Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 1: Particle number size distribution, cloud condensation nuclei and their origins

Gong, Xianda; Wex, Heike; Voigtländer, Jens; Fomba, Khanneh Wadinga; Weinhold, Kay; van Pinxteren, Manuela; Henning, Silvia; Müller, Thomas; Herrmann, Hartmut; Stratmann, Frank

doi:https://doi.org/10.5194/acp-20-1431-2020

Articles | Volume 20, issue 3

https://doi.org/10.5194/acp-20-1431-2020

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

Special issue:

Marine organic matter: from biological production in the ocean...

https://doi.org/10.5194/acp-20-1431-2020

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

Articles | Volume 20, issue 3

Research article

|

06 Feb 2020

Research article |

| 06 Feb 2020

Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 1: Particle number size distribution, cloud condensation nuclei and their origins

Xianda Gong, Heike Wex, Jens Voigtländer, Khanneh Wadinga Fomba, Kay Weinhold, Manuela van Pinxteren, Silvia Henning, Thomas Müller, Hartmut Herrmann, and Frank Stratmann

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Interactive discussion

Status: closed

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

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RC1: 'Referee comment', Anonymous Referee #1, 12 Sep 2019
- AC1: 'Our responses to your review', Xianda Gong, 14 Nov 2019
RC2: 'Referee report', Anonymous Referee #2, 01 Nov 2019
- AC2: 'Our responses to your review', Xianda Gong, 14 Nov 2019

Peer-review completion

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

AR by Xianda Gong on behalf of the Authors (14 Nov 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (24 Nov 2019) by Kimitaka Kawamura

RR by Anonymous Referee #2 (04 Dec 2019)

Suggestions for revision or reasons for rejection

Re-review of ``Characterization of aerosol particles at Cape Verde close to sea and cloud level heights - Part 1: particle number size distribution, cloud condensation nuclei and their origins''

The authors have done a nice job responding to most of my comments. A few follow-up comments:

1) Having now read the companion paper focusing on INPs, I disagree with the authors' statement that these papers are inextricably linked as each paper stands on its own. To say that they are inextricably linked is to say that if Part 2 is not accepted for publication for some reason, then Part 1 should fall as well, and vice versa. I don't think that this is the case (and this discussion somewhat academic since both papers appear to be of high-quality). The only commonality that I see is that some of the MarParCloud measurements are discussed in the current manuscript, while others are discussed in the other manuscript, without a bit of cross-referencing mentioned at times. Again, I recommend to the editor that the Part 1 and Part 2 be removed from the title of each paper.

2) What does it mean when the authors say that ``the PSND measurements are more precise than the backward trajectories; therefore, we used the PSND to do particle classification rather than the backward trajectories.''? While a measured size distribution may be used to draw inferences about particle emissions sources and subsequent atmospheric processing, I don't think that these inferences can be very definitive. Indeed, the backtrajectories do provide information about both of these processes (i.e., continental vs. marine origin and atmospheric residence time of air parcels above a given surface type). Arguably, the best way to go would be to combine trajectories with chemical composition measurements, as was done by Fomba et al., 2014. As the authors note, Fomba et al. also examined a longer data set and found more aerosol types. In sum, I do not find the authors' response on this point compelling as to why the present methodology is superior. I recommend that the authors better connect the measurements in the present study to the 5-type classification scheme of Fomba et al., 2014.

3) I apologize that my comments on Figure 12 were confusing; however, the authors' assumptions were precisely what I was looking for. Thank you.

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RR by Anonymous Referee #1 (05 Dec 2019)

ED: Reconsider after major revisions (06 Dec 2019) by Kimitaka Kawamura

AR by Xianda Gong on behalf of the Authors (07 Dec 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (12 Dec 2019) by Kimitaka Kawamura

RR by Anonymous Referee #2 (02 Jan 2020)

ED: Publish as is (13 Jan 2020) by Kimitaka Kawamura

AR by Xianda Gong on behalf of the Authors (13 Jan 2020) Manuscript

Short summary

We characterized the aerosol particles in Cabo Verde at sea and cloud levels. We found four well-separable types of PNSDs, with the strongest differences between air masses coming from the ocean compared to from the African continent. During the strongest observed dust periods, CCN concentrations were 2.5 higher than during clean marine periods. The hygroscopicity of the particles did not vary much between different periods. Aerosol at sea level and on the mountaintop was well in agreement.