Estimation of Suspended Sediment Concentration in the Yangtze Main Stream Based on Sentinel-2 MSI Data

Round 1

Reviewer 1 Report

This manuscript proposed a new method for SSC estimation in the Yangtze river using Sentinel-2 data, including necessary discussion about data preprocessing, accuracy analysis and case studies. It is well-written and properly organized. However, there are still some details that require further explanations and revision.

 

1.      Line 133-134, why the temporal window is set to 12 h?  It seems too long for match-ups between the satellite and ground data pairs.

As to me, such a 12 h temporal window may contribute to the low accuracy of the SSC (MRE of 51.91%). Have you tested the SSC accuracy for a shorter temporal window (e.g., 3h) ?

2.      Line 133-134, the expression of “the spatial window to 3 pixels” is ambiguous. What’s the standard of determining matchups based on the 3-pixel window?

3.      Line 201, why the SGI threshold is set to -0.5? It requires explanation.

4.      Line 394, 3.5.1. Yibin Reach

The number of images is too few, and other important factors (such as precipitation) are excluded. Therefore, the spatial variation analysis seems not very solid.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors target to estimate SSC in the Yangtze river using Sentinel-2 data. The manuscript is very well written and the overall approach is interesting. I rate the study useful for the water quality evaluation community. I only have several minor recommendations for further improvements listed below.

(1)    Abstract: the logic linkage between the first two sentences is weak. It seems to be lack of a sentence that describing the significance of spaceborne SSC observations.

(2)    When presenting relationships, the significance level is suggested to be given (not only R2).

(3)    I recommend the authors to update the map of China with a standard one (more clear and detailed boundary).

(4)    Section 3.2: Equations (7)-(8) are suggested to be moved to the method section (also please check the numbering).

(5)    Grammar and spelling errors need to be corrected throughout the manuscript.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Very complete and interesting paper.

Some minor remarks are listed on the joined file.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf