On the suitability of the Thorpe–Mason model for calculating sublimation of saltating snow

Sharma, Varun; Comola, Francesco; Lehning, Michael

doi:https://doi.org/10.5194/tc-12-3499-2018

Articles | Volume 12, issue 11

https://doi.org/10.5194/tc-12-3499-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-12-3499-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 12, issue 11

Research article

|

09 Nov 2018

Research article |

| 09 Nov 2018

On the suitability of the Thorpe–Mason model for calculating sublimation of saltating snow

Varun Sharma, Francesco Comola, and Michael Lehning

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Final revised paper (published on 09 Nov 2018)
Supplement to the final revised paper
Preprint (discussion started on 15 Mar 2018)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'On the suitability of the Thorpe-mason model for calculating sublimation of saltating snow', Anonymous Referee #1, 10 Apr 2018
- AC1: 'Reply to comments by Referee #1', Varun Sharma, 31 Aug 2018
RC2: 'Review of tc-2018-33', Anonymous Referee #2, 28 May 2018
- AC2: 'Reply to comments by Referee #2', Varun Sharma, 31 Aug 2018
AC3: 'Comments to all Referees', Varun Sharma, 31 Aug 2018
AC4: 'Difference file between original and revised manuscript', Varun Sharma, 31 Aug 2018

Peer-review completion

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

AR by Varun Sharma on behalf of the Authors (31 Aug 2018) Manuscript

ED: Referee Nomination & Report Request started (07 Sep 2018) by Florent Dominé

RR by Anonymous Referee #2 (20 Sep 2018)

RR by Anonymous Referee #1 (21 Sep 2018)

Suggestions for revision or reasons for rejection

The efforts of the authors to address the review comments is noted and many of the confusions and ambiguities were clarified. Admittedly, this is not a manuscript focused on the turbulence modeled with the LES used to transport particles. However, the conclusions of this manuscript are explicitly dependent on this model, and have been shown by the manuscript to only exist BECAUSE of the LES. As such, care should be taken to not include tangential results without the necessary supporting evidence. At hand there are still a couple points of contention that should be addressed prior to publication.

Response A.14: It is unclear whether this is the complete answer to the comment or not. Please clarify if this is a typo.

Response A.21: The authors responded to a question of the impact of surface sublimation on suppression of vertical motions. However, the question posed was actually on the potential presence of a temperature gradient in the atmosphere as could be found in a typical stable boundary layer in calm wind over snow. However, as is mentioned below, it is suggested that these comments on vertical suppression just be removed altogether. It is unclear whether it was intended to imply that there is no such temperature gradient in nature with turbulent mixing, or that such a temperature gradient only exists if there is actively sublimating surface snow?

Author Response Page 4, First paragraph: “with the air is so close” Please correct
Author Response Page 4, Last Paragraph “lighther”

Track Changes version of Manuscript:

Page 5 Line 3: Please add citation that these values are typical for saltation.
P6 L15-16: Do you mean “or”

Section 3.1 The use of LES is very attractive to many people in hydrology and snow science, but the complexity of such an endeavor is often the limiting factor. Please explicitly cite the software used, be it in-house code or a modified commercial product? It is appreciated that the governing equations of motion are included, but for a model of this nature, a note on where the code was actually developed (or ideally, available) would be beneficial to the community. As well, please note in the main body of text that is LES of a channel flow.

P8L22: “to decelerate”
P10L7: Fix units
P10L8: “Mean wind speeds.” It may be stationary, but it is still a turbulent flow.

P10L13-17: This doesn’t seem to be supported by the supplement. It is not clear that there was vertical suppression because of sublimation, only vertical suppression during saltation. This
claim seems like it would need further investigation, for example a comparison with saltation without sublimation to show the actual impact of the cooling. Obviously TKE drops, but that is insufficient to show SUPPRESSION of vertical motions by thermal effects. The buoyancy is a function of vertical motions, so that is a bit of a circular argument. I suggest removing comment of any causal relationship between sublimation and vertical motion suppression until the referenced future research is conducted.

Supplementary Material:

The information now included in the document supplement is helpful in grounding the manuscript solidly in the cryospheric field of study, and will likely help connecting the manuscript from a purely numerical study to a broader snow science audience.

-Figure 1: The 40% reduction in windspeed with the presence of saltation is substantial and should be commented on. There are numerous wind tunnel (and some field) studies addressing momentum extraction from the wind by particles in saltation. This 40% should be put in context of previous work to add credibility to an inherently complex model of a “simple” scenario to be found in nature.

-It is claimed in the manuscript that turbulent mixing of different temperatures is responsible for the regeneration of warm dry air that then results in different rates of sublimation for LES. It would be illuminating to have a movie showing an animation of evidence of that process, as it is the heart of the conclusions presented here.

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ED: Publish subject to minor revisions (review by editor) (01 Oct 2018) by Florent Dominé

AR by Varun Sharma on behalf of the Authors (03 Oct 2018) Manuscript

ED: Publish as is (12 Oct 2018) by Florent Dominé

AR by Varun Sharma on behalf of the Authors (21 Oct 2018)

Short summary

The Thorpe-Mason (TM) model describes how an ice grain sublimates during aeolian transport. We revisit this classic model using simple numerical experiments and discover that for many common scenarios, the model is likely to underestimate the amount of ice loss. Extending this result to drifting and blowing snow using high-resolution turbulent flow simulations, the study shows that current estimates for ice loss due to sublimation in regions such as Antarctica need to be significantly updated.