The enhancement of droplet collision by electric charges  and atmospheric electric fields

Guo, Shian; Xue, Huiwen

doi:https://doi.org/10.5194/acp-21-69-2021

Articles | Volume 21, issue 1

https://doi.org/10.5194/acp-21-69-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-21-69-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 1

Research article

|

05 Jan 2021

Research article |

| 05 Jan 2021

The enhancement of droplet collision by electric charges and atmospheric electric fields

Shian Guo and Huiwen Xue

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Final revised paper (published on 05 Jan 2021)
Preprint (discussion started on 31 Jan 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Comments to the manuscript with ID “acp-2019-1140”', Anonymous Referee #1, 04 Apr 2020
- RC3: 'review', Anonymous Referee #3, 16 Apr 2020
RC2: 'Interactive comment on “The enhancement of droplet collision by electric charges and atmospheric electric fields” by Shian Guo and Huiwen Xue', Anonymous Referee #2, 13 Apr 2020
AC1: 'Response to the Referee #1', Huiwen Xue, 11 Jun 2020
AC2: 'Response to the Referee #2', Huiwen Xue, 11 Jun 2020
AC3: 'Response to the Referee #3', Huiwen Xue, 11 Jun 2020

Peer-review completion

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

AR by Huiwen Xue on behalf of the Authors (09 Jul 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Aug 2020) by Patrick Chuang

RR by Anonymous Referee #1 (02 Sep 2020)

Suggestions for revision or reasons for rejection

Comments to the manuscript with ID “acp-2019-1140” General comments:
A summery of previous works and the key point of this study have been improved substantially. However, the language and presentation can still be improved. A moderate revision is needed before it can be considered for publication.
Specific comments:
1. L.42: Why “cloud top is positively charged and the cloud base is negatively charged”?
2. L.67: “researches”à“studies”. Please also check the use of “researches” in other places
of the manuscript.
3. L.71: “investigate”à”investigated”
4. L.75: How do they affect climate system?
5. L.83: Stokes flow
6. L.85-88: check the tense of verbs.
7. L.88: The sentence “The roles of electric charges and fields on precipitation acceleration still needs to
be studied” is very abrupt. Could you please elaborate more on this and its link to
previous sentences?
8. L.98: “The more accurate method for ”à”A more ...method to”. Please also check the
application of “the” in the last paragraph of the introduction.
9. L.126: collide and coalesce ...
10. L.175: to be “solved”
11. L.182: kinetic or dynamic viscosity? Also, \nu is the common symbol representing kinetic
viscosity and \mu for the dynamic viscosity. Please check these symbols carefully in the
manuscript to improve the readability of the manuscript.
12. L. 188: “right side”àright hand side.
13. L. 195: Please check the expression of N_Re. Also, please specify that it is the particle
Reynolds number.
14. L. 199-200: “U” is a scalar here and velocity is a vector.
15. L.204: Could you please estimate the N_Re using the typical values of droplet velocity,
diameter, and the kinetic viscosity of air? Can it really be as large as 5000? More
importantly, why Eq.6 applies to cases with N_Re<5000?
16. Is Eq. 10 an empirical Eq?
17. Please clarify the assumptions employed in Eq.11.
18. F_e in Eq. 12 is a vector, which looks like a scalar in the sentence below Eq.12. Please
check the font style carefully throughout the manuscript.
19. For the sentences above Eq.12, can you simply say “apply Coulomb’s law to point
particles” or something like that to improve the readability?
20. L.242: How does “the line connecting the centers” affect the electric force?
21. Are your q_1 and q_2 in Eq. 12 and 13 the same? Why do you define them twice?
22. L.251: “the first two terms of Eq. (13)”. Please check the wording of explaining each item in Eqs all through the manuscript. You may explicitly write down those terms and explain the physical meaning of them.
23. L.291: “the convenience” or you may say “To save the computational power,”
24. L.293: I don’t understand this “the two droplets can either collide or not depending on the initial horizontal distance ”
25. L.402: Did you mean “net” effect?
26. L.409: “negatively-charged”
27. L. 407-409: I don’t understand how the overall negatively charged collector and the
collected droplet can attract each other. Could the author elaborate more on this?
28. L. 417: “and can be used to represent cloud droplets”àwhich are the typical size of cloud droplets.

Referee Report: PDF

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ED: Reconsider after major revisions (14 Oct 2020) by Patrick Chuang

AR by Huiwen Xue on behalf of the Authors (26 Oct 2020) Author's response Manuscript

ED: Publish as is (11 Nov 2020) by Patrick Chuang

AR by Huiwen Xue on behalf of the Authors (14 Nov 2020)

Short summary

Observations in previous studies show that cloud droplets carry electric charges. We are curious about whether the electric interaction enhances the collision of cloud droplets. The effect of the electric charge and atmospheric electric field on the raindrop-formation process is studied numerically. Results indicate that a cloud with a small droplet size is more sensitive to an electric charge and field, which could significantly trigger droplet collision and accelerate raindrop formation.