Wind conditions for snow cornice formation in a wind tunnel

Yu, Hongxiang; Li, Guang; Walter, Benjamin; Lehning, Michael; Zhang, Jie; Huang, Ning

doi:https://doi.org/10.5194/tc-17-639-2023

Articles | Volume 17, issue 2

https://doi.org/10.5194/tc-17-639-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-17-639-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 17, issue 2

Research article

|

08 Feb 2023

Research article |

| 08 Feb 2023

Wind conditions for snow cornice formation in a wind tunnel

Hongxiang Yu, Guang Li, Benjamin Walter, Michael Lehning, Jie Zhang, and Ning Huang

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Final revised paper (published on 08 Feb 2023)
Preprint (discussion started on 23 Mar 2022)

Interactive discussion

Status: closed

RC1:
'Comment on tc-2022-27', Anonymous Referee #1, 21 Apr 2022

Investigations of snow cornice development is worthwhile since its collapse is strongly related to the snow avalanche release; I cannot agree with you more. In this study, the leading-edge technology including the closed-circuit wind tunnel and the shadow graph imaging technologies. I appreciate very much for the efforts by authors. However, that is all. Similar experiments in the wind tunnel were carried out more than 35 years ago by a master student as shown below and much more meaningful outcomes were obtained.

Naitou, A. and Kobayashi, D., Experimental Study on the Generation of a Snow Cornice, Low temperature science. Series A, Physical sciences, 44, 91-101, 1986.

https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/18521/1/44_p91-101.pdf

Unfortunately, the text is written in Japanese. However, it cannot be an excuse, since English summary is attached, in which the wind speed of 4 to 8 m/s is suitable for the cornice formation, and the capture coefficient of drifting snow is also referred. Incidentally, I suppose some of the authors can recognize Chinese characters and are understandable what is mentioned in the test as well more or less. Please read through carefully. Dependencies on not only the air temperature but also crystal shape, which are listed as the future work in the submitted manuscript, have been already studied. Thus, from my point of view, nothing looks new and no findings which deepen our understandings of the snow cornice formation mechanism are introduced in the submitted manuscript.

Further, the discussions, in which authors argue the similarities between the wind tunnel experiments and the observations in the fields, look odd. As is common for the researchers working on blowing/drifting snow, the blowing threshold wind speed in nature is around 5 m/s at 2 to 3 m high (not 11 m/s !), which roughly corresponds to the friction velocity of 0.2 to 0.3 m/s. If you assume, Ut 0.4m=3.2 m/s in the wind tunnel corresponds to Ut2.8m=11m/s in the field, friction velocity and the roughness length will be calculated extremely large (roughly u*=2.4 m/s, z0=0.235m !!; in usual former should be 0.3 to 0.4 m/s and the latter the order of 10-4 m). Thus, discussions below line 175 in this manuscript sound meaningless.

Preferably, missing link between the 4 cm long and 5 mm thick cornice observed in the wind tunnel and the several-meter scale of cornice formed leeside of the mountain ridge should be also referred to answer the motivation in the introduction part.

Citation: https://doi.org/10.5194/tc-2022-27-RC1
- AC1: 'Reply on RC1', Hongxiang Yu, 19 May 2022
  
  The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2022-27/tc-2022-27-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/tc-2022-27-AC1
RC2:
'Comment on tc-2022-27', Holt Hancock, 04 May 2022

Thank you for the opportunity to review this manuscript.

Please see attached PDF for my comments.

Citation: https://doi.org/10.5194/tc-2022-27-RC2
- AC2: 'Reply on RC2', Hongxiang Yu, 19 May 2022
  
  The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2022-27/tc-2022-27-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/tc-2022-27-AC2

Peer review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (25 May 2022) by Melody Sandells

AR by Hongxiang Yu on behalf of the Authors (05 Aug 2022) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (05 Sep 2022) by Melody Sandells

RR by Holt Hancock (26 Sep 2022)

RR by Anonymous Referee #3 (21 Nov 2022)

Suggestions for revision or reasons for rejection

In this paper, the authors reproduce the development process of snow cornice by wind tunnel experiments in cold room, then constructed a conceptual model using the experiment results. They also applied their conceptual model to actual field observations to verify the practicality of the conceptual model.
As they showed in their paper, although snow cornice is one of the factors that cause avalanches, our understanding of its development process is still insufficient. Therefore, snow cornice role in the avalanche is not sufficiently taken into account in avalanche prediction. For this point, their study may contribute to the avalanche prediction thorough the modeling of the developmental process of snow cornice.
On the other hand, as noted in their paper, wind tunnel experiments and field observations of snow cornice have been conducted as previous studies, although they are few in number. Previous studies have reported that snow cornices develop under moderate wind conditions.
The results of their experiments show similar results. In this sense, the present study can be positioned as an example of wind tunnel experiments on snow cornice development, and it must be said that the results of the experiments themselves have little scientific impact.
Their advantage should be that they made more detailed measurements, but it is not clear how their results play a significant role in the interpretation of what has already been reported. For example, they only mentioned that the difference between their result and previous one is caused by wind tunnel size difference, they did not discuss concretely from the scientific view. Therefore, under the present, it is difficult to find the scientific role of their detailed measurements to develop understanding snow cornice development. The comparisons between their conceptual model calculations and actual field observations are only a qualitative comparison due to the limitations of the conceptual model.
For these reasons, it must be said that, at this stage, the scientific value of their study is insufficient for publication in the TC.
There is no doubt that a lot of hard work went into this study. The experimental results have sufficient credibility. The manuscript itself is also well described, including the description of the methodology.
Before resubmitting the manuscript, I strongly recommend that the authors reorganize the manuscript to clarify what new scientific findings they have derived from this study and how their finding contribute to advance the scientific topic of the developmental process of snow cornice.
Then they should concretely clarify their scientific contribution in the manuscript.

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RR by Anonymous Referee #4 (11 Dec 2022)

ED: Publish subject to minor revisions (review by editor) (15 Dec 2022) by Melody Sandells

AR by Hongxiang Yu on behalf of the Authors (03 Jan 2023) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (23 Jan 2023) by Melody Sandells

AR by Hongxiang Yu on behalf of the Authors (24 Jan 2023) Author's response Manuscript

Short summary

Snow cornices lead to the potential risk of causing snow avalanche hazards, which are still unknown so far. We carried out a wind tunnel experiment in a cold lab to investigate the environmental conditions for snow cornice accretion recorded by a camera. The length growth rate of the cornices reaches a maximum for wind speeds approximately 40 % higher than the threshold wind speed. Experimental results improve our understanding of the cornice formation process.