Resolving Surface Heat Island Effects in Fine-Scale Spatio-Temporal Domains for the Two Warmest Metropolitan Cities of Korea

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript analyzes high-resolution surface urban heat island (SUHI) characteristics in Busan and Daegu—the two hottest metropolitan areas in South Korea—based on ECOSTRESS data. The topic is novel and interesting, the methodology is appropriate, and the overall work is substantial. Overall, this is a well-conducted work. Nevertheless, several issues should be addressed before publication:

L59–60: The statement "SUHI has a closer connection to human perception of heat intensification" is inaccurate. In fact, air temperature—or the atmospheric urban heat island (AUHI)—has a more direct influence on human thermal perception.

The manuscript lacks a review of recent advances in fine-scale urban heat island studies, particularly those utilizing ECOSTRESS data.

Figure 3. Please provide the RMSE and Bias values.

Section 2.3.1. Add the reference) for the landuse dataset.

The quality of most figures is relatively low. It is recommended to redraw them to enhance visual clarity and overall presentation quality.

Author Response

We sincerely thank the reviewer for the valuable and constructive comments. Your thoughtful feedback has greatly helped us to improve the clarity and overall quality of the manuscript. All comments have been carefully considered and addressed in the revised version. Detailed responses to each point are provided below.

 

Comments and Suggestions for Authors and Reply

This manuscript analyzes high-resolution surface urban heat island (SUHI) characteristics in Busan and Daegu—the two hottest metropolitan areas in South Korea—based on ECOSTRESS data. The topic is novel and interesting, the methodology is appropriate, and the overall work is substantial. Overall, this is a well-conducted work. Nevertheless, several issues should be addressed before publication:

 

#Comment 1

L59–60: The statement "SUHI has a closer connection to human perception of heat intensification" is inaccurate. In fact, air temperature—or the atmospheric urban heat island (AUHI)—has a more direct influence on human thermal perception.

Reply: We agree with the reviewer that atmospheric UHI (AUHI) more directly influences human thermal perception. Accordingly, the sentence in the introduction has been revised to clarify that SUHI represents the surface thermal environment associated with human heat exposure rather than human perception itself.

Revised sentence:

“While atmospheric UHI (AUHI) more directly affects human thermal perception, SUHI reflects the surface thermal environment that people are exposed to, influencing heat-related illnesses, cooling energy demand, and surface thermodynamic processes such as evapotranspiration.”

#Comment 2

The manuscript lacks a review of recent advances in fine-scale urban heat island studies, particularly those utilizing ECOSTRESS data.

Reply: A paragraph reviewing recent ECOSTRESS-based urban heat studies has been added to the Introduction. This revision incorporates up-to-date literature on fine-scale SUHI and diurnal thermal analyses and clarifies the relevance and positioning of the present study within these advances.

#Comment 3

Figure 3. Please provide the RMSE and Bias values.

Reply: RMSE and bias values between ECOSTRESS and GK-2A LST datasets have been added to Figure 3 and described in the caption for clarity.

#Comment 4

Section 2.3.1. Add the reference for the landuse dataset.

Reply: A reference for the official land-cover dataset guidelines has been added to Section 2.3.1. The citation now appears at the end of the sentence describing the 95 % classification-accuracy standard.

Added reference (Reference 49): Ministry of Environment, Republic of Korea. Guidelines for Land-Cover Map Construction (MoE Ordinance No. 1577, 19 December 2022); Ministry of Environment: Sejong, Republic of Korea, 2022. (in Korean)

#Comment 5

The quality of most figures is relatively low. It is recommended to redraw them to enhance visual clarity and overall presentation quality.

Reply: We appreciate the reviewer’s comment. All figures have been replaced with higher-resolution versions to improve visual clarity and overall presentation quality. The original high-resolution figure files have also been included in the revised submission for reference.

Reviewer 2 Report

Comments and Suggestions for Authors

This study investigates the fine-scale spatiotemporal dynamics of surface urban heat islands in Busan and Daegu using high-resolution ECOSTRESS and GK-2A datasets. The topic is both relevant and timely, aligning well with the scope of Remote Sensing. The integration of multi-source LST data to reveal sub-district-level diurnal variations offers valuable insights into urban thermal processes. However, the manuscript in its current form contains several major limitations that necessitate a major revision prior to a final decision. Specific comments are provided below:

1. The abstract lacks clear structure and quantitative detail, hindering readers' comprehension of the paper’s core contributions. It is recommended to reorganize the content and incorporate key quantitative metrics to better highlight the main findings.
2.  The selected keywords do not sufficiently reflect the methodological innovations or central findings of the study. Revising them to include terms related to the analytical approach or key outcomes would improve discoverability and relevance.
3.  While the introduction is logically structured, it suffers from several shortcomings: the background on UHI physical mechanisms and the climatic specificities of Busan and Daegu is overly generalized; the literature review lacks synthesis and fails to clearly articulate research gaps; and the scientific novelty and objectives of the study are not defined with adequate specificity. The introduction relies heavily on older references; incorporating recent authoritative studies would strengthen the contextual framing and relevance of the research.
4.  The “compensation scheme” introduced for diurnal adjustment is not sufficiently detailed, lacking explicit mathematical formulation and parameter definitions. This omission compromises the verifiability and reproducibility of the method. A complete mathematical description should be provided in the revised manuscript.
5.  Although Line 173 notes that only 61 ECOSTRESS scenes were used (2020–2022), the manuscript does not address how the pronounced data gap in winter—due to persistent cloud cover—impacts the reliability of the derived "seasonal diurnal patterns."
6.  In Figure 2, the date formats are inconsistent (e.g., “9 June 2022” vs. “June 1, 2020”). A uniform date format should be adopted throughout all figure captions to maintain consistency.
7.  There is an inconsistency in the caption of Figure 4: the annotation “SC for Science Park” does not correspond to the marker “SP” shown on the map. This should be corrected to ensure clarity.
8.  Section 4.1.1 remains largely descriptive. It should be enhanced with physical explanations for key observed patterns, such as the similar SUHII levels between spring and summer.
9.  The numerical values in Table 2 display inconsistent decimal precision. Standardizing the number of decimal places throughout the table is necessary to adhere to academic formatting standards.
10.  The analysis accompanying Figure 7 is descriptive and lacks mechanistic insight. The interpretation should address the underlying causes of the thermal hierarchy across land use types and the notable evening LST reversal between industrial and commercial areas.
11.  While Section 4.2 provides valuable spatial patterns of LHI, it lacks mechanistic depth. The analysis should elaborate on the physical drivers of the rapid heating (e.g., 1.9 °C/h in industrial areas) and cooling rates, and link these dynamics to anthropogenic factors such as operational schedules or energy consumption. Furthermore, the implications of identified hotspots for urban planning or public health risk assessment remain unexplored.
12.  The Discussion section does not sufficiently address the mechanistic underpinnings of key findings and fails to translate these into actionable policy recommendations. A deeper interpretation of the results in the context of urban climate adaptation is needed.
13.  The discussion section lacks some few more up to date references to justify novelty and literature additions. And to enhance the manuscript's rigor, a 'Limitations' subsection should be incorporated into the Discussion.

Author Response

We sincerely thank the reviewer for the valuable and constructive comments. Your thoughtful feedback has greatly helped us to improve the clarity and overall quality of the manuscript. All comments have been carefully considered and addressed in the revised version. Detailed responses to each point are provided below.

 

Comments and Suggestions for Authors and Reply

This study investigates the fine-scale spatiotemporal dynamics of surface urban heat islands in Busan and Daegu using high-resolution ECOSTRESS and GK-2A datasets. The topic is both relevant and timely, aligning well with the scope of Remote Sensing. The integration of multi-source LST data to reveal sub-district-level diurnal variations offers valuable insights into urban thermal processes. However, the manuscript in its current form contains several major limitations that necessitate a major revision prior to a final decision. Specific comments are provided below:

#Comment 1   

The abstract lacks clear structure and quantitative detail, hindering readers' comprehension of the paper’s core contributions. It is recommended to reorganize the content and incorporate key quantitative metrics to better highlight the main findings.

Reply: The abstract has been revised to improve clarity and structure while incorporating key quantitative details. It now follows a clear flow of background–objective–approach–results–implications. Quantitative metrics such as maximum SUHI intensity (10 °C in Daegu and 7 °C in Busan), differences from coarse-resolution data (up to 8 °C), peak industrial LSTs (47 °C and 43 °C), and hourly intensification rates (2.0 °C h⁻¹ and 1.9 °C h⁻¹) have been added to highlight the study’s main contributions.

#Comment 2

The selected keywords do not sufficiently reflect the methodological innovations or central findings of the study. Revising them to include terms related to the analytical approach or key outcomes would improve discoverability and relevance.

Reply: The keywords have been revised to better reflect the study’s analytical approach and main findings. The final set includes Surface urban heat island (SUHI); locational heat intensification (LHI); ECOSTRESS; GK-2A; diurnal; land-use density, which represent both the methodological framework and the core outcomes of the research.양식의 맨 위양식의 맨 아래

#Comment 3

 While the introduction is logically structured, it suffers from several shortcomings: the background on UHI physical mechanisms and the climatic specificities of Busan and Daegu is overly generalized; the literature review lacks synthesis and fails to clearly articulate research gaps; and the scientific novelty and objectives of the study are not defined with adequate specificity. The introduction relies heavily on older references; incorporating recent authoritative studies would strengthen the contextual framing and relevance of the research.

Reply: We appreciate the reviewer’s constructive comments. The Introduction has been substantially revised to address all the mentioned concerns.

(1) Clarification of UHI mechanisms and regional climatic context:

To address the reviewer’s comment, a new paragraph was added in the Introduction to clarify the physical mechanisms underlying UHI formation and to describe the distinct climatic characteristics of Busan and Daegu, providing a more specific and contextually grounded background.

(2) Improved synthesis of literature and clearer articulation of research gaps:

The literature review was reorganized to synthesize previous findings and clearly identify the research gap, emphasizing the lack of fine-scale, diurnal SUHI analyses for the two cities.

(3) Enhanced specificity of novelty and objectives:

The novelty and objectives were refined to specify how this study integrates ECOSTRESS and GK-2A data to overcome spatial–temporal limitations and to investigate land-use-dependent SUHI–LHI behaviors.

(4) Incorporation of recent authoritative studies:

To address this comment, a new paragraph reviewing recent ECOSTRESS-based studies was added to the Introduction. This addition incorporates up-to-date research on fine-scale and diurnal SUHI analyses, strengthening the contextual framing and relevance of the study.

#Comment 4

 The “compensation scheme” introduced for diurnal adjustment is not sufficiently detailed, lacking explicit mathematical formulation and parameter definitions. This omission compromises the verifiability and reproducibility of the method. A complete mathematical description should be provided in the revised manuscript.

Reply: In the revised manuscript, we kept the original mathematical expressions for the daily deviation (Equation 3) and the adjusted ECOSTRESS LST (Equation 4), but we added clearer definitions of the parameters used in these equations to improve verifiability and reproducibility. These additions provide explicit parameter definitions and a clearer description of how the seasonal reference and daily adjustments are computed, thereby addressing the reviewer’s concerns about methodological clarity and reproducibility.

 

#Comment 5

 Although Line 173 notes that only 61 ECOSTRESS scenes were used (2020–2022), the manuscript does not address how the pronounced data gap in winter—due to persistent cloud cover—impacts the reliability of the derived "seasonal diurnal patterns."

 

Reply: We appreciate the reviewer’s insightful comment. A clarification has been added in Section 4.1.1 to explain the impact of the limited winter data on the reliability of the derived seasonal diurnal pattern. Specifically, we note that the scarcity of valid ECOSTRESS scenes and potential residual cloud effects may lead to slight underestimation of winter LST and a flattened SUHI peak, resulting in lower reliability compared to other seasons.

 

#Comment 6

 In Figure 2, the date formats are inconsistent (e.g., “9 June 2022” vs. “June 1, 2020”). A uniform date format should be adopted throughout all figure captions to maintain consistency.

Reply: We have revised the caption to use a uniform “Month Day, Year” format and applied the same formatting consistently across all figure captions in the manuscript.

#Comment 7

 There is an inconsistency in the caption of Figure 4: the annotation “SC for Science Park” does not correspond to the marker “SP” shown on the map. This should be corrected to ensure clarity.

Reply: The label “SC” in the caption of Figure 4 was a typographical error. It has been corrected to “SP” to match the marker shown on the map. All annotations in the figure caption now correspond correctly to the labels in the figure.

#Comment 8

 Section 4.1.1 remains largely descriptive. It should be enhanced with physical explanations for key observed patterns, such as the similar SUHII levels between spring and summer.

Reply: Section 4.1.1 has been revised to include physical explanations for the seasonal patterns. The text now clarifies that the similar SUHII levels in spring and summer arise because increased solar radiation warms both urban and rural areas by comparable amounts, keeping their temperature contrast relatively stable. It also explains that in autumn and winter, reduced solar radiation, lower sun angles, and stronger nighttime cooling weaken overall surface warming and urban heat storage, which collectively suppress the urban–rural temperature contrast. These additions provide a clearer interpretation of the observed seasonal differences.

#Comment 9

 The numerical values in Table 2 display inconsistent decimal precision. Standardizing the number of decimal places throughout the table is necessary to adhere to academic formatting standards.

Reply: The underlying data were originally computed with two-decimal precision, but some values appeared with a single decimal place due to formatting during table preparation. We have corrected the formatting so that all values in Table 2 are now consistently displayed with two decimal places.

#Comment 10

 The analysis accompanying Figure 7 is descriptive and lacks mechanistic insight. The interpretation should address the underlying causes of the thermal hierarchy across land use types and the notable evening LST reversal between industrial and commercial areas.

Reply: We acknowledge the reviewer’s point. As the quantitative analysis of the underlying mechanisms for the observed thermal hierarchy and evening LST reversal was not conducted in this study, only a concise explanatory note was added at the end of Section 4.1.2. Instead, a more detailed discussion based on contextual interpretation with relevant literatures has been provided in Section 5.3.

#Comment 11

 While Section 4.2 provides valuable spatial patterns of LHI, it lacks mechanistic depth. The analysis should elaborate on the physical drivers of the rapid heating (e.g., 1.9 °C/h in industrial areas) and cooling rates, and link these dynamics to anthropogenic factors such as operational schedules or energy consumption. Furthermore, the implications of identified hotspots for urban planning or public health risk assessment remain unexplored.

Reply: We appreciate the reviewer’s valuable comment. Since this study focused on identifying spatial and temporal patterns rather than conducting a quantitative analysis of the underlying mechanisms, only a brief explanatory note was added at the end of Section 4.2 to describe the possible physical drivers of the rapid heating and cooling in industrial areas. A more detailed discussion based on relevant literature and contextual interpretation has been included in Section 5.3, where the observed LHI dynamics and hotspot implications are discussed with greater clarity.

#Comment 12

 The Discussion section does not sufficiently address the mechanistic underpinnings of key findings and fails to translate these into actionable policy recommendations. A deeper interpretation of the results in the context of urban climate adaptation is needed.

Reply: We thank the reviewer for this insightful comment. In the revised manuscript, we expanded the Discussion section to clarify the mechanistic drivers behind the observed diurnal patterns and land-use-specific LHI behaviors. Specifically, additional sentences were included in Sections 5.1–5.3 to explain the physical and anthropogenic factors governing the diurnal variations, including the roles of building morphology, morning humidity, and operational heat release in industrial areas. We also incorporated concise policy-relevant implications, highlighting the importance of fine-scale monitoring, heat-risk assessment, and targeted mitigation strategies for industrial districts. These additions provide clearer interpretation of the findings in the context of urban climate adaptation.

#Comment 13

 The discussion section lacks some few more up to date references to justify novelty and literature additions. And to enhance the manuscript's rigor, a 'Limitations' subsection should be incorporated into the Discussion.

 

Reply: We appreciate the reviewer’s constructive suggestions. To address this comment, recent studies utilizing ECOSTRESS for fine-scale SUHI analysis have been incorporated into the Discussion section (Wang et al., 2025 [44]) to better contextualize the novelty and methodological advancement of this work. In addition, a new subsection (Section 5.4, “Limitation”) has been added to explicitly describe the methodological assumptions, potential uncertainties, and future improvement strategies, thereby enhancing the rigor and transparency of the study.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revision made significant improvements. I have no further comments and recommend it for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

The revised version has addressed the issues I raised. The manuscript is well-structured, and the overall quality of the paper has been improved. I recommend its acceptance.