Observation of Sediment Plume Dispersion Around Ieodo Ocean Research Station in the Middle of the Northern East China Sea Using Satellites and UAVs

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents a study of a plume of material suspended in ocean water in a shallow area of southern Korea. The study combines information from satellites, UAVs, remote sensing and field measurements, which is why it is appropriate to the object of the journal and allows us to know the integration between these procedures, also over time since the initial studies. It brings some interesting methodological insights as well.

The abstract seems to be excessively long, although its content is correct. Part of the final conclusions could be summarized.

Keywords should be one or two words at most, not key phrases. Nor should the words of the title be influenced by the keywords.

The introduction is well-written and presents all the information needed to understand the study. However, the objectives of the study and its original contributions are not clearly presented at the end of this section.

In the methodology, provide version data and details of the software used, as indicated in the instructions to the authors. Indicate the size of the spatial resolution in m of the TPXO8 data in Table 1.

Water sampling using UAVs and a suspended vessel is an interesting methodological contribution. There is sufficient bibliographic information on this, so they should properly cite a source.

With respect to the measurement of SPM, the procedure used is not the usual one in this type of analysis nor the temperatures used; It would be necessary to indicate a bibliographic reference of the procedure used.

Line 292, 684, 691 it is not necessary to indicate the year of the study.

In the results section, equations are presented in the text. The calculations must be in a section of the methodology dedicated to the mathematical and statistical calculations that are appropriate, presenting the equations and with what application the information is processed (a spreadsheet or similar).

Graphic materials is interesting and helps to understad the study.

Figure 10 is interesting and could indicate the meteorological events that occurred during the measurement period, to understand how rain or cloudiness affect it. It is curious that the maximum temperatures are reached at the end of August, which could indicate meteorological stability, while between the 10th and the 16th there seems to be significant intraday variability.

In the conclusions, an introductory paragraph is not necessary, but rather to respond to the objectives of the study.

The bibliography is adequate and sufficient and only needs to be adapted to the style indicated by the journal.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a comprehensive study of the Ieodo plume, a suspended sediment feature in the East China Sea, using an integrated remote sensing approach that combines satellite (Sentinel-2, GOCI-II) and unmanned aerial vehicle (UAV) observations. The work is timely, and offers valuable insights into the plume’s characteristics, dynamics, and a proposed generation mechanism based on the Bernoulli effect. However, several aspects require further clarification, elaboration, and correction to enhance the manuscript's scientific rigor, clarity, and impact.

 

Major Comment

As noted in the manuscript, plume optical signatures vary (green vs. brown), suggesting potential contributions from different optically active constituents (e.g., phytoplankton, colored dissolved organic matter) beyond mineral sediments. Relying solely on a TSS threshold for detection may therefore be insufficient. In future work, target detection algorithms (e.g., spectral unmixing, machine learning classifiers) applied to high-spectral-resolution data could better distinguish the “Ieodo plume” signal from other water types and improve detection sensitivity, especially for weak or developing plumes. A discussion on these potential methodological advancements would greatly strengthen the outlook and applicability of the research.

 

Specific Comments

1. The abstract states the plume is "known as the leodop plume," while the main text consistently uses "Ieodo plume." Please unify the terminology throughout the manuscript, including the title, abstract, figures, and captions.

 

2. The methodology mentions using both Sentinel-2 Level-1C (L1C) and Level-2A (L2A) products. Please clarify the specific rationale for using both levels. Additionally, please explain how plume identifications made from Sentinel-2 (10 m) were spatially correlated or validated with GOCI-II observations (250 m). Was the correspondence purely qualitative/geolocational, or were there quantitative comparisons (e.g., spatial overlap statistics)? Also, please discuss the potential for GOCI-II to miss smaller plume features due to its coarser spatial resolution, and how the integrated UAV observations help mitigate this limitation.

 

3. The study uses a threshold of TSS > 10 g m⁻³ from GOCI-II to define plume presence. However, the manuscript notes that the plume appears in different colors (e.g., green or brown) in optical imagery, which may indicate varying compositions or particle sizes. Please discuss the potential limitations of using a single TSS threshold for detection. Could this threshold miss plumes dominated by organic particles or finer sediments with different scattering properties? A brief consideration of how the threshold was validated for this specific site and plume type would strengthen the methodology.

 

4. The study successfully collected surface water samples via UAV. It would be valuable to perform a statistical analysis of the in-situ SPM data (even with a limited number of samples) to characterize the range and typical concentrations within the plume area. This could help establish a more site-specific link between optical properties (from UAV/satellite) and SPM levels and inform the validation of satellite-derived TSS products in this dynamic environment.

 

5. Please discuss how the consistency between UAV-observed plume features and GOCI-II TSS maps was assessed. Were there instances where the plume was clearly visible in UAV imagery but not detected by the GOCI TSS threshold? Furthermore, a brief discussion on the known performance, applicability, and uncertainties of the GOCI-II TSS product in the East China Sea, particularly around Ieodo, would provide important context for interpreting the results. If available, cite any regional validation studies.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf