Equidistant Nodes Orthogonal Polynomial Fitting for Harmonic Constants of Long-Period Tides Based on Satellite Altimeter Data
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
In this paper, the equidistant node orthogonal polynomial fitting (ENOPF) method is employed to fit the harmonic constants of the T/P satellite altimeter data and the gridded altimeter data from the Data Unification and Altimeter Combination System (DUACS) to obtain the full-field harmonic constants of the long-period tidal constituents in the Bohai Sea, Yellow Sea, and East China Sea (BYECS). This study is interesting. However, the publication can only be recommended after major revision and solving the following problems.
1. It is recommended that the author briefly describe the relationship between tides and wave height in the introduction section, and whether there is a certain coupling relationship between them. It is believed that it is necessary to cite and discuss the following references in the article.
For example,
Peng Q, Jin S (2019) Significant wave height estimation from space-borne cyclone-gnss reflectometry. Remote Sens 11(5). https://doi.org/10.3390/rs11050584
Li W, Cardellach E, Fabra F, Ribo S, Rius A (2020) Assessment of spaceborne gnss-r ocean altimetry performance using cygnss mission raw data. IEEE Trans Geosci Remote Sens 58(1):238-250. https://doi.org/10.1109/tgrs.2019.2936108
Bu J, Yu K, Park H, Huang W, Han S, Yan Q, Qian N, Lin Y (2022) Estimation of swell height using spaceborne gnss-r data from eight cygnss satellites. Remote Sens 14(18):4634. https://doi.org/10.3390/rs14184634
2. What does the color bar in Figure 3 represent? Suggest adding a title for the color bar
3. There is an error in the numbering of the formula in Section 3. Please carefully check and revise it.
4. In Figure 12, is the unit of the number in the color bar in cm? I suggest indicating it in the diagram for the convenience of readers.
5. In the conclusion section, future research work should focus on addressing what issues and provide further descriptions.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The work presented by the authors is quite interesting and innovative, and fully meets the expectations of the journal.
However, the manuscript lacks precision and the presentation of the results is also rather difficult to follow due, in my view, to a problem with the structuring of the manuscript and also to certain lengths.
Major comments
Introduction
line 43 - add a reference concerning this sentence
Line 78-79 - add the reference Ray and Erofeeva, (2014)
line 86-89 - for the long period you can also speak about the sea level rise e.g. Lee et al., Frontier in Marine Science, 2022
line 92-93 you speak about the long-period tidal constituents (Sa, Ssa) you must explain which phenomenum is correlated to these components and why you choose only these two ones?
if I remember correctly, they correspond to meteorological phenomena!
Data and methods
line 113 you start "the study region is 117.5 - 131° E, 24-41°N" you must add some geographical infomation for example the study region is located in the china sea (117.5 - 131° E, 24-41°N), this represents a surface area of XX km2."
in figure 1 add some geographical information : yellow sea, China sea, Bohai sea, South Corea, and some city like Shangaï Dailan
Figure 1a and 1b can be merged!
Line 142-147 you used more or less X-Track as reference for coastal areas you must define the correction done (if I remenmber e.g. instrumental corrections, sea state, environmental ones, inverse barometer ...) and you must put that the processing chain was developped by CTOH and LEGOS and it is now distributed by AVISO+.
Methodological part is quite clear,
The only point that bothers me is that you have carried out various tests by varying M1 and N1 and M2 and N2 but all the maps obtained are very similar, so I don't think you must put all the maps. From my point of view , I'll put only the two extreme cases, the first map and the last, and say that the cotidal chart maps are constant for all the parameters tested, as shown in figure 5. Do the same for figure 6.
Results
line 302 - you write "RMSEs of the ENOPF method and the DUACS data are less than 2cm" this is true for DUACS data but not for ENOPF for me it is more but it is difficult because Figure 7 and 9 lacks the mean values and standard deviation for each parameters and also for each amplitudes and phases for Sa and SSA for each method/model I will first put all the Sa parameters and then all the Ssa parameters.
By doing this, Figure 8 and 10 are no longer necessary!
3.3 cotidal charts...
Line 416-417 Chaotic is not the good term, from my point of view,you can said "high frequency information" another point in the X-Track dataset it seems you have also these high frequencies! From my point of view ENOPF have a less high frequency content and smooths the data!
line 423 - you write "improving the resolution infinitely" this is for me not clear you cannot increase infinitely the resolution you are limited in terms of resolution by two factors the wavelengths of the phenomena observed and the native resolution of the data, I could be wrong, but in this case you need to be more precise and explain it better.
Still in part 3.3, the point which for me is the most difficult to follow is the part associated with figures 11 and 12, which also requires you to look at figures 2 and 3 on the X-track data.
From my point of view, I'll do something simpler but much easier to understand: I'll look at the difference map along the traces between the various models and the X-track data.
Then I'll compare the maps of the different models.
You will then need to rework your conclusion in the light of these new observations.
Minor comments
Abstract:
give numerical results that prove the interest of your method
Introduction:
line 42 - after "Accurate ocean tidal simulation" gives some references
line 54 - you write "with higher resolution" gives some numerical values (range) of these higher resolutions.
In my opinion, the manuscript needs to be reworked before it can be accepted. I therefore recommend some major changes.
line 83-84 you write "Richard D. ray build a new model..." replace by "Ray and Eroffeva (2014) build a model"
line 85 - you write "Kantha used" replace by "Kantha et al. (1998) used.."
Data and methods
line 113-114 be more precise... you write " Figure 1(a) shows the distribution of the water depth, track of satellite observation and tide gauge stations." replace by "Figure 1a shows the distribution of the water depth in gradations of blue ranging from 0 to more than 3000m, the tracks of altimetry satellite (white line) and 62 tide gauge stations (red dots) througout the BYECS. The tide gauge data and stations used in this study come from the the tide gauge network known as ......."
Line 151-153 delete this sentence is not necessary to repeat that now.
may be you can merged figure 2 and 3 - 2a X- track amplitude and 2b phase lag.
line 293-294 you write " the results obtained by the ENOPF method and the DUACS data are more consistent, and the errors of the FES2014 model and the EOT20 model are" add after "very closed which confirm the observations done by Hart-Davis et al., 2021) and "
Results
line 298-299 you can reduce this sentence : "the same observation can be done when the comparison is done with the X-track data."
3.3 Cotidal Charts of ENOPF method
line 392 you write " aresolution of 2'x2' " put using brackets the same distances in km;
line 83 : delete "new"
line 84 - delete "new"
line 108 - replace "discusses" by "highlights some conclusions and discusses...."
line 114 - replace "track" by "tracks"
line 178 - add a space after nodes
line 398 - replace gap by difference
line 398 - replace "actual measured results" by "X-track amplitude data"
line 403-404 - delete "The ET20 model .....FES2014 model" you've already said that shorten, replace by "For ET20, "
line 409 - replace "actual satellite" by "X-track"
line 473 delete "can"
Author Response
Please see the attachment
Author Response File: Author Response.docx
