Comparison of measured and calculated collision efficiencies at low temperatures

Nagare, B.; Marcolli, C.; Stetzer, O.; Lohmann, U.

doi:https://doi.org/10.5194/acp-15-13759-2015

Articles | Volume 15, issue 23

https://doi.org/10.5194/acp-15-13759-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-15-13759-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 15, issue 23

Research article

|

15 Dec 2015

Research article |

| 15 Dec 2015

Comparison of measured and calculated collision efficiencies at low temperatures

B. Nagare, C. Marcolli, O. Stetzer, and U. Lohmann

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Final revised paper (published on 15 Dec 2015)
Preprint (discussion started on 23 Apr 2015)

Interactive discussion

Status: closed

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

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RC C2767: 'Review of the manuscript “Estimating collision efficiencies from contact freezing experiments” by B. Nagare, C. Marcolli, O. Stetzer, and U. Lohmann.', Anonymous Referee #1, 20 May 2015
RC C3350: 'review : Estimating collision efficiencies from contact freezing experiments', Anonymous Referee #2, 08 Jun 2015
RC C3785: 'Referee report acp-2015-210', Anonymous Referee #3, 18 Jun 2015
AC C7133: 'Response to Referees', Claudia Marcolli, 23 Sep 2015

Peer-review completion

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

AR by Claudia Marcolli on behalf of the Authors (01 Oct 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (02 Nov 2015) by Athanasios Nenes

RR by Anonymous Referee #1 (11 Nov 2015)

Suggestions for revision or reasons for rejection

Comments on the revised manuscript “Comparison of measured and calculated collision efficiencies at low temperatures” by Nagare et al.

In the revised manuscript, authors include many clarifications and details that improved the paper significantly. Some of the most notable changes are:

a) in the experimental section, there are new details and clarifications as well as a discussion on possible uncertainties;

b) a better discussion of the role of electric charge was added. Figure 2 shows all charge measurements and variations. As noted in the response to reviewers, sensitivity analysis showed that droplet charge is a crucial parameter that is not well constrained in the present setup and authors intend to improve this for future measurements;

c) the total collision efficiency measurements and experimental errors are now presented in Figure 8, in contrast with estimations from various theoretical schemes;

d) the discussion of different theoretical estimations is improved, recognizing the importance of phoretic forces, the possible presence of significant electric charges and dependence on temperature. The authors found that most sensitive parameters were the electric charge for electrophoresis (illustrated in Figure 7) and the temperature for thermophoresis and diffusiophoresis. One aspect needs to be included as a minor revision in the text and conclusions is that all presented theoretical schemes were developed and applied mostly for rain conditions at temperatures above 0 deg C.

Authors noted that an accurate description of collision efficiencies below 0 deg C requires a better characterization of thermophoresis and diffusiophoresis in the accumulation mode, and a need for additional experimental data of collision efficiencies, especially at low temperatures. Based on these changes, and many significant improvements, I recommend the paper for publication in the Atmospheric Chemistry and Physics.

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RR by Anonymous Referee #3 (22 Nov 2015)

ED: Publish subject to technical corrections (27 Nov 2015) by Athanasios Nenes

AR by Claudia Marcolli on behalf of the Authors (01 Dec 2015) Author's response Manuscript

Short summary

We determined collision efficiencies of cloud droplets with aerosol particles experimentally and found that they were around 1 order of magnitude higher than theoretical formulations that include Brownian diffusion, impaction, interception, thermophoretic, diffusiophoretic and electric forces. This is most probably due to uncertainties and inaccuracies in the theoretical formulations of thermophoretic and diffusiophoretic processes.