Validation of acetonitrile (CH<sub>3</sub>CN) measurements in the stratosphere and lower mesosphere from the SMILES instrument on the International Space Station

Fujinawa, Tamaki; Sato, Tomohiro O.; Yamada, Takayoshi; Nara, Seidai; Uchiyama, Yuki; Takahashi, Kodai; Yoshida, Naohiro; Kasai, Yasuko

doi:https://doi.org/10.5194/amt-13-2119-2020

Articles | Volume 13, issue 4

https://doi.org/10.5194/amt-13-2119-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-13-2119-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 13, issue 4

Research article

|

29 Apr 2020

Research article |

| 29 Apr 2020

Validation of acetonitrile (CH₃CN) measurements in the stratosphere and lower mesosphere from the SMILES instrument on the International Space Station

Tamaki Fujinawa, Tomohiro O. Sato, Takayoshi Yamada, Seidai Nara, Yuki Uchiyama, Kodai Takahashi, Naohiro Yoshida, and Yasuko Kasai

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Final revised paper (published on 29 Apr 2020)
Preprint (discussion started on 26 Aug 2019)

Interactive discussion

Status: closed

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

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RC1: 'Referee Comment on amt-2019-261', Anonymous Referee #1, 04 Oct 2019
- AC1: 'Reply to anonymous reviewer #1', Tamaki Fujinawa, 12 Dec 2019
RC2: 'Review of "Validation analysis of deriving acetonitrile ..."', Hugh C. Pumphrey, 31 Oct 2019
- AC2: 'Reply to reviewer #2, Dr. Hugh C. Pumphrey', Tamaki Fujinawa, 12 Dec 2019
EC1: 'Repost of missing Figure 1 from page C4 of the review by RC2', Alyn Lambert, 01 Nov 2019

Peer-review completion

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

AR by Tamaki Fujinawa on behalf of the Authors (09 Jan 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (22 Jan 2020) by Alyn Lambert

RR by Anonymous Referee #1 (14 Feb 2020)

Suggestions for revision or reasons for rejection

No longer ascribing measurements in the upper stratosphere to recent biomass burning activity is a significant improvement.

I see no real change in the grammar, including the awkwardly worded title. I will make a suggestion for the title:

Validation of acetonitrile (CH3CN) measurements in the stratosphere and lower mesosphere from the SMILES instrument on the International Space Station

and I will point out a sentence that requires rewriting:

The difference between the two decreases down to less than 10 % at an upper altitudes than 4.8 hPa.

and I will leave it at that.

>The relative difference between AOS1 and AOS2 is approximately 12 ppt (30 %) with
>the maximum at 15.7 hPa, indicating that the difference between the two AOSs is
>due to sensitivity differences.

The word “indicating” suggests that the magnitude of the difference and/or the pressure level at which the maximum difference occurs somehow proves that the discrepancy is due to “sensitivity differences.” I don’t really follow that logic. At the very least, I think you should rephrase (“We believe the discrepancy is due to sensitivity differences in the two AOSs” or “It is likely that these discrepancies between the two AOSs result from sensitivity differences”) to something less definitive, unless there is proof provided here that I am missing.

You seem to basically attribute the inconsistencies between the AOSs to problems in the instrument characterization during manufacturing. I don’t know if this means you see similar effects (higher VMR from AOS 1) for all molecules, weak or strong, from band A, or whether the problem relates to difficulties in properly characterizing instrumental effects in the shape of the stronger, overlapping HCl spectral feature, which then pollutes the retrieval using the weak CH3CN spectral feature. I am imagining it is the latter.
This would be beyond the scope of this paper, but as food for thought, would it be possible to refine the instrument characterization to achieve improved agreement between the two instruments? I don’t know how many moving parts go into that characterization.

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ED: Publish subject to minor revisions (review by editor) (20 Feb 2020) by Alyn Lambert

AR by Tamaki Fujinawa on behalf of the Authors (13 Mar 2020) Author's response Manuscript

ED: Publish as is (24 Mar 2020) by Alyn Lambert

AR by Tamaki Fujinawa on behalf of the Authors (25 Mar 2020) Manuscript

Short summary

We performed an error analysis of SMILES observations for acetonitrile and a validation using the MLS observations by extracting the coincident points between SMILES and MLS data. The major error sources for the SMILES observations were quantitatively estimated. At upper pressure levels the difference between the two datasets increased because of an uncertainty in MLS observations. The results showed that SMILES has an advantage in measuring acetonitrile in the upper stratosphere and mesosphere.