Contribution of different processes to changes in tropical lower-stratospheric water vapor in chemistry–climate models

Smalley, Kevin M.; Dessler, Andrew E.; Bekki, Slimane; Deushi, Makoto; Marchand, Marion; Morgenstern, Olaf; Plummer, David A.; Shibata, Kiyotaka; Yamashita, Yousuke; Zeng, Guang

doi:https://doi.org/10.5194/acp-17-8031-2017

Articles | Volume 17, issue 13

https://doi.org/10.5194/acp-17-8031-2017

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

Special issue:

Chemistry–Climate Modelling Initiative (CCMI) (ACP/AMT/ESSD/GMD...

https://doi.org/10.5194/acp-17-8031-2017

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

Articles | Volume 17, issue 13

Research article

|

04 Jul 2017

Research article |

| 04 Jul 2017

Contribution of different processes to changes in tropical lower-stratospheric water vapor in chemistry–climate models

Kevin M. Smalley, Andrew E. Dessler, Slimane Bekki, Makoto Deushi, Marion Marchand, Olaf Morgenstern, David A. Plummer, Kiyotaka Shibata, Yousuke Yamashita, and Guang Zeng

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Final revised paper (published on 04 Jul 2017)
Preprint (discussion started on 08 Nov 2016)
Supplement to the preprint

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 #1, 07 Dec 2016
- AC1: 'Reply to RC1', Kevin Smalley, 20 Mar 2017
RC2: 'Review', Anonymous Referee #2, 15 Jan 2017
- AC2: 'Reply to RC2', Kevin Smalley, 20 Mar 2017

Peer-review completion

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

AR by Kevin Smalley on behalf of the Authors (20 Mar 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Apr 2017) by Paul Young

RR by Anonymous Referee #1 (04 Apr 2017)

RR by Anonymous Referee #2 (24 Apr 2017)

Suggestions for revision or reasons for rejection

In the revised version, Smalley et al. have addressed some issues raised by reviewers. However, the authors have decided to ignore the suggestion that more in-depth analysis would make the paper stronger. It is repeatedly stated that the linear regression shown in this paper is superior to "simply comparing [H2O]entry to observations"; these statements make little sense to this reviewer (obviously the questions posed are different), and also does not help to make the paper stronger (I recommend deleting these sentences). My main concern remains that a linear regression is useful to detect correlations and common properties, but not more. In my opinion the paper overstates the results when claiming that the linear regressions shown provide insights into processes. Case in point is the Brewer-Dobson result where some models have a positive BDC coefficient (CNRM-CM5-3, NIWA-UKCA; p6/L29: All pages/lines refer to the manuscript version with changes highlighted). The paper does not explain to the reader why the authors expect the coefficient to be negative, and it would have been easy to check a few model fields as to why the coefficient in these models is positive. A brief mechanistic discussion (there's plenty of papers discussing the Newtonian cooling and ozone/other tracers that can be used for reference) would be helpful.

The revised manuscript has a supplement with 13 figures with proper caption but no text whatsoever. I could spot only one reference to the supplement in the manuscript (p3/L13). Please integrate the supplement better with the manuscript, and provide a very brief description (along with a title like "Supplementary Material for ...") in the supplment.

Finally, the text deserves some careful checking; for example the first sentence of the introduction ("... so increasing it will lead ...") or the last sentence of Section 3.1 ("... show something similar ...").

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ED: Reconsider after minor revisions (Editor review) (03 May 2017) by Paul Young

AR by Kevin Smalley on behalf of the Authors (15 May 2017) Author's response Manuscript

ED: Publish subject to technical corrections (29 May 2017) by Paul Young

AR by Kevin Smalley on behalf of the Authors (30 May 2017) Author's response Manuscript

Short summary

This paper explains a new way to evaluate simulated lower-stratospheric water vapor. We use a multivariate linear regression to predict 21st century lower stratospheric water vapor within 12 chemistry climate models using tropospheric warming, the Brewer–Dobson circulation, and the quasi-biennial oscillation as predictors. This methodology produce strong fits to simulated water vapor, and potentially represents a superior method to evaluate model trends in lower-stratospheric water vapor.