Traveling Ionospheric Disturbances Characteristics during the 2018 Typhoon Maria from GPS Observations
Round 1
Reviewer 1 Report
Comments:
*Line 54, The authors comment that the GPS observation data provides allows for monitoring the ionspheric disturbances in the case of earthquakes, perhaps they might find interesting the following reference: Yang, H., Monte Moreno, E., & Hernández-Pajares, M. (2019). ADDTID: An alternative tool for studying earthquake/tsunami signatures in the ionosphere. Case of the 2011 Tohoku earthquake. Remote Sensing, 11(16), 1894.
*Section 3 results and discussions: does a thorough analysis of the properties of the ionospheric disturbances in the time interval from 10:00 to 12:00 UT. Although the results are consistent with the trajectory of the typhoon, it might be of interest for the reader to compare the results with the traveling ionospheric disturbances of normal days. This might add value to the results in the sense that the authors might discard that the detected disturbances are not part of typical climatology of this time of the year. For instance, they should show that the typical disturbances at this time of the year, show a morphology different from the one they found for instance in figure 6.
Another question that might complete the work that is presented, is if there is an aftermath or prior activity. Do the ionospheric disturbances continue to appear when the typhoon moves away?, Is just only a burst as shown in the paper, or there are ripples left behind in the trajectory? Are there ripples that arrive in advance of the main signature?
*Line 112. The authors use a zero phase Butterworth filter, which is correct. Perhaps the authors could show the power density spectrum of the signal, mention the components of the signal and compare it with the cut-off frequencies they have selected. Thus, the reader would see clearly that the main source of energy is inside this band. In section 3.4 the authors analyze the characterstics of the discurbance spectrum, thus details of the implementation of the filter are of interest. In relation to the spectrograms shown in section 3.4, the authors should indicate also the filter attenuation specially at the lower frequency cut-off.
*Note (not necessary of this work, could be considered in future work), the zero phase filtering consists of filtering twice, in both directions, which eliminates the phase component [see Hamming, Digital Filters]. Therefore, a filter with worse phase properties, but with a better behaviour at the lower cut-off frequency than the butterworth could be considered. For instance a Chebychev or elliptic filter. This would allow for understanding a bit better what is happening arround the frequency peak at 1.6mHz.
*Line 168. The authors selected seven stations out of the 150 possible stations. Why such a low number?, Why are they clustered at the south? One suggestion for future work (not necessary for this one), is to use a higher number of stations in order to get a more dense map, and interpolate between the pierce points in order to have a local smooth distribution of the TEC changes, and be able to detect the properties of the wave fronts (i.e. wavelength, velocity, azimuth and wavelength) authomatically.
*Section 3.4. The authors show an spectrogram besides the waveform. The authors should give details of how they computed the spectrogram. In order to understand the relationship between the waveform and the spectrogram, they should specify the kind of window, and most important, the length and overlap of windows. Also the frequency analysis method, is it a periodogram, or an AR derived spectral analysis?. Is the amplitude represented in a logarithm scale?. The logarithmic scale might make clear possible components of a frequency a bit higher than 1.6mHz, that might be of interest.
*Line 233. The authors mention that reference [16] says that the peak of 1.6mHz is consistent with the gravity waves. Perhaps the authors could enrich the text, by writing a couple of sentences justifying the physical origins of this resonance.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors, please find in attachment a series of suggestions and comments, regarding your paper.
Comments for author File: 
Comments.pdf
Author Response
Response: Thanks very much for your good suggestions and corrections in English, which have greatly improved our manuscript. In the revised manuscript, we have been revised all according to your suggestion.
Reviewer 3 Report
The observation interval (10UT -12UT) is too small for analysis. In addition the typhoon eye was too close to GPS receivers during that time. You should increase the analysis interval to the time when the typhoon eye moved to the end of the trajectory in figure 1.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
Your new statement (lines 127 - 129) is unexpected and requires further detailed analysis of meteorological parameter distributions during the Typhoon Maria.
Author Response
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Author Response File: Author Response.docx
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.
