NO<sub>2</sub> seasonal evolution in the north subtropical free troposphere

Gil-Ojeda, M.; Navarro-Comas, M.; Gómez-Martín, L.; Adame, J. A.; Saiz-Lopez, A.; Cuevas, C. A.; González, Y.; Puentedura, O.; Cuevas, E.; Lamarque, J.-F.; Kinninson, D.; Tilmes, S.

doi:https://doi.org/10.5194/acp-15-10567-2015

Articles | Volume 15, issue 18

https://doi.org/10.5194/acp-15-10567-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-15-10567-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 15, issue 18

Research article

|

25 Sep 2015

Research article |

| 25 Sep 2015

NO₂ seasonal evolution in the north subtropical free troposphere

M. Gil-Ojeda, M. Navarro-Comas, L. Gómez-Martín, J. A. Adame, A. Saiz-Lopez, C. A. Cuevas, Y. González, O. Puentedura, E. Cuevas, J.-F. Lamarque, D. Kinninson, and S. Tilmes

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Final revised paper (published on 25 Sep 2015)
Preprint (discussion started on 22 May 2015)

Interactive discussion

Status: closed

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

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RC C3790: 'Review of Gil al., NO2 seasonal evolution in the North Subtropical free troposphere', Anonymous Referee #1, 18 Jun 2015
- AC C4956: 'Reply to reviewer 1', Manuel Gil, 16 Jul 2015
RC C3813: 'Review of "NO2 seasonal evolution in the North Subtropical free troposphere" by Gil-Ojeda et al.', Anonymous Referee #2, 19 Jun 2015
- AC C4957: 'Reply to reviewer 2', Manuel Gil, 16 Jul 2015
AC C5037: 'Revised manuscript', Manuel Gil, 18 Jul 2015

Peer-review completion

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

AR by Manuel Gil on behalf of the Authors (07 Aug 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Aug 2015) by Michel Van Roozendael

RR by Anonymous Referee #1 (26 Aug 2015)

Suggestions for revision or reasons for rejection

Section 4 on the Optimal Estimation Method has been improved and more details are now given by the authors. However, my main concern about the fact that aerosols are not included in the OEM retrieval remains unaddressed. I ask for the third time the question: Why with an AOD of 0.02 did you decide not to include aerosols in the OEM retrieval ? Is this point discussed in the existing literature ? If not, sensitivity tests should be performed to justify your choice. I have also the following specific comments on the new version of Section 4:

Page 9, lines 5-7: the trace of the A matrix gives the number of independent pieces of information (DFS). I don’t see any typical DFS values in the manuscript.

Page 9, lines 8-14: The total retrieval error is given by the sum of the smoothing error, the retrieval noise and the forward model parameter error. What you describe here are some of the parameters needed to calculate these errors but you don’t give any estimates of these errors. These estimates should appear in the new version of the manuscript. This would help the reader to have a better idea about the quality of your profile retrieval.

Page 10, lines 6-7: ‘AKs are near zero for altitudes lower than 0.5km and higher than 5km’. Then the question is: what is the shape of the AKs between 0.5 and 5km ? Why not showing an example of AKs ?

Page 10, lines 7-8: ‘The retrieved profiles have been obtained for altitudes up to 6km’. I don’t understand this sentence since it is mentioned a couple of lines above that your altitude grid covers the 0-10 km range with a layer thickness of 100m.

Technical corrections:

Section 4 is for me part of the methodology. So, I would move it to Section 2, which could be reorganized in 2 sub-sections: 2.1 for MGA and 2.2 for OEM.

Page 1, line 19: ‘O2-O2’: 2 should appear in subscript.
Page 3, line 2: ‘Ziemke 2001’ should be ‘Ziemke et al., 2001’
Page 3, line 28: ‘limits’ should be replaced by ‘its limits’
Page 4, lines 13 and 14: ‘Gomez et at.’ Should be replaced by ‘Gomez et al.’
Page 4, line 20: ‘See’ -> ‘see’
Page 9, line 6: ‘the independent pieces’ -> ‘the number of independent pieces’
Page 19, line 5 and page 23, line 4: ‘O4’: 4 should be in subscript

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ED: Reconsider after minor revisions (Editor review) (27 Aug 2015) by Michel Van Roozendael

AR by Manuel Gil on behalf of the Authors (06 Sep 2015) Author's response Manuscript

ED: Publish subject to technical corrections (07 Sep 2015) by Michel Van Roozendael

AR by Manuel Gil on behalf of the Authors (09 Sep 2015) Author's response Manuscript

Short summary

The NO2 seasonal evolution in the free troposphere (FT) has been established for the first time, based on a remote sensing technique (MAXDOAS) and thus avoiding the problems of the local pollution of in situ instruments. A clear seasonality has been found, with background levels of 20-40pptv. Evidence has been found on fast, direct injection of surface air into the free troposphere. This result might have implications on the FT distribution of halogens and other species with marine sources.

NO2 seasonal evolution in the north subtropical free troposphere

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Interactive discussion

Peer-review completion

NO₂ seasonal evolution in the north subtropical free troposphere