Drivers of cloud droplet number variability in the summertime in the southeastern United States

Bougiatioti, Aikaterini; Nenes, Athanasios; Lin, Jack J.; Brock, Charles A.; de Gouw, Joost A.; Liao, Jin; Middlebrook, Ann M.; Welti, André

doi:https://doi.org/10.5194/acp-20-12163-2020

Articles | Volume 20, issue 20

https://doi.org/10.5194/acp-20-12163-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-20-12163-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 20

Research article

|

27 Oct 2020

Research article |

| 27 Oct 2020

Drivers of cloud droplet number variability in the summertime in the southeastern United States

Aikaterini Bougiatioti, Athanasios Nenes, Jack J. Lin, Charles A. Brock, Joost A. de Gouw, Jin Liao, Ann M. Middlebrook, and André Welti

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Final revised paper (published on 27 Oct 2020)
Supplement to the final revised paper
Preprint (discussion started on 17 Mar 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of “Drivers of cloud droplet number variability in the summertime Southeast United States”', Anonymous Referee #1, 04 Apr 2020
- AC1: 'Response to Reviewer 1', Aikaterini Bougiatioti, 23 Jun 2020
RC2: 'Comments on "Drivers of cloud droplet number variability in the summertime southeast United States "', Anonymous Referee #2, 22 Apr 2020
- AC2: 'Response to Reviewer 2', Aikaterini Bougiatioti, 23 Jun 2020

Peer-review completion

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

AR by Aikaterini Bougiatioti on behalf of the Authors (24 Jun 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Jun 2020) by Lynn M. Russell

RR by Anonymous Referee #2 (28 Jul 2020)

Suggestions for revision or reasons for rejection

he authors have sufficiently responded to reviewer comments, improving figures, improving the clarity, making it clear what cases are night/day and rural/urban, and clearly indicating the importance of these results.

The figures have been improved however, I highly recommend using images for your plots instead of vector graphics. Especially in the supplement where there are so many vector graphics. Currently it takes a while to load each figure and it is cumbersome to scroll through the document.

Below are additional comments/suggestions. Note: line numbers in comments are based on the text version with track changes.

Line 41 "3 to 5 times" for what scenario? If Na were consistent between night and day? Or if sigmaw were consistent? Something else?

Line 120 could you provide some evidence or cite a relevant publication with evidence indicating that assuming the aerosol are internally mixed is a reasonable assumption.

Line 160 – I understand droplets are only formed for positive updraft velocities, but is sigma w calculated from the entire vertical velocity distribution (or just positive velocities)? You mention the gaussian distribution has a mean of zero (which mean there are negative and positive values), but you also say you only use the positive updraft velocities, so it's not clear.

Line 178-180 – reference table 3

Line 245 "These calculations help understand" - suggest rewording

Line 256 – change 'low' to 'lowest'

Line 307 – its driven mainly by Na (very little by kappa). I suggest changing 'characteristics' to 'concentrations' and note kappa had little influence (same for the following sentence).

Line 317-321 this was already mentioned earlier in this section. I suggest removing these last 3 sentences.

Line 352 – suggest changing 'strong' to 'high'

Line 358- change 'does' to 'do' and change 'important' to 'large'

Line 419 – add 'of' before 'a'

Table 2. reference equation 2 as the equations used to determine the contributions.

Figure 1. What measurement or model was used to determine BL height.

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ED: Publish subject to minor revisions (review by editor) (01 Aug 2020) by Lynn M. Russell

AR by Aikaterini Bougiatioti on behalf of the Authors (26 Aug 2020) Author's response Manuscript

ED: Publish as is (28 Aug 2020) by Lynn M. Russell

AR by Aikaterini Bougiatioti on behalf of the Authors (01 Sep 2020)

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Short summary

The number concentration of droplets in clouds in the summertime in the southeastern United States is influenced by aerosol variations but limited by the strong competition for supersaturated water vapor. Concurrent variations in vertical velocity magnify the response of cloud droplet number to aerosol increases by up to a factor of 5. Omitting the covariance of vertical velocity with aerosol number may therefore bias estimates of the cloud albedo effect from aerosols.