Characteristics of Three-Dimensional Sound Propagation in Western North Pacific Fronts

Round 1

Reviewer 1 Report

The authors have improved the manuscript according to this reviewer remarks

Author Response

Thank you very much for having considered and allowing me to submit a revised draft of our manuscript.

Best regards,

Jiaqi Liu

Reviewer 2 Report

Section 1 can be improved. Change the format of the citations and try to situate the topics. It also moves the discussion on Figure 1 to the next section.

Section 2 must be improved. In this section the numerical model used for the numerical simulation is presented. Why do you also mention Parabolic equation theory, if you don't use it? Furthermore, the equations deriving from ray theory must be introduced more effectively. You must properly introduce the equation, list in detail the variables contained in it with a concise description of the meaning. To make them more readable show them in a bulleted list. In this way the reader will be able to understand the contribution of each variable.

Section 3 must be improved. This section should be revised. You should first describe how the experimental measurements were performed. Adequately introduce the sensors used to measure these quantities. Add them in a table, giving all the specifications of these sensors and the tolerances. It would be advisable to also add some figures showing the sensors used. It also moves the part where you introduce the noise source and how the measurements were made to the beginning of the section. Only after having adequately introduced the experimental measures does he move on to report the results. first introduce the experimental results and then the numerical ones and finally propose a comparison. You must also review the figures, in some of them the legend is missing.

Section 5 must be improved. Paragraphs are missing where the possible practical applications of the results of this study are reported. What these results can serve the people, it is necessary to insert possible uses of this study that justify their publication. They also lack the possible future goals of this work. Do the authors plan to continue their research on this topic?

19) oceanfront. Introduce adequately the topic

29-30) Use the following format for citations: Sokolov et al. [6]. I have seen that you often use this correction, so I will not repeat this advice again, it also applies to the other occurrences.

61) “Figure 1” Do not show any Figures in the introduction, in this section you just have to introduce the work. Move this discussion to the next sections.

117-125) Try to better explain equations (1) and (2). List the variables (T, Ti, T0, Tb) and add an explanation for each of them. You could do it first for the temperature and then say that the same equations can be used to describe the salinity distribution.

120) Try to enrich the captions of the figure 2, the reader should be able to read the figure without the need to retrieve the information in the paper. Try to summarize the essential parts of the Figure and what you want to explain with it. Where are x and z?

134) Try to better explain equations (3). List the variables (T, Ta, w) and add an explanation for each of them

141) usntil ? Maybe until

144) Try to better explain equations (4). List all the variables and add an explanation for each of them

146) Add the Coppen version of this equation

152-153) normal mode theory, ray theory, parabolic equation theory and finite-element modelling. Introduce adequately these topics.

166) Show the Helmholtz equation as numebered equation and  list all the variables and add an explanation for each of them.

169) Try to better explain equations (5). List all the variables and add an explanation for each of them

173) Try to better explain equations (6) and (7). List all the variables and add an explanation for each of them. Do the same for all the other equations in this section.

231-233) Adequately introduce the sensors used to measure these quantities. Add them in a table, giving all the specifications of these sensors and the tolerances. It would be advisable to also add some figures showing the sensors used.

244-252) Figures 5-9 refer to the same area. It would be advisable to refer to the same area so that a comparison can be made.

244)Figure 5 caption: etopo1 data . Introduce adequately the topic

244) Figure 8. Legend of the colored map is missing

259) Explain the meaning of the Figure 10.b. Where are the values of the sound speed profile?

272-283) Move this section at the beginning of the section 3.

301-302) depth hydrophones. Introduce the sensor, add specifications, add a photo

302-304) Where is this comparison? You introduce it later, perhaps it would be appropriate to do it first.

318)Where is the legend of the colored map in figure 15?

Author Response

Please see the attachment.

Best regards,

Jiaqi Liu

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors addressed all the reviewer's comments with sufficient attention and modified the paper consistently with the suggestions provided. The new version of the paper has improved significantly both in the presentation that is now much more accessible even by a reader not expert in the sector, and in the contents that now appear much more incisive. The detailed description of the figures makes them easier to understand for the reader.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

In the paper authors consider 3D effects (horizontal refraction) in the sound propagation in the ocean in the presence of temperature front.

Authors present experimental results and comparison with theoretical modeling.

Statement of the problem is interesting and (in principle) experimental results are interesting as well, however methodology of modeling is unclear.

First of all in the section 2.2 there are set of mistakes(misprints) in equations (6-8).  time (t) and temperature in Eq(5) are denoted by one and the same letter.  What is connection with amplitudes A_j(x,y,z) in Eq(6) and amplitude A(x,y,z) in Eq(8)?  What is dimension of A? Eq (8) is incorrect from the point of view of dimension (equation itself and in exponent). Value "zeta" in (7) is not explained, k₀ (wave number) is identified as "wave beam" (line166). What is connection of values in (6-8) with intensity in (9)? In my opinion in (6-8) and (9) identical notations must be used.

Next, authors analyze results of experiment with the low-frequency sound source (in frequency domain about 100 Hz) in the ocean (Figure 12), where vertical line array was used as receiver.  Depth of deployment is not denoted. If it is a few km then what is influence of probable significant drifting of VLA under influence of wind and currents? Can it mask 3D effects or change interpretation of data? 

Next for low frequency sound propagation more appropriate is Parabolic equation (in 3D version or in 2D combining with vertical modes). Why authors use ray approximation?

So, in conclusion, presentation of material  must be substantially revised

Author Response

Dear Reviewer,

Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses below and my revisions/corrections in the re-submitted files. 

Best wishes!

Jiaqi Liu

Author Response File: Author Response.docx

Reviewer 2 Report

Jiaqi Liu et al. Characteristics of three-dimensional sound propagation

The paper  describes the result of an experimental study on the impact of oceans fronts  on sound propagation.

The paper is quite long with many illustrations. Initially are there several paragraphs not directly relevant for the presentations this e paper.  The authors are advised to consider reductions thereby increasing the readability of the paper

The experimental work is relevant and appears to of good quality, but that is difficult to review . This reviewer therefore concentrates on the use of models in the paper. First, all models are approximation of some sort. The environmental inputs may be poor representation of the real environment and the code itself may poorly implemented with significant errors. Still the use of models is useful especially for the understanding provided that the models have been adequately tested and validated for relevant scenarios .

The discussion following Figure 13 needs improving. Fundamental questions not answered are

• In the opinion of the authors, are the agreement experiment and modeling, good, satisfactory, or bad. What are causing the discrepancies , the model, or the measurements?
• Define specifically what are the references to 2D and 3D model, these are generic terms with different meaning to different people.
• The list of refences is missing many central references on modelling, for instance to the Bellhop model of Michael Porter and the book by Jensen et al, Computational Ocean Acoustics.
• Expand ref 18 to explain this a model and not  a PhD thesis

There are many questions like this. The authors need to reexamine the paper and decide what the they want to convey to the readers and cut out material not needed

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Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses below and my revisions/corrections in the re-submitted files. 

Best wishes!

Jiaqi Liu

Author Response File: Author Response.pdf

Reviewer 3 Report

The presented article is devoted to investigations of acoustic waves propagation in the areas of oceanic fronts both by experimental observations and numerical simulations. A set of experiments have been performed at the western North Pacific fronts.

Autors compare results of the experiments with 2D and 3D theoretical models and conclude that oceanic front act as an acoustic lens that could strongly affect the acoustic wave propagation.

In many important cases 3D models provide more good coincidence with the experimental data compared with 2D models. This can be an evidence that the horizontal refraction in the three-dimensional impact of oceanic front and topography cannot be ignored. Authors thoroughly discuss all details of the investigations.

I consider the otained results in the article are scientifically valuable and new, and should be published in the JMSE.

I suppose that the article can be published in present form, but the English of the article should be thoroughly checked. I have noticed many  missprints and places that requre minor language corrections.

For instance:

Line 5: "are is introduced" probably should be "is introduced".

Line 77: "phenomena. Using" probably should be "phenomena, using".

Line 79: "In the yellow sea" probably should be "In the Yellow sea".

Line 82: "their study sound propagation" probably should be "they study sound propagation".

Line 98-99: "structure. There is" probably should be "structure, there is".

Formula 5: "Sea surface temperature" probably should be "Sea surface sound speed on temperature and salinity".

Formula 7: What is ξx,y,z(s) meanig? It should be explained below the formula.

Line 219: "the minimum sound speed" probably should be "the maximum sound speed".

Line 276: "The warm water on" probably should be "The warm water is on".

Line 306: "The refraction angle symbol" What is symbol? The meaning is unclear.

Line 312: "so different invariant depth" What is invariant depth? The meaning is unclear.

Line 372: "It is discussed" should be excluded. Repetition.

Line 374: "of 8km Figure 16" probably should be "of 8km in Figure 16"

Etc.

Author Response

Dear Reviewer,

Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses below and my revisions/corrections in the re-submitted files. 

Best wishes!

Jiaqi Liu

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Once again I should remark my misunderstanding of theoretical background of this paper:

• the value that the authors call as "eikonal" (line 165), strictly speaking, is not such, it can be concerned with S (commonly accepted notation, having dimension of length), but must be explained;
• the commonly accepted equations of geometric optics (acoustics) do not include time, and one must either write the commonly accepted equations or explain how the equations written by the authors associated with them.
• Line 166: the authors write "Helmholtz equation" , apparently referring to equation (7), below, line 169, they write the "eikonal equation"  (7), but it is NOT eikonal equation and NOT Helmholtz equation", 
• authors introduce values  or vector "dzeta" (Eq(9) and string 170) we can see that it has dimension sec/m (inverse to speed), at the same time in the line 171 the same value must have dimension of length
• etc

In my opinion authors did not clarify mathematical/theoretical background of the paper and it can not be published 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf