The importance of Aitken mode aerosol particles for cloud sustenance in the summertime high Arctic – a simulation study supported by observational data

Bulatovic, Ines; Igel, Adele L.; Leck, Caroline; Heintzenberg, Jost; Riipinen, Ilona; Ekman, Annica M. L.

doi:https://doi.org/10.5194/acp-21-3871-2021

Articles | Volume 21, issue 5

https://doi.org/10.5194/acp-21-3871-2021

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

https://doi.org/10.5194/acp-21-3871-2021

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

Articles | Volume 21, issue 5

Research article

|

15 Mar 2021

Research article |

| 15 Mar 2021

The importance of Aitken mode aerosol particles for cloud sustenance in the summertime high Arctic – a simulation study supported by observational data

Ines Bulatovic, Adele L. Igel, Caroline Leck, Jost Heintzenberg, Ilona Riipinen, and Annica M. L. Ekman

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Final revised paper (published on 15 Mar 2021)
Preprint (discussion started on 28 Jul 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review Bulatovic et al. (2020)', Anonymous Referee #1, 21 Aug 2020
- AC1: 'Reply to referee's comments #1', Ines Bulatovic, 02 Nov 2020
RC2: 'Bulatovic et al.', Anonymous Referee #2, 26 Aug 2020
- AC2: 'Reply to referee's comments #2', Ines Bulatovic, 02 Nov 2020

Peer-review completion

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

AR by Ines Bulatovic on behalf of the Authors (04 Nov 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (05 Dec 2020) by Franziska Glassmeier

RR by Anonymous Referee #1 (07 Dec 2020)

Suggestions for revision or reasons for rejection

The authors have substantially improved the manuscript and have included the reviewers’ suggestions. The discussion has been expanded and now better embeds the study in the existing literature. Similarly, the introduction has been restructured and additional relevant studies are cited. All figures have been improved according to the suggestions. I still have a few minor comments which should be addressed prior to final publication, which are listed below.

Specific comments

Line 46: “cloud liquid growth” should rather be “cloud liquid water increase”
Line 47, line 50: “water vapor” instead of “vapor”
Line 274: How are IWP and LWP defined (i.e. including or excluding precipitation)?
Line 293: consider changing “is better” with “performs better”
Line 300: RAMS also produces vertical bands of increased rain throughout the cloud, e.g. at hours 8 and 9. Can you explain those? Again, is the autoconversion similar for both models? Or is the autoconversion rate especially high in RAMS? You show the condensational growth of raindrops, but (if available) it could be interesting to have a look at the conversion rate from cloud droplets to rain drops.
Figure 3: Thanks very much for including the cloud top and base height. However, how did you calculate cloud top and base height? Please add this information.
Line 367: “the cloud base altitude changes…”
Line 411: “when no accumulation mode particles are present”
Line 439: “vary” instead of “very”
Line 452: “in the two models”
Line 456 ff: I appreciate the additional discussion of the radiative budget in the simulations. Did you also analyze the impact of SW radiation at the surface (as done in Figure 10 for LW radiation)? I would assume that especially (and most likely only) in summer there might also be an impact. Or did you only investigate SW radiation at the model top, as written in line 461?
Also, did you look at the net surface LW and SW radiation? Overall it would be interesting to see, how the net surface energy balance changes for the inclusion of Aitken mode particles and how these results could be extrapolated to the summertime high Arctic radiative budget.
Line 681: Apart from the choice of prescribed/prognostic ICNC/INPs, secondary ice formation may also play a relevant role in determining the cloud evolution, especially in summertime Arctic MPCs (Sotiropoulou et al., 2020; doi: 10.5194/acp-20-1301-2020) and at the temperatures shown in Figure 1. However, this is not mentioned at all. Are secondary ice processes omitted (in the first version of the manuscript I read they are)? Does this also introduce additional uncertainties or effects (i.e. a potentially higher ice fraction and a decreased influence of Aitken mode particles)? This could also be mentioned in e.g. Section 5.2.

Referee Report: PDF

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RR by Anonymous Referee #2 (19 Dec 2020)

ED: Publish subject to minor revisions (review by editor) (07 Jan 2021) by Franziska Glassmeier

AR by Ines Bulatovic on behalf of the Authors (15 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (03 Feb 2021) by Franziska Glassmeier

AR by Ines Bulatovic on behalf of the Authors (12 Feb 2021)

Short summary

We use detailed numerical modelling to show that small aerosol particles (diameters ~25–80 nm; so-called Aitken mode particles) significantly influence low-level cloud properties in the clean summertime high Arctic. The small particles can help sustain clouds when the concentration of larger particles is low (<10–20 cm^-3). Measurements from four different observational campaigns in the high Arctic support the modelling results as they indicate that Aitken mode aerosols are frequently activated.