Characterizing Temporal Dynamics of Urban Heat Island in a Rapidly Expanding City: A 39 Years Study in Zhengzhou, China
Round 1
Reviewer 1 Report
The authors use meteorogical data to analyzed the temporal changes of the UHI effect and the relationship between the UHI effect and indicators of rapid urbanization in Zhengzhou. The research is innovative and valid. However, there have some problems need to be revised.
Major problems:
1.Clarify the concept of research object. Firstly,there have two keywords(urban heat island and urban warming) in this manuscript. Secondly, the authors intend to answer the research question of changes in urban climate and UHI with rapid urbanization in line 80. Thirdly, the authors illustrated this study examine the long-term urban heat island and climate change in line 107. What's the difference between UHI and urban warming, urban climate , climate change. If they are the same , please united the name . If they are different, please discuss the difference of them.
2.In study area, the authors should explain the special reasons of choosing Zhengzhou city as an example. Such as the urban-rural dual structure is obvious. It is not suitable to introduce the basic information in study area.
3.The urban heat island intensity should be introduced detailed in line 134-135. For instance, the authors should explained the situation when UHII >0,<0 or =0.
4.In results section, the authors only illustrated the basic regular in figures, it is lack of analyze deeply.
5.In 4.2 and 4.3, the authors can compare the temperature-based temporal dynamics of UHI intensity and diurnal variations in atmospheric UHI intensity across the four seasons in urban area with rural area. It can rich the research workload.
6. The countermeasure, suggestion and outlook should be supplied.
Minor problems:
1.The China should be included in keywords.
2.The authors illustrated the urban population will exceed 66%, the specific region should be supplied in line 42.
3.The surplus '.' should be removed in line 59 and line 241. The 6,2m should be revised to 6.2m in line 111. In line 161, the authors illustrated two weather stations' temperature data indicate that the cities are warming up quickly. However, there only have one city in this research.
4.The 3.4 Analysis methods and tools can be integrated into results. For example, we measure the correlation coefficients for urbanization data and atmospheric by SPSS 26.
5. Maybe *** represent the correlation is significant at the 0.01 level, ** represent the correlation is significant at the 0.05 level, and * represent the correlation is significant at the 0.1 level.
6.Some sentences is lack of logic in line 291-295.
7.Is the urban expansion indicator same as the socio-economic development. If they are the same. I suggest integrate conclusion 3 and conclusion 4 into one conclusion.
8.In section 4.4 the correlation between atmospheric UHI intensity and urban socioeconomic growth. The authors should explain the relationship of population,population density,GDP ,urbanization rate and built-up area with atmospheric UHI intensity. For example, according following references we can know the built-up area expand can enhance PM2.5, while the PM2.5 have a impact on urban heat island.
Spatial and temporal heterogeneity of urban land area and PM2.5 concentration in China. Urban Climate,2022,45,101268. doi:https://doi.org/10.1016/j.uclim.2022.101268.
A Specific Study on the Impacts of PM2.5 on Urban Heat Islands with Detailed in Situ Data and Satellite Images. Sustainability,2019,11(24),7075. doi:https://doi.org/10.3390/su11247075.
The authors could refer to the relevant references to illustrate the relationship of population,population density,GDP ,urbanization rate with atmospheric UHI intensity as follow:
Differences between the daytime and nighttime heat island intensity from the perspectives of sea–land breeze and local climate zones. npj Urban Sustainability doi:10.1038/s42949-022-00055-z.
Author Response
Dear reviewer, Dear editor,
We appreciate the time and effort that you dedicated to providing feedback on our
Manuscript. We are grateful for the insightful comments and valuable improvements
to our paper.
We have discussed all comments carefully and have made the conscientious correction.
Revised parts are marked in the new version. The main corrections in the paper and the responses to the reviewers' comments (red words) are in a flowing attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper is very well structured and the theme is well described. The conclusions are clear and the references up to date. The paper can be published in its current form.
Author Response
Dear reviewer, Dear editor,
We appreciate the time and effort that you dedicated to providing feedback on our Manuscript. We are grateful for the insightful comments and valuable improvements to our paper.
Reviewer 3 Report
There's some very interesting research here, but not yet framed in a way worthy of publication. with some significant rewrites and a little more information added this will be a very good paper.
Abstract
19-21: This is a sentence fragment, I suggest removing the period on line 19 to combine with the previous sentence.
28: I don't know what you mean by "due to the specificity" of Chinese cities. I'd remove the phrase in quotes, or replace it with ", specifically for Chinese cities".
Introduction
35: I suggest you change "since this summer" to "In the current summer of 2022" since readers of the future shouldn't have to look up the date of publication.
41: I wouldn't suggest that urbanization affects climate change so much as it affects how the population experiences climate change.
44: replacement of the natural surface layer is redundant with the expansion of urban impervious layers. I would suggest replace "surface layer" with "vegetation", which in my opinion is not mentioned enough in this paper.
59-60: studies don't show that UHI is measured via surface or atmosphere; instead you should say that studies typically divide into atmosphereric and surface UHI. Then IMEDIATELY define what you mean by this. What you refer to as "atmospheric UHI" is measured by themometers located some distance above the ground, while what you refer to as "surface UHI" is measured by satellite. Both involve huge misconceptions that most papers (including this one) often fail to discuss. Most people believe that a thermometer exposed only to air is only measuring air temperature, but in fact it is also measuring the thermal infrared environment, and will register a higher temperature if near a large warm object, even if the air temperature does not change. This is why it is good you are using official weather stations: they are all placed in wide grassy fields (or should be) so that the infrared influences are standardized. Surface temperature measured by satellite suffers an even more obvious fault: for a city, much of what you are looking at is rooftops! This is not representative at all of what people experience. You should discuss these differences and emphasize the importance of using the standard placement of thermometers as you do in your work.
61: you mention boundary layer UHI, but never define it. Either don't mention it or explain it in more detail, particularly how it is measured. I believe it is rarely measured, but instead inferred from the output of high resolution weather models.
61-62: this sentence is redundant with the first sentence in the paragraph, awkwardly worded, and strangely placed after some discussion of different aspects of UHI. I suggest deleting it or attaching part of it to the first sentence of the paragraph.
76: the sentence beginning "In particular" is a fragment and should be revised. The preceding sentence is confusing because in this paper "temporal" refers to climate scale of decades, while here it happens to refer to the diurnal scale. Rewrite.
77: "Two Approaches" refers to two different ways to achieve the same goal. But in this case you are merging two types of analysis. It should be reworded.
80: for 1) I think you mean: "What kind of changes in urban climate and UHI are observed with rapid urbanization in Zhengzhou?"
82: for 2) I think you mean: "What are the differences of daytime UHI compared to night time UHI?"
Study Area
90: do you mean population density (people/area) or total population?
Material and Methods - do you really need to say "material"? Perhaps "Data Sets and Methods" is a better title.
108: I think "temporal trends" is more applicable than "temporal variation"
117-120: It would be helpful to the reader to briefly describe the beginning and end states. fore example the urban station went from "low plants" to "campact high-rise"
124-125: terms such as urbanization index and urbanization rate need to be defined. They are not defined in appendix A3 either.
149-150: Instead of "More values of UCR..." write "Higher values of UCR..." But the bigger problem is the interpretation given. Basically if the UCR = 1 then the built up perimeter is a circle, and UCR can never be less than 1. Higher values of UCR indicate a lack of compactness in the urban pattern, and I don't understand how this is interpreted as "greater urban built-up land occupancy". I'd also need to know how the perimeter is defined.
150-151: the first phrase of the sentence "If the urban land outreach changes in the form of infill," is awkwardly phrased. Not sure if I can do better, perhaps "If areas between urban peninsulas protruding from the perimeter fill in,"?
154-158: Here should be a sketch of what you will do in the next section: plots of annual average UHI versus time; UHI calculated at different times of day versus time, which scatter plots will be performed, etc. Also, since only very basic statistics is being applied, there is absolutely no reason to mention that R and Excel are being used. That's like mentioning which brand of hammer you are using to build a house: nobody cares because all basic tools are the same.
Results
167-168: I'm not sure it's fair to compare Zhengzhou to the global land trend. If you can pick out a similar latitude band it would be better, though such information may be hard to come by. If you can't find it, it's okay.
Figure 2: the split of urban temperature into a lower and upper graph is unnecessarily confusing. It would be better to keep one graph with a vertical dotted line marking the change in growth. The vertical stretching of the two scatter graphs can be reduced.
176: instead of saying both urban and rural stations "used" the same LCZ, say they "had" the same LCZ.
180: because the single reference for the relationship between urbanization and warming is for Zhengzhou, this sentence should end with "...main causes of urban warming for Zhengzhou." Otherwise a single reference looks strange, there are thousands of studies showing the link between urbanization and warming in general.
185-186: I don't understand the use of the term "transitivity" in this context. Do you mean "variability"?
190: When people read "climate change" they immediately think "global climate change". I suggest using "local climate change" here and elsewhere.
Figure 3 and dicussion: in the early years the negative UHI in winter and autumn and positive in spring and summer suggests that leaf loss in trees in important. Trees tend to cool during the day but keep objects warm at night due to emission of thermal IR. Daily average UHI are difficult to interpret because daytime and nighttime effects tend to be opposite. In the unlikely case you know the vegetation types around the urban area through time this would be worth mentioning. the reduction in UHI for the first decade is very interesting and should at least be mentioned even if it can't be explained from the information available. some investigation is warranted.
205-206: I wouldn't use the terms "significant" and "detrimental". Call them what they are: positive and negative. Why isn't the large negative UHI significant? I'd call it extremely significant. In fact it's perhaps the most interesting part of this paper and deserves some attempt at explanation if you can find one, or some mention of what can be done to find an explanation. It's very possible that the rural station was surrounded by high trees, so did not undergo as much radiative cooling as the urban station, but this situation changes with leaf loss in the winter. Fir versus deciduous trees will change the seasonal impact. Find the type of trees around the rural station vs what used to be around the urban station. It would take a direct inquiry to someone who has managed the two stations for a long time to get this information, but would be well worth the effort.
220-232: the effect of trees and leaf loss could be discussed here after you get the information on tree types. Remember that solar effects are dominant at 2 pm, thermal IR effects dominate at night. 8 am will line up more with the 2 am IR effects; 8 pm more with the 2 pm solar effects. I do have to complement you on the choice of times, I think it's better than the more obvious choices of 12 and 6 am/pm.
Tables 1,2: I suggest eliminating the p value, and R2 and correlation coefficient are basically the same information so you only need one of them. In its place, use something like the average absolute deviation from the line, or the mean square error. R or R2 indicates goodness of fit without a measure of the size of the error, so MSE or average absolute error tells you the size of the error. You should in fact combine these into one table once you eliminate the extra indicators. Equation of the line, R2, MSE or mean absolute error (my preference) and you are good. Later on you mention the signficance of UCR, why isn't that in these tables??
Figure 6: I don't understand why the UCR would be broken up into different periods on the left, yet have a single scatter plot on the right. I also don't understand why the other urban characteristics like population, area etc aren't plotted when this is. Did you only want to take up space with the most significant plot?
252-255: I don't understand why you would say an increase in UCR indicates the urbanzed area replaced the central urban area. Doesn't make sense because they are different locations, so replaced in what way? Also UCR indicates compactness, which is different from saying the urban area increases.
Overall section: why don't you do a multivariable linear regression involving all measures of urbanization?
Discussion
269: Both heat capacity and evaporation capacity are important, almost equally. Throughout this paper the evaporation has been ignored, you can't discuss UHI without evaporative cooling! Thermal IR is also neglected in this paper, and though minimized if the weather stations are in large grassy fields the effect should be mentioned just to point out that in this case it is a less significant contributor. But if tall trees or tall buildings surround the field, thermal IR becomes VERY important at night!
288-289: of COURSE replacing permeable with impermeable surfaces is part of urban sprawl, but you need to relate this to the reduced evaporative cooling. Impermeable surfaces don't allow evaporation of surface water, or storage of surface water. That's why permeability is significant.
Conclusions
218-319: I don't understand "This warming rate increased by 0.23 °C/decade and 0.43 °C/decade, respectively, compared to neighboring rural areas." What do each of these two numbers represent? We are first told it increased 0.67 C/decade, so why do we now have two?
329: if you had done a multivariable linear regression, this Rsquare value would summarize them all. But instead you just pick the highest one and didn't even mention which one it was.
Overall: summary numbers should be stated here, you only did one.
335-337: I disagree that these parameters provide a "complete" way to characterize the UHI. They didn't describe the negative dip in UHI in the early years, or the differences in time of day. This gets into vegetation, building morphology, etc. Many other papers have done the same thing as done here, so presenting it as a new approach does not give due credit to those who came before you.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 4 Report
The article analyses the characteristics of atmospheric UHI changes in Zhengzhou based on long-term observed meteorological data for the past years.
The work is local, lacking reference to other countries with similar problems. I propose to add a chapter exclusively on the study of the literature on urban development and the impact of buildings on the temperatures in these cities. Nowadays, these solutions can be found to inhibit the formation of so-called heat islands or high temperatures in towns in general.
Please try to avoid obvious statements such as.
1. Studies have stated that urbanization processes and human activities increase energy consumption and carbon emissions, which causes the greenhouse effect to occur.
2the increase in anthropogenic heat in urban areas (due to industrial production, automobile emissions, fossil fuels, etc.) also contributes to warming. These are the primary reasons for Zhengzhou's escalating urban climate change. -like everywhere
3. As in other Chinese cities and Asian cities such as South Korea and Japan urban policies and urbanization strategies play an important role as drivers of urbanization in China, which is also an indirect factor in urban warming.
4. Summer has the highest UHI intensity, spring is the second, and winter is 327 the weakest in the same climate zone as Zhengzhou city. - In which cities in the northern hemisphere are the situation different?
The authors described the UHI index for one city, and this is valuable. However, the problems of climate change caused by urban development are problems of the whole world, and in some countries, the fight against these negative effects has already been undertaken, so the article should not describe the current situation but give solutions, such as those taken from other countries
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The quality of the manuscript has been improved significantly after revision. There only have one problem existed. In section 4.4, the authors analyzed the correlation between atmospheric UHI intensity and urban socioeconmic growth by quantitative analysis. The qualitative analysis should be supplied too. The authors could refer to the section of 4 analysis of influencing factors in the following reference: Spatio-temporal evolution and factors of climate comfort for urban human settlements in the Guangdong-Hong Kong-Macau Greater Bay Area.Front.Environ.Sci,2022,10:1001064. doi:10.3389/fenvs.2022.1001064.
Beating the urban heat: Situation, background,impacts and the way forward in China. Renewable and Sustainable Energy Reviews,2022,161:112350. doi:https://doi.org/10.1016/j.rser.2022.112350.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
The authors devoted themselves to studying the temporal dynamics of the urban heat island in a rapidly developing city, analyzing the material changes of the UHI effect and the relationship between the UHI effect and indicators of rapid urbanization in Zhengzhou, China. In doing so, they drew on experiences described in nearly 700 items in the literature, referring to similar cases within China and many other urbanized areas worldwide. In doing so, they pointed out not only the worsening effect of urban heat islands but also the solutions needed to prevent it. Although the data analysis refers to Zhengzhou city, many readers will find in this article their own town and the problems we face around the world
Author Response
Dear reviewer, Dear editor,
We would like to appreciate the time and effort that you dedicated to providing feedback on our manuscript. We are grateful for the insightful comments, remarks and valuable improvements to our paper.
We will continue to work hard and look forward to cooperating with you one day.
Thank you for your time again!
