Particle shape accounts for instrumental discrepancy in ice core dust size distributions

Simonsen, Marius Folden; Cremonesi, Llorenç; Baccolo, Giovanni; Bosch, Samuel; Delmonte, Barbara; Erhardt, Tobias; Kjær, Helle Astrid; Potenza, Marco; Svensson, Anders; Vallelonga, Paul

doi:https://doi.org/10.5194/cp-14-601-2018

Articles | Volume 14, issue 5

https://doi.org/10.5194/cp-14-601-2018

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

https://doi.org/10.5194/cp-14-601-2018

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

Articles | Volume 14, issue 5

Research article

|

03 May 2018

Research article |

| 03 May 2018

Particle shape accounts for instrumental discrepancy in ice core dust size distributions

Marius Folden Simonsen, Llorenç Cremonesi, Giovanni Baccolo, Samuel Bosch, Barbara Delmonte, Tobias Erhardt, Helle Astrid Kjær, Marco Potenza, Anders Svensson, and Paul Vallelonga

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Final revised paper (published on 03 May 2018)
Supplement to the final revised paper
Preprint (discussion started on 29 Nov 2017)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Comment on "Particle shape accounts for instrumental discrepancy in ice core dust size distributions"', Anonymous Referee #1, 23 Dec 2017
- AC3: 'Reply to RC1', Marius Simonsen, 02 Feb 2018
- AC4: 'Reply to RC1', Marius Simonsen, 02 Feb 2018
RC2: 'Review of cp-2017-149', Anonymous Referee #2, 27 Dec 2017
- AC2: 'Author reply to RC2', Marius Simonsen, 02 Feb 2018
- AC5: 'Author reply to RC2 v.2', Marius Simonsen, 02 Feb 2018
EC1: 'Preliminary editor's comment', Eric Wolff, 04 Jan 2018
- AC1: 'Author reply to EC1', Marius Simonsen, 02 Feb 2018

Peer-review completion

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

ED: Reconsider after major revisions (13 Feb 2018) by Eric Wolff

AR by Marius Simonsen on behalf of the Authors (13 Feb 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Feb 2018) by Eric Wolff

RR by Anonymous Referee #2 (10 Mar 2018)

Suggestions for revision or reasons for rejection

This manuscript by Simonsen and colleagues has much improved. I accept most answers and rebuttals to my first comments. I am not yet convinced about a few aspects that should still be addressed, though and recommend minor revisions at this stage.

Minor Comments:

1. At the end of section 3.1 you state that the Abakus, after calibration does not measure particles smaller than 1.8 um. This may be misunderstood. As I understand it, the Abakus can indeed measure particles below 1.8 um, but your calibration is not capable of going that small, possibly due to your choice of the smallest polystyrene sphere standard diameter of 1.5 um. If you had smaller standards could the calibration resolve smaller particles?

2. In its present state, section 3.5 is just some copy-pasted text from other sections and absolutely useless for anyone wanting to apply your calibration to their data. These instructions don’t need to be in the main text either. I suggest to put step-by-step instructions in the supplementary with both Abakus and CC data, and only Abakus data. You can use your data as an example.

3. Let’s go back to that factor 10 in the counting efficiency. I understand that if the calibration moves some counts to other bins, there may be a shift in the Abakus/CC ratio in certain bins. But not in the total counts. Your new figure 5d shows that in the raw data, the Abakus counts less small particles than the CC. This makes sense to me, as coincidence loss should be more probable for small particles than for large ones. Still, considering what we know about CC and Abakus detection limits, as well as coincidence loss, in my opinion the total Abakus count (summed over all bins) should to be lower than the total CC count. Could you add something about these two values in the discussion? Also, in Appendix F you state “If two small particles coincide in the Abakus detector, their combined shadow will make them look like a larger particle”. You then compare small and large particle concentrations to total concentrations to conclude that coincidence loss is negligible. Your assumption is incorrect. The problem is not that two small particles combine to form one large. Loss occurs when one particle crosses the beam, and any smaller particle crossing at the same time (on either side of the large particle) will not be counted. Your method to show that coincidence loss in negligible is therefore incorrect or at least insufficient.

4. Page 6, line 1: I think you mean Figure 4, not 5.

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ED: Publish subject to minor revisions (review by editor) (29 Mar 2018) by Eric Wolff

AR by Marius Simonsen on behalf of the Authors (05 Apr 2018) Author's response Manuscript

ED: Publish as is (06 Apr 2018) by Eric Wolff

AR by Marius Simonsen on behalf of the Authors (10 Apr 2018)

Short summary

Ice core dust size distributions are more often measured today by an Abakus laser sensor than by the more technically demanding but also very accurate Coulter counter. However, Abakus measurements consistently give larger particle sizes. We show here that this bias exists because the particles are flat and elongated. Correcting for this gives more accurate Abakus measurements. Furthermore, the shape of the particles can be extracted from a combination of Coulter counter and Abakus measurements.