Estimating Sound Speed Profile by Combining Satellite Data with In Situ Sea Surface Observations

Round 1

Reviewer 1 Report

The authors proposed a method combining EOF with SOM to derive the SSP. The proposed method increased the accuracy of estimating the SSP when it is applied to the combined data of satellite sea surface observations and the in-situ measurements rather than satellite sea surface data only. The authors may consider adding the discussion of seasonal variations of their results. The authors may also need to specify the limitations of applying the optimized parameters to the nearby regions around the in-situ measurement location.

Line 177: “loss” should be “losing”.

Line 300: “deep below it” can be modified to “the deeper layers”.

Author Response

Dear Editor and Reviews:

We thank you very much for giving us an opportunity to revise our manuscript. We appreciate editor and reviewers very much for their positive and constructive comments and suggestions on our manuscript entitled “Estimating sound speed profile by combining satellite data with in-situ sea surface observations”. (ID: electronics-1937341).

Based on these comments and suggestions, we have made careful modifications on the original manuscript. We hope the new manuscript will meet the journal’s requirement. You will find our point-by-point responses to the reviews’ comments in the text below, and the corresponding revisions in the new manuscript marked as a “track-changes” version.

Reviewer#1, Concern # 1: Line 177: “loss” should be “losing”.

Author response: We have made the correction according to the reviewer’s comment.

Author action: we have re-written the ‘loss’ as ‘losing’.

Reviewer#1, Concern # 2: “deep below it” can be modified to “the deeper layers”.

Author response: We have made the correction according to the reviewer’s comment.

Author action: we have re-written the ‘deep below it’ as ‘the deeper layers.

Author Response File: Author Response.pdf

Reviewer 2 Report

This article focused on a method to estimate the SSP based on the SOM. The results are clearly investigated including errors and estimates. 

Author Response

Dear Editor and Reviews:

We thank you very much for giving us an opportunity to revise our manuscript. We appreciate editor and reviewers very much for their positive and constructive comments and suggestions on our manuscript entitled “Estimating sound speed profile by combining satellite data with in-situ sea surface observations”. (ID: electronics-1937341).

Based on these comments and suggestions, we have made careful modifications on the original manuscript. We hope the new manuscript will meet the journal’s requirement. You will find our point-by-point responses to the reviews’ comments in the text below, and the corresponding revisions in the new manuscript marked as a “track-changes” version.

Reviewer#2, Concern # 1: This article focused on a method to estimate the SSP based on the SOM. The results are clearly investigated including errors and estimates.

Author response: We are appreciated that the reviewers pointed out the mistakes of the manuscript. It has been revised according to the comments of reviewers.

Author Response File: Author Response.pdf

Reviewer 3 Report

The presented manuscript mainly contributes to the improvement of sound speed profile estimation by combining usual sea surface observations data with satellite data. Overall, it is an interesting topic. Multiple-source data collection and processing is a promising field of research. Meantime, I would like to point out the followings: 

1. What are the new contributions of this manuscript compared to the authors’ previous article cited as reference [19] in this manuscript?

2. The introduction started with good background knowledge, addressed the tackled scientific issue, and surveyed the related works from the literature. However, I would still encourage the authors to enrich the content with more recent publications in the field.

3. Section 2 depicted the suggested methodology and that is where I found that the presentation lacks a clear and direct explanation of the utilized method. My advice is to start from what the previous method uses, what measurements are already available, what mathematical representations can structure the previous method, and then after addressing the lack of accuracy in determining a quantity or a measure, develop your new contribution in engaging the satellite data and how you enhanced the accuracy of estimating the aimed factor (in your case, the SSP). Doing so, I believe the article becomes more interesting to read.

To support the previous note, please reconsider the placement of figure 1.

In line 118, the authors stated that higher orders of s might introduce excessive noise. What is the highest s to truncate the additive unwanted noise?

In line 124, the sentence is missing the main verb.

In the same section, please pay attention to the proper alignment of all equations, and strictly comply with the template in citing references. Examples are equations (1) and (2) and the intext citation of the references [22] and [16].

4. The title of section 3 is misspelled. It should be ‘Data’ instead of ‘Date’.

The sentence ‘’ As EOF processing requires samples at the same depth, the SSP sample is considered complete only it samples depths from shallow than 5 m to deeper than 475 m and the remaining profiles were cubic interpolated to the nominal depths of senser on the slack-line(5,10,15,20,25,35,40,50,75,100,125,150,175,200,225,275,325,400,425,475)’’  is very long and unclear sentence with many spelling and grammar mistakes. It lacks spacing at some points and includes over spacing at other points. A revision is required.

Have you tried to simply combine the data from multiple sources using the conventional combiners such as SC, EGC, MRC, or maximum likelihood combiner? If yes, how did you find your approach over these combiners? If no, what is your justification not to use them?

5. The results section has adequately presented the main results and achievements. I would only recommend some proofreading.

Check the grammar in line 207.

Check the meaning in lines 211-213.

6. I disagree with the heading title of section 5. The authors previously provided discussions alongside the presented results in section 4. It would be more appropriate to change the title to ‘’Conclusion’’. Meantime, it would be great to include the improvement percentage in the accuracy achieved under the tested scenarios. You may also include any other achievements in numbers. 

Author Response

Dear Editor and Reviews:

We thank you very much for giving us an opportunity to revise our manuscript. We appreciate editor and reviewers very much for their positive and constructive comments and suggestions on our manuscript entitled “Estimating sound speed profile by combining satellite data with in-situ sea surface observations”. (ID: electronics-1937341).

Based on these comments and suggestions, we have made careful modifications on the original manuscript. We hope the new manuscript will meet the journal’s requirement. You will find our point-by-point responses to the reviews’ comments in the text below, and the corresponding revisions in the new manuscript marked as a “track-changes” version.

Reviewer#3, Concern # 1: What are the new contributions of this manuscript compared to the authors’ previous article cited as reference [19] in this manuscript?

Author response: Compared with the reference [19], this manuscript discusses the estimation relationship of various oceanographic observation parameters to the sound speed profile.

Author action: we have revised the sentence “This could not be described by remote sensing parameters alone, so multi-source pa-rameters are added to strengthen the study of this area [19].”

Reviewer#3, Concern # 2: The introduction started with good background knowledge, addressed the tackled scientific issue, and surveyed the related works from the literature. However, I would still encourage the authors to enrich the content with more recent publications in the field.

Author response: According to the comments of reviewers, we have added three references in recent years.

Author action: We have added the following reference:

[20] J. Huang, Y. Luo, Y. Li, J. Shi, X. Zheng and J. Wang, "Analysis of Sound Speed Profile in the South China Sea based on Empirical Orthogonal Function Algorithm," 2021 OES China Ocean Acoustics (COA), 2021, pp. 166-171, doi: 10.1109/COA50123.2021.9520009.

[22] Zhenyi Ou, Ke Qu, Chen Liu, "Estimation of Sound Speed Profiles Using a Random Forest Model with Satellite Surface Observations", Shock and Vibration, vol. 2022, Article ID 2653791, 8 pages, 2022. https://doi.org/10.1155/2022/2653791.

[23] C. Chapman and A. A. Charantonis, "Reconstruction of Subsurface Velocities From Satellite Observations Using Iterative Self-Organizing Maps," in IEEE Geoscience and Remote Sensing Letters, vol. 14, no. 5, pp. 617-620, May 2017, doi: 10.1109/LGRS.2017.2665603.

Reviewer#3, Concern # 3: Section 2 depicted the suggested methodology and that is where I found that the presentation lacks a clear and direct explanation of the utilized method. My advice is to start from what the previous method uses, what measurements are already available, what mathematical representations can structure the previous method, and then after addressing the lack of accuracy in determining a quantity or a measure, develop your new contribution in engaging the satellite data and how you enhanced the accuracy of estimating the aimed factor (in your case, the SSP). Doing so, I believe the article becomes more interesting to read.

To support the previous note, please reconsider the placement of figure 1.

In line 118, the authors stated that higher orders of s might introduce excessive noise. What is the highest s to truncate the additive unwanted noise?

In line 124, the sentence is missing the main verb.

In the same section, please pay attention to the proper alignment of all equations, and strictly comply with the template in citing references. Examples are equations (1) and (2) and the intext citation of the references [22] and [16].

Author response: We are sincerely grateful to the reviewers for their valuable comments.

we have added a paragraph to the second part.

For the question on line 118, it is explained in lines 120-122. (A threshold of 95%, which is the proportion of variances, is commonly used to determine the number of modes of the EOF used. According to an analysis of the experimental data, three orders of EOFs are used in SSP modeling here.)

We have corrected the grammar in line 124 according to the reviewer's requirements.

We have revised the equations and references as required by reviewers.

Author action: We have added a paragraph to the second part.

In line 124, the sentence is changed to "The matrix of anomalies in the SSP of the ocean is X=[X1,...XM]∈R"

We have revised the equations and references as required by reviewers.

Reviewer#3, Concern # 4: The title of section 3 is misspelled. It should be ‘Data’ instead of ‘Date’.

The sentence ‘’ As EOF processing requires samples at the same depth, the SSP sample is considered complete only it samples depths from shallow than 5 m to deeper than 475 m and the remaining profiles were cubic interpolated to the nominal depths of senser on the slack-line(5,10,15,20,25,35,40,50,75,100,125,150,175,200,225,275,325,400,425,475)’’  is very long and unclear sentence with many spelling and grammar mistakes. It lacks spacing at some points and includes over spacing at other points. A revision is required.

Have you tried to simply combine the data from multiple sources using the conventional combiners such as SC, EGC, MRC, or maximum likelihood combiner? If yes, how did you find your approach over these combiners? If no, what is your justification not to use them?

Author response: Thanks the reviewers for their valuable comments.

As for the combiner problems, no other Combiner is used in this article. Because it is not sure whether other combinations can be used for SSP estimation. In this paper, the SOM model is used to evaluate various parameters effectively, and the optimal input parameters are found. We believe that there will be more efficient and convenient combiner in the future, which is also an important direction to improve our work in the future. It is believed that these combinations will be more discussed in the future research on multi-source parameter estimation profiles.

Author action: we have re-written the ‘Date’ as ‘Data’.

We have revised the long sentences and corrected the grammatical errors. The following is a corrected sentence:

“As EOF processing requires samples at the same depth, the SSP sample is considered completed only when its samples depths shallower than 5 m and deeper than 475 m. And the remaining profiles were cubic interpolated to the nominal depths of senser on the slack-line

(5,10,15,20,25,35,40,50,75,100,125,150,175,200,225,275,325,400,425,475).”

Reviewer#3, Concern # 5: The results section has adequately presented the main results and achievements. I would only recommend some proofreading.

Check the grammar in line 207.

Check the meaning in lines 211-213.

Author response: We have made correction according to the reviewer’s comment.

Author action: Line 207 "consider" has been changed to "considered".

We have made correction according to the reviewer’s comment of lines 211-213.

Reviewer#3, Concern # 6: I disagree with the heading title of section 5. The authors previously provided discussions alongside the presented results in section 4. It would be more appropriate to change the title to ‘’Conclusion’’. Meantime, it would be great to include the improvement percentage in the accuracy achieved under the tested scenarios. You may also include any other achievements in numbers.

Author response: We have made correction according to the reviewer’s comment.

Author action: "Discussions" has been changed to " Conclusion". In addition, some percentage data was added to describe the test results.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors have sufficiently addressed my concerns. I can see the revised manuscript is now much improved.