Causes and Impacts of Decreasing Chlorophyll-a in Tibet Plateau Lakes during 1986–2021 Based on Landsat Image Inversion
Round 1
Reviewer 1 Report
Please, see the attached file (review report_28122022).
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
Pang et al establish an inversion model of Chl-a concentration by combining in situ measurement of Chl-a and Landsat reflection spectrum, and further retrieve the mean annual Chl-a concentration in the past 35 years of 318 lakes in the TP. It is an interesting study and worthy to be published in Remote Sensing. However, a significant revision is needed before the paper is accepted.
1, About the reliability of the Chl-a result. The authors should give the relationship of Chl-a concentration and reflection and then give the estimation of accuracy of Chl-a concentration.
2, The relationship between Chl-a and water quality is needed. This relationship can be achieved by analyzing in-situ measurements of water quality.
3, Line 23-26, The authors give a detailed analysis of Chl-a concentration variation in different periods. My suggestion is that long-term variation of Chl-a concentration is needed.
4, The language should be greatly improved. At the present stage, there are too many errors.
I just give some examples:
Line 13-14, anthropogenic activity, human activities?
Line 20-21, with the help of geographic information system (GIS) technology and by spatial statistical analysis.
Line 30, consistent?
Line 33-34, rephrase this sentence.
Line 80, 94, its affecting factors, the influencing factors?
Line 87, inverse
Line 102 and 103, Most of the TP lakes are > 30 m deep
Line 194, 209, input
Line 270, 271, slightly, slight
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
This is a review for a study of the Chl-a in lakes of Tibetan Plateau during 1986-2021. Generally, the manuscript is written clearly and logically. The methods are commonly used in this kind of a study and are well described. The figures itself were understandable and with consistent style. I have just two main concerns:
· Start or end year should be changed to: 1986-1994; 1995-2004; 2005-2011; 2012-2021. Periods shouldn’t have overlapping years Then the question arises to which period years 1995, 2004, and 2011 belongs? Based on the figures 6 and 9, couldn’t the periods 2004-2011 and 2011-2021 be as one period (2005-2021)? Because both seems to have very little change. So, I would have only 3 periods: (1986) up to 1994; 1995-2004; and 2005 to date (2021).
· The second concern I have is concerning the salinity parameter. In freshwater lakes salinity plays insignificant role and is not considered as important water quality parameter. The range of the salinity values are not very high, so therefore it is understandable that it has no impact of Chl-a. Are the salinity values originating from one lake? The range of the values are not typical for the entire TP region. The salinity of 20-25 psu is quite high and is closer to the sea salinity than fresh lake water. Therefore, also the references used here are about the sea (134 and 135).
I have some small suggestions and comments:
Line 76: instead of “in site” should be “in situ”.
Fig. 3: Font should be larger for the text.
Fig. 4: Add units to the axes and make the font larger. And Lucky for the one high Chl-a value in both sets. Just wondering what the results would be without those points?
Fig. 5: Make the fonts larger of the axes. The Latitude subfigure y-axes is upside down and statistics are not readable.
Fig. 6: Make the fonts larger of the axes.
Fig. 7: Make the fonts larger of the axes of the subfigure.
Line 260: Already LSWT are already written out on line 136, no need to do it here again.
Figs. 10 and 11: Make the fonts larger of the axes. The y-axes of Chl-a subfigures should be on the same scale.
Line 309, 315, 351, 352, and 378: delete an extra space.
Fig. 12: Make the fonts larger of the axes.
Lines 349-352: The abbreviations should in the brackets not the full names.
Fig. 13: Nice figure but play with transparency is not good (it is actually white colour), but it makes the reading of the figure impossible. Go with just red or blue. The title of the figure is not explanatory enough.
Line 388-396. This paragraph is confusing.
Fig. 14: Make the fonts larger of the axes.
Line 412: Should be “Secchi”
Line 418: “In situ” should be in italic.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
This paper is mainly about using the Landsat images to build an inversion model to detect Chl-a concentration and finding the causes leading to the changes of the lake Chl-a concentration in TP. The Google Earth Engine was used to manage the remote sensing image series, which would save time. The structure of this paper have been well organized and the details of the methods have also been conveyed to us clearly. However, there are still some issues existing in the paper.
First, in the Fig.1, the lake whose area is larger than 10km2 should be well-marked, because those lakes are the main research objects. Second, the details about depart the whole time series into 4 parts need more word. Because large part of the context is connected to this conclusion, especially the causes analysis. Third, many environmental factors were analyzed, but which is the first cause or causes?
The important results in the Figure are supposed to be well-marked and the spatial distribution of the environmental factors need to be more clearly. The PCA, for example, could be used to find the important causes of the changes.
The paper just needs minor adjustment and it will be more reasonable after that.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Unfortunately your ms. still contains several flaws and inaccuracies, and therefore you have to improve it before acceptance. One example: no-one can believe that the lakes in TP have only two trophic levels. For sure there are more trophic levels such was indicated in my first review report.
Author Response
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