the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 Sep 2023
Bayesian physical–statistical retrieval of snow water equivalent and snow depth from X- and Ku-band synthetic-aperture-radar demonstration using airborne SnowSAR in SnowEx17
Abstract. A physical-statistical framework to estimate Snow Water Equivalent (SWE) and snow depth from SAR measurements is presented and applied to four SnowSAR flight-line data sets collected during the SnowEx’2017 field campaign in Grand Mesa, Colorado, USA. The physical (radar) model is used to describe the relationship between snowpack conditions and volume backscatter. The statistical model is a Bayesian inference model that seeks to estimate the joint probability distribution of volume backscatter measurements, snow density and snow depth, and physical model parameters. Prior distributions are derived from multilayer snow hydrology predictions driven by downscaled numerical weather prediction (NWP) forecasts. To reduce noise to signal ratio, SnowSAR measurements at 1 m resolution were upscaled by simple averaging to 30 and 90 m resolution. To reduce the number of physical parameters, the multilayer snowpack is transformed for Bayesian inference into an equivalent single- or two-layer snowpack with the same snow mass and volume backscatter. Successful retrievals, defined by absolute convergence backscatter errors ≤ 1.2 dB and local SnowSAR incidence angles between 30° and 45° for X- and Ku-band VV-pol backscatter measurements, were achieved for 75 % to 87 % for all grassland pixels with SWE up to 0.7 m and snow depth up to 2 m. SWE retrievals compare well with snow pit observations showing strong skill in deep snow with average absolute SWE residuals of 5–7 % (15–18 %) for the two-layer (single-layer) retrieval algorithm. Furthermore, the spatial distributions of snow depth retrievals vis-à-vis LIDAR estimates have Bhattacharya Coefficients above 94 % (90 %) for grassland pixels at 30 m (90 m resolution), and values up to 76 % in mixed forest and grassland areas indicating that the retrievals closely capture snowpack spatial variability. Because NWP forecasts are available everywhere, the proposed approach could be applied to SWE and snow depth retrievals from a dedicated global snow mission.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(5945 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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AC1: 'Comment on egusphere-2023-1987', Siddharth Singh, 28 Sep 2023
Please add the reference that is cited in the paper:
Pan, J., Durand, M., Lemmetyinen, J., Liu, D., and Shi, J.: Snow water equivalent retrieved from X- and dual Ku-band scatterometer measurements at Sodankylä using the Markov Chain Monte Carlo method, The Cryosphere Discuss. [preprint], https://doi.org/10.5194/tc-2023-85, in review, 2023.
Citation: https://doi.org/10.5194/egusphere-2023-1987-AC1 -
RC1: 'Comment on egusphere-2023-1987', Anonymous Referee #1, 11 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1987/egusphere-2023-1987-RC1-supplement.pdf
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AC2: 'Reply on RC1', Siddharth Singh, 02 Dec 2023
I sincerely appreciate the time and effort you have dedicated to reviewing our manuscript.
I have carefully addressed each of your suggestions and made the necessary revisions to enhance the overall quality of the manuscript. In line with your recommendations, I have attached the revised version of the manuscript in the same PDF file (without tracking as it is easier to determine the line number). I have posted the revised manuscript with changes highlighted as 'Author Comment'.
If you have any further comments or queries, please do not hesitate to reach out. I am more than willing to make additional adjustments to ensure the manuscript meets the highest standards.
Once again, thank you for your time and valuable input. I look forward to hearing your thoughts on the revised manuscript.
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AC2: 'Reply on RC1', Siddharth Singh, 02 Dec 2023
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RC2: 'Comment on egusphere-2023-1987', Anonymous Referee #2, 17 Nov 2023
General Comments
The authors of this manuscript use a Bayesian physical-statistical model to retrieve snow depth using data that was acquired during SnowEx’17, including pit data, ASO lidar acquisitions and the X- and Ku-band SnowSAR data. The methods presented by the authors are clearly defined, with encouraging results with error ranges of about 20cm SWE. The paper is methodologically and analytically sound, but does lack context of why certain methods are being employed, and the representation of results in figures need to be improved. For instance, in the Introduction it was overall well written to describe the need for remote sensing of snow and how SnowEx’17 is an attempt to address this concern. I do feel that the end of this section needs to be improved to detail to the reader what the specific objectives of this manuscript are. For instance, the authors provide an indication that they are looking to test a physical-statistical framework to derive SWE – but what are the objectives that can be completed to evaluate this?
The paper is very detailed in its methods of preparing the data for the model, and the modeling itself. What I think is lacking here is the reason that you are completing some of these steps. For instance, in section 4.1.1. you discuss in detail how you divide the snowpack with multiple layers into a snowpack with 1 or 2 layers, but never state why a 2 layer pack would be useful (that snowpack generally has a wind slab and depth hoar layer).. The justification for many of the steps in this paper need to have a bit better context provided.
Overall the paper is of publication quality in terms of its research, but the presentation could be improved, with my general and specific comments provided here.
Section 2. Previous Work
Line 55: “Time-series observations are available presently from tower measurements, albeit at the point scale of the tower footprint”. I think I know what study/setup you’re referring to here, but you have not referenced the papers that have been published based on them. Also, a sentence that states why you are not using a tower approach in this work would be useful.
Line 86: “demonstrated the utility of a couple multi-layer snow hydrology coupled with a..” – do you mean “snow hydrology model coupled…”?
Line 133-134: “the second is the prior of the backscatter… the prior of the snowpack physical…” this sentence is a little unclear, please revise.
Line 144: “assuming that we have good understanding” grammar issue here “assuming that we have a good understanding”.
Table 1: I may have missed it, but why are all the datasets being upscaled to 90m? I also noticed this discussed in lines 175-176, but there was no justification as to why – please include.
Line 299: “from the multilayer snowpack simulated by MSHM as for the single layer case” I’m not sure what you are trying to say here.
Line 366: “restructingthe” – restricting the
Figure 7 – None of the panels have a letter denoting which panel they are. The panels with the red box should be made into a new figure that zooms into the distribution of values within the red box – there are discussions in the Results section of what’s happening here, but it is difficult for the reader to confirm what the text is saying graphically because it is far too small.
Figure 8, 9, 10, 11 also has no panel labels.
Line 433: “Fig. A7” – where is A7?
Line 445: “Fig A8” – where is A8? Be specific when referring to the appendix.
Line 477: “Fig A11” – where?
Line 534: “including water, forest (4500) and proximity” – what does 4500 refer to?
Table 7: There is a note in the caption that “shaded rows correspond to large local MARE” – however there are no shaded rows in the table.
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AC3: 'Reply on RC2', Siddharth Singh, 02 Dec 2023
I sincerely appreciate the time and effort you have dedicated to reviewing our manuscript.
I have carefully addressed each of your suggestions and made the necessary revisions to enhance the overall quality of the manuscript. In line with your recommendations, I have attached the revised version of the manuscript in the same PDF file (without tracking as it is easier to determine the line number). I have posted the revised manuscript with changes highlighted as 'Author Comment'.
If you have any further comments or queries, please do not hesitate to reach out. I am more than willing to make additional adjustments to ensure the manuscript meets the highest standards.
Once again, thank you for your time and valuable input. I look forward to hearing your thoughts on the revised manuscript.
-
AC4: 'Reply on RC2', Siddharth Singh, 02 Dec 2023
I sincerely appreciate the time and effort you have dedicated to reviewing our manuscript.
I have carefully addressed each of your suggestions and made the necessary revisions to enhance the overall quality of the manuscript. In line with your recommendations, I have attached the revised version of the manuscript in the same PDF file (without tracking as it is easier to determine the line number). I have posted the revised manuscript with changes highlighted as 'Author Comment'.
If you have any further comments or queries, please do not hesitate to reach out. I am more than willing to make additional adjustments to ensure the manuscript meets the highest standards.
Once again, thank you for your time and valuable input. I look forward to hearing your thoughts on the revised manuscript.
Citation: https://doi.org/10.5194/egusphere-2023-1987-AC4
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AC3: 'Reply on RC2', Siddharth Singh, 02 Dec 2023
Interactive discussion
Status: closed
-
AC1: 'Comment on egusphere-2023-1987', Siddharth Singh, 28 Sep 2023
Please add the reference that is cited in the paper:
Pan, J., Durand, M., Lemmetyinen, J., Liu, D., and Shi, J.: Snow water equivalent retrieved from X- and dual Ku-band scatterometer measurements at Sodankylä using the Markov Chain Monte Carlo method, The Cryosphere Discuss. [preprint], https://doi.org/10.5194/tc-2023-85, in review, 2023.
Citation: https://doi.org/10.5194/egusphere-2023-1987-AC1 -
RC1: 'Comment on egusphere-2023-1987', Anonymous Referee #1, 11 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1987/egusphere-2023-1987-RC1-supplement.pdf
-
AC2: 'Reply on RC1', Siddharth Singh, 02 Dec 2023
I sincerely appreciate the time and effort you have dedicated to reviewing our manuscript.
I have carefully addressed each of your suggestions and made the necessary revisions to enhance the overall quality of the manuscript. In line with your recommendations, I have attached the revised version of the manuscript in the same PDF file (without tracking as it is easier to determine the line number). I have posted the revised manuscript with changes highlighted as 'Author Comment'.
If you have any further comments or queries, please do not hesitate to reach out. I am more than willing to make additional adjustments to ensure the manuscript meets the highest standards.
Once again, thank you for your time and valuable input. I look forward to hearing your thoughts on the revised manuscript.
-
AC2: 'Reply on RC1', Siddharth Singh, 02 Dec 2023
-
RC2: 'Comment on egusphere-2023-1987', Anonymous Referee #2, 17 Nov 2023
General Comments
The authors of this manuscript use a Bayesian physical-statistical model to retrieve snow depth using data that was acquired during SnowEx’17, including pit data, ASO lidar acquisitions and the X- and Ku-band SnowSAR data. The methods presented by the authors are clearly defined, with encouraging results with error ranges of about 20cm SWE. The paper is methodologically and analytically sound, but does lack context of why certain methods are being employed, and the representation of results in figures need to be improved. For instance, in the Introduction it was overall well written to describe the need for remote sensing of snow and how SnowEx’17 is an attempt to address this concern. I do feel that the end of this section needs to be improved to detail to the reader what the specific objectives of this manuscript are. For instance, the authors provide an indication that they are looking to test a physical-statistical framework to derive SWE – but what are the objectives that can be completed to evaluate this?
The paper is very detailed in its methods of preparing the data for the model, and the modeling itself. What I think is lacking here is the reason that you are completing some of these steps. For instance, in section 4.1.1. you discuss in detail how you divide the snowpack with multiple layers into a snowpack with 1 or 2 layers, but never state why a 2 layer pack would be useful (that snowpack generally has a wind slab and depth hoar layer).. The justification for many of the steps in this paper need to have a bit better context provided.
Overall the paper is of publication quality in terms of its research, but the presentation could be improved, with my general and specific comments provided here.
Section 2. Previous Work
Line 55: “Time-series observations are available presently from tower measurements, albeit at the point scale of the tower footprint”. I think I know what study/setup you’re referring to here, but you have not referenced the papers that have been published based on them. Also, a sentence that states why you are not using a tower approach in this work would be useful.
Line 86: “demonstrated the utility of a couple multi-layer snow hydrology coupled with a..” – do you mean “snow hydrology model coupled…”?
Line 133-134: “the second is the prior of the backscatter… the prior of the snowpack physical…” this sentence is a little unclear, please revise.
Line 144: “assuming that we have good understanding” grammar issue here “assuming that we have a good understanding”.
Table 1: I may have missed it, but why are all the datasets being upscaled to 90m? I also noticed this discussed in lines 175-176, but there was no justification as to why – please include.
Line 299: “from the multilayer snowpack simulated by MSHM as for the single layer case” I’m not sure what you are trying to say here.
Line 366: “restructingthe” – restricting the
Figure 7 – None of the panels have a letter denoting which panel they are. The panels with the red box should be made into a new figure that zooms into the distribution of values within the red box – there are discussions in the Results section of what’s happening here, but it is difficult for the reader to confirm what the text is saying graphically because it is far too small.
Figure 8, 9, 10, 11 also has no panel labels.
Line 433: “Fig. A7” – where is A7?
Line 445: “Fig A8” – where is A8? Be specific when referring to the appendix.
Line 477: “Fig A11” – where?
Line 534: “including water, forest (4500) and proximity” – what does 4500 refer to?
Table 7: There is a note in the caption that “shaded rows correspond to large local MARE” – however there are no shaded rows in the table.
-
AC3: 'Reply on RC2', Siddharth Singh, 02 Dec 2023
I sincerely appreciate the time and effort you have dedicated to reviewing our manuscript.
I have carefully addressed each of your suggestions and made the necessary revisions to enhance the overall quality of the manuscript. In line with your recommendations, I have attached the revised version of the manuscript in the same PDF file (without tracking as it is easier to determine the line number). I have posted the revised manuscript with changes highlighted as 'Author Comment'.
If you have any further comments or queries, please do not hesitate to reach out. I am more than willing to make additional adjustments to ensure the manuscript meets the highest standards.
Once again, thank you for your time and valuable input. I look forward to hearing your thoughts on the revised manuscript.
-
AC4: 'Reply on RC2', Siddharth Singh, 02 Dec 2023
I sincerely appreciate the time and effort you have dedicated to reviewing our manuscript.
I have carefully addressed each of your suggestions and made the necessary revisions to enhance the overall quality of the manuscript. In line with your recommendations, I have attached the revised version of the manuscript in the same PDF file (without tracking as it is easier to determine the line number). I have posted the revised manuscript with changes highlighted as 'Author Comment'.
If you have any further comments or queries, please do not hesitate to reach out. I am more than willing to make additional adjustments to ensure the manuscript meets the highest standards.
Once again, thank you for your time and valuable input. I look forward to hearing your thoughts on the revised manuscript.
Citation: https://doi.org/10.5194/egusphere-2023-1987-AC4
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AC3: 'Reply on RC2', Siddharth Singh, 02 Dec 2023
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Cited
Siddharth Singh
Michael Durand
Edward Kim
Ana P. Barros
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(5945 KB) - Metadata XML