Modeling the influence of snow cover temperature and water content on wet-snow avalanche runout

Vera Valero, Cesar; Wever, Nander; Christen, Marc; Bartelt, Perry

doi:https://doi.org/10.5194/nhess-18-869-2018

Articles | Volume 18, issue 3

https://doi.org/10.5194/nhess-18-869-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/nhess-18-869-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 18, issue 3

Research article

|

19 Mar 2018

Research article |

| 19 Mar 2018

Modeling the influence of snow cover temperature and water content on wet-snow avalanche runout

Cesar Vera Valero, Nander Wever, Marc Christen, and Perry Bartelt

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Final revised paper (published on 19 Mar 2018)
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Preprint (discussion started on 07 Mar 2017)
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Interactive discussion

Status: closed

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

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RC1: 'Review of ’Modeling the influence of snowcover temperature and water content on wet snow avalanche runout’ by C. VERA VALERO et al.’', Jan-Thomas Fischer, 12 May 2017
- AC1: 'Reply to Reviewer 1', Cesar Vera, 20 Oct 2017
RC2: 'Review of "Modeling the influence of snowcover temperature and water content on wet snow avalanche runout" by Vera Valero and co-authors.', Guillaume Chambon, 06 Sep 2017
- AC2: 'Reply to Reviewer 2', Cesar Vera, 20 Oct 2017

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (01 Nov 2017) by Sven Fuchs

AR by Cesar Vera on behalf of the Authors (14 Dec 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (19 Dec 2017) by Sven Fuchs

RR by Guillaume Chambon (15 Jan 2018)

Suggestions for revision or reasons for rejection

Overall, I consider that the authors satisfactorily addressed reviewers’ comments. The revisions contributed to improve the paper, which is now easier to read and more to the point. Some issues could certainly have been clarified even further, in particular regarding model formulation. The authors could have used the present paper as an opportunity to better explain the physics behind some of the equations introduced in the model (e.g. Eq.(7) or Eq.(16)), which would have constituted a useful complement to previous, more theoretical, publications. However, I consider that the paper is now suitable for publication as it stands. I have nevertheless a few additional comments, related mainly to newly-introduced paragraphs or statements, that the authors may want to take into account prior to submitting their final version.

1/ P.2, l.24-29. I still do not understand the relations implied between the low “cohesive strength” of wet snow and the size of the snow granules, and between the size of the granules and the effective viscosity and cohesion of the flow. Please consider adding further information / references on these issues, or simplifying these statements. From what I understand, the important message here is that wet snow avalanches tend to have larger viscosities and cohesion; speculative and questionable interpretations on the microstructural origin of these trends are probably not necessary.

2/ P.7, l.136-139. It is not clear how the newly-added sentences starting with “The basal boundary…” connect with Eq. (7). Does it mean that Eq. (7) only account for processes active at the base? I would have thought that shear-induced dilation or compaction can also occur in the bulk of the flow (as in granular materials)?

3/ P.12. Is the amount of erodible snow determined similarly to the initial fracture depth, i.e. based on the location of highest LWC in the snowpack? If so, this information would need to be stated more clearly in the text. Moreover, recalling again, at the end of this paragraph, how the erodibility coefficient were obtained, would certainly be useful.

4/ P.14-15. The newly added sentence - “This two-dimensional procedure avoids the problem of defining a one-dimensional measure of avalanche runout ” - appears at odd with the next paragraph, which specifically deals with the definition of avalanche runout!

5/ P.18, l.419. I do not understand why the authors refer here to extreme avalanches with a return period greater than 300 years, while it is said previously (p.13, l.298-299) that the Voellmy-Salm parameters used correspond to the class of “small” avalanches with return periods of 10-30 years?

6/ P.19, l.444-445. The sentence “The average scores of all…” seems fully redundant with the one just 4 lines before: “The average of the four…”.

7/ P.20. I do not understand the newly added paragraph starting with “The role of mass entrainment…”. In this section, only changes in snow mass are considered, while snow temperature and LWC are held constant. Hence, why do the authors point that “the permutations did not include dry, cold snowcovers”? Furthermore, the conclusion that “snow quality (temperature, moisture) is more important than the snow amount”, besides being not supported by the presented data, appears in complete contradiction with what is said in the following section. Please clarify this issue. More generally, I still believe that discussing, if possible, the relative contributions of changes in the initial mass versus changes in the entrained mass would be interesting.

8/ Sec.4.3. In their answer to J.T. Fischer, the authors mention that this section dealing with grid resolution will be amended to make its message clearer. Yet, this section was in fact only marginally modified in the revision. Similarly, my query to expand the last paragraph of the section, was not really addressed (this last paragraph has actually been removed). I think that expanding on the answer to J.T. Fischer, and adding a paragraph comparing the influence of changes in resolution versus changes in initial and boundary conditions, would be a great addition in the context of the present study, compared to a mere “naked” investigation of the effect of resolution.

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RR by Jan-Thomas Fischer (15 Jan 2018)

ED: Publish subject to minor revisions (review by editor) (17 Jan 2018) by Sven Fuchs

AR by Cesar Vera on behalf of the Authors (03 Feb 2018) Author's response Manuscript

ED: Publish as is (08 Feb 2018) by Sven Fuchs

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Short summary

Snow avalanche motion is strongly dependent on the temperature and water content of the snow cover. In this paper we use a snow cover model, driven by measured meteorological data, to set the initial and boundary conditions for wet-snow avalanche calculations. The snow cover model provides estimates of snow depth, density, temperature and liquid water content. These initial conditions are used to drive an avalanche dynamics model. The runout results are compared using a contigency analysis.