Increased Warming Efficiencies of Lake Heatwaves Enhance Dryland Lake Warming over China

Round 1

Reviewer 1 Report

1.The article selected lakes in China as the case study, but did not find out how the lakes were identified, what is the area of the selected lakes and what is the sample size?

2.I don't see a clear division of climate zones in Figure 1(a), please check again.

3.The article only examines the effect of summer lake heat waves on lake warming, while in the context of continued global warming in the 21st century, lake heat waves will begin to span multiple seasons, and some lakes will even reach permanent heat wave status. For this reason, a single discussion of the effect of summer lake heat waves on lake warming is clearly poor.

4.Before using Air2water, training and validation of the model should be carried out so that it can be demonstrated that the model can be effectively used to simulate lake surface water temperature in this paper.

5.The lack of validation of lake heat waves allows for an assessment of the model's ability to simulate lake heat wave events by comparing simulation results with satellite observations.

6.There is an error in the formatting of line 281, also check the full text for errors.

7.The article lacks a description of the discussion section, which is a serious mistake.

8.Native English still needs to be upgraded by a native language professional.

9.The format of references still has errors, please pay attention to check.

Author Response

Thank you for your efforts to this manuscript. We highly appreciate you for the insightful comments and constructive suggestions, which enabled us to significantly improve our manuscript's quality. Point-by-point responses to each comment are provided in the following pages (original comments in black and our responses in blue).

We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in the Remote Sensing.

Best regards,

Yuchen Wu and Fei Ji

Author Response File: Author Response.pdf

Reviewer 2 Report

In the context of global warming, high temperature and heatwave have received widespread attentions. This manuscript studies the warming efficiencies of lake heatwaves on lake water temperature, and finds that the lake heatwaves in dryland of China are stronger than those in humid regions. However, there are some questions that the authors need to answer.

1. The author used ERA5 data with a resolution of 0.25 ° for long-term data simulation calculations. How did the author consider the impact of low spatial resolution of ERA5 data on the recognition ability of smaller lakes?

2. Please explain the meaning represented by the colors in Figure 1(a). Is AT an abbreviation for air temperature in Figure 1(b)? Please provide a clear definition.

According to my understanding, Figure 1(b) depicts the air temperature growth trend from 1950 to 2020, with different climatological annually averaged AI values. That is to say, this is actually the trend of temperature changes in different locations classified by AI values within China. I think the authors need to provide a clearer explanation of Figure 1(b) in the text.

3. In Figure 3(a), there is a very significant stage difference in temperature anomalies before and after 1990. In addition, interannual fluctuations in temperature anomalies are more pronounced. I hope the author can briefly explain the reasons in the article.

4. Line 241, ‘……(a) Time series of mean summer LSWT (blue) and air temperature (red) anomalies……’, Is the air temperature here only the temperature at the location of the lake?

5. The title of Figure 4. ‘……The left column shows the time series changes in the four climate zones. The red line in the left column represents all lakes in China, while the blue line shows lakes with significant trends in both LSWT and air temperature (p value < 0.1). The solid circles 264 represent significant LSWT trends.’  Please carefully check if this explanation is incorrect? I was a bit confused when comparing the figures and text explanations.

Furthermore, does the blue and red in Figure 4(e) completely overlap? The red and blue dashed lines in the graph represent trends. Are the solid red and blue lines the average temperature? How should the significance represented by the solid blue line be understood?

6. Figure 7. The annual total duration of lake heat waves fluctuates greatly on a time scale. Would drawing a total trend line or a phased trend line in the figure 7 be more helpful in analyzing its changes?

7. Lines 307-309. ‘……In terms of regional distribution, the total duration of lake heatwaves was most extensive in southern China's humid region and Xinjiang's desert region.’ What is the evidence for this statement?

8. The author needs to pay attention to the font type and size in the Figures.

Author Response

Thank you for your efforts to this manuscript. We highly appreciate you for the insightful comments and constructive suggestions, which enabled us to significantly improve our manuscript's quality. Point-by-point responses to each comment are provided in the following pages (original comments in black and our responses in blue).

We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in the Remote Sensing.

Best regards,

Yuchen Wu and Fei Ji

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript entitled "Increased warming efficiencies of lake heatwaves enhance dryland lake warming over China" provides an in-depth analysis of the impact of climate change on Lake Surface Water Temperatures (LSWTs) in China, with a particular emphasis on lake heatwaves.

This research underscores the vital importance of lakes within ecosystems and highlights a global trend of increasing LSWTs, a phenomenon more acute in arid regions than in their humid counterparts. The study introduces the concept of lake heatwaves—periods of abnormally high LSWT, which are pivotal in assessing climate impacts on lacustrine environments.

The paper aims to dissect the patterns of LSWT across different Chinese climatic zones from 1950 to 2020, employing satellite LSWT data alongside the air2water model. It delves into the summer LSWT trends within various zones and examines how lake heatwaves influence these patterns.

The findings reveal a distinct trend of rising LSWTs, notably in the dryland lakes of central Inner Mongolia, with lake heatwaves showing increased frequency and severity, particularly in semi-arid locales. The study identifies these heatwaves as a significant driving force behind the amplified warming of LSWTs, with these events being more intense and enduring in arid regions. A positive feedback loop between lake warming and heatwaves, which exacerbates dryland LSWT warming, is also uncovered, emphasizing the heightened susceptibility of these lakes to climatic shifts and elevated greenhouse gas levels.

While the study implies that dryland lakes have a higher 'warming efficiency' during heatwaves—presumably quantifying the change in LSWT relative to air temperature changes and suggesting a greater sensitivity of these lakes to air temperature fluctuations during such periods—the concept itself requires clarification.

However, the paper's methodological framework and data analysis remain opaque.

1. The criteria for the selection of satellite data needs to be scrutinized. The specific lakes studied, the time span covered, and the spatial resolution are critical details that must be transparent and justified. Furthermore, the techniques for processing this data—addressing noise, gaps, or anomalies—and the influence of these methods on the outcomes warrant a comprehensive explanation.

2. The approach to managing discrepancies in spatial and temporal resolutions needs elucidation.

3. The study should expand on the assumptions within the air2water model—how it represents lake dynamics and its appropriateness for the lakes in question. A discussion on the limitations of the model and their possible effects on the study's conclusions is essential.

4. The methodological soundness of the research should be assessed. Details on how the integration of satellite data with the air2water model serves the research objectives are necessary, along with a consideration of alternative methodologies.

In sum, to affirm the study's validity and its contribution to our understanding of climate change effects on lake temperatures, a rigorous examination of its methodological choices and analytical procedures is imperative.

Author Response

Thank you for your efforts to this manuscript. We highly appreciate you for the insightful comments and constructive suggestions, which enabled us to significantly improve our manuscript's quality. Point-by-point responses to each comment are provided in the following pages (original comments in black and our responses in blue).

We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in the Remote Sensing.

Best regards,

Yuchen Wu and Fei Ji

Author Response File: Author Response.pdf

Reviewer 4 Report

This is an excellent high merit paper, and I find it highly suitable for publication.

Figures are very good, analysis is very good and extensive of lake temperature and trends in China for many decades, showing a clear warming signal.

Methods and analysis are excellent.

My only minor comments to address are:

Please elaborate a bit more on the potential ecosystem impacts of "lake heat waves" -- in the oceans coral reefs and other things are impacted, I am assuming that lake heat waves could also tip ecosystems such that fish species are impacted etc

Please discuss potential sources of error in satellite lake temperature retrievals.

Please elaborate more in the conclusion on the heightened sensitivity of dryland lakes to air 419 temperature changes during heatwaves. Hypotheses for WHY the dryland lakes are more sensitive. Is it the combined increase in solar heating of the water in addition to the transfer of higher air temps to the lakes?

Author Response

Thank you for your efforts to this manuscript. We highly appreciate you for the insightful comments and constructive suggestions, which enabled us to significantly improve our manuscript's quality. Point-by-point responses to each comment are provided in the following pages (original comments in black and our responses in blue).

We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in the Remote Sensing.

Best regards,

Yuchen Wu and Fei Ji

Author Response File: Author Response.pdf

Reviewer 5 Report

The manuscript presents an interesting topic related to lake surface temperature changes in China. It is well organized and the findings are clearly presented. However, some additional issues should be considered before final publication. 

1. The manuscript shows many figure related to different metrics. It will be better to show the values with a colorbar with different colors but not a single hue.

2. Some necessary definition of the Nash-Sutcliffe efficiency index should be provided in the manuscript. Meanwhile, the structure of the air2water model and also its inputs should be introduced too.

3. How to get the aridity index in this study? It is based on which product. Have you considered the changes of this index over the study period?

4. For the estimation of the lake heatwaves, how do you consider the LST gaps induced by cloud cover in your study?

5. About the uncertainy of LSWT estimation over the TP, I think it should be related to the uncertainty of air temperature in this region. The observational uncertainties you indicated should be explained further. In Figure 2, there is no legend to show the content of this figure.

6. The modest resurgence cannot be clearly observed in Figure 3. In contrast, I think there is a continuous decline from 1955 to 1993.

7. Similar as Figure 2, the subfigure should provide the content in the figure but not only in the caption. Please check similar problem in other figures.

8. L254-258: I don't know what you want to express in this sentence. It shows limited connection with the LSWT warming at different climatic zones.

9. There is no LSWT information in the semihumid region in Figure 4. Meanwhile, there are different expressions for the third region with subhumid and semihumid.

10. Figure 5: It is hard to get the actual meaning of lake abundance and lake coverage. Please use another terms in the figure.

11. Why the analysis in section 3.4 focuses on the dryland LSWT warming? There is no obvious difference when compared with other zones.

12. For Figure 6, it will be better to show the lakes in one figure but with the boundaries of different climatic zones.

13. About the lake warming, some discussions should be added about the impact from lake size on the warming rate. Meanwhile, there are studies have drafted the changes in lake carbon dioxide (10.59717/j.xinn-geo.2023.100025 ) and nitrogen (10.1016/j.xinn.2021.100158), whether there are some inner connections between them. 

The langugage is fine. 

Author Response

Thank you for your efforts to this manuscript. We highly appreciate you for the insightful comments and constructive suggestions, which enabled us to significantly improve our manuscript's quality. Point-by-point responses to each comment are provided in the following pages (original comments in black and our responses in blue).

We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in the Remote Sensing.

Best regards,

Yuchen Wu and Fei Ji

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Better version. 

Thank you for your hard work and dedication in refining your manuscript. I am confident that your efforts will be well-received by the academic community, making a valuable contribution to the field.