Drought Monitoring over Yellow River Basin from 2003–2019 Using Reconstructed MODIS Land Surface Temperature in Google Earth Engine

Round 1

Reviewer 1 Report

The paper proposes the use of the Annual Temperature Cycle model to calculate drought indices in the Yellow River basin. The theme is relevant in a context of climate change and large-scale analysis. Some improvements are needed before final acceptance for publication.

Lines 82-85: It is not clear why “normalization methods are less affected by external environments”. Which characteristics of the VCI and TCI can “reduce the uncertainty in drought monitoring”?

Line 100: What’s “ecosystem of the drought”? This expression deserves a short explanation.

Line 114: The meaning of ATC should be written the first time it appears in the text.

Affected area of the Yellow River seems to be a particular region inside the Yellow river basin. The authors could explain what’s the affected area of the Yellow River.

Lines 204 and 205: the number of tables 2 and 3 are wrong. The right numbers are 3 and 4.

Figure 2: I don’t understand why it is called fitting triangle. In fact, the geometric shape is a trapezoid.

The authors could improve the description of the determination of a, b, c, d in Equations 3 and 4.

Line 276: “different differences” sounds strange.

In figure 4 (b, d, f), the unit in axis x is °C, but TCI, VHI and TVDI are nondimensional.

Lines 318-320: the authors should explain why “ATC model is more sensitive to the changes in drought” and consequently why “the ATC LST data can be used to more effectively monitor the regional drought status and its change trend”.

Line 335: R² is coefficient of determination?

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Major:

1 – The introduction section is a little bit lacking in proving the most recent studies in the area of drought monitoring. I suggest adding the following literature and providing some discussions about the differences and similarities of the results achieved by this study and the findings of these articles.

Jiang, S., Wei, L., Ren, L., Xu, C. Y., Zhong, F., Wang, M., ... & Liu, Y. (2021). Utility of integrated IMERG precipitation and GLEAM potential evapotranspiration products for drought monitoring over mainland China. Atmospheric Research, 247, 105141.

Gavahi, K., Abbaszadeh, P., Moradkhani, H., Zhan, X., & Hain, C. (2020). Multivariate assimilation of remotely sensed soil moisture and evapotranspiration for drought monitoring. Journal of Hydrometeorology, 21(10), 2293-2308.

Chen, S., Zhang, L., Zhang, Y., Guo, M., & Liu, X. (2020). Evaluation of Tropical Rainfall Measuring Mission (TRMM) satellite precipitation products for drought monitoring over the middle and lower reaches of the Yangtze River Basin, China. Journal of Geographical Sciences, 30(1), 53-67.

2 – I suggest that the authors provide more discussion and justification for the novelty of this study. Numerous research has been done over the past few years in the area of drought monitoring by comparing and contrasting various drought indices. Especially since the study area is not that large. The same calculations can be performed over the entire mainland of China, without a dramatic increase in the computational burden, and significantly enrich the contribution of the article.

3 – The authors can explain more about the rationale behind choosing this set of indices. What are the advantages and disadvantages of these compared to SPI and PDSI and has been mentioned in the introduction section?

4 – Again to further enrich the discussions provided, I suggest comparing their results with SPI and/or PDSI and provide a detailed explanation on significant differences if any.

5 – Why NDVI was chosen from Aqua satellite while LST is from Terra? Please provide some reasoning.

6 – MODIS LST is also available at 8-day (MOD11A2 or MYD11A2) period with so much fewer NoData pixels, have the authors considered using that to tackle the sparsity of LST data?

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

See the attached file for my comments

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors have fully addressed my comments and I suggest the publication of the manuscript in RS.

Author Response

Dear reviewer,

       Thanks very much for your kind work and consideration on publication of our paper. On behalf of my co-authors, we would like to express our hreat appreciation to editor and reviewers.

       Thank you and best regards.

       Yours sincerely,

Dr. Haoming Xia

Institute: College of Geography and Environment, Key Laboratory of Geospatial                    Technology for Middle and Lower Yellow River Regions, Henan Key                          Laboratory of Earth System Observation and Modeling, Henan                                University, Kaifeng 475004, China

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