Evolution and Built-Up Age Dependency of Urban Thermal Environment

Round 1

Reviewer 1 Report

This manuscript (remotesensing-2830953) tries to integrate the global artificial impervious areas to analyze the impacts of built-up age and urban development intensity (UDI) on land surface temperatures (LST) in Hefei, the capital of Anhui province of China from 2000 to 2019. The authors revealed that the vital importance of annual development activities on urban thermal environment. While this manuscript has offered some findings, there are still a number of problems to be resolved. In particular, I have the following comments and concerns:

(1) The term "urban development intensity (UDI)" needs to be carefully defined at the beginning of this manuscript.

(2) Please explain more clearly the reasons for selecting "Hefei in Anhui, China" as the study area, because this city is not a big city or a rapidly-growing city, as compared with the first-class cities in China.

(3) From Line 63 to Line 66: the authors have mentioned that: "no study has attempted to evaluate the temporal change of the effect of UDI on UHI, and whether the UHI-UDI relationship would evolve over time as urbanization intensifies remains poorly understood". These statements are subjective and arbitrary, please revise.

(4) The innovation should be clearly justified that the manuscript contains sufficient contributions to the new body of knowledge from the international perspective. In particular, the authors need to look further into the latest research in this field. Actually, the literature review is not enough. This is because the temporal analysis of land surface temperature and urban built-up development were not new in urban climate research (please refer to below for example).

Exploring the connection between morphological characteristic of built-up areas and surface heat islands based on MSPA. Urban Climate, 2024, 53: 101764

An Evaluation of Different Landscape Design Scenarios to Improve Outdoor Thermal Comfort in Shenzhen. Land. 2024; 13(1):65.

(5) In this study, the Aqua MODIS 8-day composite products (version 5) of land surface temperature with a spatial resolution of 1000 m were selected. The spatial resolution is too coarse for a city, why not obtain the land surface temperature from the Landsat remote sensing images with a spatial resolution of 30 m?

(6) In this study, the Global Artificial Impervious Area data was used to calculate built-up age. However, these calculation procedures are not correct enough. The actual built-up age data should be available from the local land use and urban planning departments.

(7) Why the authors use the nighttime light data DMSP/OLS and VIIRS and albedo to perform attribution analysis on the relationship between LST and built-up age? For example, why not use the land use and land cover data directly?

(8) The Land use and land cover map from Tsinghua (http://data.ess.tsinghua.edu.cn/) was only available before 2017, not 2018.

(9) I am afraid that the Maximum Value Composite (MVC) approach was just suitable for the normalized difference vegetation index (NDVI), not the land surface temperatures.

(10) Why the quantitative relationships between the urban development and urban heat islands have been analyzed by using only the univariate linear regression equation?

(11) In future research, I suggest the influences of the morphological pattern of land use should also be taken into account (see the above references).

(12) In the Discussion Sections, how to link the findings and conclusions in this paper with the previous findings and conclusions?

(13) In the Conclusion Sections, the authors need to provide the shortcomings of this current study.

Moderate editing of English language required.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Summary: 

This manuscript explores the relationship between built-up age, urban development intensity, and land surface temperatures in Hefei, China, from 2000 to 2019. It finds that the temporal stability of spatial patterns challenges traditional space-for-time concepts in land surface temperature studies and emphasizes a noteworthy increase in sensitivity to urban development intensity, underscoring the importance of regulating land surface temperatures and addressing urban heat island effects. I think the authors did a good job in designing the experiment and interpreting the results. The results are innovative and worth sharing within the remote sensing community about urban heat island studies. This manuscript is well-written and needs some minor changes as follows before acceptance.  

1. Indicator of human activity: Is the night light the only effective indicator of human activity? Are there any other factors that are important but were omitted from the analysis?  

2. Location sensitivity: Are the results location-sensitive? Can similar conclusions be drawn if the same methodology is applied to different locations? A discussion on the generalizability of findings across diverse settings would enhance the manuscript’s robustness.   

3. Limitations in conclusions: While the study is commendable, it is essential to acknowledge and discuss limitations. Please address any limitations of this study, such as sample size, experiment conditions, analytical techniques, and errors. This adds transparency and helps readers understand the scope and potential boundaries of the findings in this manuscript.  

4. Future research: Talk about the potential avenues for future research directions based on the current study. Will the research extend to other regions, broadening the geographical scope? Is there a plan to extend the 19-year timeframe from 200 to 2019 to draw more generalized conclusions? Providing insights into future research directions adds depth to the manuscript.

L9: “earth surface” -> the earth surface 

L16: “put forward” -> puts forward 

L19: “measure to the impact” -> measure of the impact 

L29: “affects” -> affect

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript "Evolution and Built-up Age Dependency of Urban Thermal Environment" integrated global artificial impervious areas to analyze the impacts of built-up age and urban development intensity (UDI) on land surface temperatures (LST) in Hefei, the capital of Anhui province of China from 2000 to 2019.

Overall, the research is clear and meaningful. The topic is within the scope of the journal and is well-investigated. However, I have a few concerns about the datasets and adopted methodology, which is required to clarify to make a final decision on this work.

1.      To enrich the literature in the introduction and discussion section, please have a look at

·         https://www.sciencedirect.com/science/article/abs/pii/S0048969723055651

·         https://ieeexplore.ieee.org/abstract/document/10227512

·         https://www.sciencedirect.com/science/article/pii/S0360132321001396

·         https://www.mdpi.com/2073-445X/11/9/1461

·         https://www.sciencedirect.com/science/article/pii/S2325426222000067

·         https://www.ingentaconnect.com/content/asprs/pers/2021/00000087/00000002/art00006

·         https://link.springer.com/article/10.1007/s13351-021-0023-4

2.      Authors have utilized different datasets at different Spatial resolutions, Especially some at 1km and some with 30m resolution. I am wondering how those datasets were compared by downscaling/upscaling. How were the uncertainties/anomalies confirmed?

3.      There is 15 15-minute time lag between the “ equatorial crossing” for Landsat 5  (09:45 am) and 7 (10:00 am); please indicate whether this is no obstacle to the analysis.? 

4.      Please clearly indicate all the pre-processing steps adopted and information regarding the “Scan line error” for Landsat 7.

5.      Methodology of this work is a bit confusing. Please polish it extensively and provide a detailed methodology flowchart to understand the flow and connection of each method/analysis adopted.

6.      Consider reporting the limitations and future aspects of this work. 

Moderate editing of English language required

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report

Dear authors.

I am grateful for the opportunity to review the article "Evolution and built-up age dependency of urban thermal environment". The article is devoted to an actual scientific problem. The article has many advantages including a new approach to LST with built-up. I will indicate only controversial and unclear points that require explanation by the authors. I sincerely hope that the answers to my questions will improve the quality of the article. And as a result, the article will be accepted.

The article does not mention the authors' previous research results on the urban heat island in Hefei, so it is difficult to imagine how the heat island situation occurs in Hefei? If possible, the authors can provide a graph showing the change in LST over time of Hefei and Anhui province in China to clearly see the UHI effect and prove that the assumption in lines 96-97 is correct.

I suggest that: through the 8-day Modis image using the GEE tool (google earth engine), it is possible to build a chart of average day temperature and average night temperature over the years to show surface temperature trends. increased to clarify the heat island effect in Hefei.

I think the quality of the article would be significantly improved if the authors included some more images and analysis of the urban development process through urban planning maps of Hefei and Anhui province during the period 2000 -2019 yr.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you for incorporating my previous comments and suggestions. This manuscript can be accepted in present form.

Author Response

Thank you for your decision and constructive comments on my manuscript.

Reviewer 3 Report

Author's revisions are satisfictory and can be accepted.

Minor editing of the English language is required before publication.

Author Response

Thank you for your decision and constructive comments on my manuscript.