Review Reports

Round 1

Reviewer 1 Report

All the figures needed to be formatted properly. In the figures the text size and font are not consistent. Some of the data and trends are not clear. 

Language needs some improvement. 

Author Response

All the figures needed to be formatted properly. In the figures the text size and font are not consistent. Some of the data and trends are not clear.

Response: Thanks for your comments. These figures are not clear because of the low resolution inserted in the word (only 96 dpi). All the figures are revised and submitted to the Editorial Office with the JPEG formats (Font: Times New Roman, Size: >= 12) at a high resolution (e.g. 300 dpi or 600 dpi). The details for these figures can be seen in the attached figure files. The revised figures are inserted in the text of the revision.

Language needs some improvement.

Response: Thank you. The language has been improved by all the authors. Please check it in the revision with the tracking mode in word.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Editor, Dear Authors,

I went through this manuscript, which analyzes the potential effects of urbanization on precipitation extreme based on empirical and statistical analyses of historical series.

The work is well organized, well written and has an acceptable scientific interest.

To my opinion it can be accepted in its present form.

Best Regards.

Author Response

Dear Editor, Dear Authors,

I went through this manuscript, which analyzes the potential effects of urbanization on precipitation extreme based on empirical and statistical analyses of historical series.

The work is well organized, well written and has an acceptable scientific interest.

To my opinion it can be accepted in its present form.

Best Regards.

Response: Thanks for your kind comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

The article has tried to analyze the potential effects of urbanization on precipitation extremes in the Pearl River Delta Region. The subject matter is within the scope of the journal. The authors are suggested to address the following comments.

1.      The paper presented an analysis between precipitation extremes and urbanization. However, this relationship is difficult to be quantified directly, or be classified with certainty. Since, precipitation is a climatological phenomenon that is corelated with temperature, cloud formation, humidity, etc., a more in-depth analysis is required to draw the conclusions presented in the paper. Even though the findings from the current paper are useful, the authors are suggested clearly indicate the limitations of the analysis.

2.      A very similar paper titled “Impacts of Urbanization on Variations of Extreme Precipitation over the Yangtze River Delta” already exists in the same journal (Kang et al. 2021, Water, 13, 150. https://doi.org/10.3390/w13020150). Please be sure to streamline the discussion on the specific scientific contributions of this paper. 

3.      Please discuss the statistical methods used for trend analysis.

4.      Do not use abbreviations in the abstract. For example, please define SDII.

5.      In Figure 2, the significant changes at 0.05 level are not clearly visible.

Author Response

The article has tried to analyze the potential effects of urbanization on precipitation extremes in the Pearl River Delta Region. The subject matter is within the scope of the journal. The authors are suggested to address the following comments.

1. The paper presented an analysis between precipitation extremes and urbanization. However, this relationship is difficult to be quantified directly, or be classified with certainty. Since, precipitation is a climatological phenomenon that is corelated with temperature, cloud formation, humidity, etc., a more in-depth analysis is required to draw the conclusions presented in the paper. Even though the findings from the current paper are useful, the authors are suggested clearly indicate the limitations of the analysis.

Response: We agree with these comments. The relationships between urbanization and the precipitation extremes are extremely complicated. In this work, we attempt to analyze the possible impact of urbanization on precipitation extremes based on the urban-rural comparative analyses, which is relatively convenient and fast to interpret their relationships. Of course, this simple method has several shortcomings to address the complex linkage between rapid urbanization and changes in precipitation extremes. Thus, the in-depth analyses and further discussion are updated in Section 3.5. Thank you again.

For example, the limitations of our work are shown as follows:

“Overall, our findings based on the urban-rural comparative analyses in observation data are relatively convenient and fast to interpret the contribution of urbanization to the changes in precipitation extremes. Generally, this method is feasible for the region with high-density observation gauges because these dense stations can better capture the variations of precipitation extremes. Of course, there are several shortcomings to the proposed method. Firstly, the weighted-average method is used to identify the urban-rural differences, which may weaken the contribution of urbanization to precipitation extremes because the urbanization effects show obvious local-scale features. Secondly, as we all know, the role of urbanization in the precipitation extremes is associated with many factors, such as the geographical and climate contexts, spatial and temporal scales, precipitation types, and so on. Thus, it should be noted that the statistical analyses are unable to clarify the complex physical mechanism of urban-induced changes in precipitation extremes, although the quantitative results may help us to understand the possible role of urbanization in precipitation changes. Therefore, to get more insight into the underlying physical process of how urbanization affects extreme precipitation, the climate model-based dynamic experiments together with a refined analysis of high-resolution observation data are needed for future research.”

2. A very similar paper titled “Impacts of Urbanization on Variations of Extreme Precipitation over the Yangtze River Delta” already exists in the same journal (Kang et al. 2021, Water, 13, 150. https://doi.org/10.3390/w13020150). Please be sure to streamline the discussion on the specific scientific contributions of this paper.

Response: Thanks for your comments. As we mentioned in Section Introduction, several studies have paid attention to the role of urbanization in precipitation total and extremes. The work of Kang et al. (2021) is a typical one, which mainly focuses on the changes in precipitation extremes over YRD (Suzhou-Wuxi-Changzhou, six indices of precipitation extremes, during 1980-2016) and their relationship to urbanization.

The main differences can be found in the text, and the brief explanations are listed as follows:

• In our work, we exhaustively examine the spatiotemporal variations of precipitation extremes over PRD using the long-term observation data (1961-2017) and the 12 indices of precipitation
• We proposed two indicators to identify the urbanization effects on precipitation extremes, i.e. one is based on the urban-rural difference series and the other is based on the change rate of precipitation extremes during different periods (e.g. pre-urban and post-urban), but the work of Kang et al. uses one indicator.
• We assess the possible effects of urbanization on precipitation extremes from the spatial and temporal scales, but the work of Kang mainly focuses on the temporal changes. “Spatially, urbanization plays a little role in altering the spatial patterns in precipitation extremes, mainly influenced by the terrain and other geographical environment drivers. However, urbanization may induce greater variations in the distribution of precipitation extremes, with the high values tending to urban areas.”
• We investigate the relationship between urbanization levels and urbanization’s contribution to the changes in precipitation from the perspective of spatial (urbanized, urbanizing, rural) and temporal (1961-1990 and 1991-2017) scales, but the Kang’s work discusses the relationship from the spatial scale using the different urbanization stations.

3. Please discuss the statistical methods used for trend analysis.

Response: Thank you for your suggestion. The methods for trend analysis have been added in Section 2.5.

“2.5. Trend detection of precipitation extremes

In this work, three common methods, involving the linear regression, nonparametric Mann-Kendall test, and Theil-Sen’s slope method, are projected to analyze the trends of extreme precipitation indices over PRD. These methods are widely used to examine monotonic trends in hydrometeorological time series, and their details can be found in previous studies [2, 8, 14, 22, 42, 51-53]. Statistically, the significance level of trend detection for precipitation extremes is set as 0.05 for all the methods.”

4. Do not use abbreviations in the abstract. For example, please define SDII.

Response: Thank you. We revise the abstract with no abbreviations. In the revision, the SDII has changed into “the mean precipitation intensity”.

5. In Figure 2, the significant changes at 0.05 level are not clearly visible.

Response: Thank you. The significant changes are noted in the slope values of trends at a “*” sign in Figure 2. Only the SDII shows a significant increase for rural and urbanizing series from 1961 to 2017 (red solid line and number). We revise it and make it more clear.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The review comments were adequately addressed. Thank you for the efforts.