Alternative Approach for Tsunami Early Warning Indicated by Gravity Wave Effects on Ionosphere
Round 1
Reviewer 1 Report
Comments on the manuscript “Alternative approach for tsunami early warning indicated by gravity wave effects on lower ionosphere” by Foroodi et al.
In this manuscript, ionospheric responses to the tsunami induced by the 2011 Tohoku earthquake were studied using double-frequency measurements of the Global Positioning System (GPS) and ionosonde. Clear ionospheric disturbances were both observed by the GPS and ionosonde on the tsunami day. Tsunami-induced Internal Gravity Waves (IGWs) were detected in the bottom side ionosphere, which was about 25 minutes earlier than tsunami’s first detection. This research provided new potential for tsunami’s early warning. However, the following points should be considered and improved:
Major Comments
Description on observation results and its further discussion were made together in 4. Results section. And then the authors gave similar discussion in 5. Discussion part. It would be better to only give observation results description in results part and further discussion in discussion part.
Other Comments:
line 110: text error.
line 137: text error. Lacking of the corresponding equation
line 144: text error.
Line 264: text error. Lacking of the corresponding equation
Line 360: 4. Discussion -> 5. Discussion
Author Response
Thank you so much for the comments,
for revised version, "Please see the attachment".
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The Comment is in the attached file.
Comments for author File: Comments.pdf
Author Response
Thank you so much for the comments,
for revised version, "Please see the attachment".
Author Response File: Author Response.pdf
Reviewer 3 Report
Paper Review on: “Alternative approach for tsunami early warning indicated by 2 gravity wave effects on lower ionosphere”. By Foroodi et al.
The authors used multiple instruments to investigate the properties of the see level displacement (SLD) and that of the induced internal gravity wave (IGW). They claim that the IGW and SLD have similar propagation properties. They indicated that the wave from the tsunami travel in an oblique manner as they travel in the atmosphere hence, the IGW wave can be detected by the receiver station ~ 25 min earlier than the tsunami itself. Therefore, the tsunami induced IGW can be used for tsunami early warning system. While is study is interest and contain some relevant ideas, the overall presentation needs to be improved and some claims are not consistent with the figures. The following are main concerns:
The introduction did not show why the study is being conducted. The Tohoku tsunami has been studied by many researchers, authors should explain what they are doing differently or the science question they intend to answer or the knowledge gap they intend to fill.
The position of the authors regarding the geomagnetic disturbance on the event day is not clear. Please discuss more about the presence of the geomagnetic effect on the results in section. Also, the conventional calm/quiet geomagnetic period is < 3 not > 5 as claimed by the authors.
Line 147: equation 6 is missing.
Figure 5 shows that PRN 18 is further away than PRN 22 and 29, hence the signal is expected to be observed at PRN 22 and 29 before PRN 18. However, Figure 6 shows that signal arrival at most stations for PRN 18 compare to PRN 29 which is closer to the source. Same problem with Figure 8. Why is that? Authors should explain in the manuscript.
Lines 241: Authors should explain how they obtained phase and meridional velocity from FFT.
I suggest author should including coordinate location in Table 1 and 2 will help readers.
The results from digisonde and RO satellite are not convincing at all in their present form.
I did not see any significant difference in the foF2 variation between the different days. This is not convincing at all as claimed by the authors.
Also, it is not clear what the authors are trying to explain at line 342 to 349. Please re-word and make better clarification and discussions for the significance of the IED profile in study.
It would be helpful if authors can overlay the day before or day after in Figure 16.
Line 368, ‘ …were significant higher than….’ This is inconsistent with Figure 13, I cannot see any obvious difference.
The discussion in the present form looks more like a conclusion. There is need for lot of improvement on this before any publication. For discussion section, I would expect authors to focus on explaining and evaluating what they found, showing how it relates to other literatures and research questions, and making an argument in support of their over finding/conclusion.
Comments for author File: Comments.pdf
Author Response
Thank you so much for the comments,
for revised version, "Please see the attachment".
Author Response File: Author Response.pdf
Reviewer 4 Report
In the present analysis the authors investigated the effects of internal gravity waves driven by tsunami on the bottm ionosphere in order to understand if vTEC can be used as earlier tsunami warning than the typical detection. They developed an interesting technique which is able to give a warning more than 20 minutes before the tsunami first detection. In my opinion, the paper is well written and the conclusion are well supported by the results. As a consequence it can be published as it is.
Author Response
Dear Reviewer,
We would like to express our great appreciation for the time you invested in reading our manuscript and your valuable comment.
Round 2
Reviewer 3 Report
Authors provided some responses to the reviewer’s concerns, but didn’t fully address other significant concerns raised as highlighted below.
The position of the authors regarding the geomagnetic disturbance on the event day is not clear. Please discuss more about the presence of the geomagnetic effect on the results in section. Also, the conventional calm/quiet geomagnetic period is < 3 not > 5 as claimed by the authors.
Authors should acknowledge that during tsunami event, the geomagnetic Kp was up to 5 unit and explain what effect this high Kp index would have on their results.
Figure 5 shows that PRN 18 is further away than PRN 22 and 29, hence the signal is expected to be observed at PRN 22 and 29 before PRN 18. However, Figure 6 shows that signal arrival at most stations for PRN 18 compare to PRN 29 which is closer to the source. Same problem with Figure 8. Why is that? Authors should explain in the manuscript.
Authors has not provided clear explanations to the point raised above. They should explain why the enhanced wave oscillation were first seen at PRN 18 (further away) rather than PRN 22 and 29 closer to the tsunami waves.
Also, the frequency of wave oscillations for PRN 29 (Figure 6) are quite different from that is PRN 18 and 22, why? This explanation should be included in the text as well.
I did not see any significant difference in the foF2 variation between the different days. This is not convincing at all as claimed by the authors.
The foF2 result, Figure 13 is still not convincing. It generally looks like a day-to-day variability. The enhancement here is not significant. It is within the range of error for the set thresholds. Authors may used error bars to prove their point though or remove the Figure entirely from the manuscript.
Comments for author File: Comments.pdf
Author Response
Thank you for your concern to clarify the mentioned issues. The comments and their responses are attached.
Author Response File: 
Author Response.docx
