Individual Wave Propagations in Ionosphere and Troposphere Triggered by the Hunga Tonga-Hunga Ha’apai Underwater Volcano Eruption on 15 January 2022
, Xuemin Zhang 2, Yang-Yi Sun 1, Fei Wang 3, Tien-Chi Liu 4,5, Chi-Yen Lin 4,5, Yongxin Gao 6, Jun Lyu 7, Xiaobing Jin 8, Xiaoli Zhao 8, Xiang Cheng 8, Pengyu Zhang 1, Qiyu Chen 1, Dixin Zhang 1, Zhiqiang Mao 1 and Jann-Yenq Liu 4,5,9Round 1
Reviewer 1 Report
The manuscript presents the analysis of the GNNS TEC and ground barometers observations during the Hunga Tonga-Hunga Ha'apai underwater volcano eruption of January 15, 2022. The analysis presents very interesting and new measurements of both atmospheric pressure and ionospheric total electron content associated the the volcano eruption. Anyway the paper is very poor from the physical point of view since it reported only observations without any robust discussion about possible interpratation of such measurements. So I recommend a rejection encourging a resubmission after a substantial revision of the paper.
Major comments
First: the introduction is very poor. Please expand the introduction referring to previous results and modelling. It could be useful also for your discussion and interpretation of the observations you found.
Second:
Line 82: What did you used? vTEC or sTEC? It is not clear from the text. It is an important problem since the sTEC depends on the location of the satellite, while the vTEC does not depend on the satellite position and, thus, can be used to make reliable comparison between different TEC measuments from different satellites. In addition, is you used vTEC, please explain what method you used to evaluate the vTEC from sTEC. If you do not used the correct procedure, the method would influence the results. Please read Ciraolo et al. [2007] (Calibration errors on experimental slant total electron content (TEC) determined with GPS).
Line 107: Please explicit the method since it is totally "vague". What are the equation you used? Also in this case the results depends on what TEC did you used (vTEC or sTEC?!?!?!). How did you evaluated the line in Figure 1 panel 2? It is completely vague and unclear.
Third: The discussion is non-existent. How can a scientific paper exist without a robust discussion? For example the authors can discuss about any related coupling model between volcano eruption, the atmosphere and the ionosphere, or any possible numerical results about existing model that can explain the physics behind the observations showed.
Author Response
Responses to the Reviewer #1
Comments and Suggestions for Authors
The manuscript presents the analysis of the GNNS TEC and ground barometers observations during the Hunga Tonga-Hunga Ha'apai underwater volcano eruption of January 15, 2022. The analysis presents very interesting and new measurements of both atmospheric pressure and ionospheric total electron content associated the the volcano eruption. Anyway the paper is very poor from the physical point of view since it reported only observations without any robust discussion about possible interpratation of such measurements. So I recommend a rejection encourging a resubmission after a substantial revision of the paper.
Major comments
First: the introduction is very poor. Please expand the introduction referring to previous results and modelling. It could be useful also for your discussion and interpretation of the observations you found.
Reply:
We have include the references of the previous studies (Heki, 2006, Dautermann et al., 2009 and Shults et al., 2016), which examined the TEC perturbations triggered by the volcanoes on land, in the revision (lines 53-61). However, the Tonga volcano is an underwater volcano. The eruption of the underwater volcano was rarely observed and never been reported. On the other hand, this study focuses on the new findings that the discrepancy in the propagation velocity of TEC and air pressure away from the underwater volcano. This is never been reported in the previous studies.
Second:
Line 82: What did you used? vTEC or sTEC? It is not clear from the text. It is an important problem since the sTEC depends on the location of the satellite, while the vTEC does not depend on the satellite position and, thus, can be used to make reliable comparison between different TEC measuments from different satellites. In addition, is you used vTEC, please explain what method you used to evaluate the vTEC from sTEC. If you do not used the correct procedure, the method would influence the results. Please read Ciraolo et al. [2007] (Calibration errors on experimental slant total electron content (TEC) determined with GPS).
Reply:
The estimation of TEC utilizing the electromagnetic signals transmitted from the GNSS satellites is not a novel technology. We estimate GNSS TECs by utilizing the traditional method (Liu et al., 1996). Note that the method has been listed in the reference in the previous version (lines 86-89).
We agree with the reviewer’s suggestion that sTEC depends on the location of the satellite, however, we utilized the TEC from the geostationary satellites in this study. The TEC is not a function of the satellite location. We utilized the BDS geostationary satellites that advance in having sTEC variations at fix ionosphere pierce points.
We fully agree with the comments. The absolute TEC values can be obtained through the correct procedure (Ciraolo et al., 2007). We remove influence from the absolute TEC by utilizing a moving average of 1-hour (lines 117-120). The residual of the TEC values are further utilized to investigate the propagation velocity associated with the eruption of the volcano.
Line 107: Please explicit the method since it is totally "vague". What are the equation you used? Also in this case the results depends on what TEC did you used (vTEC or sTEC?!?!?!). How did you evaluated the line in Figure 1 panel 2? It is completely vague and unclear.
Reply:
The method has been interpreted in the reference (Liu et al., 1996). We also added a brief statement in the revision (lines 86-89). The derivation of TEC is not a new method.
The BDS sTECs in this study are computed by utilizing the pseudoranges and phases of the dual-frequency signals that are transmitted from the BDS GEO satellites (G1, G2, and G3) to the ground-based GNSS receivers (Sun et al., 2013, 2017; Chen et al. 2022 and references therein).
Third: The discussion is non-existent. How can a scientific paper exist without a robust discussion? For example the authors can discuss about any related coupling model between volcano eruption, the atmosphere and the ionosphere, or any possible numerical results about existing model that can explain the physics behind the observations showed.
Reply:
Thank you for the comments. In fact, the observations in the MVP-LAI system is a part of the discussions in the manuscript for investigating the ~10% difference of the propagation velocity between the TEC perturbations and air pressure. The authors also added some statements to extend the discussion (lines 204-243).
Reviewer 2 Report
Review on the manuscript
Individual wave propagations in ionosphere and troposphere triggered by the Hunga Tonga-Hunga Ha'apai underwater volcano eruption on 15 January 2022
The manuscript presents some of the first results of a study of disturbances in the troposphere and ionosphere caused by the eruption of the Tonga volcano on January 15, 2022.
Undoubtedly, this event is important for atmospheric research. The authors consider the propagation of acoustic-gravity waves due to a volcanic eruption based on the analysis of TEC data from five geostationary satellites, ground-based barometers and seismometers. The authors gave a representative data set.
Two main results are formulated in the manuscript: fluctuations in the horizontal component of the soil were detected during the appearance of an increase in atmospheric air pressure and the velocity of wave propagation in the ionosphere was 10% higher than in the troposphere.
In my opinion, there are some ambiguities in the manuscript.
1. It is not clear how the authors estimated the propagation velocity of the disturbance in the ionosphere according to the TEC data?
2. Figure 3 shows that the TEC Front peak is ahead of the peak of the air pressure perturbation. The manuscript discusses the relationship between pressure perturbation times and the second TEC peak. What is the essence of this comparison? What explanation can the authors give?
3. It is not clear how atmospheric air pressure disturbances cause horizontal ground motions? What is the reason for this phenomenon?
The volume of the manuscript is small. I recommend that the authors be invited to resubmit it as the Brief Report.
Author Response
Responses to the Reviewer #2
Comments and Suggestions for Authors
Review on the manuscript
Individual wave propagations in ionosphere and troposphere triggered by the Hunga Tonga-Hunga Ha'apai underwater volcano eruption on 15 January 2022
The manuscript presents some of the first results of a study of disturbances in the troposphere and ionosphere caused by the eruption of the Tonga volcano on January 15, 2022.
Undoubtedly, this event is important for atmospheric research. The authors consider the propagation of acoustic-gravity waves due to a volcanic eruption based on the analysis of TEC data from five geostationary satellites, ground-based barometers and seismometers. The authors gave a representative data set.
Two main results are formulated in the manuscript: fluctuations in the horizontal component of the soil were detected during the appearance of an increase in atmospheric air pressure and the velocity of wave propagation in the ionosphere was 10% higher than in the troposphere.
In my opinion, there are some ambiguities in the manuscript.
- It is not clear how the authors estimated the propagation velocity of the disturbance in the ionosphere according to the TEC data?
Reply:
We estimated the propagation velocity of the TEC by utilizing the front peak from the ionosphere pierce points aligned away from the volcano in Figure 2b (lines 120-123). This can avoid the influence from the rapid conjugate effect in the ionosphere.
- Figure 3 shows that the TEC Front peak is ahead of the peak of the air pressure perturbation. The manuscript discusses the relationship between pressure perturbation times and the second TEC peak. What is the essence of this comparison? What explanation can the authors give?
Reply:
Thank you for the comments. In previous studies, the TEC perturbations are generally considered to be caused by the arrivals of the waves in the lithosphere and/or atmosphere due to the acoustic-gravity waves. In this study, we found that the TEC perturbations lead obvious changes in air pressure ~12 minutes. This drives us to investigate the causal mechanism of the leading in TEC. Associated statements have been added in the revision for the references (lines 222-237).
- It is not clear how atmospheric air pressure disturbances cause horizontal ground motions? What is the reason for this phenomenon?
Reply:
Thank you, again. This is a very good comment. Numerous previous studies reported that ground vibrations can drive changes in air pressure. Meanwhile, air pressure data are utilized to calibrate records in seismic data. Although the causal mechanisms are not fully understood, changes in atmosphere drives variations in ground motions can be expected.
In this study, the ground vibrations are triggered by the Lamb waves. Significant ground vibrations at two horizontal components (Figures 3c, d) could be resulted from the Lamb waves that mainly propagate in the horizontal sphere. Meanwhile, the density of the air is obviously smaller than it of the crust. Ground vibrations at the vertical component are difficult to be triggered by the Lamb waves mainly propagating in the horizontal sphere. Associated statements have been added in the revision (lines 238-243).
The volume of the manuscript is small. I recommend that the authors be invited to resubmit it as the Brief Report.
Reply:
Thank you for the suggestion. We would like to submit it as a Communication.
Author Response File: 
Author Response.docx
Reviewer 3 Report
The authors presneted the first results for Tonga volcanic eruption. I can reccommend this paper for publication but I would like to see more discussion about the results. I understand that this paper is mainly observation study and there are not so many equivalent eruptions for comparison, but if authors add at least one similar study it will be fine.
Author Response
Responses to the Reviewer #3
Comments and Suggestions for Authors
The authors presneted the first results for Tonga volcanic eruption. I can reccommend this paper for publication but I would like to see more discussion about the results. I understand that this paper is mainly observation study and there are not so many equivalent eruptions for comparison, but if authors add at least one similar study it will be fine.
Reply:
Thank you very much.
Discussions have been added in the revision (lines 206-247).
References associated with the study have been added in the revision.
Reviewer 4 Report
The paper is devoting to the important problem - the Earth's ionosphere response on great volcanic explosions. The Hunga-Tonga-Ha'apai volcanic eruption occurred on 15 January 2022 is the unique event due to grandiosity of its ejecta scale and intensity. Thus, it is very important to study atmospheric effects including TEC disturbances invoked by this event.
The paper is written quite well. However, the following questions and comments should be taking into account by the authors:
1) There are no analysis of other published research results deal with TEC anomalies caused by the Hunga-Tonga volcano eruption. A few publications have already published. See, for example, https://doi.org/10.1002/essoar.10510440.1.
2) It is not clear what TEC data are considered in this study - STEC or VTEC? Please, describe briefly TEC extraction and the following TEC-processing methodology.
3) Please, describe your TEC-filtering method. What frequencies were rejected (below than ... /higher than ...)?
4) Figure 1. I am not sure that the ocean bottom topography is important. Perhaps, tectonic plate boundaries much more informative? Where 26 barometers are installed? It is impossible to see it from the figure. Please, highlight their locations.
5) Figure 2a. The envelope line is not coincide with many of the first TEC-peaks which are shown in the figure. Please, explain this situation.
6) The TEC-disturbances apparent velocity equal to 335 m/s is too small to be an acoustic wave at the 350 km altitude. More likely the gravity wave is observed.
Author Response
Responses to the Reviewer #4
Open Review
Comments and Suggestions for Authors
The paper is devoting to the important problem - the Earth's ionosphere response on great volcanic explosions. The Hunga-Tonga-Ha'apai volcanic eruption occurred on 15 January 2022 is the unique event due to grandiosity of its ejecta scale and intensity. Thus, it is very important to study atmospheric effects including TEC disturbances invoked by this event.
The paper is written quite well. However, the following questions and comments should be taking into account by the authors:
1) There are no analysis of other published research results deal with TEC anomalies caused by the Hunga-Tonga volcano eruption. A few publications have already published. See, for example, https://doi.org/10.1002/essoar.10510440.1.
The reference (https://doi.org/10.1002/essoar.10510440.1) has been added in the revision (lines 211-217).
2) It is not clear what TEC data are considered in this study - STEC or VTEC? Please, describe briefly TEC extraction and the following TEC-processing methodology.
Reply:
The estimation of TEC utilizing the electromagnetic signals transmitted from the GNSS satellites is not a novel technology. We estimate GNSS TECs by utilizing the traditional method (Liu et al., 1996). The BDS sTECs in this study are computed by utilizing the pseudoranges and phases of the dual-frequency signals that are transmitted from the BDS GEO satellites (G1, G2, and G3) to the ground-based GNSS receivers (Sun et al., 2013, 2017; Chen et al. 2022 and references therein) (lines 86-89). Meanwhile, instead of orbiting satellites, we utilized the BDS geostationary satellites that advance in having sTEC variations at fix ionosphere pierce points.
3) Please, describe your TEC-filtering method. What frequencies were rejected (below than ... /higher than ...)?
Reply:
We remove influence from the absolute TEC by utilizing a moving average of 1-hour (lines 117-120). Associated statements “To mitigate the influence from TEC diurnal variations and to keep the essentials of the TEC perturbations, simultaneously, we utilized the simple process of subtracting a 1-hour running average from the BDS sTECs to illustrate the eruption-triggered perturbations.“ have been added in the revision (lines 119-122).
4) Figure 1. I am not sure that the ocean bottom topography is important. Perhaps, tectonic plate boundaries much more informative? Where 26 barometers are installed? It is impossible to see it from the figure. Please, highlight their locations.
Reply:
We have redrawn the Figure 1. We also provide the data utilized in this study. All the information can be retrieved from the data storage shown in the manuscript.
5) Figure 2a. The envelope line is not coincide with many of the first TEC-peaks which are shown in the figure. Please, explain this situation.
Reply:
Thank you for the comment. In our opinion, the best way for reporting the original appearance of the extreme event is showing the raw data with less human processing.
Therefore, we illustrate the raw sTEC data in Figure 2a. On the other hand, we plotted the retrieved data through the removal of 1-hour running average in Figure 2b. The envelope line (i.e., ~335 m/s) is obtained from the first TEC-peaks in Figure 2b. The envelope line is also plotted in Figure 2a for the references. We understood that many of the first TEC-peaks are not coincided by the envelope line in Figure 2a due to that the raw sTEC data with an amplified scale for adapting the distance from the volcano in Y-axis.
6) The TEC-disturbances apparent velocity equal to 335 m/s is too small to be an acoustic wave at the 350 km altitude. More likely the gravity wave is observed.
Reply:
The authors fully agree with the comment. The velocity of ~335 m/s is lower than the acoustic speed of ~800 m/s in the ionosphere and is close to the gravity wave regime. Lin et al. (2022) reported the Lamb waves with a velocity of ~340 m/s propagating in the ionosphere for a long distance, which is the major component of the eruption induced waves in the atmosphere. Therefore, the velocity of ~335 m/s is dominated by the Lamb waves in the ionosphere (lines 211-221).
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
In the revised version, the authors competely missed the points I wrote in the previous revision. I asked them to improve the description of the method used for their a anlysis and they pratically did not include it in the revised version. Anyway, the most important point is the improvement os their discussion. They explicitly answer that they included "some statements to extend the discussion". What is this? A physical resarch paper or a newspaper which shows some data? It seems that they did not correclty interpret the TEC data they obtained. So, I suggest again to reject the paper untill the authors would not try to interpret their results.
Author Response
The method has been shown in the previous version.
Reviewer 2 Report
The Reviewer thanks the authors for the revision of the manuscript.
The authors answered the questions of the Reviewer. They made addition changes to the text, added a few references and the Discussions section. As a result, the article has become clearer and it can be recommended for submission. However, it contains grammatical errors, so some grammar editing is required.
Author Response
Thank you very much.
We have carefully revised the English in the manuscript.
Reviewer 4 Report
I think that the manuscript can be published in its present form.
Author Response
Thank you very much.
