Transformation and ageing of biomass burning carbonaceous aerosol over tropical South America from aircraft in situ measurements during SAMBBA

Morgan, William T.; Allan, James D.; Bauguitte, Stéphane; Darbyshire, Eoghan; Flynn, Michael J.; Lee, James; Liu, Dantong; Johnson, Ben; Haywood, Jim; Longo, Karla M.; Artaxo, Paulo E.; Coe, Hugh

doi:https://doi.org/10.5194/acp-20-5309-2020

Articles | Volume 20, issue 9

https://doi.org/10.5194/acp-20-5309-2020

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

https://doi.org/10.5194/acp-20-5309-2020

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

Articles | Volume 20, issue 9

Research article

|

06 May 2020

Research article |

| 06 May 2020

Transformation and ageing of biomass burning carbonaceous aerosol over tropical South America from aircraft in situ measurements during SAMBBA

William T. Morgan, James D. Allan, Stéphane Bauguitte, Eoghan Darbyshire, Michael J. Flynn, James Lee, Dantong Liu, Ben Johnson, Jim Haywood, Karla M. Longo, Paulo E. Artaxo, and Hugh Coe

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Final revised paper (published on 06 May 2020)
Preprint (discussion started on 28 Feb 2019)

Interactive discussion

Status: closed

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

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RC1: 'Reviewer's comments', Anonymous Referee #1, 29 Mar 2019
RC2: 'Transformation and aging of biomass carbonaceous aerosol', Anonymous Referee #2, 23 Apr 2019
RC3: 'Review', Anonymous Referee #3, 30 Apr 2019
AC1: 'Final Author Response', Hugh Coe, 02 Jan 2020

Peer-review completion

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

AR by Hugh Coe on behalf of the Authors (06 Jan 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (22 Jan 2020) by Sergey A. Nizkorodov

RR by Anonymous Referee #1 (06 Feb 2020)

Suggestions for revision or reasons for rejection

The authors’ have made many positive changes to the manuscript or specifically answered nearly all questions in response to referee comments. The manuscript has improved and its associated discussion is helpful for clarification. I recommend publication after the remaining main issue below is addressed.

The overriding remaining main issue with the paper is related to asserting that the conclusions from the single case study are representative. It is unfortunate that there are no measurements of another fire plume, such as one with a higher MCE and lower initial OM to CO ratio, which could be analyzed for this paper. It could have helped to actually bridge the OM-to-CO-ratio gap between emissions and regional haze observations (asserted on P3 L26 as being bridged by this analysis), esp. the data from Flight B742 shown in Figure 8. The result is that nothing can be definitively said about the differences in OM to CO ratios in the regional haze observations and this is ultimately stated in the abstract and conclusion section. While the case study shown of one plume certainly indicates there is limited evidence of net increase in aerosol mass, this finding is presented as a generalized conclusion of the study. It is not necessary for the authors to show the representativeness of this conclusion, as long as it is clear that it arose from a single case study. Assertions that it was representative should be removed from the manuscript. In particular, the title and abstract should be revised to reduce the implication of general representativeness from the single case study analyzed.

Minor comment related to rBC mixing state:
Since the last paragraph of the introduction (P3 L24) mentioned “mixing state of BC”, it was expected that the fraction of coated rBC-containing particles to the total number of rBC-containing particles (in effect quantifying rBC mixing state) would have been reported, esp. as a function of plume age for the case study. Were there uncoated rBC-containing particles in the fresh emissions and did they accumulate coatings as they aged? Alternatively, if nearly all of the rBC-containing particles had measureable coatings, would a conclusion about their aging indicate that the thick coatings close to the source evaporated as they aged? At P6 L34, consider making a new paragraph about the rBC coating thickness, starting with a statement such as “nearly all rBC-containing particles had measureable coatings” or whatever the case may be. Another such statement could be added to the beginning of the paragraph discussing Figure 12 (P9 L22). Otherwise, P11 L27 appears to be the only place where the mixing state of rBC-containing particles is mentioned. The rBC mixing state information (qualitative or quantitative) could be useful to the modeling community.

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RR by Anonymous Referee #2 (14 Feb 2020)

ED: Publish subject to minor revisions (review by editor) (18 Feb 2020) by Sergey A. Nizkorodov

AR by Hugh Coe on behalf of the Authors (10 Mar 2020) Author's response Manuscript

ED: Publish as is (15 Mar 2020) by Sergey A. Nizkorodov

AR by Hugh Coe on behalf of the Authors (18 Mar 2020) Manuscript

Short summary

We flew a large atmospheric research aircraft across a number of different environments in the Amazon basin during the 2012 biomass burning season. Smoke from fires builds up and has a significant impact on weather, climate, health and natural ecosystems. Our goal was to quantify changes in the properties of the smoke emitted by fires as it is transported through the atmosphere. We found that the major control on the properties of the smoke was due to differences in the fires themselves.