The CNES CLS 2022 Mean Sea Surface: Short Wavelength Improvements from CryoSat-2 and SARAL/AltiKa High-Sampled Altimeter Data

Round 1

Reviewer 1 Report

       This article presents a new and more precise mean sea surface (MSS) model achieved by combining data from various missions. Special attention was paid to ensuring the homogeneity of the oceanic content and using processing techniques to enhance high-frequency data and correct for oceanic variability. The validation results show significant improvement compared to the previous model from 2015. This new sea surface model generation will aid oceanographic and climate research.

In general, the results of this manuscript are reliable, and the research is of great scientific importance. However, the writing in this manuscript is atrocious, especially since the inferior quality of the pictures; the tables are not standardized.

Line 63: Does the MP data refer to the low-frequency data from the SARAL/Altika and CryoSat-2 satellites?

Line 103: What exactly does "ocean content" mean here?

Line 115: Explain these two regional effects in detail.

Line 136: A high signal-to-noise ratio should benefit the data from satellite observations, so why does it degrade the accuracy of the estimate here?

Figure 4: The graph on the left has no vertical axis label, and the vertical coordinates here are the elevation. The information in the diagram is not clearly explained, for example, the reference to "thin lines" in line 143 is not found, and the abbreviations in the diagram should be explained.

Function 1, 2: What do ???? and ?⃗ stand for here?

Line 141: Standard writing. “emperor sea mounts chain” to “Emperor Seamount Chain”.

Line 247: What’s the kronecker's symbol mean here? What do j and i stand for here?

Function 3: What do j and i stand for here?

Figure 8: This picture should be explained in more detail here.

Line 273: Which two images are being referred to here?

Line 286: What does "LEADS" mean, and is it "leads"?

Figure 11: The locations or current zones of Gulf Stream and Kuroshio should be marked on the map. It is also for the Eurasian and Pacific plates.

Line 313: The full name should be given for the first occurrence of the abbreviation, such as PSD.

Section 4.3.: It is recommended that more detailed explanations be provided to improve the article’s readability. For example, add the formulae for "Ture SLA spectrum,” "SLA spectrum with CNES15," and "SLA spectrum with CNES22".

Line 353: “Arctic,” not “arctic”.

It is recommended that the sources of error and the degree of influence of the MSS in the Arctic be further discussed, as the area of sea ice cover in Arctic waters and the method of extraction of leads can also affect the final MSS accuracy. This is also the case for sea ice-covered areas around the Antarctic. In addition, is there evidence to confirm that sea ice cover has a loading function on the ocean that causes sea levels in these areas to differ from those in the open ocean? Finally, the reference list needs to be amended in accordance with the reference format specified by MDPI, and all image in the text is too low resolution.

Overall, the article is of high scientific value. However, in terms of the writing of the manuscript, it does not directly qualify as a formally published article, and it is recommended to revise and resubmit it.

 

Author Response

Dear Reviewer,

Please see the attachment

Regards

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,
dear editor,

the paper provides a new estimate of mean sea surface. Mean sea surfaces (MSS) are crucial for oceanographers. The new MSS comes along with a bunch of improvements compared to the previous version. Therefore, I rate the paper to be a very important step forward.

What is the reason to already publish the CNES_CLS 2022 MSS, when several aspects in coastal and arctic regions are not yet solved and finished?

Knowing the authors, I know the calculations have been carried out with the greatest care and precision possible. Therefore, I wonder why so little value has been put into the appearance and comprehensibility of the paper. It begins with an inconsistent look of the figures. These figures and your words are the signature of the paper and it seems the authors do not care much about them. I know about the hard work to make figures look great. It is a lot of work. But consider this: In the sea level (SL) community basic answers to pressing questions of our time are provided. That is why the very best of abilities should be used to showcase the results of SL- and climate research in general. Papers, conferences, media are the communication channels to communicate with the outside world. And if figures in a paper, presentation or for the media do not demonstrate that the scientists care about their work, who would want to care about the results? Therefore, I kindly ask the authors to give the figures a uniform and razor sharp appearance with equal sized text, equal sized frames for the world maps, equally looking color bars, and so on and on. The findings in the figures are the result of the work of so many scientists and engineers and have been carried out with so much care and precision. So far, the figures do not talk about this precision and care at all. There is much room for improvement.

The same holds true for the red line of the narrative that is missing in sections throughout the paper. The paper is designed with that red line in the introduction, why not pick it up in each section, show the results and bring them back to the red line?

Additionally it is of crucial importance to explain what has been done instead of writing about that it has been done. This is a major point. And the authors should ask themselves if the reader would be able to understand their argumentation.

Further, the sloppy wording at times leaves the reader lost when for example "it", "them" can have several meanings, abbreviations are not explained, "missions" are not specified, time forms are mixed and so on. It is important to be very precise with the used words to exactly describe what should be said, leaving no room for interpretation. I remember a time when scientist strived for perfection in their papers to build faith in their work. Try to follow their footsteps. Also, as I am not a native speaker myself, I know about the importance of letting a native speaker correct a paper for grammar, wording and passive voice check, before submission.

These "small" changes of red line, precise explaining, wording, and the appearance of the figures will transform the paper into the very strong paper it could be.

COMMENTS
 
- It is important especially in the introduction, abstract and conclusion to be precise about the "missions". Define them, explain them and name them for example as altimetric satellite missions instead of missions. The user might be unfamiliar in the field and would not be able to understand and follow the topic right away.

- L69-73
This is a very important section. Please explain why the period 1993 - 2012 is used as reference period.

- L85-L89
Explain the problems when using SLAs (in ice regions) from a different time span as for to the open ocean. Especially the transition between open ocean and arctic must have been treated with special care? The text is missing an explanation.

- L94-L96
The sentence leaves the reader with ample space for interpretation. Please be precise.

L119-L122
What can be done about that fact of a not continuous seasonal coverage? Or does one have to live with it, or has to be careful with the data? Explain.

- L184 and L200
2.4.1 Ocean data for validation
2.4.2 Arctic sea level data for validation
-> The captions try to distinguish between "open ocean sea level data" and "arctic ocean sea level data". Please be precise in the wording. In this case the readers wonder as Arctic sea level data is ocean data as well.

- L184
Section 2.4.1
The data used for the validation of the MSS estimates has been described. However, the validation procedure has not been discussed. The reader does not know how the validation has taken place and how the data has had to be changed or adapted after the validation.

- L200
Section 2.4.2
The validation has been described. However, the outcome has not been discussed. The referenced table 3 is not self explaining.

- L217
What denotes "r0"? Please explain.

- L259
Giving a reason for the use of the geoid model over land might be useful. How does this procedure support the use of the MSS?

- L271-L272
The sentence does not make sense. What is meant by "the points of a same MSS"?

- L273
"The two maps below"
The common way of referencing would describe the figure unambiguously. E.g. "The maps in figure X ... "

- L273-L284
Don’t the paragraphs rather belong to section 4.2 Differences between CNES_CLS 2022 and CNES_CLS 2015?

- L286
Why should the mean sea surface CNES_CLS 2022 MSS be published while parts of it are still missing?

- L367ff
The conclusions do not reflect the greatness of the work performed to produce the CNES_CLS 2022 MSS. The abstract is much stronger. Why not take the red line of the paper and finish it.


ABBREVIATIONS missing

Explain all abbreviations at first use!
This !has to be done! in order to become a strong paper. Unexplained abbreviations can be found in tables and captions as well. A few examples:
L17    MSLA
L18    SSH
L94    GFO
L96    T/P has not been explained
L121    T/P, J1, J2, and J3 ERM have not been explained yet
L313    PSD, come on it is only explained in figure 13
L458    Table SAR LRM TFMRA DAC


FIGURES

- The research within the figures is usefully chosen, however, the appearance of the figures is very poor. The letter size between figures varies greatly. It varies even within figures. It would be very useful to produce the figures using the same format of letter size for headline, x- and y-axes, units and legends.

- The resolution of all figures is too low. The authors have to find a way to implement razor sharp images. We are living in 2023 ;-)

- It would be nice if the format of the figures would match as well. Especially between the world maps. Also, a common format for the legends would be useful. So far, each figure seems to be from a different paper.

Fig 1   
The resolution of the figure is too low. The figure is not readable.
The figure is very useful and well arranged!
The letter size is too small, please enlarged!
The figure caption: Overview of the missions -> Overview of the satellite missions / or altimeter missions / or satellite altimeter missions (to be exact)

Fig 2
The resolution of the figure is too low. The figure is not readable.
The figure is very useful and well arranged!
The letter size is too small, please enlarged!
The figure caption: The global mean is missing in the caption!

Fig 3
The resolution of the figure is too low. The figure is not readable.
The letter size is too big.
The x and y label are too small.

Fig 4
The resolution of the figure is too low. The figure is not readable.
The letter size is too small
The x and y label are too small.
Parts a and b are not well arranged.

Fig 5
The resolution of the figure is too low. The figure is not readable.
The x, y and color bar label are too small.
Caption: I urge the authors to explicitly write what can be seen. In this caption the "new correlation model" is not self explaining. Please specify the model in the caption.

Fig 6
The figure is blurry. No units on the color bar. Letter size is too small, except for the headline where it is too large.

Fig 7
The resolution of the figure is too low. The figure is not readable.
The letter size is too small
The x and y label are too small.

Fig 8
The resolution of the figure is too low. The figure is blurry.
The letter size of x-, y- and color bar label is too small.
The caption is not sufficient.

Fig 9
The resolution of the figure is too low. The figure is blurry.
The letter size of x-, y- and color bar label is a bit too small.
The figure caption is rudimentary.

Fig 10
The resolution of the figure is too low. The figure is blurry.
The letter size of head line, x-, y- and color bar label is too small.

Fig 11
The figure is blurry.
The letter size of x-, y-axis and color bar can be enlarged.

Fig 12
The figure is blurry.
The letter size of x-, y-axis and color bar can be enlarged.

Fig 13
The resolution of the figure is too low. The figure is blurry.
The x-tick-lines belong to the wavelength (top-axis) and not to the wavenumber (bottom-axis)! See two different examples doi:10.5194/essd-14-1493-2022 and doi:10.1175/JPO-D-13-0153.1.

Fig 14
The letter size of headline, color bar label and unit are too large.

Fig 15
The headline is cryptic and too large in letter size

Fig 17
The resolution of the figure is too low. The figure is blurry.
The axis and color bar label are too small


TABLES

Tab 1
Is there a reason for the different appearance of table one as compared to the other tables?

Tab 3
Table 3 is not self explaining.

Tab 4
It would be useful to add the cycles of the low resolution satellite missions as well!!
Leave a space between the + in the first line: Jason-1+Jason-2+Jason-3
-> Jason-1 + Jason-2 + Jason-3
Caption: Satellite altimeter missions

WORDING selected wording corrections

L20    takes into account of altimetric noises
    -> takes account of altimetric noises (or)
    -> takes into account altimetric noises
L33    In practice, goal is
    -> In practice, the goal is
L49    propose
    -> I would use another word, e.g. present
L50    method
    -> methods
L64    High-Resolution
    -> high resolution
L67    that was used
    -> that were used
L67    used is presented
    -> used are presented
L83    between the three missions
    !! which missions do you mean? Please specify.
L103    dataset
    -> datasets
L111    relatively to the 1993 year.
    -> relatively to the year 1993.
L117    This aspect is also one of major improvement
    -> please rephrase
L159    The Table 1 shows
    -> Table 1 shows
L195    red colored noise
    -> red noise
L216    In Brief, ...
    -> In brief, ...
L239    Long Wavelength Errors
    -> long wavelength errors
L266    and it corresponding error is
    -> and the corresponding errors are
L437    Small scales features
    -> Small scale features

Author Response

Dear reviewer,

Please see the attachment,

Regards.

Author Response File: Author Response.docx

Reviewer 3 Report

The article discusses modern methods for determining MSS both in terms of noise filtering algorithms and technical methods of altimetry. The accuracy of building a new modern MSS and the reasons for it are estimated.  The new version of MSS is presented. The article will undoubtedly be useful to many readers.

The following minor inaccuracies should be corrected.

18 and 71 SSH should be defined

56 SLA should be defined here, not at line 71

Figures 4,5,12 and 17 have not enough resolution, it is need to correct

Author Response

Dear Reviewer,

Please see the attachment,

Regards.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The author has revised the manuscript according to the comments. It could be published now.