Round 1

Reviewer 1 Report

Review of revised version of:  jmse-1616366: ‘The effects of sound velocity profile to the convergence zone in deep water’

The revised version addresses some of the critical remarks made by this reviewer about the original manuscript, and overall, the paper is improved.  The addition of transmission loss data from the East Indian Ocean in March introduces information from a different season, and provides readers comparative results of the behavior sound propagation in different ocean conditions.  However, the new material has also introduced many new questions, and I have reservations about accepting the revised version.  I have tried to make useful suggestions to help clarify the message in parts of the text where the messages the authors are trying to convey are ambiguous and vague, to the extent of causing confusion.  In some instances, the text is so confusing that I cannot make useful suggestions.  These and others are listed below in specific comments.  As was the case with the original version, there are far too many corrections of English usage, spelling errors and some inaccurate statemens in the revised version to list them all separately.  I have provided an annotated version of the article pdf that contains all the corrections that should be made.  The paper should be revised to account for all the comments.

Specific comments

I remain convinced that the theoretical development of the horizontal distance of a ray in section 3 is not significantly different from the presentation in the third edition of ‘Fundamentals of Ocean Acoustics’, Brekhovskikh and Lysanov (see sections 2.3 and 2.4, pp 41-43) and if I were the editor, would ask that the material be moved to an appendix.  I will leave that to the editor’s decision.  However, I will insist that one aspect be changed, the use of ‘span’ to define the horizontal range or distance of a ray.  ‘Span’ should be replaced by ‘horizontal range’ or ‘horizontal distance’ of the ray; either of these provides a superior description of the quantity.  I have made these changes throughout the text and they should be used in the final version.

I did not mention this in the first review, but will do so here as a matter of education.  In fluids (ie in the ocean), compressional wave propagation is independent of direction.  The correct term in referring to the propagation of the wave is therefore ‘sound speed’ and NOT ‘sound velocity’.  Velocity is a vector, and implies magnitude and direction.  Speed is a scalar quantity that has only magnitude.  The compressional wave in water propagates with the same speed (magnitude) in all directions, and is therefore a scalar quantity.

Equation 2 line 141: I believe lg refers to the natural logarithm, Log refers to the logarithm to base 10.  Also, you need to specify that ‘All quantities in (2) are in dB.’

Line 152: What do you mean by 'interval 50 Hz'?  I don't understand.  Is this the interval over which TL is averaged?  It is not a third octave band width for all frequencies, so is there a reason for choosing this band width?

Figure 5: There are two black curves in the right panel of this figure, why?  What is the meaning of each one?  Please explain in the text or in the caption.

Line 166: I agree that the comparison is very close, but it should not be stated as 'amazing'.  We should not be 'amazed' by comparisons between data and models.  I realize I made a side comment in my first review that the result was amazingly good, but I should have said ‘remarkably good’.  I apologize for this mistake.

Figure 6: ‘Numerical’ is mis-spelled in all the panels.

Lines 202-206: This is an awkward description of a CZ, it would be embarrassing to publish it as it is written.  Instead try this:  'If there is a depth excess in the deep water waveguide, some deep refracted sound rays do not touch the ocean bottom.  These rays are refracted upward to the sea surface and are focused together to form a CZ close to the surface.

Line 285-286: What is meant  by 'modeling parameter'?  I don't understand.  Do you mean that you are using model parameters to account for unknown changes in the sound speed profile?  Or do you simply mean that the complex changes cannot be represented by simple changes in model parameters.  Please explain more clearly in the text.

Line 302: I think it is important to state that the range is greater for the different ocean conditions in March.  I would have expected this from the SSP.  Figure 10 clearly shows that there is a longer range for the March EIO data.

Line 317: ‘incidence angle’: You have to be careful in using this term to describe the angle.  Incidence angle refers to angles measured from the vertical, grazing angles refer to angles measured from the horizontal.  I think you are using the latter, so a better term to use is the propagation angle.

Line 321: ‘The sound rays are not reflected..” What do you mean by this statement about reflected rays?  I do not understand why rays would be reflected at these depths in the ocean.  At what depths would they be reflected?  It seems to me that the propagation angle is large at the depths between 1000 and 2000 m so the refraction in that region is strong and the rays enter the isothermal layer at large propagation angles.  Do you mean instead that the rays are strongly refracted?  This statement is at best confusing and it should be explained more clearly in a revision.

Lines 329-332: This part of the text makes absolutely no sense to me, I do not understand what message you want to convey so I cannot suggest an appropriate text for the revision.  This part needs to be explained more clearly.

Lines 370-375: The statements in this part of the text are contrary to what I see in figure 11.  The explanations presented here make no sense to me.  I am sure other readers will reach the same conclusion.  This part should be revised.

 

 

 

 

 

 

Comments for author File: Comments.pdf

Author Response

1：

The revised version addresses some of the critical remarks made by this reviewer about the original manuscript, and overall, the paper is improved.  The addition of transmission loss data from the East Indian Ocean in March introduces information from a different season, and provides readers comparative results of the behavior sound propagation in different ocean conditions.  However, the new material has also introduced many new questions, and I have reservations about accepting the revised version.  I have tried to make useful suggestions to help clarify the message in parts of the text where the messages the authors are trying to convey are ambiguous and vague, to the extent of causing confusion.  In some instances, the text is so confusing that I cannot make useful suggestions.  These and others are listed below in specific comments.  As was the case with the original version, there are far too many corrections of English usage, spelling errors and some inaccurate statemens in the revised version to list them all separately.  I have provided an annotated version of the article pdf that contains all the corrections that should be made.  The paper should be revised to account for all the comments.

Specific comments

Point 1:

I remain convinced that the theoretical development of the horizontal distance of a ray in section 3 is not significantly different from the presentation in the third edition of ‘Fundamentals of Ocean Acoustics’, Brekhovskikh and Lysanov (see sections 2.3 and 2.4, pp 41-43) and if I were the editor, would ask that the material be moved to an appendix.  I will leave that to the editor’s decision.  However, I will insist that one aspect be changed, the use of ‘span’ to define the horizontal range or distance of a ray.  ‘Span’ should be replaced by ‘horizontal range’ or ‘horizontal distance’ of the ray; either of these provides a superior description of the quantity.  I have made these changes throughout the text and they should be used in the final version.

Response 1:  I have accepted your suggestion and revisions the paper. We have simplified section 3.2. The “span” has been replaced by ‘horizontal range’ throughout the paper.

Point 2:

I did not mention this in the first review, but will do so here as a matter of education.  In fluids (ie in the ocean), compressional wave propagation is independent of direction.  The correct term in referring to the propagation of the wave is therefore ‘sound speed’ and NOT ‘sound velocity’.  Velocity is a vector, and implies magnitude and direction.  Speed is a scalar quantity that has only magnitude.  The compressional wave in water propagates with the same speed (magnitude) in all directions, and is therefore a scalar quantity.

Response 2:  Thank you for your explanation. The “sound velocity” has been replaced by ‘sound speed’ throughout the paper.

Point 3:

Equation 2 line 141: I believe lg refers to the natural logarithm, Log refers to the logarithm to base 10.  Also, you need to specify that ‘All quantities in (2) are in dB.’

Response 3: Thank you for your correction, I have revised our paper in line 141.

Point 4:

Line 152: What do you mean by 'interval 50 Hz'?  I don't understand.  Is this the interval over which TL is averaged?  It is not a third octave band width for all frequencies, so is there a reason for choosing this band width?

Response 4: 'interval 50 Hz' means that the center frequency interval 50 Hz in 50–2000 Hz, such as the center frequencies are 50 Hz，100 Hz，150 Hz，200Hz…… and the value of the SL at the center frequency is calculated in a third octave band width below 1000Hz,width band 200 Hz for the central frequencies above (or equal to) 1000 Hz. When the center frequency become lager the third octave band width is lager, so the band width 200Hz is considered. And this method has been used in Ref [22]. And some detailed expressions have been improved in this paragraph.

Point 5:

Figure 5: There are two black curves in the right panel of this figure, why?  What is the meaning of each one?  Please explain in the text or in the caption.

Response 5: To reduce uncertainty errors, 8 wide band signals (TNT charges) are used here. The 8 black curves mean each of them, and the red curve is the average value. Detailed revisions have been improved in this paragraph.

Point 6:

Line 166: I agree that the comparison is very close, but it should not be stated as 'amazing'.  We should not be 'amazed' by comparisons between data and models.  I realize I made a side comment in my first review that the result was amazingly good, but I should have said ‘remarkably good’.  I apologize for this mistake.

Figure 6: ‘Numerical’ is mis-spelled in all the panels.

Response 6: Thank you for your correction, the “amazing” has been replaced by “agrees well” in Line 166. ‘Numberical’ is mis-spelled and all of them have been replaced by ‘Numerical’ in panels.

 

Point 7:

Lines 202-206: This is an awkward description of a CZ, it would be embarrassing to publish it as it is written.  Instead try this:  'If there is a depth excess in the deep water waveguide, some deep refracted sound rays do not touch the ocean bottom.  These rays are refracted upward to the sea surface and are focused together to form a CZ close to the surface.

Response 7: Thank you for your correction, I have accepted your modifications in line 202-206.

Point 8:

Line 285-286: What is meant  by 'modeling parameter'?  I don't understand.  Do you mean that you are using model parameters to account for unknown changes in the sound speed profile?  Or do you simply mean that the complex changes cannot be represented by simple changes in model parameters.  Please explain more clearly in the text.

Response 8: I mean that the complex changes cannot be represented by simple changes in model parameters. Some detailed revisions have been improved in this paragraph.

Point 9:

Line 302: I think it is important to state that the range is greater for the different ocean conditions in March.  I would have expected this from the SSP.  Figure 10 clearly shows that there is a longer range for the March EIO data.

Response 9: Yes. The difference in the SSP between March and August in EIO may affect the CZ range, and some detailed revisions have explain bellow the paragraph of the Fig13, where the detailed changes are described.

Point 10:

Line 317: ‘incidence angle’: You have to be careful in using this term to describe the angle.  Incidence angle refers to angles measured from the vertical, grazing angles refer to angles measured from the horizontal.  I think you are using the latter, so a better term to use is the propagation angle.

Response 10: Thank you for your correction, we check the whole text about using ‘incidence angle’ and ‘grazing angles’, we decided to use the “grazing angles” which is more commonly used in marine acoustics.

Point 11:

Line 321: ‘The sound rays are not reflected.” What do you mean by this statement about reflected rays?  I do not understand why rays would be reflected at these depths in the ocean.  At what depths would they be reflected?  It seems to me that the propagation angle is large at the depths between 1000 and 2000 m so the refraction in that region is strong and the rays enter the isothermal layer at large propagation angles.  Do you mean instead that the rays are strongly refracted?  This statement is at best confusing and it should be explained more clearly in a revision.

Response 11: Thank you for your suggestions. I may have made a mistake. At the depth of 1000-2000m, extensive constant sound speed layer , sound rays propagate along approximate a straight line in the EIO, ‘The sound rays are not reflected.’ is  an error. We have revised this paragraph more carefully and make the passage more understandable.

Point 12:

Lines 329-332: This part of the text makes absolutely no sense to me, I do not understand what message you want to convey so I cannot suggest an appropriate text for the revision.  This part needs to be explained more clearly.

Response 12: I may have made a mistake. This part is mainly explain the CZ range not the width of the CZ, we removed this paragraph.

Point 13:

Lines 370-375: The statements in this part of the text are contrary to what I see in figure 11.  The explanations presented here make no sense to me.  I am sure other readers will reach the same conclusion.  This part should be revised.

Response 13: Thank you for your suggestions. Some detailed revisions have been improved in this paragraph which is highlighted.

Author Response File: Author Response.pdf

Reviewer 2 Report

The article has been considerably improved regarding the quality of the information and the presentation of data that corroborates the results.

However, it is still necessary and profound language and stile review. The text is sometimes very confusing, what makes it difficult to understand. I have added some suggestions for this correction (see the attached proofed text), but I strongly suggest to go for a professional editor. 

My comments:

The term “shadow zone” is mentioned twice on the text. Frist in lines 34-35 “The transmission loss (TL) difference inside the CZ and shadow zone can reach 10-20 dB [1].” and in lines 178-181 “The TLs in the first shadow zone for the EIO are relatively small due to losses in the ocean bottom. In the EIO 2019 and EIO 2021 experiments, because of the different receiving depth, further simulation analysis is needed below”. In both cases, the information brought to the context of the article seems irrelevant, since there are no further discussions about the shadow zone in the results of the experiment. My suggestion is to delete the sentences.

Line 42: … CZ propagation. (Period not comma)

Lines 42-44: Stephen and John observed the effect of sound velocity profile structures made the travel time arrive early in the North Pacific at low and mid-frequencies[8-9]. … concluding that …… (see also style correction in the text.

Line 45: Give more information why the expression from Beilis is et al. and Bongiovanni et al. is complicated.

Line 46: In the North Atlantic 49 Ocean, CZs are seen to appear at intervals of approximately 65 km. Where this information comes from? From [12] or E.M. Podeszwa?

Podeszwa is not listed in the reference list. [12] is not Podeszwa.

Line 57-60: Give more information about the conclusions from Fan et al.

Line 63-65: Give more information about the conclusions from Li et al.

Line 65-67: Give more information about the conclusions from Piao et al.

Line 88-90: The text “The sound channel axis is deep and there is a thick 88 constant sound velocity layer in the channel. The special environmental characteristics 89 may significantly affect sound propagation.” is more a conclusion text and should be moved accordingly.

Line 94: the term ”underwater signal recorders (USRs)” is used only once in the text. After that the more appropriate term hydrophone is used. I suggest using hydrophone all over the text.

Line 115-118: It is said that “The XBTs are interval 10 km along the track”. If yes, the XBT’s profile seen in figure 3 is an average SV profile?

Line 148-150: the sentence “The black curve is the original signal and the red curve is the signal that the reflected wave by the sea surface is set to zero.” should be placed on the figure’s caption.

Line 150-151: The sentence “The bandwidth was one-third octave for the central frequencies below 1000 and 200 Hz for the central frequencies above (or equal to) 1000 Hz.” is too confusing. Needs revision.

Line 164-165: The sentence … with the same receiver depth 164 of 255 m or 285 m. is confusing. The information is clearer on the captions from Figure 6.

Lines 167-168: There is no reference regarding the bottom acoustic parameters from EIO.

Line 178: … and the CZ width of the EIO is narrower than that in the SCS. Give the numbers.

Figure 7: Is the graphic on the right side of this figure is illustrating the text above? If yes it should be called on the text. If not, why is it there? Divide in figure 7a and 7b.

Equation 5: It seem there is a mistake on the numerator equation five – 2m_i is not equal to k²(z) cos² a(z)

Line 263: vertical distribution of what? Sound velocity values?

Line 266: give references of whom has “widely used” the linear approximation method.

Line 272: what is a “special ray”. This mut be defined.

Line 317: Incidence angle is related to the vertical. According to the explanation the term grazing angle (relative to the horizontal seafloor) would be more correct.

Line 323: Use the same terminology along the article. Changing from grazing to incidence angle makes the text more difficult to follow.

Line 329–332: The sentence “Form Figures 11, we can see that the sound ray refract slightly because of the relatively slowly varying of sound speed in the mixed channel layer of the EIO, thus the inverted sound ray that do not touch the bottom bound together tightly when they reverse return water body.” Is confusing.

Figure 13: Not clear what the green, blue and red lines indicate.

Line 391-392: Yes, they do. However, for the SCS the errors of the environmental and simulated data are considerably different (4 times). Any explanation for that?

Line 393-394: … SCS, the width of first CZ in the EIO is narrower than that in the SCS.  This information is not on the table.

Comments for author File: Comments.pdf

Author Response

2：

The article has been considerably improved regarding the quality of the information and the presentation of data that corroborates the results.

However, it is still necessary and profound language and stile review. The text is sometimes very confusing, what makes it difficult to understand. I have added some suggestions for this correction (see the attached proofed text), but I strongly suggest to go for a professional editor. 

My comments:

The term “shadow zone” is mentioned twice on the text. Frist in lines 34-35 “The transmission loss (TL) difference inside the CZ and shadow zone can reach 10-20 dB [1].” and in lines 178-181 “The TLs in the first shadow zone for the EIO are relatively small due to losses in the ocean bottom. In the EIO 2019 and EIO 2021 experiments, because of the different receiving depth, further simulation analysis is needed below”. In both cases, the information brought to the context of the article seems irrelevant, since there are no further discussions about the shadow zone in the results of the experiment. My suggestion is to delete the sentences.

Response: Thank you for your correction, “shadow zone” in lines 34-35, the first appearance is mainly to illustrate the importance of the CZ, we recommend keeping without deleting. The next appearance, I have accepted your suggestion to delete it, and revisions have been improved in these sentences.

Line 42: … CZ propagation. (Period not comma)

Response: Thank you for your correction, I have corrected it in the text.

Lines 42-44: Stephen and John observed the effect of sound velocity profile structures made the travel time arrive early in the North Pacific at low and mid-frequencies[8-9]. … concluding that …… (see also style correction in the text.

Response: Thank you for your correction, I have corrected it in the text.

Line 45: Give more information why the expression from Beilis is et al. and Bongiovanni et al. is complicated.

Response: I have corrected this sentence in the text. More factors makes the expression complicated that are not conducive to practical use.

 

Line 46: In the North Atlantic 49 Ocean, CZs are seen to appear at intervals of approximately 65 km. Where this information comes from? From [12] or E.M. Podeszwa?

Podeszwa is not listed in the reference list. [12] is not Podeszwa.

Response: The whole sentence and this information comes from Ref [12], and check the page number in new edition of the book. expression in this sentence.

 

Line 57-60: Give more information about the conclusions from Fan et al.

Line 63-65: Give more information about the conclusions from Li et al.

Line 65-67: Give more information about the conclusions from Piao et al.

Response: We have sorted out the second paragraph, and the more information about the respective results/conclusions of these researchers have been given. Some detailed revision also been improved in the paper.

 

Line 88-90: The text “The sound channel axis is deep and there is a thick 88 constant sound velocity layer in the channel. The special environmental characteristics 89 may significantly affect sound propagation.” is more a conclusion text and should be moved accordingly.

Response: Thank you for your correction, I have accepted your suggestion and revisions have been improved in these sentences. This sentence has been moved to the “conclusion” section.

 

Line 94: the term ”underwater signal recorders (USRs)” is used only once in the text. After that the more appropriate term hydrophone is used. I suggest using hydrophone all over the text.

Response: I have accepted your suggestion, hydrophone is used in the text.

 

Line 115-118: It is said that “The XBTs are interval 10 km along the track”. If yes, the XBT’s profile seen in figure 3 is an average SV profile?

Response: In figure 3 is a sound speed profile (SSP) that Measuring by CTD in whole depth at the receivers. In short-distance sound propagation, this slow change has little effect on the result analysis.

 

Line 148-150: the sentence “The black curve is the original signal and the red curve is the signal that the reflected wave by the sea surface is set to zero.” should be placed on the figure’s caption.

Response: Thank you for your reminder. In Figure 5 I have marked the legend.

 

Line 150-151: The sentence “The bandwidth was one-third octave for the central frequencies below 1000 and 200 Hz for the central frequencies above (or equal to) 1000 Hz.” is too confusing. Needs revision.

Response: The value of the SL at the center frequency is calculated in a third octave band width below 1000Hz, band width 200 Hz for the central frequencies above (or equal to) 1000 Hz. And some detailed expressions have been improved in this paragraph.

 

Line 164-165: The sentence … with the same receiver depth 164 of 255 m or 285 m. is confusing. The information is clearer on the captions from Figure 6.

Response:  I have improved this sentence in our text. Removed “of 255 m or 285 m”.

Lines 167-168: There is no reference regarding the bottom acoustic parameters from EIO.

Response: Yes, you are right, but unfortunately we have not found any published literature on bottom acoustic parameters from EIO. We have used experimental acoustic data to determine bottom acoustic parameters. And Examined using seafloor substrate types.

Line 178: … and the CZ width of the EIO is narrower than that in the SCS. Give the numbers.

Response: I have accepted your suggestion, “……EIO is narrower about 2-3 km than that in the SCS”, and this sentence has been revised in the text.

 

Figure 7: Is the graphic on the right side of this figure is illustrating the text above? If yes it should be called on the text. If not, why is it there? Divide in figure 7a and 7b.

Response: We have described the range of CZ in detail on the right panel, and divide in a) and b), in Figure 7.

 

Equation 5: It seem there is a mistake on the numerator equation five – 2m_i is not equal to k²(z) cos² a(z)

Response: Yes, Thank you for your correction. Eq.(5), the power 2 index is a slip of the pen, there is no power 2 index from Eq.(3). We have revised in the text. But we have simplified the equations in this section.

 

Line 263: vertical distribution of what? Sound velocity values?

Response: Yes, it means vertical distribution of Sound velocity values. Detailed expressions have been improved in this sentence.

 

Line 266: give references of whom has “widely used” the linear approximation method.

Response: The linear approximation method is used in Rf.[1], and gives the citation in the text.

Line 272: what is a “special ray”. This must be defined.

Response: ‘special ray’ is the ray ‘with a grazing angle of 0° at the seabed ‘ that have been described. We revised it as “this ray”.

 

Line 317: Incidence angle is related to the vertical. According to the explanation the term grazing angle (relative to the horizontal seafloor) would be more correct.

Line 323: Use the same terminology along the article. Changing from grazing to incidence angle makes the text more difficult to follow.

Response: Thank you for your correction, we check the whole text about using ‘incidence angle’ and ‘grazing angles’, we decided to use the “grazing angles” which is more commonly used in marine acoustics. And some detailed revision also been improved in the paper. We have checked the same terminology along the article.

 

Line 329–332: The sentence “Form Figures 11, we can see that the sound ray refract slightly because of the relatively slowly varying of sound speed in the mixed channel layer of the EIO, thus the inverted sound ray that do not touch the bottom bound together tightly when they reverse return water body.” Is confusing.

Response: I may have made a mistake. This part is mainly explain the CZ range not the width of the CZ, we removed this paragraph.

Figure 13: Not clear what the green, blue and red lines indicate.

Response: We have added a description for Figure 13(New Revision is Fig12), and the red , black, blue lines for EIO 2019,EIO 2021,SCS 2018 respectively, in all the figures.

 

Line 391-392: Yes, they do. However, for the SCS the errors of the environmental and simulated data are considerably different (4 times). Any explanation for that?

Response:  I think that maybe the errors due to segmentation of the SSP, because of different measurement accuracy in depth. When we simulated use Eq.(4), we use the segmentation of the SSP.

 

Line 393-394: … SCS, the width of first CZ in the EIO is narrower than that in the SCS.  This information is not on the table.

Response:  We can get that the width of first CZ in the EIO is 4/6km, and that is 7km in SCS in Simulated data on the table. So we say that ‘the width of first CZ in the EIO is narrower than that in the SCS.

Author Response File: Author Response.pdf

Reviewer 3 Report

see attached file 

Comments for author File: Comments.pdf

Author Response

3:

On Line 118, it is said that “the SVP is range-independent” in the analysis. What about

the bathymetry, slightly range-dependent according to Figs. 3-4? Is this variation included

in the computations with RAM?

Response: Yes. The bathymetry is range-dependent according to Figs. 3-4, and this variation included in the computations with RAM.

 

On Line 158, I suppose that VAL should be VLA (vertical line array).

Response: Yes, Thank you for your correction. That should be VLA. It has been revised in the text.

The sentence on Lines 148-150 could be expressed more clearly. I think that the caption

of Fig. 5 should also include info on the black and red curves.

Response: Thank you for your reminder. In Figure 5 I have marked the legend on the black and red curves. And some detailed expressions have been improved in this paragraph.

 

The theoretical background in Secs. 3.1-2, Lines 184-261 there including the ray equations,

is well known from several text books. Reference is made to the book [1]. The presentation

could certainly be shortened.

Response: I have accepted your suggestion, Section 3.2 has been simplified.

 

I suppose that the emission angles for the rays in Fig. 11 cover the whole angle interval.

Is this correct? Please explain the blue curve more carefully, also in the figure caption.

Response: The emission angles for the rays in Fig. 11 cover the angle of [-8.5°,8.5°]，because of the grazing angle of 0° at the seabed. We have explained the blue curve more carefully in the text.

“Horizontal refraction” is mentioned on p. 11-12. This term is often used for “refrac-

tion out of the vertical plane connecting source and receiver.” However, 3D effects are not

discussed in the present paper, and another term could be preferred to avoid confusion.

Preferably use the same colors in all figures, to differ between the two EIO cases and the

SCS case. At present, different colors are used in, for example, Figs. 12 and 13.

Response: Thank you for your suggestions. We have revised this paragraph more carefully and make the passage more understandable. We have used the same colors in all figures, to differ between the two EIO cases and the SCS case. We have correct the figures, and the red , black, blue lines for EIO 2019,EIO 2021,SCS 2018 are used in all the figures, respectively.

Please check the page numbers for refs [5] and [7].

Response: Thank you for your suggestions. The page numbers for refs [5] and [7] have been checked in References.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I am satisfied with the response from the authors.  The revised version adequately addresses the remarks and suggestions that were made in the review.  There are a few editorial changes that need to be made, but these are minor and can be done by the authors in preparing their final version.  I think researchers in underwater acoustics will find the new results for the EIO very interesting.  I have provided the changes in an annotated pdf file of the revised version

Comments for author File: Comments.pdf

Author Response

Thank you for your correction,  some mis-spelled have been corrected in the figures; and some detailed revisions have been improved  under your suggestions.

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

Review of: JMSE 1571430

This paper presents new data of acoustic transmission loss from an experiment in the East Indian Ocean to study convergence zone sound propagation.  The data reveal the presence of convergence zones, the first zone at a range of about 58 km.  The results are compared with converence zone ranges from experimental transmission loss data from a similar deep ocean environment in the South China Sea.  The authors then use ray theory to calculate the range to the convergence zone from measurements of the sound speed profile at each site.  Results of the calculation and modeling of the sound field with the parabolic equation are in excellent agreement with the experimental results.

Apart from the presentation of new experimental data from the East Indian Ocean, there is really nothing new in this paper.  The theoretical development in section 3.2 is a repeat of well-known theory (for at least 60 or 70 years) that appears in graduate school courses.  The discussion in comparing the convergence zones for the two oceans is awkward at best, and could be improved.  In my view, the paper could be revised as a short letter to show: the new transmission loss data for the two oceans; a statement that the authors use ray theory with a linear approximation for the sound speed change with depth (equation 11 with the diagram in figure 2), and a brief discussion to compare the different results for the convergence zones.  From this perspective, I recommend rejecting the original draft and use the suggestions in my review to write a short letter.

Comments:

I have provided an annotated file of corrections and suggestions that the authors can use in revising their work.  There are simply too many to write out separately.  Particularly, I have given many suggestions for correct terminology in describing the ray quantities; the terms used are likely to cause confusion.  In other parts of the paper, the discussions are awkward to the degree that the message is not clear.  Please note the suggestions for improvements.  Some of the more serious comments from the annotated file are listed below.

1. The authors show results from an experiment in August in the East Indian Ocean. Was the experiment in the South China Sea done at the same time of year, ie mid-summer? Are the conditions of sound speed profile shown in the paper typical of other times of the year?  Although the paper shows a new result for the East Indian Ocean, the work is based on only one time of year.  Of more interest would be whether the propagation conditions change with different seasons, and how the changes in sound speed profile affect the convergence zone ranges.
2. After equation 2, provide reference for the source levels that are used. If it is not published in a previous paper, the results should be shown here.
3. In section 3, you are using ray theory and a linearized sound velocity profile to determine the convergence zone range. So why not simply state that? It is not necessary to repeat a development that can be found in basic text books or in graduate school assignments.
4. Transmission loss in the shadow zone: From the values of sound speed and density of the sea bed material, I would not say the bottom was 'hard'. A hard bottom would reflect a greater fraction of the energy, so the losses would be less. Instead, I would say that the TL in the shadow zone is relatively small due to losses in the ocean bottom.

 

Comments for author File: Comments.pdf

Reviewer 2 Report

The paper deals with the analysis of experimental data in two different regions, but with similar SVP structures, regarding the behavior of sound waves to form convergence zones. The results show that the two models give very similar results for the first convergence zone. But gives no discussion about the second convergence zone. Moreover, the article makes no consideration about the validity of the models (it only shows that the models give very similar results as the one observed on the experiment. More discussion is needed.

 

Abstract – Line 4: Not clear what "different parts of the ocean" means. Different areas? Different depth ranges? Different environments (shelf, slope, deep ocean basins)?

Introduction: The whole text is very confused and difficult to follow. Needs deep grammar and style review.

Introduction: Several researchs are listed along this section. However, there is only the description of what the authors did, and nothing is said about the respective results/conclusions of these researchs. For example: Zhang et al. [13] analyzed the CZ characteristics and the calculation method for the CZ range and width based on the WKBZ theory, and concluded what?? Lin et al. [18] analyzed the effect of CZ on sonar detection performance by simulation data in deep sea. With which results?

Introduction – page 2 - lines 12-13: Be more specific about these “special characteristics” of the EIO.

Methods and Experiment Introduction – 1^st pararagraph: Please clarify the relevance of the study being conducted at the EIO.

Methods and Experiment Introduction – page 3 – 3^rd pararagraph – lines 6-8: The water depths of the EIO and SCS experiments are 3500 m and 3700 m respectively, which are basically the same. Is this a premise or an assumption? If premise, please indicate reference.

Methods and Experiment Introduction – page 3 – 3^rd pararagraph – lines 11-12: What is the lateral resolution of the CTS/XBT casts? In other words, how many casts (or how far from each other), were necessary to determine that SV structure? Please clarify.

The term glancing angle is used along the text. Despite the term glancing angle has a very similar meaning as grazing angle, in acoustics the second term is more widely used. In page 9, last paragraph, line 6, the term grazing angle is used. Moreover, the term incidence angle, which is related to the normal, is also used (page 9, last paragraph, line 7). Unify the term to avoid confusion.

2.3 Sound propagation data analysis – page 4 – 1^st paragraph – line 9: Were these values measured on the sediment or estimated from the literature?

3.1 The conditions of forming the CZ – page 5 second paragraph – line 4: This explanation should come before the term conjugated depth is mentioned on the text.

3.3 Numerical simulation and analysis the CZ phenomenon of the two sea areas – page 9 – last paragraph – line 9: to clarify the explanation, the “horizontal refraction distances” should be elucidated on figure 9.

3.3 Numerical simulation and analysis the CZ phenomenon of the two sea areas – page 10 – 1^st paragraph – line 1-2: The used of different terms to mean the same thing, makes the text more confusing. Looks like it has been written by different authors.

Table 1: Why no consideration is done about the second CZ, which have positions very different than those annotated by the experiment? Differences between the results (errors) should be expressed also in percentage.

Reviewer 3 Report

Comments to the Author

Based on the experimental data of similar scenes collected in the East Indian Ocean (EIO) and the South China Sea (SCS), this paper observed the significant impact of sound velocity profile (SVP) on deep-water CZ, and further explained the CZ characteristics difference between EIO and SCs by theoretical derivation and numerical simulation. The derived expression can predict the CZ distance quickly and simply. The research results are of great significance for underwater acoustic detection in the deep sea.

My main concerns are as follows:
1) Is Section 3.2 the theoretical derivation given for the first time in the paper? If not, references should be given.

2）The content of the second paragraph of the introduction of the paper needs to be further sorted out. At present, it is simply listed. “The effect of sound velocity profile……”  take this as the theme to reorganize this paragraph of the paper.

3）Check your usage of East Indian Ocean and Eastern Indian Ocean. Eastern Indian Ocean occurs in figures.