Use of a MODIS Satellite-Based Aridity Index to Monitor Drought Conditions in the Pearl River Basin from 2001 to 2021

Round 1

Reviewer 1 Report

Dear Authors,

the paper is well written and the topic is relevant for the scientific community.

However, I think the manuscript needs minor revisions before publishing in the Journal. I have reported my main concerns in the following:

 - The literature reviews donsn't addres the whole international community but it is mostly limited to area of study.

- The advantages and disvantages in using SbAI index instead others more common ones isn't discussed. Several studies have demostrated the superios of SPI for example. Moreover, some other used nonstationary SPI (NSPI) approach that looks very promising.

- The advantages and sidvantages of MODIS respect to others products are not highligthed

- Amy indication about various time scale, i.e. moving

 windows of 1-,3-, 6-, 9-, and 12-month, has been discussed and  its systematic impact on the results of  such studies has not been considered or evaluated.

- Do you have analyzed also drought duration, drought severity, drought intensity, drought inter-arrival time?

Author Response

Thank you for your comments. We have revised the manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Natural hazards are a huge threat to human beings. Global warming has increased the likelihood of the occurrence of floods and droughts. This study, using a MODIS satellite-based aridity index (SbAI), investigated spatiotemporal changes in drought conditions in the subtropical Pearl River Basin. The study is valuable to understand the long-term changes in wet and drought conditions in humid and sub-humid regions. Also, it could an important reference to identify seasonal droughts or water shortages in large-scale regions. The data used in this study were primarily MODIS satellite images. The imagery have been used for various climate change detection at global and regional scales before. The image quality and analysis results are also reliable. Based on the current status, I personally think, a minor revision is required before possible publication in the journal IJGI. Here are some detailed suggestions for further modification:

Major issues:

1. A detailed comparison with previous studies in the arid and semi-arid regions should make in order to find the differences in the trends of drought condition changes.

2. In the study, the authors stated that the areas with increased drought conditions are more likely impacted by human activities such as water withdrawal for irrigation and industrial uses, and fast urbanization and increased impervious surfaces and resultant reduction in water storage capacity. The authors should provide more quantitative facts in the study to support their conclusions.

Minor issues:

1. Line 258

The last one in Figure 2, SbAI changing rate is not for “Monsoon season”, it should be the “month”. And the style of the last one should be the same as the previous one.

2. Line 155-161

There are too many sentences to introduce MOD09GA; may be rephrasing this part could be better.

3. Line 492

In conclusion 1, why is June mentioned in the first sentence? the sentence mostly stated about the annual trend. Possibly, the trend in June can be moved to the sentence that discusses the monthly trend.

4. Line 461-463

The content is similar as the lines 386-389. In the discussion, the human activities in the Pearl River Delta and the land use change from 2000 to 2021 should be described, so as to prove the impacts of human activities.

Author Response

Thank you for your comments. We have revised the manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript entitled “Use of a MODIS satellite-based aridity index to monitor drought conditions in the Pearl River Basin from 2001 to 2021” has high potential with a clear and cohesive objective. The results bring innovative contributions to science that also enable applications in decision-making by managers in the most diverse areas (impacts on agriculture, economy, health, urban planning, etc.).

However, I consider that the work needs improvement, for example, the authors should better discuss the results, mainly justify the observed trends. A monthly climatic characterization, at the beginning of the results, of the variables that most contribute to the variation of the aridity index, for example, precipitation, air temperature and evapotranspiration would be interesting.

Other considerations for corrections, adjustments and additions are listed below:

1. Review and standardize citations throughout the text. For example, in the first and second paragraphs the references are cited by numbering, in the third paragraph there is the nominal identification of the authors.

2. In Figure 1, the map of the spatial distribution of precipitation appears to be the authors' results, withdraw and insert into results.

3. Insert the p-value in the table or the Z statistic followed by the statistical significance symbol. For example, the following reference can contribute to the presentation and discussion of the results:

https://0-doi-org.brum.beds.ac.uk/10.1007/s00704-019-02816-w

4. Based on the indication of the work in the previous item, it would also be important if the authors presented the magnitude and the beginning of the trend.

In view of the above, my opinion is: necessary revisions.

Comments for author File: Comments.pdf

Author Response

Thank you for your comments. We have revised the manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors answered the requests satisfactorily. My suggestion is to accept the manuscript for publication.