Seasonal and spatial changes in trace gases over megacities from Aura TES observations: two case studies

Cady-Pereira, Karen E.; Payne, Vivienne H.; Neu, Jessica L.; Bowman, Kevin W.; Miyazaki, Kazuyuki; Marais, Eloise A.; Kulawik, Susan; Tzompa-Sosa, Zitely A.; Hegarty, Jennifer D.

doi:https://doi.org/10.5194/acp-17-9379-2017

Articles | Volume 17, issue 15

https://doi.org/10.5194/acp-17-9379-2017

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

https://doi.org/10.5194/acp-17-9379-2017

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

Articles | Volume 17, issue 15

Research article

|

07 Aug 2017

Research article |

| 07 Aug 2017

Seasonal and spatial changes in trace gases over megacities from Aura TES observations: two case studies

Karen E. Cady-Pereira, Vivienne H. Payne, Jessica L. Neu, Kevin W. Bowman, Kazuyuki Miyazaki, Eloise A. Marais, Susan Kulawik, Zitely A. Tzompa-Sosa, and Jennifer D. Hegarty

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Final revised paper (published on 07 Aug 2017)
Preprint (discussion started on 06 Mar 2017)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review comments on “Seasonal and Spatial Changes in Trace Gases over Megacities from AURA TES Observations” by Cady-Pereira et al.', Anonymous Referee #1, 05 Apr 2017
- AC2: 'Response to first reviewer', Karen Cady-Pereira, 17 May 2017
- AC3: 'revised manuscript', Karen Cady-Pereira, 17 May 2017
RC2: 'review', Anonymous Referee #2, 11 Apr 2017
- AC1: 'Response to second reviewer', Karen Cady-Pereira, 17 May 2017
- AC4: 'revised manuscript', Karen Cady-Pereira, 17 May 2017

Peer-review completion

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

AR by Karen Cady-Pereira on behalf of the Authors (18 May 2017) Author's response

ED: Referee Nomination & Report Request started (25 May 2017) by Anja Schmidt

RR by Anonymous Referee #1 (05 Jun 2017)

RR by Anonymous Referee #2 (18 Jun 2017)

Suggestions for revision or reasons for rejection

The revised manuscript by Cady-Pereira et al. well address most of the reviewer comments. The figures are significantly improved, and there is additional discussion about the relationship between remote sensing measurements and surface concentrations. I only have a few remaining requests, which are either further clarifications or reiterating a point made in the previous review which the authors chose not to address. These constitute minor revisions.

New comments:

The “Lagos” measurements aren’t really over Lagos — they’re all to the west, over what seems to be rural land areas. The authors need to be careful that their results are interpreted as being indicative of urban Lagos concentrations; otherwise, it’s not clear how this fits within the framing of the “megacities” aspect of the paper.

It’s not clear which pixels across the entire transects (e.g., Fig 12) are used to represent “Lagos” in Fig 11. This is in contrast to MCMA, where Fig 6 shows the portion of the transect (dashed vertical lines) that is used to represent the city. For example, NH3 levels in the Lagos transects peak at latitudes north of 7 N, but elsewhere in the manuscript it is indicated that the most urban impacted area of the transect is 6.4 N - 7 N (page 13, lines 11-14).

13.8: extra space

Revisiting previous comments: mine (with original page/line numbers), their response (A), and my additional response (R)

3.24 - 32: This discussion struck me as a bit narrow, not really considering the science questions and literature associated with these species as much as it was brief mention of papers the authors have written studying these species with TES.

(A) The objective of this section was to provide some brief information to the readers as to why the species are interesting, not to provide a thorough review of the current science questions for each species.

R: Yes, but surely some of the brief information regarding why these species are interesting might be present in articles from outside the TES group? Please expand the set of literature considered here.

9.30: Why? This seems like a rather random thing to do. Is one of the goals of this paper really to evaluate the MIROC model accuracy? Is the MIROC model to be used for some analysis to help explain the TES data later on? After reading the entire paragraph it seems the only point is to make the claim that TES can see data at finer scales than larger models. This is a rather obvious point, given the spatial dimension of the TES footprint vs the model resolution, and does little to quantify anything useful for the satellite data or modeling community. One could imagine using an aggregate of satellite data to see if the coarse model gets at least a good estimate of what it is built to estimate, namely average concentrations at the 300 km scale, but that goes way beyond the analysis provided here. As such, I strongly suggest just removing this paragraph entirely, and the associated summary of this point in the abstract.

(A) Here too we believe we should keep this section, as an additional confirmation of the well know capability of large scale models to replicate “normal” large scale events, and their difficulty in modeling extreme events. For those researchers interested in CH3OH, it also illustrates the information content of TES CH3OH.

R: I still disagree. The authors admit this is “additional confirmation” of something that is “well known”. So, I don’t see what it adds.

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ED: Reconsider after minor revisions (Editor review) (29 Jun 2017) by Anja Schmidt

AR by Karen Cady-Pereira on behalf of the Authors (03 Jul 2017) Author's response Manuscript

ED: Publish as is (04 Jul 2017) by Anja Schmidt

AR by Karen Cady-Pereira on behalf of the Authors (05 Jul 2017)

Short summary

Air quality is a major issue for megacities. Our paper looks at satellite measurements over Mexico City and Lagos of several trace gases gases related to air quality to determine the temporal and spatial variability of these gases, and it relates this variability to local conditions, such as topography, winds and biomass burning events. We find that, while Mexico City is known for severe pollution events, the levels of of pollution in Lagos are much higher and more persistent.