Surface Currents Derived from SAR Doppler Processing: An Analysis over the Naples Coastal Region in South Italy

Round 1

Reviewer 1 Report

My previous comments have been well addressed through revision. 

Author Response

Thank you for the positive evaluation and for the time and comments provided to us to improve the work.

Reviewer 2 Report

The paper can be accepted for publication. 

Author Response

Thank you for the positive evaluation and for the time spent with our work.

Reviewer 3 Report

< Specific comments>

The manuscript "Surface currents derived from SAR Doppler processing: an analysis over the Naples coastal region in South Italy " is within the scope of Journal of Marine Science and Engineering.

In this study authors investigate the combined use of both Envisat calibrated amplitude and Doppler data, in conjunction with hindcast wind information from meteorological models as well as wind and wind-Doppler models developed for C-Band systems. And, used this data to perform an integrated analysis aimed at interpreting the surface currents measurements derived by the Doppler analysis. The issue of ocean current is a very increasingly important issue in oceanography.

Although the authors have modified the manuscript based on the previous review comment already. But, in the manuscript and data still are not well presented. Especially, the data is very insufficient. The main comment include:

1.In this study, the selected data utilized refer to the period 2004-2010. However, this data is already 10-16 years ago. Is the current marine environmental condition the same as 10-16 years ago? The author should reinforce the reasons for choosing the period 2004-2010 data for analysis.

2. In this study, the author has mentioned "for this area it we addressed the use of an ENVISAT data archive composed by 47 images acquired over an ascending orbit in the period from 2002 to 2010" in section 6. But I don't understand why only 47 images in the period from 2002 to 2010 are used?

3. The author is a total of 5 images that have been selected for the subsequent numerical analysis on the Doppler characteristics (2004: 2 images; 2005: 1 image; 2006: 1 image; 2010: 1 image;). Is the amount of such data very insufficient? How representative and explanatory power are these analysis results?

4.Discussion: this manuscript is not have discussed section. Although the authors have added some discussion content in section 7: result of the manuscript. But, these contents are very insufficient. the R1- suggestions have not been appropriately corrected or answered. For example, this journal has an international audience. How does the international audience basin view these results? How do these translate to other world oceans? etc.

Author Response

 

COMM.: Although the authors have modified the manuscript based on the previous review comment already. But, in the manuscript and data still are not well presented. Especially, the data is very insufficient. The main comment include:

COMM. 1: In this study, the selected data utilized refer to the period 2004-2010. However, this data is already 10-16 years ago. Is the current marine environmental condition the same as 10-16 years ago? The author should reinforce the reasons for choosing the period 2004-2010 data for analysis.

ANS: we have added in the abstract (line 32) what already specified at lines 436-440 of the revised version, that this work contains a case study aimed at presenting a methodology for the analysis of Doppler derived surface current measurements. Our aim is neither to discover/describe/explain any specific behaviour of the currents in the Gulf of Naples, nor to perform statistically significant analysis for the validation of any model. We have already specified in the last review the motivation for choosing the Envisat data with respect to Sentinel-1 or current X-Band sensors (i.e. the operation mode and the swath coverage).

In order to address the comment of the reviewer regarding the variability of the oceanographic features we underline that, the water circulation in the area has been described in details from the late 90’s revealing the main current patterns were unchanged during the last decades. The only variability was the seasonal one as reported in Pennetta et al., (1998), Romano et al., (2010)  and in Iermano et al., (2016).

Honestly, we do not understand the benefit of the specification about the present sea current regime. In other words, if the sea current regime or meteorological condition are changed, the observation would change but the methodology could be anyway applied, hopefully providing and explanation of the observation based on the wind information derived from the models.

Pennetta, A. Valente, D. Abate, G. Boudillon, T. De Pippo, M. Leone, F. Terlizzi, Influenza della morfologia costiera sulla circolazione e sedimentazione sulla piattaforma continentale campanolaziale tra Gaeta e Cuma (Italia meridonale), Bollettino Società Geologica Italiana, 117 (1998), pp. 281-295. (In Italian)

Romano, A. Ausili, N. Zharova, M. C. Magno, B. Pavoni, M. Gabellini, Marine sediment contamination of an industrial site at Port of Bagnoli, Gulf of Naples, Southern Italy, Marine Pollution Bulletin, Volume 49, Issues 5–6, 2004,Pages 487-495,ISSN 0025-326X, https://doi.org/10.1016/j.marpolbul.2004.03.014.

Iermano, I.; Moore, A. M. and Zambianchi, E. Impacts of a 4-Dimensional Variational Data Assimilation in a Coastal Ocean Model of Southern Tyrrhenian Sea. J. Marine Syst., 2016, Vol. 154, pp-157–71.

 

COMM. 2: In this study, the author has mentioned "for this area it we addressed the use of an ENVISAT data archive composed by 47 images acquired over an ascending orbit in the period from 2002 to 2010" in section 6. But I don't understand why only 47 images in the period from 2002 to 2010 are used?

ANS. In the revised version we already specified that the period 2002-2010 cover almost the whole operative live of the ENVISAT sensor, which has been chosen for the peculiarities discussed in the answer to the previous comment. We have also clarified that, on ascending orbits, 47 were the available acquisitions covering, at best, the area of interest. We believe that this number provides an indication, even though rough and relative, of the number of cases of interest with respect to the total number of available scenes.

 

COMM. 3: The author is a total of 5 images that have been selected for the subsequent numerical analysis on the Doppler characteristics (2004: 2 images; 2005: 1 image; 2006: 1 image; 2010: 1 image;). Is the amount of such data very insufficient? How representative and explanatory power are these analysis results?

ANS.: On the dataset, we found 5 images showing considerable backscattering levels and interesting Doppler patterns. Then we have just discussed the situation that comes to light from results by applying the said methodology. We are not sure what the Reviewer intends with “very insufficient”: As already specified in the answer to the first comment, we further stress the work intend to discuss a case study for a proposed methodology for the analysis of surface current measurements. To this aim the data are, to our opinion, sufficient.

COMM: 4: Discussion: this manuscript is not have discussed section. Although the authors have added some discussion content in section 7: result of the manuscript. But, these contents are very insufficient. the R1- suggestions have not been appropriately corrected or answered. For example, this journal has an international audience. How does the international audience basin view these results? How do these translate to other world oceans? etc.

ANS.: As specified in the work, differently from application of SAR to wind and waves, surface current measurements derived by Doppler analysis are somehow of difficult interpretation. We have presented a methodology for the analysis of surface current Doppler measurements and we have discussed the results pertinent to a case study. We have specified in the discussion that tests and efforts are suggested as further development, especially in areas characterized by the availability of independent surface current measurements. We have not addressed the geophysical analysis of specific current observation that could be extended to oceans in the World but we believe that, hopefully, we have provided to the international audience a step of innovation toward the analysis of SAR Doppler measurements over sea regions.

Round 2

Reviewer 3 Report

< Specific comments>

The manuscript "Surface currents derived from SAR Doppler processing: an analysis over the Naples coastal region in South Italy" is within the scope of Journal of Marine Science and Engineering.

The authors have modified the manuscript based on the previous review comment already. Data, results, and discussion, etc. are well presented in the manuscript. However, I suggest the author proceed the English language and style are fine/minor spell check for the manuscript before publication.

Author Response

Thank you for the positive response and also for the suggestion to improve English style. We provided a new revised version with English language refinements.