the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 15 Oct 2024
The Modulation of Synoptic Weather Patterns and Human Activities on the Diurnal Cycle of Summertime Canopy Urban Heat Island in Yangtze River Delta Urban Agglomeration, China
Abstract. The pronounced excess urban warming phenomenon during summer in the Yangtze River Delta Urban Agglomeration (YRDUA) has emerged as a significant challenge to the health and economy of urban residents amidst the accelerating urbanization process. Despite its undeniable importance, few studies have investigated the diurnal variability patterns of the canopy urban heat island (CUHI) in this region from the perspective of synoptic weather patterns (SWP) and human activities. This study integrated multiple source datasets, including meteorological station observations, high-resolution satellite imagery, and reanalysis data, to systematically analyze the diurnal patterns of the CUHII in YRDUA. Using objective classification and a machine learning model, we discovered notable diurnal patterns of CUHI intensity (CUHII), particularly higher levels of CUHII at night compared to day. Further analysis revealed that among six SWPs, type 2, dominated by subtropical high pressure, generated the strongest CUHII, while type 4, influenced by the combined effects of southwestern moisture transport and southward cold air incursions, resulted in the lowest CUHII. Additionally, the study found that key indicators such as landscape percentage (PLAND), largest patch index (LPI) and anthropogenic heat flux (AHF) exhibited an increasing trend over recent years, with higher values in the east and lower in the west, aligning well with the spatio-temporal patterns of the CUHII. These findings collectively confirmed the central roles of SWPs and human activities as the main drivers of CUHI phenomena. Simulations using the RF model further indicated the diurnal asymmetry in the modulation of the CUHI by SWPs and human activities: SWPs exerted a more pronounced influence on day CUHII, while human activities dominated night CUHII. Furthermore, the study delved into the impact mechanisms of heatwave (HW) events on the diurnal cycle of the CUHII. During HW periods, the amplification effect of day CUHII was stronger than night CUHII, and the presence of HW events significantly reduced the diurnal amplitude of the CUHII. In conclusion, this study not only provided scientific insight into the complex driving mechanisms of the CUHI diurnal cycle in YRDUA, but also offered a theoretical foundation for evaluating urban overheating issues and developing effective mitigation strategies.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2745 KB) - Metadata XML
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Supplement
(795 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-3111', Anonymous Referee #3, 23 Dec 2024
The study focuses on the contribution of the canyon urban heat island intensity in the daytime and nighttime by analysing different datasets. The analysis is comprehensive and the whole story is also very organised. However, I have one major comment which suggests the author address.
Until now, studies have focused a lot on the mechanism of the canyon UHI, especially the intensity. Many previous studies have also focused on the reason for UHI. The study has two main conclusions: 1) CUHI is larger during nighttime and under the high-pressure system; 2) synoptic weather patterns have a more pronounced influence on day CUHII, but human activities dominated night CUHII. Â These two points are not new findings; they can be easily found and learnt from the previous literature and even textbooks. Thus, what is the significant contribution of the current work? Indeed, authors applied more advanced and updated analysis methods, yet what are the new findings, which are similar to the previous or different to the previous?
I would also suggest the authors reconstruct the abstract and introduction. The current version of the abstract cannot fully reflect significance. In the introduction, authors should highlight the combination of the synoptic and human activities! Similarly, more discussion and explanation should focus on section 3.3 in the results. The analysis and results in the previous sections are a bit lengthy, which makes the focus of the article not sharp enough.
Â
Minor comments:
Line 154, reference format typo.
Please also indicate the data period and temporal resolution of the ERA5 dataset.
Section 2.3.1: More explanation of the calculation of CUHII. There are 43 USs and 27 RSs, for each US, which RS is selected to be linked with to get the CUHII?
Citation: https://doi.org/10.5194/egusphere-2024-3111-RC1 -
AC2: 'Reply on RC1', Yuanjian Yang, 01 Jan 2025
Dear Reviewer and Editors:
We are sincerely grateful to the editor and reviewer for their valuable time for reviewing our manuscript. The comments are very helpful and valuable, and we have addressed the issues raised by the reviewer in the revised manuscript. Please find our point-by-point response (in blue text) to the comments (in black text) raised by the reviewer. We have revised the paper according to your comments (highlighted in red text of the revised manuscript).
Sincerely yours,
Dr. Yuanjian Yang, representing all co-authors
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AC2: 'Reply on RC1', Yuanjian Yang, 01 Jan 2025
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RC2: 'Comment on egusphere-2024-3111', Anonymous Referee #4, 29 Dec 2024
This study presents a comprehensive and detailed analysis of the diurnal drivers of the Canopy Urban Heat Island Intensity (CUHII) in the Yangtze River Delta Urban Agglomeration. The manuscript utilizes multiple datasets and methods, making it a robust piece of research. However, the manuscript appears a bit lengthy and the novelty of the findings is not clearly articulated. I have the following comments and questions, and need specific revisions/answers:
In the methodology section, I suggest including a workflow that outlines the datasets and methods used in the study.
Figure 1b: It is unclear whether the reference station shown in Figure 1b is the same as the one mentioned in Section 2.3.1. Could you please clarify this in the manuscript?
Line 205: The statement, "After 18:00 BJ, as the solar altitude angle decreases, the effective radiation in suburban areas gradually increases, accelerating atmospheric heat loss," is confusing. Typically, as solar altitude decreases, radiation decreases, which should not lead to an increase in effective radiation in suburban areas. Could you please provide a more detailed explanation or consider revising this statement for accuracy?
Line 210: The manuscript states, "Before sunrise, between 0:00 and 7:00, the cooling rates of urban and suburban temperatures are similar, causing the CUHII to gradually increase to its daily maximum value of 0.65 °C." However, it is generally understood that urban areas, due to their heat storage in built materials and the canopy structure, would have a slower cooling rate compared to suburban areas. Please provide reasons that support this claim of similar cooling rates.
What factors contribute to the similarity in CUHII magnitude during the night and daytime in July?
Line 425: Are there any potential reasons or mechanisms that could explain the significant decrease in daytime WS during Heat Wave?
While the study provides valuable insights into the modulation of CUHII by SWPs and human activities in the YRDUA, it would be beneficial to discuss whether these findings can be extrapolated to other regions.
Â
Minor Comment:
Line 71: Please provide the full name of the WPSH at its first mention.
Citation: https://doi.org/10.5194/egusphere-2024-3111-RC2 -
AC1: 'Reply on RC2', Yuanjian Yang, 01 Jan 2025
Dear Reviewer and Editors:
We are sincerely grateful to the editor and reviewer for their valuable time for reviewing our manuscript. The comments are very helpful and valuable, and we have addressed the issues raised by the reviewer in the revised manuscript. Please find our point-by-point response (in blue text) to the comments (in black text) raised by the reviewer. We have revised the paper according to your comments (highlighted in red text of the revised manuscript).
Sincerely yours,
Dr. Yuanjian Yang, representing all co-authors
-
AC1: 'Reply on RC2', Yuanjian Yang, 01 Jan 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-3111', Anonymous Referee #3, 23 Dec 2024
The study focuses on the contribution of the canyon urban heat island intensity in the daytime and nighttime by analysing different datasets. The analysis is comprehensive and the whole story is also very organised. However, I have one major comment which suggests the author address.
Until now, studies have focused a lot on the mechanism of the canyon UHI, especially the intensity. Many previous studies have also focused on the reason for UHI. The study has two main conclusions: 1) CUHI is larger during nighttime and under the high-pressure system; 2) synoptic weather patterns have a more pronounced influence on day CUHII, but human activities dominated night CUHII. Â These two points are not new findings; they can be easily found and learnt from the previous literature and even textbooks. Thus, what is the significant contribution of the current work? Indeed, authors applied more advanced and updated analysis methods, yet what are the new findings, which are similar to the previous or different to the previous?
I would also suggest the authors reconstruct the abstract and introduction. The current version of the abstract cannot fully reflect significance. In the introduction, authors should highlight the combination of the synoptic and human activities! Similarly, more discussion and explanation should focus on section 3.3 in the results. The analysis and results in the previous sections are a bit lengthy, which makes the focus of the article not sharp enough.
Â
Minor comments:
Line 154, reference format typo.
Please also indicate the data period and temporal resolution of the ERA5 dataset.
Section 2.3.1: More explanation of the calculation of CUHII. There are 43 USs and 27 RSs, for each US, which RS is selected to be linked with to get the CUHII?
Citation: https://doi.org/10.5194/egusphere-2024-3111-RC1 -
AC2: 'Reply on RC1', Yuanjian Yang, 01 Jan 2025
Dear Reviewer and Editors:
We are sincerely grateful to the editor and reviewer for their valuable time for reviewing our manuscript. The comments are very helpful and valuable, and we have addressed the issues raised by the reviewer in the revised manuscript. Please find our point-by-point response (in blue text) to the comments (in black text) raised by the reviewer. We have revised the paper according to your comments (highlighted in red text of the revised manuscript).
Sincerely yours,
Dr. Yuanjian Yang, representing all co-authors
-
AC2: 'Reply on RC1', Yuanjian Yang, 01 Jan 2025
-
RC2: 'Comment on egusphere-2024-3111', Anonymous Referee #4, 29 Dec 2024
This study presents a comprehensive and detailed analysis of the diurnal drivers of the Canopy Urban Heat Island Intensity (CUHII) in the Yangtze River Delta Urban Agglomeration. The manuscript utilizes multiple datasets and methods, making it a robust piece of research. However, the manuscript appears a bit lengthy and the novelty of the findings is not clearly articulated. I have the following comments and questions, and need specific revisions/answers:
In the methodology section, I suggest including a workflow that outlines the datasets and methods used in the study.
Figure 1b: It is unclear whether the reference station shown in Figure 1b is the same as the one mentioned in Section 2.3.1. Could you please clarify this in the manuscript?
Line 205: The statement, "After 18:00 BJ, as the solar altitude angle decreases, the effective radiation in suburban areas gradually increases, accelerating atmospheric heat loss," is confusing. Typically, as solar altitude decreases, radiation decreases, which should not lead to an increase in effective radiation in suburban areas. Could you please provide a more detailed explanation or consider revising this statement for accuracy?
Line 210: The manuscript states, "Before sunrise, between 0:00 and 7:00, the cooling rates of urban and suburban temperatures are similar, causing the CUHII to gradually increase to its daily maximum value of 0.65 °C." However, it is generally understood that urban areas, due to their heat storage in built materials and the canopy structure, would have a slower cooling rate compared to suburban areas. Please provide reasons that support this claim of similar cooling rates.
What factors contribute to the similarity in CUHII magnitude during the night and daytime in July?
Line 425: Are there any potential reasons or mechanisms that could explain the significant decrease in daytime WS during Heat Wave?
While the study provides valuable insights into the modulation of CUHII by SWPs and human activities in the YRDUA, it would be beneficial to discuss whether these findings can be extrapolated to other regions.
Â
Minor Comment:
Line 71: Please provide the full name of the WPSH at its first mention.
Citation: https://doi.org/10.5194/egusphere-2024-3111-RC2 -
AC1: 'Reply on RC2', Yuanjian Yang, 01 Jan 2025
Dear Reviewer and Editors:
We are sincerely grateful to the editor and reviewer for their valuable time for reviewing our manuscript. The comments are very helpful and valuable, and we have addressed the issues raised by the reviewer in the revised manuscript. Please find our point-by-point response (in blue text) to the comments (in black text) raised by the reviewer. We have revised the paper according to your comments (highlighted in red text of the revised manuscript).
Sincerely yours,
Dr. Yuanjian Yang, representing all co-authors
-
AC1: 'Reply on RC2', Yuanjian Yang, 01 Jan 2025
Peer review completion
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Tao Shi
Yuanjian Yang
Lian Zong
Min Guo
Ping Qi
Simone Lolli
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2745 KB) - Metadata XML
-
Supplement
(795 KB) - BibTeX
- EndNote
- Final revised paper