Observation of secondary ice production in clouds at low temperatures

Korolev, Alexei; DeMott, Paul J.; Heckman, Ivan; Wolde, Mengistu; Williams, Earle; Smalley, David J.; Donovan, Michael F.

doi:https://doi.org/10.5194/acp-22-13103-2022

Articles | Volume 22, issue 19

https://doi.org/10.5194/acp-22-13103-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-22-13103-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 22, issue 19

Research article

|

12 Oct 2022

Research article |

| 12 Oct 2022

Observation of secondary ice production in clouds at low temperatures

Alexei Korolev, Paul J. DeMott, Ivan Heckman, Mengistu Wolde, Earle Williams, David J. Smalley, and Michael F. Donovan

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Final revised paper (published on 12 Oct 2022)
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Preprint (discussion started on 27 Jun 2022)
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Interactive discussion

Status: closed

CC1:
'Review of the study “Observation of secondary ice production in clouds at low temperatures”, authored by Alexei Korolev, Paul DeMott, Ivan Heckman, Mengistu Wolde, Earle Williams, David J. Smalley and Michael F. Donovan.', Alex Khain, 07 Jul 2022
The study provides the first in-situ observation of secondary ice production at temperatures as low as -27°C. These observations are unique and important. I recommend to accept the paper with minor revisions.

Minor comments are:

line 40. The formation of ice by droplet freezing is not mentioned. Since the temperature measured was higher than the temperature of homogeneous drop freezing, the standard immersion drop freezing takes place at T=-27C is. Can the authors evaluate the rate of this immersion freezing of drops (for instance using standard Bigg formula)? Note that according to the observations presented in this study, the zones of high concentration of ice crystals coincide with the zones of significant peaks in droplet concentration and LWC.

Please discuss the possible role of the freezing of drops, which concentration is several orders higher than that of ice crystals, in production of cloud ice. It would be reasonable to refer in this context the study by Khain et al. (2022), in which A. Korolev is a co-author.

Can you compare the rates of immersion drop freezing and the rates of the mechanisms of primary ice nucleation mentioned in the paper?

Line 68. The study Qu et al, (2019) is not presented in the reference list. If you mean the study published in J. Geophys. Res. (see list of references below), that study shows that only secondary ice production can explain in-situ observations. The fraction of ice produced by primary nucleation was evaluated as several per cents at all temperatures. In my view, the study by Qu et al, (2019) was the first paper that reproduced size distributions ice and water observed in-situ measurements and showed that SIP plays a crucial role in the formation of such distributions. So, the statement in the current study that “Such approach may lead to underrepresentation of the role of secondary ice and result in biases in simulations” is not attributed to the study by Qu et al. (2019).

Line 75. Here reference to Qu et al. (2019) as well as to Phillips et al. (2017) should be included. In these studies simulations with a bin-microphysics cloud model reproduced ice size distributions formed by SIP by drop-ice and ice-ice collisions.

Line 78. The important attempt to understand the fundamental mechanisms of SIP by drop freezing was carried out by Staroselsky et al., 2021.

Line 128. Fig. 1. Please pay attention on the high correlation between droplet concentration and LWC, on the one hand, and the concentration of ice particles. In my opinion, this correlation shows the key role of drops in the formation of ice particle concentration. I believe that this high correlation decreases the number of possible SIP mechanisms, at least in the present case study.

References
Khain A, Pinsky M., and A. Korolev, 2022: Combined effect of the Weber-Bergeron-Findeisen mechanism and large eddies on microphysics of mixed-phase stratiform clouds. J. Atmos. Sci, Volume 79: Issue 2, 383–407, https://doi.org/10.1175/JAS-D-20-0269.1
Phillips V., J-I. Yano, M. Formenton, E. Ilotoviz, V. Kanawade, I. Kudzotsa, J. Sun, A. Bansemer, A. Detwiler, A.P. Khain and S. Tessendorf, 2017: Ice multiplication by break-up in ice-ice collisions. Part 2: Numerical simulations. J. Atmos. Sci., 74, 2789 – 2811.
Staroselsky A., R.Acharya, and A. Khain, 2021: Toward a theory of the evolution of drop morphology and splintering by freezing. J. Atmos. Sci. 78, 10, 3181–3204, https://doi.org/10.1175/JAS-D-20-0029.1
Yi Qu, A. Khain, Vaughan Phillips, Eyal Ilotoviz, Jacob Shpund, Sachin Patade, Baojun Chen, 2019: The role of ice splintering on microphysics of deep convective clouds forming under different aerosol conditions: simulations using the model with spectral bin microphysics. J. Geophys. Res. 125, Issue3;,125, e2019JD031312.https://doi.org/10.1029/2019JD031312
Citation: https://doi.org/10.5194/egusphere-2022-491-CC1
- AC1: 'Reply on CC1', Alexei Korolev, 15 Sep 2022
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-491/egusphere-2022-491-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2022-491-AC1
RC1:
'Comment on egusphere-2022-491', Thomas Leisner, 25 Jul 2022

The authors report in situ aircraft observations of sharply constrained regions within a nimbostratus cloud with a strongly enhanced ice number concentration due to small and pristine ice particles.

They attribute this to secondary ice processes being effective at the low (~ -26°C) temperatures of the observation.

The observations have been made with a very comprehensively equipped aircraft in an important type of cloud and the presented data are of very high quality. Therefore, the dataset is of substantial scientific interest and should be published. I will most certainly stimulate discussion and advance secondary ice understanding.

I have one main point with the discussion and interpretation of the data that should be addressed before publication and a few minor remarks.

Main point:

The authors exclude primary ice nucleation because turbulent diffusion should smear out INP concentrations sufficiently to exclude very localized maxima. On the other hand, they invoke turbulence as the main cause of the observed strong heterogeneity in this cloud. Might this also be used to explain the observations with primary ice nucleation? E.g. a layer of dust-rich air might be entrained from cloud top?

Vice versa one could argue that turbulence should smear out the conditions favorable for SIP as well.

It seems that all 6 mechanisms discussed in Korolev and Leisner (2020) could be dismissed due to the uniformity and scarcity of larger ice particles as seen from Fig. 3 (presence of larger ice particles would favor mechanisms 2, 3, 6) and larger liquid drops (which would favor mechanisms 1, 4) and due to the fact that temperatures were continuously below the frost point (excludes mechanism 5).

Therefore, any attribution of the observed small ice to either primary nucleation or SIP seems hard to justify. I suggest that the authors discuss these issues somewhat more in detail.

Nevertheless, I agree with the authors that some form (maybe even a hitherto not invoked process) of SIP is “the most plausible reason” (line 216) but I find the statement in the abstract “the first in-situ observation of SIP at temperatures as low as -27°C” too strong.

Minor remarks:

It is hard to assign the ice particle images in Fig. 2 to Fig. 1 as the attribution to regions is very cursory. May I suggest to split this image into four parts (before region 1, region 1, between region 1 and two and region 2)? This would probably also allow to use a somewhat larger scale which would allow to see finer details (e.g. the “fragile branches” (line 258) Alternatively, the regions may be separated by frames in Fig. 2.

Line 210ff: Why don´t you show the humidity data in the layer between the cloud layers?

Line 299: What is the meaning of “480”?

Line 92: Riming might be another process changing the pristine SIP particles.

Line 39 below -38°C

Citation: https://doi.org/10.5194/egusphere-2022-491-RC1
- AC2: 'Reply on RC1', Alexei Korolev, 15 Sep 2022
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-491/egusphere-2022-491-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2022-491-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Alexei Korolev on behalf of the Authors (19 Sep 2022) Author's response Author's tracked changes Manuscript

ED: Publish as is (22 Sep 2022) by Alexander Laskin

AR by Alexei Korolev on behalf of the Authors (22 Sep 2022)

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Short summary

The present study provides the first explicit in situ observation of secondary ice production at temperatures as low as −27 °C, which is well outside the range of the Hallett–Mossop process (−3 to −8 °C). This observation expands our knowledge of the temperature range of initiation of secondary ice in clouds. The obtained results are intended to stimulate laboratory and theoretical studies to develop physically based parameterizations for weather prediction and climate models.