A new balance formula to estimate new particle formation rate: reevaluating the effect of coagulation scavenging

Cai, Runlong; Jiang, Jingkun

doi:https://doi.org/10.5194/acp-17-12659-2017

Articles | Volume 17, issue 20

https://doi.org/10.5194/acp-17-12659-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-17-12659-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 17, issue 20

Research article

|

25 Oct 2017

Research article |

| 25 Oct 2017

A new balance formula to estimate new particle formation rate: reevaluating the effect of coagulation scavenging

Runlong Cai and Jingkun Jiang

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Final revised paper (published on 25 Oct 2017)
Preprint (discussion started on 07 Mar 2017)

Interactive discussion

Status: closed

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

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RC1: 'Interactive comment on “A new balance formula to estimate new particle formation rate: reevaluating the effect of coagulation scavenging” by R. Cai et al.', Anonymous Referee #1, 02 May 2017
RC2: 'Review of the manuscript by Cai and Jiang', Anonymous Referee #2, 23 May 2017
AC1: 'Author comments', Jingkun Jiang, 15 Jun 2017

Peer-review completion

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

AR by Jingkun Jiang on behalf of the Authors (15 Jun 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (16 Jun 2017) by Veli-Matti Kerminen

RR by Anonymous Referee #2 (21 Aug 2017)

Suggestions for revision or reasons for rejection

Cai & Jiang - second review

The authors have done a good job in answering most of my comments and those of the other rewiewer.

I still, however, think that additional explanations are needed to a couple of my initial concerns.

1. Derivation of A7 and A6 in the Appendix and double summation term in eq. A7:

Isn't the message in A7 self-evident? I.e. the rate of change of particle concentration in range k....u is
equal to condensational growth into range (I) minus condensation out of range (Ju) plus coagulation into
range minus coagulation out of range ?

and

In A6, the rate of change of particle concentration above size k is equal to condensational growth into
the range (I) minus collision rate in the range ?

In my view, the only slightly difficult part to formulate is the coagulation into range term in A7, and this
is not thoroughly explained here (and perhaps, slightly wrong?).
Let's say that we have a linear bin structure in volume so that v1 = 1, v2 = 2, ....., vk = k, ..... and we
are looking at the range from 7 to 10, i.e. dN(7,10)/dt.
According to the indexing in eq. A5, the following index-pairs contribute to the coagulation source-term
into the range: 1 and 5, 2 and 4, 3 and 3, 4 and 2, 5 and 1, 1 and 6, 2 and 5, 3 and 4, 4 and 3, 5 and 2,
4 and 3, 1 and 7, 2 and 6, 3 and 5, 4 and 4, 5 and 3, 6 and 2, 7 and 1.
The factor (1/2) takes care of the double counting and this is correct.
But what about the 5 first pairs in the list? They also produce particles into the range 6 to 7 which is not
in the range 7 to 10 ? Please explain!
Also, what if you have a different bin structure, say logarithmically spaced? Then, the conditions under
the summation term on the third term of the right hand side of equation A7, i.e. v(i) + v(j+1) = v(g) cannot
hold? If the equation in its current form is only applicable for a linearly spaced bin structure, it must be
clearly stated.

In my original review, I suggested removing most of the derivations in the Appendix. As they are located
in the Appendix, they might as well stay there, if the authors wish so.

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ED: Reconsider after minor revisions (Editor review) (21 Aug 2017) by Veli-Matti Kerminen

AR by Jingkun Jiang on behalf of the Authors (28 Aug 2017) Author's response Manuscript

ED: Reconsider after minor revisions (Editor review) (31 Aug 2017) by Veli-Matti Kerminen

AR by Jingkun Jiang on behalf of the Authors (07 Sep 2017) Author's response Manuscript

ED: Publish subject to technical corrections (13 Sep 2017) by Veli-Matti Kerminen

AR by Jingkun Jiang on behalf of the Authors (14 Sep 2017) Author's response Manuscript

Short summary

Widely used formulae underestimate the atmospheric new particle formation (NPF) rate when intense NPF events are analyzed. This is caused by the underestimation or neglect of the coagulation scavenging effect. To address this issue, a new formula was theoretically derived. Aerosol down to ~ 1 nm was measured in Beijing and used together with data reported in the literature to test the new formula and others. Implications for NPF rates in various atmospheric environments are discussed.