Interpretation of Signals Recorded by Ocean-Bottom Pressure Gauges during the Passage of Atmospheric Lamb Wave on 15 January 2022

Round 1

Reviewer 1 Report

The eruption of the Hunga Tonga – Hunga Ha’apai volcano on January 15, 2022 leads to generate the water disturbances in various parts of the World Ocean. This phenomenon is studied intensively during last year; all physical mechanisms are understood and applied for an interpretation of real data. The high density of scientific publications makes it difficult to correctly analyze the differences in the results of different authors using the same theoretical models and experimental data. Nevertheless, even the intersection of results in different articles turns out to be useful leading to greater reliability of the conclusions drawn. The work under review, which analyzes bottom pressure perturbations associated with the passage of atmospheric waves, is no exception. Authors used the shallow-water theory for analysis of the records of the bottom pressure sensors located in the area of the Japanese Islands. Of particular interest are the energy estimates of the wave components, which have not been made in other studies, and this is the novelty of the theoretical analysis. The analysis of in-situ data (DONET, DART) confirms the validity of theoretical concepts presented in the work.

In fact, I have no fundamental objections to the results obtained and can recommend the article for publication. In my opinion, the author's analysis is close to the analysis made in the work [33[ to which there is a link, but "in passing", while the difference in approaches could have been better explained.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper by Nosov et al. focuses on investigating the physics behind the generation of pressure variations at the ocean floor with the aim of devising a method to distinguish free gravity waves in records collected by bottom pressure sensors. The analysis of in-situ data from DONET and DART provides empirical validation for the proposed theoretical concepts.

The derived method presented in the article is accurate, the data is comprehensive, and the simulation process is convincing. Therefore, I believe that this article deserves acceptance after a minor revision.

 

Line 54: Regarding the DONET tsunami records during the 2022 Tonga volcanic eruption, I recommend referring the following paper. This study utilizes DONET data for tsunami early warning purposes.:

https://doi.org/10.1785/0220220098

 

Line 56: Although this study did not utilize S-net data, I highly recommend that the authors consider introducing this observational system as well. S-net provides an even larger set of observations compared to DONET during this event:

 

 

• https://doi.org/10.1186/s40623-022-01614-5

•  

 

Line 111: Please clarify the physical significance of this factor. It would be beneficial to include the content from Lines 158-160 at this point for better context and understanding.

 

Line 354: I agree with this viewpoint, and I believe that the biggest error in the entire process of simulation lies here. The authors need to explain thoroughly how to evaluate the errors caused by complex bottom relief.

 

Line 407: The reviewer does not agree with this statement. The free gravity waves in the variations of bottom pressure also depend on the depth. According to the Green’s Law, the tsunami amplitude is inversely proportional to the fourth root of water depth, which is reflected by the bottom pressure.

 

Line 570: Why does the waveform represented by the green dotted line exhibit such a prominent negative phase? What could be the underlying mechanism behind its formation?

 

Line 599: In this figure, it appears that the quantity index (delta) is more correlated with the propagation direction of the Lamb wave rather than the direction of the slope. For example, despite KMB08 having a relatively shallow water depth (1924 m), its quantity index is significantly smaller compared to the deeper MRG28 (2499 m). The water depth of DONET stations can be found at: https://www.seafloor.bosai.go.jp/st_info/

 

Line 685: In the final of the article, I suggest that the authors consider discussing the proportion of energy contributed by “tsunamis triggered by Lamb waves” and “free gravity waves”.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Brief summary:

The manuscript deals with free gravity tsunami waves generated by an atmospheric Lamb wave, caused by the explosive eruption of the Hunga Tonga - Hunga Ha'apai volcano. A theory for the generation of free gravity tsunami waves is presented based on the authors' previous publications [6, 7] and supplemented for underwater slopes. Observations on bottom pressure gauges and ground-based barographs are analyzed in the Japan Islands region where underwater slopes exist. The observations match quite well with the theoretical calculations and simulations.

General comments:

The manuscript is well organized and clearly written. It is technically correct, figures are informative, and conclusions are supported by the experiments. English is perfect.

Detailed comments:

Equation 2 and line 143: The glyph of water density rho is different than elsewhere in the manuscript.

Line 146: "system (1)-(2)" should be "system (2)-(3)".

Line 371: "isobate" should be "isobath".

Lines 435 and 476: The unit of the radius of the kernel is missing.

Supplementary material in the separate file:

VideoS3: "depth enhancement" should be "depth reduction".

VideoS4: "depth reduction" should be "depth enhancement".

Author Response

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Author Response File: Author Response.pdf