CH4, CO2, CO observations over Alaska to test surface flux models and inventories and find a good correlation between model-simulated and observed differences between partial column-averaged representing lower troposphere below 3000m and above. The difference between the lower and mid-troposphere is used to avoid a need for accurately matching the seasonal cycle in the global and hemispheric scale and to focus on the impacts of the regional emissions and sinks. The application of the method can be considered successful overall, and progress in surface flux modeling was demonstrated, some future improvements are still desirable, as mentioned further in the review. The manuscript is well written and can be published after minor revision.

Detailed comments

Line 75 The target is ‘to evaluate the ability of current land surface flux models’, but the conclusions indicate that the goal is not fully achieved – separating contributions of model simulated fluxes from inside and outside the study domain is difficult, as well as separating the impacts of surface fluxes from meteorology and tracer transport. It would be natural to extend evaluation target to a combination of the surface flux models and the transport model.

Line 224 References may be needed to point to past results, and GCP-CH4 regional estimates are available for comparison.

Line 245-250 Justification for the setting of 3000 m as a boundary between PBL and free troposphere was not discussed (any suitable reference?), while the PBL heights diagnosed from potential temperature, humidity, and tracer profiles are often lower than 3000 m. As there is a good volume of evidence on the connection between tracer and potential temperature profiles in the troposphere (Jin et al, 2021), an alternative approach would be to test lower altitude for separator or make it linked to isentropic vertical coordinate.

Line 295 Here, one would guess that using inversion optimized fluxes, even made with another transport model would give a better match with observations than the unoptimized models and inventories used in the study (as mentioned on Line 510).

Line 503 Said: “Modeled North Slope CH4 is underestimated throughout the measurement period pointing to deficiencies in the wetland flux specifications over this ecoregion”. What is the confidence level for this conclusion, given that the impact of the fluxes from outside of the study domain is considered significant, as discussed in Section 3.1.11?

Line 508 Authors cite the improvements since the survey by Fisher et al (2014). This looks like a good point, should it be supported by a table or figure in the analysis?

Technical corrections

Line 141 fix square to round brackets
Line 173 what does sw mean in pco2sw? – need description
Line 190 Table 1. In second LPJ-wsl reference – year is missing
Line 264 words ‘CH4 enhancements’ can be removed - appear twice in a sentence

References

Jin, Y., Keeling, R. F., Morgan, E. J., Ray, E., Parazoo, N. C., and Stephens, B. B.: A mass-weighted isentropic coordinate for mapping chemical tracers and computing atmospheric inventories, Atmos. Chem. Phys., 21, 217–238, https://doi.org/10.5194/acp-21-217-2021, 2021

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ED: Publish subject to minor revisions (review by editor) (17 Sep 2021) by Christoph Gerbig

AR by Colm Sweeney on behalf of the Authors (26 Sep 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (05 Oct 2021) by Christoph Gerbig

Short summary

The Arctic Carbon Atmospheric Profiles (Arctic-CAP) project demonstrates the utility of aircraft profiles for independent evaluation of model-derived emissions and uptake of atmospheric CO₂, CH₄, and CO from land and ocean. Comparison with the Goddard Earth Observing System (GEOS) modeling system suggests that fluxes of CO₂ are very consistent with observations, while those of CH₄ have some regional and seasonal biases, and that CO comparison is complicated by transport errors.