The absorption Ångström exponent of black carbon: from numerical aspects

Liu, Chao; Chung, Chul Eddy; Yin, Yan; Schnaiter, Martin

doi:https://doi.org/10.5194/acp-18-6259-2018

Articles | Volume 18, issue 9

https://doi.org/10.5194/acp-18-6259-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-18-6259-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 9

Research article

|

04 May 2018

Research article |

| 04 May 2018

The absorption Ångström exponent of black carbon: from numerical aspects

Chao Liu, Chul Eddy Chung, Yan Yin, and Martin Schnaiter

Download

Final revised paper (published on 04 May 2018)
Preprint (discussion started on 04 Oct 2017)

Interactive discussion

Status: closed

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

- Printer-friendly version

- Supplement

RC1: 'comments for "The Absorption Ångström Exponent of black carbon: from numerical aspects".', Anonymous Referee #1, 02 Nov 2017
- AC1: 'A short reply from Chao Liu', Chao Liu, 04 Nov 2017
- AC2: 'Response to Reviewer # 1', Chao Liu, 26 Dec 2017
RC2: 'Review of The "Absorption Ångström Exponent of black carbon: from numerical aspects" by Liu et al.', Anonymous Referee #2, 20 Nov 2017
- AC3: 'Response to Reviewer # 2', Chao Liu, 26 Dec 2017
SC1: 'Comment on Liu et al.'s modelled AAEs', J. C. Corbin, 24 Nov 2017
- AC4: 'Response to Dr. Corbin', Chao Liu, 26 Dec 2017

Peer-review completion

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

AR by Chao Liu on behalf of the Authors (26 Dec 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Jan 2018) by Ari Laaksonen

RR by Anonymous Referee #1 (15 Jan 2018)

RR by J. C. Corbin (05 Feb 2018)

Suggestions for revision or reasons for rejection

The Editor has requested my feedback on whether the revised manuscript sufficiently addressed my comments. Unfortunately, I cannot answer this question in the affirmative. I would define “sufficiently addressed” as either (i) disagreeing with a comment and providing an evidence-based argument for such disagreement, or (ii) agreeing with a comment and providing a modified manuscript which remains self-consistent. In the two most substantial cases, it appears that the authors have agreed with my comments, but not modified the manuscript in response. Therefore, I believe that major revisions to the revised manuscript would be required for it to send a self-consistent and unambiguous message.

Of my six comments, three addressed a lack of literature context (#3, 4, 5), one (#1) addressed the inaccuracy with which the manuscript uses technical language, and two (#2, #6) addressed the degree to which the manuscript contributes to scientific progress. The latter two (#2 and #6) are the ones I consider most substantial, although I do not see that #1 was addressed sufficiently either.

Regarding #2, my comment related to the fact that the authors have based their calculations on an invalid reinterpretation of literature results (the assumption that a change in mobility diameter can be used to infer coating thicknesses). In my original comment I provided a solution for the authors to avoid this problem without much more work. The modified manuscript has not changed this assumption, although the authors appear to agree with my comment (there is a new statement that "the conclusions must be viewed with some caution" on page 7). This makes the manuscript appear non-self-consistent.

Regarding #6, my comment related to the treatment of the real and imaginary parts of the complex RI as independent being inconsistent with literature. The authors appear to agree (according to their adding a similar statement on page 10), but have not altered the analysis as a result. Again, this makes the manuscript appear not to be self-consistent. Reading between the lines, I believe that the authors intended for their calculations to demonstrate the impact of uncertainty in the RI values. This I would understand, but according to the current revision I cannot be sure that this is what the authors intended. If it is, then it should be clearly stated and the entire manuscript adjusted accordingly.

Hide

ED: Reconsider after major revisions (05 Feb 2018) by Ari Laaksonen

AR by Chao Liu on behalf of the Authors (15 Mar 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (29 Mar 2018) by Ari Laaksonen

RR by J. C. Corbin (06 Apr 2018)

ED: Publish subject to technical corrections (10 Apr 2018) by Ari Laaksonen

AR by Chao Liu on behalf of the Authors (10 Apr 2018) Author's response Manuscript

Short summary

The absorption Ångström exponent (AAE) of black carbon (BC) is widely accepted to be 1.0, although observational estimates give a quite wide range of 0.6–1.1. This study investigates BC AAE numerically using realistic particle properties and accurate numerical models. The significantly influence of BC microphysical properties on BC AAE is revealed by simple linear formulas, and the widely accepted BC AAE value of 1.0 is not correct for even small BC with wavelength-independent refractive index.