the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Nov 2024
Snow Particle Fragmentation Enhances Snow Sublimation
Abstract. Fragmentation of snow particles, where dendritic snowflakes transform into spherical shapes upon impact with surface and other particles during drifting and blowing snow events, plays a critical role in shaping snow dynamics. This phenomenon is important because it influences the size distribution and concentration of snow particles, affecting mass flux and sublimation rates. Currently, prevailing drifting and blowing snow models ignore the snow particles fragmentation, leading to heightened uncertainties in predicting flow structures and sublimation rates. Here, we aim to quantitively investigate the impact of snow particle fragmentation on sublimation. We establish a drifting and blowing snow model considering the snow particle fragmentation process and investigated the effects of fragmentation on drifting and blowing snow. The results show that fragmentation enhances the sublimation of blowing snow and changes the airborne particle size distribution. The sublimation rate of saltating snow particles increases 11 % on average, and that of suspension snow particles increases 76 % on average, when the friction wind speed is between 0.3 m/s to 0.5 m/s. These findings have important implications for improving the physical dynamic model of drifting and blowing snow, which may contribute to predictions in snow hydrology and climate models.
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RC1: 'Comment on egusphere-2024-3218', Anonymous Referee #1, 27 Nov 2024
This paper addresses the dynamics and thermodynamics of drifting and blowing snow with a modeling approach. It emphasizes on the fragmentation of initially mainly dendritic ice crystals shattered to smaller rounded particles due to collision or impact on the surface during saltation and suspension processes. The consequences of such breaking mechanisms on snow sublimation dynamics are quantitatively assessed again from a modeling perspective.
Given the scarce knowledge on these processes, this paper deals with a highly important and relevant question and makes a valuable contribution to further understanding drifting snow dynamics and associated sublimation, both important processes in large parts of the world, such as polar ice sheets, and high latitude regions in Alaska, Canada, Scandinavia, Eurasia, and High-Mountain Asia.
The model presented in this paper explicitly implements fragmentation of snow particles and is based on an otherwise established and validated model framework (Thorpe and Mason, 1966; Comola et al., 2017; Huang and Shi, 2017). The model is validated with two observational data sets (Schmidt,1982; Pomeroy and Male, 1992) showing good agreement. A more comprehensive validation would have been desirable but is probably not feasible due to the lack of suitable validation data. Model simulations are performed in two configurations, (1) particle fragmentation disabled and (2) particle fragmentation enabled, both over a range of friction velocities which are used as proxies for different wind speed conditions. Then, results of the two series of simulations are quantitatively compared evaluating the effect of fragmentation on particle size distribution, saltation and suspension particle number, airborne mass concentration and mass flux, and most importantly the sublimation rate. These results clearly show the relevance and influence of particle fragmentation on the investigated quantities notably the increase of sublimation at all simulated wind conditions.
The paper nicely sheds light on processes of snow drift, particle fragmentation, and associated sublimation dynamics and therefore constitutes a valuable contribution in this domain. Below, I am suggesting some minor revisions necessary to clarify a few points and to fill in where small additions are needed. Major revisions though are needed for language, readability, and clarity of the paper. Instead of listing all these points, I am providing an annotated manuscript with corrections, suggestions, and language revisions for integration into a better readable and understandable manuscript.
Specific comments:
- I suggest revising the abstract better focusing on the objectives and the results of the paper. In its present form, it does not fully reflect the content and contribution of the paper.
- The novelty of the paper, i.e., the new elements of the model and the relevance and implications of the results could be better highlighted (abstract, introduction, and conclusion).
- The introduction is rather minimalist. A bit more background on past and current drifting snow models would be desirable and useful, including a brief discussion of some fundamental studies, e.g., Thorpe and Mason, Pomeroy et al., Dery and Yau, etc. Also, the specific objectives of the paper and the applied methodology to address the research questions could be put in evidence more prominently .
- Section 2 should clearly distinguish between the existing model components and the new additions to better identify the innovations in the modeling process.
- Section 3.4, lines 198-202: Numbers or content of this paragraph seem wrong. Please verify and correct.
- 10: Has the behavior for longer simulations (beyond 10 seconds) been investigated? What are the expected implications? Is consolidation expected and if so at which level and after how much time?
- Section 3.5.2, lines 212-213: Message not clear – please try to clarify.
- I would suggest a short Discussion Section before the conclusions in which the following points are briefly addressed: (1) Coherence of obtained results: Some of the results with particle fragmentation implemented are rather obvious, e.g., a modified particle size distribution, enhanced sublimation due to an increased specific surface area of more and smaller transported particles, etc. Other results are less intuitive and could be further discussed. (2) I would also appreciate a paragraph elaborating on how the results and findings can be used in spatially distributed surface energy balance studies. What are the implications for snow surface properties, e.g., albedo, snow microstructure, and for seasonal totals of sublimation, and finally snowpack mass balance? A few points are already mentioned at the end of the conclusion section but are not discussed earlier.
- Conclusion: At the beginning and before the discussion of the results, the model and the methodology used should be summarized.
- The author contributions appear inconsistent with the order of authors.
Minor comments (with line no. reference):
- (Sub-)Section title style: incoherent capitalization, adapt to journal style.
- 1: “…transformation from dendritic to spherical shapes…”; rather use “rounded”, spherical suggests too much a regular geometry.
- 17/18: what is the difference between DSS and BSS? The abbreviations are not used anymore in the manuscript after their introduction.
- 100: what is “turbulence velocity variance”? Please clarify.
- 120: what exactly is meant with “vertical grid” here? Please explain.
- 205: what does “steep extent” mean? Please clarify.
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RC2: 'Comment on egusphere-2024-3218', Anonymous Referee #2, 16 Dec 2024
I echo the comments from the first reviewer. There are a couple notable limitations to the paper.
- Observations show a variety of crystal habits that can contribute to blowing snow, and even dendritic crystals can have various amounts of riming on them. How can this be factored into your model? How may this impact the validation to prior work?
- The validation of the model is limited and not thoroughly explained/discussed. Did you consider comparing your model results to other blowing snow observation studies such as those conducted in Franklin Bay (Gordon et al. 2009) or at Mizuho station, Antarctica (Nishimura and Nemoto 2005)? Think about this from the perspective from an observer… what observations do we need to validate the model? I would elaborate on what your results mean. Figure 5 suggests it is critical that our observations are capable of detecting particles < 100 um in diameter. It’s unclear how this relates to height above ground. Overall, the presentation of results is more limited than what it should be.
See specific comments below. The paper needs major review for language. I have provided some suggestions for some issues, but this is by far not a complete list.
Line 30: Strike ‘the’
Line 31-32: Sentence reads weird. Perhaps: This work used a statistical mechanics model to calculate the fragmented number of particles from the perspective of energy and mass balance and simply analyzed the effects of fragmentation on the particle size distribution.
Line 50: reintroduce
Line 101: Had some trouble understanding this sentence. Is this what you mean?
…Equation 10 is used to determine whether it is broken. The number of snow particles N is calculated and l represents the ratio…
Line ~10: crushing = shattering or fragmenting?
Figure 3: Move the legend a bit to the right or put a box around it. At first glance the legend symbol for P&M 92 could be interpreted as a data point.
Figure 4: In legend, should read ‘snowstorm’ Caption: ‘Comparison of suspension sublimation rates with other blowing snow models. I think it would be better to put height on the y-axis. I would also go to a higher height. Practically, we are only going to have observations at heights z > 0.1m.
Figure 6: How do the PSDs change with height? Once again, I’m thinking about this with my observer hat on.
Line 161: Not a complete sentence. How do results change by mean particle size which will vary depending on location and environmental conditions?
Line 212: strike the 2nd ‘the’
Friction velocity: there are various comments that discuss how properties change with wind speed although results are for friction velocity. While friction velocity is directly related to wind speed, you also have roughness length and stability considerations to think about so, I’d be careful with how section 3.4 is worded.
Citation: https://doi.org/10.5194/egusphere-2024-3218-RC2
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