Global distribution of  CO<sub>2</sub> in the upper troposphere and stratosphere

Diallo, Mohamadou; Legras, Bernard; Ray, Eric; Engel, Andreas; Añel, Juan A.

doi:https://doi.org/10.5194/acp-17-3861-2017

Articles | Volume 17, issue 6

https://doi.org/10.5194/acp-17-3861-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-17-3861-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 17, issue 6

Research article

|

21 Mar 2017

Research article |

| 21 Mar 2017

Global distribution of CO₂ in the upper troposphere and stratosphere

Mohamadou Diallo, Bernard Legras, Eric Ray, Andreas Engel, and Juan A. Añel

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Final revised paper (published on 21 Mar 2017)
Preprint (discussion started on 06 Jun 2016)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review', Anonymous Referee #3, 21 Jun 2016
- AC1: 'Answer to anonymous referee #1', Mohamadou Diallo, 29 Nov 2016
RC2: 'acp 2016-0382', Anonymous Referee #1, 21 Jun 2016
- AC2: 'Answer to anonymous referee \#2', Mohamadou Diallo, 29 Nov 2016
RC3: 'Review of Diallo et al., Global distribution of CO2 in the Upper-Troposphere and Stratosphere', Anonymous Referee #2, 21 Jun 2016
- AC3: 'Answer to anonymous referee \#3', Mohamadou Diallo, 29 Nov 2016
RC4: 'An insufficient evaluation', Anonymous Referee #4, 28 Jun 2016
- AC4: 'Answer to anonymous referee \#4', Mohamadou Diallo, 29 Nov 2016

Peer-review completion

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

AR by Mohamadou Diallo on behalf of the Authors (29 Nov 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (08 Dec 2016) by Gabriele Stiller

RR by Anonymous Referee #1 (12 Dec 2016)

RR by Anonymous Referee #2 (30 Dec 2016)

Suggestions for revision or reasons for rejection

Global distribution of CO2 in the Upper-Troposphere and Stratosphere
Diallo et al.

Revised version

I find the manuscript improved with most of the reviewer suggestions addressed (although not all). I would like to see the following comments addressed but they are mostly technical clarifications of methods. Most importantly there is now an uncertainty analysis, which was one of my main comments in the first round. And awkward sentence structure still needs to be addressed.

Specific comments:

Abstract: some awkward wording in here

p 1 L14: more readily than what
p3 L16 represents is redundant
P3 L 18-20 grammar (Despite its potential ... our knowledge) (should modify Co2, not knowledge)
p5 L7 - specify "major disagreements between the model and observations occur in winter"
p6 L20 section
p7 how many and which sites? aircraft obs used at all? specify quantitative criteria for choosing sites ("high enough elevation to neglect variability..." is not quantitative). This was raised by reviewer 4 and was not addressed in the first round. The boundary condition could be shown or over time at given latitude, showing the condition as it goes from 1999 to 2000.

p7 L21 Is there a discontinuity in time from switching between the two initialization products?

p8 L5-9. This is a good explanation of what effect the pre-2000 initialization might have. Although this section notes that the uncertainty prior to 2005 should then be higher, later on in the paper (p19) this is not mentioned - this should be incorporated somehow in the uncertainty analysis. I would recommend an uncertainty be placed on the initialization values that is based on uncertainties in carbon tracker and in the confidence of the pre-2000 initialization method. Then it could be added (in quadrature) to the uncertainty from the spread of the trajectories.

p13 L16: the mean value over what location? I was under the impression that a single particle was released (for the ER-2 flights) at every one location (one particle per location)? Or are there multiple particles launched per flight measurement? L17 how is the Confidence interval estimated? Presumably from the standard deviation of the particle sampling over some number of particles - how many per location?

Fig3. This is a big improvement over the previous version of the comparison. Note in caption that the dashed line is the 1:1 line. I don't see why both the correlation coefficient and R^2 are needed if one is just the square of the other?

Fig 4. What does EI mean in the legend? Perhaps it should be CO2-model or reconstruction. In the caption as well, I would describe the black line as the vertical profiles from the model-reconstructed CO2.

p14 and figures 3&4: how is the CI calculated? Is only the scatter of particles considered, or is there a different error analysis being done here to account for additional possible sources of uncertainty?

p14-15 units should be on Delta throughout this section - this must be in ppm. Also in caption of Fig 3.

p19: uncertainty. line 5: why average over 11 years? Shouldn't each point in the global distribution, which is monthly, have its own uncertainty? I see that this average is used in the figure, but for the product, the uncertainty should exist for every month for every year, yes? Also clarify if this is a standard error or standard deviation (i.e. did you divide by the square root of the number of trajectories or not?). I believe this should be the standard error. See comment above about incorporating a second error by assigning an uncertainty on the initialization values as well.

Do the longer transit times have higher standard deviations because the trajectories have more time to spread out more essentially, so they hit the 500 hPa boundary at different latitudes and times, giving larger spread? I might add a sentence to explain this.

fig 7a caption: black triangles, not orange. Approximately how many CONTRAIL profiles were averaged here? (over the whole month and latitude band?).

p21 L4: uniformise

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RR by Anonymous Referee #3 (02 Jan 2017)

RR by Anonymous Referee #4 (05 Jan 2017)

ED: Reconsider after minor revisions (Editor review) (10 Jan 2017) by Gabriele Stiller

AR by Mohamadou Diallo on behalf of the Authors (03 Feb 2017) Author's response Manuscript

ED: Publish subject to technical corrections (21 Feb 2017) by Gabriele Stiller

AR by Mohamadou Diallo on behalf of the Authors (01 Mar 2017) Author's response Manuscript

Short summary

We construct a new monthly zonal mean CO₂ distribution from the upper troposphere to the stratosphere over the 2000–2010 period. The main features of the CO₂ distribution are consistent with expected variability due to the transport of long-lived trace gases by the Brewer–Dobson circulation. The method used to construct this CO₂ product is unique and should be useful for model and satellite validation in the upper troposphere and stratosphere.

Global distribution of CO2 in the upper troposphere and stratosphere

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Interactive discussion

Peer-review completion

Global distribution of CO₂ in the upper troposphere and stratosphere