South China Sea SST Fronts, 2015–2022
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The following is the review for:
Title
South China Sea SST fronts, 2015-2022
Authors
Igor M Belkin * , Yi-Tao Zang
Summary
The manuscript applies SST gradients, with a specific methodology, to examine fronts in specific regions associated with the South China Sea. Fronts due upwelling as well as river plumes are identified. A through analysis is doen for all the regions. Remotes sensing data set from MODIS, OSTIA are examined. I believe the paper is well written and worth publishing with what I hope are just some minor recommendations. Links should be put in the acknowledgements where the data was downloaded from.
I believe the manuscript would benefit from a discussion on how cloud cover could impact the results? Doesn’t have to be in depth, but a general description of cloud cover in the differen areas? For example is there a seasonality to the cloud cover. Another point of discussion is hwo resolution could impact the identification of gradients. Can any submesoscale fronts be identified with the current data being used.
Author Response
Response to Reviewer 1:
Reviewer 1: Summary
The manuscript applies SST gradients, with a specific methodology, to examine fronts in specific regions associated with the South China Sea. Fronts due to upwelling as well as river plumes are identified. A thorough analysis is done for all the regions. Remote sensing data set from MODIS, OSTIA are examined. I believe the paper is well written and worth publishing with what I hope are just some minor recommendations.
Reply: Thank you very much for your positive evaluation of our work.
Reviewer 1: Links should be put in the acknowledgements where the data was downloaded from.
Reply: Done.
Reviewer 1: I believe the manuscript would benefit from a discussion on how cloud cover could impact the results? Doesn’t have to be in depth, but a general description of cloud cover in the different areas? For example, is there a seasonality to the cloud cover.
Reply: The advanced cloud masking algorithm developed by JAXA specifically for the Himawari-8/9 missions allowed JAXA to produce cloud-free composites every 4 days (Bessho et al., 2016). Therefore, the cloud cover impact is insignificant. We cited Bessho et al. (2016) in our paper.
Reviewer 1: Another point of discussion is how resolution could impact the identification of gradients. Can any submesoscale fronts be identified with the current data being used.
Reply: Yes, the Himawari-8 AHI SST data have a 2-km resolution, thus allowing submesoscale fronts to be resolved. The BOA algorithm retains submesoscale features, including fronts. Thanks to the high-resolution AHI data and front-preserving BOA algorithm, our maps revealed numerous submesoscale fronts.
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Reviewer 2 Report
Comments and Suggestions for AuthorsThe study presents a high-resolution climatology of SST fronts in the South China Sea (SCS) from 2015-2022, using the AHI and the Belkin-O’Reilly Algorithm (BOA). The findings reveal complex frontal dynamics influenced by monsoonal winds, upwelling, and river outflows, with significant implications for regional oceanography and marine ecosystems. I have some few major and minor comments.
major comments.
1. The study identifies previously unreported mesoscale and submesoscale fronts—how can we verify their existence using independent datasets (e.g., in-situ observations or ECMWF model simulations)?
2. Did the study observe any long-term trends in SST fronts over the 2015-2022 period that could be linked to climate change? add it to the "5. Discussion" part.
minor comments.
line 235 "though September" should be "through September"
line 866 "surrounded with upwelling" should be "surrounded by upwelling"
line 302 "costal upwelling" should be "coastal upwelling"
line 360 "China Costal Current" should be "China Coastal Current"
line 647 "consist of " should be "consists of "
lines 77-94 try to combine all of these references into one paragraph.
All of the reference style is not MDPI style. Try use the official style guide under https://www.mdpi.com/authors/references
Line 100: It is important to point how to pre process the data. for example how were cloud contamination and other remote sensing limitations addressed when processing the Himawari-8 SST data? Just use the clear sky data?
Author Response
Response to Reviewer 2:
Reviewer 2: The study presents a high-resolution climatology of SST fronts in the South China Sea (SCS) from 2015-2022, using the AHI and the Belkin-O’Reilly Algorithm (BOA). The findings reveal complex frontal dynamics influenced by monsoonal winds, upwelling, and river outflows, with significant implications for regional oceanography and marine ecosystems. I have some few major and minor comments.
major comments.
1. The study identifies previously unreported mesoscale and submesoscale fronts—how can we verify their existence using independent datasets (e.g., in-situ observations or ECMWF model simulations)?
Reply: We carefully compared our results with various frontal maps (maps of frontal frequency and maps of SST gradients) published by our predecessors. Without any exception, all features mapped and identified in previous studies are detected and mapped in our study – with a better resolution and clarity. This excellent correspondence provides strong support for our results with regard to newly identified features (fronts, jets) that have not been reported before. Going forward (in the near future), we are going to assemble and analyze a comprehensive data base of oceanographic in-situ data to study vertical structure of oceanic fronts in the SCS and compare subsurface in-situ data with remote sensing data (SST, SSS, SSH).
2. Did the study observe any long-term trends in SST fronts over the 2015-2022 period that could be linked to climate change? add it to the "5. Discussion" part.
Reply: Given the rather limited temporal range of our data set (8 years) it would be difficult to reliably detect any long-term trend from this data set. Therefore, any discussion of climate change and its impact on SST fronts in the SCS would constitute a pure review of previous studies, whereas our paper reports original results. In the next phase of our investigation, we are going to use AVHRR SST data from 1982-2025 to study long-term variability of SST fronts in the SCS.
Reviewer 2: minor comments.
line 235 "though September" should be "through September"
line 302 "costal upwelling" should be "coastal upwelling"
line 360 "China Costal Current" should be "China Coastal Current"
line 647 "consist of " should be "consists of "
line 866 "surrounded with upwelling" should be "surrounded by upwelling"
Reply: Thank you very much for catching these typos. We fixed all of them.
Reviewer 2: lines 77-94 try to combine all of these references into one paragraph.
Reply: We believe that shorter paragraphs improve readability and comprehension of any text by facilitating visual and cognitive concentration.
Reviewer 2: All of the reference style is not MDPI style. Try use the official style guide under https://www.mdpi.com/authors/references
Reply: Done. Also, we eliminated a number of references.
Reviewer 2: Line 100: It is important to point how to preprocess the data. for example how were cloud contamination and other remote sensing limitations addressed when processing the Himawari-8 SST data? Just use the clear sky data?
Reply: The advanced cloud masking algorithm developed by JAXA specifically for the Himawari-8/9 missions allowed JAXA to produce cloud-free composites every 4 days (Bessho et al., 2016). Therefore, the cloud cover impact is insignificant. We cited Bessho et al. (2016) in our paper.
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Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsI read the revised version of the manuscript and was able to verify that all the comments I made were correctly taken into account by modifying the text or by answering my questions. However the reference style is still not correct.
For example, (Ullman and Cornillon, 1999 [18]; Ullman and Cornillon, 2001 [19]) in Line 88 should be [18,19]. Use numbers in square brackets to cite sources (e.g., [1] or [2,3] for multiple sources).
Also one minor fix:
line 71 "main coastal front off the" should be "main coastal front of the"
Author Response
Response to Round 2 Report
Reviewer: I read the revised version of the manuscript and was able to verify that all the comments I made were correctly taken into account by modifying the text or by answering my questions. However the reference style is still not correct.
For example, (Ullman and Cornillon, 1999 [18]; Ullman and Cornillon, 2001 [19]) in Line 88 should be [18,19]. Use numbers in square brackets to cite sources (e.g., [1] or [2,3] for multiple sources).
Reply: Agreed and corrected.
Reviewer: Also one minor fix:
line 71 "main coastal front off the" should be "main coastal front of the"
Reply: Corrected. Thanks for catching this typo.
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Author Response File: 
Author Response.pdf
