Spatial and Temporal Changes of Urban Built-Up Area in the Yellow River Basin from Nighttime Light Data

Round 1

Reviewer 1 Report

Dear auhtors, thanks for an interesting reading. 

I am still unsatisfied with the exploitation of the results and their cross-referencing with, for example, the dynamics of changes in land use and land cover. The introduction develops the aspects of sustainable land planning to limit the environmental impact. This interesting aspect is unfortunately not developed further in the rest of the paper.

Main comments:

- Please improve the quality of figures (more dpi)

- Is it possible to add a figure illustring the VIIRS data? to clearly understand the main input characteristics? Like a temporal series over a growing city.

- I do not understand the relevance of the expansion direction presented in 4.3. An analysis of which LC/LU elements are being urbanized would be more intersting, like how much new pressure has been put on natural lands in each cities, etc.

Other remarks:

- L19: explain GDP accronym

- L43: please rephrase ".. the conflict of ecological between.. " 

- L61: missing space between have and demonstrated

- L93: GEE was? or is?

- Table 1 and L183: What is SLOP?

- L263: missing space after (AREA) 

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

In this work, the spatial characteristics of urban built-up area expansion were generated using the eight-quadrant analysis method and combined with the statistical data of population and GDP to analyze the correlations between the light intensity of built-up areas and population and GDP to understand the changes in population and economy in the development of urban built-up area expansion.

1. The resolution of all Figures needs to be enhanced.

2. For Fig. 2, the line chart is often used to represent the temporal changes of the study area. I would suggest authors use other types of charts for data visualization.

3. The contribution of this research is not convincing. To me, nothing is wrong, but also nothing is new.

Author Response

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Reviewer 3 Report

The authors applied NTL data to analyze the spatiotemporal characteristics of urban built-up land. The authors did a perfect textbook exercise. But we have some questions:

1.What is really truly novel in the stduy with respect to research findings in the past？I did not find it.

2.Lack of appropriate hypotheses and scientific problem in Introduction.

3.How will this study contribute beyond the current literature?

4. We have some free land use data with high resolution, but why we need to use NTL data to extract built-up land?

Author Response

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Reviewer 4 Report

The presented manuscript describes an interesting study on a relevant and important topic. For the region under study (the Yellow River basin), the expansion of the urbanized area is an urgent and significant problem. The approach using night light on satellite images has long been known and has proven itself well.

The research design is correct and corresponds to the tasks set. The authors used reliable data sources. The data is processed using modern and efficient methods. The methods are fully and clearly described. The results are well presented and qualitatively illustrated.

I think that the article can be published in its current form.

Author Response

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Round 2

Reviewer 2 Report

I have no more comments. Thanks for the revision!

Reviewer 3 Report

The response can address most of the concerns. But English neet to be further improved.