A Comparison between Coastal Altimetry Data and Tidal Gauge Measurements in the Gulf of Genoa (NW Mediterranean Sea)

Round 1

Reviewer 1 Report

Comments to the Authors

This paper presents a comparison between coastal altimetry data and tidal gauge measurements in the Gulf of Genoa (NW Mediterranean Sea). The paper is clearly written but is - to my opinion - rather light weighted. Some results and issues are just presented without a deeper analysis. In any case, it contains a few interesting aspects and I recommend it for publication once the following minor points have been considered.

1. Page 1, line 17: Could you avoid writing abbreviation here. What is the RMSD?
2. Page 1, line 35: I recommend defining what does CTD stand for?
3. Page 2, line 67: Have you considered the aliasing in using the altimetry data? Could you give a short explanation about it here?
4. Page 3, line 88: Why have you chosen the FES2012? I think that there is already the newest model to use.
5. Page 8, line 234: How have you coped with datum unification when you compared the altimetric and tide gauges data? That is good if you point out something more about it here.
6. I think that the Case study should be examined a bit more in the paper.
7. I recommend to double check the English at the end.

Author Response

1. Page 1, line 17: Could you avoid writing abbreviation here. Done  What is the RMSD? It is root mean square difference
2. Page 1, line 35: I recommend defining what does CTD stand for ? It stands for Conductivity Temperature Depth but we changed with “density profiles”
3. Page 2, line 67: Have you considered the aliasing in using the altimetry data? Could you give a short explanation about it here?

Aliasing is due to the fact that tide gauge samples frequently while altimeter data every 10 days or more. This means the high frequency variability is not sampled properly. The effect is that you could have long term signals that are artifacts and not real. Nevertheless the comparison was done point to point and no spectral analysis was done on altimetry data, so there is no reason for considering aliasing.

4. Page 3, line 88: Why have you chosen the FES2012? I think that there is already the newest model to use.

It is true, but X-TRACK product provides altimetry tidal correction computed from FES2012. Tidal predictions at Genoa were performed from harmonic analysis of long sea level time-series by using Foreman method and not by using models.

5. Page 8, line 234: How have you coped with datum unification when you compared the altimetric and tide gauges data? That is good if you point out something more about it here.   We added consideration about this point in ch 2.2 lines 126-135
6. I think that the Case study should be examined a bit more in the paper.

We added some comments in ch.5  lines 339-344

I recommend to double check the English at the end. English was revised by a professional translator.

Reviewer 2 Report

Generally, I found the paper interesting and well organized, but I have one very significant question. As authors write (line 48 -50) altimetry measures the sea-level changes in the geocentric reference frame (ITRF) while the tide gauge data are referred to benchmarks on the land and direct comparison is not possible. To compare altimetry and tide gauge results one has to take into account the land movements. I would be very glad if the authors could explain if and how they corrected the tide gauge data due to land uplift?

Author Response

We added considerations about vertical land movements and why we did not correct tidal data  in ch 2.2 from line 126-135, also referring to available recent investigations.