A new method for calculating number concentrations of cloud condensation nuclei based on measurements of a three-wavelength humidified nephelometer system

Tao, Jiangchuan; Zhao, Chunsheng; Kuang, Ye; Zhao, Gang; Shen, Chuanyang; Yu, Yingli; Bian, Yuxuan; Xu, Wanyun

doi:https://doi.org/10.5194/amt-11-895-2018

Articles | Volume 11, issue 2

https://doi.org/10.5194/amt-11-895-2018

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

https://doi.org/10.5194/amt-11-895-2018

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

Articles | Volume 11, issue 2

Research article

|

14 Feb 2018

Research article |

| 14 Feb 2018

A new method for calculating number concentrations of cloud condensation nuclei based on measurements of a three-wavelength humidified nephelometer system

Jiangchuan Tao, Chunsheng Zhao, Ye Kuang, Gang Zhao, Chuanyang Shen, Yingli Yu, Yuxuan Bian, and Wanyun Xu

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Final revised paper (published on 14 Feb 2018)
Preprint (discussion started on 28 Jul 2017)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review', Anonymous Referee #1, 19 Aug 2017
- AC1: 'Response to referee #1', Chunsheng Zhao, 01 Nov 2017
RC2: 'Interactive comment on “A New Method for Calculating Number Concentrations of Cloud Condensation Nulcei Based on Measurements of A Three-wavelength Humidified Nephelometer System” by J. Tao et al.', Anonymous Referee #2, 29 Aug 2017
- AC2: 'Response to referee #2', Chunsheng Zhao, 01 Nov 2017

Peer-review completion

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

AR by Chunsheng Zhao on behalf of the Authors (01 Nov 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (06 Nov 2017) by Pierre Herckes

RR by Anonymous Referee #1 (10 Nov 2017)

Suggestions for revision or reasons for rejection

The authors have improved the manuscript and clarified some unclear sections. However, not all of my comments have been addressed in the manuscript; in addition, some obscurities remain and new ones were introduced by new text.
The language has been improved somewhat. As I expect that copyediting of the manuscript will take care of it, I only listed a few wording or grammar mistakes below.
Line numbers in my comments refer to the marked-up version of the revised manuscript, attached to the response to the reviews.

Major comments
1) Limitations
The authors do a better job now pointing out the caveats of the new method. However, one limitation is the restriction to S = 0.07% (or lower). However, some more discussion should be given considering the following:
- In my previous comments, I had pointed out that CCN counters are least accurate at low S. This uncertainty in measurements should be mentioned.
- In addition, the authors mention at the very end of the manuscript that the low S makes this method ‘more applicable for ambient measurements of clouds and fogs in the atmosphere’. Typical supersaturations in clouds range from < 0.1% (e.g. for stratus) to > 1% (for cumulus clouds). This should be mentioned and appropriate references added.
- What is the reasoning that you can assume internal mixing of the aerosol? (e.g. l. 264)
- N(CCN) is rarely measured at cloud height as surface measurements are much simpler. It always remains the question whether surface aerosol is actually connected to clouds above the measurement site. However, I do not believe that just the transport time of bringing aerosol aloft (can be as little as a few minutes) is a sufficient ageing time - as implied in l. 268 - to achieve internal mixing. Please support or reject this assumption by appropriate references.

2) Structure
The discussion of delta(kappa) is still poorly organized. I suggest starting with the calculated delta(kappa) and its sensitivity studies and then concluding that an assumption of 0.2 is sufficiently good. That way, Section 3 will be better organized and also the conclusions could be structured better.

Minor Comments
l. 21 and later in the manuscript: I don’t understand why it is restricted to ‘single source regions’. All what matters is whether the aerosol is aged or fresh – whereas the latter could originate from multiple emission sources.

l. 30: ‘nuclei’ is plural; either ‘nuclei are… ‘ or ‘nucleus is…’

l. 49: Why not adding the equation of the Angstrom exponent here (and remove it later)?

l. 51 and 52: What does R^2 refer to? In order to make it easier to read, I suggest splitting this sentence into (at least) two. That way it would also become clear what’ has’ in l. 52 refers to.

l. 62: As mentioned in my previous comments, aerosol hygroscopicity is defined as the ability of a particle (or a material in general) to take up a certain amount of water at a given RH. It is NOT a function of aerosol size as the text here suggests.

l. 68 and l. 108: Define parameters only once. Here you use two different names for rRH

l. 71 and remainder of the manuscript: ‘Composition’ is often used wrongly. ‘Component’ is the right word.

l. 172: Do you really refer to Eq.-1 here?

l. 221: I still don’t understand this sentence: what are ‘particles’ as opposed to ‘existing particles’?

l. 253-255: How is ‘too large’ or ‘too small’ defined?

l. 315: This is a very strong statement. Is this true under all conditions?

l. 318 and l. 325: In my previous comments, I had pointed out that ‘on the one hand’ and ‘on the other hand’ are used to introduce two opposing statements. However, here they introduce pretty much the same thing, i.e. the variation of kappa(c) can be quite large vs the influence of kappa(c) cannot be ignored. This should be restructured.

l. 335: A ‘cloud chamber’ is not the same as a CCN counter. In the former, a cloud is formed and the supersaturation cannot be exactly predetermined and/or measured. In a CCN counter, particles are exposed to a preset supersaturation. I assume you mean the latter here.

Technical (language) mistakes

l. 19: involves --> includes

l. 21: suitable

l. 77: ‘0.6 R^2’ seems very colloquial. Better is ‘R^2 = 0.6’.

l. 77: leads

l. 78: ..study that applied…

l. 81: ‘accurate’ might be better to use than ‘effective’

l. 82: rRH is directly connected

l. 159: Reword ‘..is found can be used’

l. 167: Define Dc here.

l. 203-205: This sentence needs to be rewritten as it is confusing: How can NCCN range to 100 nm (it is in [cm-3]); what are the units of a ‘cumulative contribution’ if it ranges from 0.2 to 0.8?

l. 217, 218: particles

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ED: Reconsider after major revisions (12 Nov 2017) by Pierre Herckes

AR by Chunsheng Zhao on behalf of the Authors (23 Dec 2017) Author's response Manuscript

ED: Publish subject to technical corrections (02 Jan 2018) by Pierre Herckes

AR by Chunsheng Zhao on behalf of the Authors (08 Jan 2018) Manuscript

Short summary

Existing chamber technologies for direct measurements of number concentration of cloud condensation nuclei (NCCN) are sophisticated and expensive. In this paper, a new method is proposed to calculate NCCN based only on measurements of a humidified nephelometer system which have accounted for influences of both aerosol size and aerosol hygroscopicity on NCCN calculation. This new method makes NCCN measurements more convenient and is capable of obtaining NCCN at lower supersaturations.