Review Reports

Round 1

Reviewer 1 Report

Dear Authors:

Thank you for the opportunity to review the manuscript.

The manuscript " Association between land surface temperature and green volume in Bochum, Germany"(sustainability-1964843) estimated the distribution of heat islands and green volume, and evaluated the relationship between these variables in a case study of Bochum, Germany. Overall, this is an interesting and well-conducted study. However, there are still some key points that should be revised. Several issues are given to authors for reference:

1) Please correct the format of the manuscript according to the journal's requirements, particularly, References, Equations. The main text should not include specific pages of references. In addition, the blank space and punctuation should be carefully checked, e.g., line 94.

2) The spatial resolution of Landsat 8 is 30m. It should be 30m*30m or 30*30m², not 30m².

3) I suggest removing the citations (or rewriting the relevant sentence) in the Abstract.

4) The Introduction and Method sections should be improved and reorganized. There are many unnecessary contents in these parts. For example, Figure 2, Table 1, Figure 3, and Figure 4. This study was focused on SUHI, not related to the canopy/boundary layer (Figure 2). Specific albedo-based surfaces and information were not used in this study. Figures 3 and 4 are from previous studies. I recommend that author rework the background, objective, method, and novelty in a more concise manner. The part of research questions and study design should be improved to capture the relevant key scientific information in a more logical and succinct manner.

5) The map of the study area should be added. The author can add administrative divisions, population, traffic networks, terrain, etc., for better understanding and linking the results and discussion sections.

6) Definition of the heat island. Herein, UHI is defined as areas with over 35°C (PET) of LST values, indicating absolute LST value. However, UHI generally refers to the LST difference between urban and rural (non-urban) areas, indicating the relative LST value or LST variation. The term "heat island" might not be suitable.

 

7) Insufficient analysis and discussion for the GV-LST part. This study focused on the correlation between LST and GV. However, the GV has various characteristics. For example, urban grassland and urban forest have different influences on LST. The contribution of vertical structure and types of green spaces on LST should be highlighted and compared in this study.

Author Response

Thank you very much for these insightful comments.  I have taken them to heart and made major revisions to the background, research design, analysis, and conclusions section, and supported these changes with additional figures and the removal of several figures.

Please see the attached word document detailing the changes point for point.

Author Response File: Author Response.pdf

Reviewer 2 Report

Congratulations, it's a great document!

Comments for author File: Comments.pdf

Author Response

Thank you very much for your insightful comments.  I have addressed them in the manuscript and provided point for point responses in the attached word document.

Author Response File: Author Response.pdf

Reviewer 3 Report

Please review the following comments along with the pdf file where suggested changes are highlighted

Minor comments

Lines 10-21. Abstract.

Average temperatures continue to rise worldwide due to climate change and, thus, in Europe, often occurring as heat waves [1]. The negative effects of climate change-related heat waves can be observed especially in urban areas [2] (p 7) where land sealing is greatest and population density. Past studies have indicated that green volume can provide climate improvement by balancing humidity and regulating temperature Brandenburg et al. [3] (pp 7–8) [4] (p 44). This study aims to estimate the distribution of heat islands and 3D vegetation volume (green volume) and test the relationship between these variables in a case study of Bochum, Germany (pop. 379k). A method to develop a temporally longitudinal 30m2 Landsat 8-based land surface temperature (LST) analysis and 30m2 LiDAR-based green volume dataset is presented, and their relationship is tested using Pearson’s correlation (n= 148,204). Results show that heat islands are moderately negatively correlated with green volume (r= -0.482; p<0.05), LST can vary as much as 28 degrees C° between heat islands and densely vegetated areas, and distribution is heterogeneous across Bochum.

Line 25. Delete “their”

Lines 28-29. Text suggestion “Therefore, thermal stress directly impacts the inhabitants' well-being and quality of life [5] (pp 290–291). Furthermore, the intensification….”

Line 37. Delete “ideally” and add it after “process”

Line 41. “statistically also” is not necessary

Line 46. Maybe the word “severe” is better

Line 52. Delete “result in an” and “in”.

Line 53. Add a comma after “example”

Line 55. Delete “and” and “it”

Line 59. Add a comma before and after “therefore”

Line 61. Change to “produces”

Line 62. Suggesting text “and thus positively affect the urban climate”

Line 69. Suggesting text “and positively impact the urban…”

Line 70. Change “fin” by “in”·

Line 74. Add “In addition,” before “dark”

Line 77. Rephase, please. No clear sentence.

Line 77. Add a comma after “water”

Line 79. Add a comma after “extent”

Line 85. Suggesting change “Thus, the urban climate has been altered…”

Line 87. Delete “own”

Line 88. Suggesting “significantly” instead of “greatly”, Delete “that of”

Line 90. Correct. “surrounding”

Line 90. Suggesting text “The UHI is a typical feature and best-known urban climate effect (Figure 1)”

Lines 95-96. Suggesting new text “UHIs are subject to diurnal and seasonal fluctuations and depend on prevailing weather conditions”

Line 97. Add a comma after “nights”

Line 104. Changed to “colder”. Add “ instead,” before “the”

Lines 106-107. Please rewrite. No clear sentence.

Line 108. Use broader instead of “larger”

Line 119. Suggestion “inhabitants of”

Line 124. Use “at” instead of “in”

Line 125. Use “live”. Change “is dependent” by “depends”

Line 125. Delete “clearly”

Lines 129-131. Text suggestion “….have established a relationship between recorded surface temperatures and NDVI as a proxy for urban structure in Berlin and other German cities…”

Line 136. Add commas before and after “therefore”. Change “major” by “significant”

Line 139. Add commas before and after “therefore”

Lines 140-142. Suggesting text “Building height and arrangement also influence temperature; for example, shading in narrow building canyons can cause delayed warming of the street space”

Line 148. Text suggestion “loss during the water phase change”

Line 159. Add “the” before latent

Line 161. Delete “to this”

Line 163. Change to “because”

Lines 166-167. Text suggestion “The green volume is a suitable environmental indicator and control instrument for climate-adapted urban development.”

Lines 170-171. Text suggestion “It contains information on an area's average vegetated volume in m3 /m2 [33] (pp 685–686).”

Lines 171-172. Define NDVI when the first time is introduced in the text

Line 174. Replace “by means of” by “using”

Line 179. Change by “GV improves climate”

Line 181. Add a comma after “temperature” and change the word “preceeded” by “preceded”

Line 194. Text suggestion “The city of Bochum is a good study area to illustrate the …….(impact of urbanization)”

Line 199. Delete “the course of”

Line 202- Add a comma after “Bochum”

Line 203. Correct the word. It is “mentioned”

Lines 205-206. Rewrite. Text suggestion “Analyzing the annual average temperature for the 1912-2011 period, a slight but steady increase of about 2 Kelvin is observed for Bochum.”

Line 209. Change “of” by “for”

Line 212. Delete “Already”

Line 213. Delete “is” and “to”. Add “will” before “double”

Line 216. Correction “question”

Line 217. Correction “homogeneity”

Line 218. Correction “spatial”

Line 219. Correction “believe”

Line 220. Replace “makes both a contribution” by “contributes”

Line 223. Add “the” before “green”

Lines 225-226. Text change suggestion “What distribution and temperature disparities across city quarters relate to human populations?”

Lines 230-232.  Text suggestion change “In a second step, the threshold for heat islands is determined based on a literature review, and the urban district subsequently maps the heat island pattern in Bochum.”

Line 233. Add a comma and a “a” after “step”

Line 234. Use “large-scale”

Line 236. Add “the” after “as”

Line 237. Use “instead” between commas

Line 243. Text change suggestion “….allow the collection of..”

Lines 251-252. Text change suggestion “For example, if the pixel size is 30m2, one image pixel represents 30m x30m on the Earth's surface”

Lines 255-256. Text change suggestion “Using the DN, assigning a value to each pixel according to its electromagnetic radiation intensity is possible.”

Line 258. Text change suggestion “For the LST analysis..”

Line 259. Delete “carried out”

Line 261. Change to “criterium for selection was…”…

Line 261. Text suggestion “..An essential criterion for selection was also the acquisition time; due to the surface temperature analysis and localization of areas with a particular…”

Line 263. Add “Therefore, “before “for”

Line 289. Start with “Equation 2”, and delete “To”. Change the comma by a dot.

Line 297. Add a comma after “i.e.”

Lines 299 and 301. Delete “in order”

Lines 312-313. Rewrite, suggestion “The emissivity is influenced by various factors, such as the water content, and depends on an object's material properties or roughness”

Line 321. NDVI is already defined, so used NDVI

Line 322. Delete de dot and replace it by a comma, and add a which before “is”

Line 347. Add “And last, “ before “the four..”

Line 400. Add “the after For”

Line 402. Add a comma after “step”. Change “to” for “into”. Change text, suggestion “The following step involved generating a DTM and a DOM by filtering the laser scanning points and subsequent interpolation to grids.”

Lines 404-407. You need to be clearer. This sentence is difficult to understand

Line 408. Use “correspond”

Line 411. Change to “because”

Lines 412-414. Text suggestion “At the same time, this resolution considered that a resolution of at least four points per recorded square meter was included”

Line 414. Add “Therefore” before “the”. Delete “used”

Lines 415-417. Text suggestion “A DOM and DTM as rasters with a ground resolution of one meter were developed from this process.”

Line 421. Better use “so”

Line 423. Replace by “calculating”

Line 425. Replace by “detecting”

Line 426. Replace by “must”

Line 433. Add reference year

Line 437. Replace by “was”

Line 447. Use “before”

Lines 447-448. Rewrite, suggestion “First, a fishnet was created in the GIS application ArcGIS Pro to adjust the recorded green volume grid of…”

Line 451. Use “Because of”

Line 463. Use “ones” instead of “areas”

Line 464. Delete the comma and use a dot after (Figure 10). Replace “whereas” by “In contrast”. Use “mixed-use”

Line 465. Use “Since” instead of “Given”. Replace “to make the distinction” by “distinguish”

Line 466 (and others). Change “on” by “in”

Line 468. Replace by “to overlay residential areas directly”

Line 469. Add “the” before “heat” and before “box”. Add a comma after “9”

Line 472. Rewrite by “in the box (b) in Figure 9”

Line 474. Add a comma after (c).

Line 475. Add a comma after east.

Line 484. Replace by “in Mitte's densely built-up and sealed inner city area”

Lines 484-487. Rephase, suggestion “The heat islands in Mitte would have merged into a central island with an east-west trending archipelago on either side because a lower PET threshold of moderate heat stress (°C > 29) was chosen.”

Lines 487-491. Rephase, Suggestion “The LST is, on average, above 30°C in all districts of Bochum that show at least moderate heat stress based on the average LST values (Figure 7). However, it is higher in Mitte and Wattenscheid with temperatures over 32°C (Fig. 11). The distribution of UHIs specifically resembles a spatially dispersed 'archepelligo' rather than a single centralized heat island.”

Line 496. Rephrase to “The resampled GV distribution in Bochum”

Line 500. Add “city” after “Buchum”

Line 501. Rephrase as “southward”

Line 502. Add a dot after “valley”. Delete “where”.

Line 528. Replace “echo” by “similar to”

Line 529. Replace “are located” by “occur”

Line 538. Is the reference year missing? In line 536 you included it

Lines 543-558. Overall, the text is hard to read it. It needs some rephrasing.

Regarding the UHI distribution using the LST method, this study supports the conceptual framework that heat islands over large heterogeneous urban regions exhibit facets of the heat island archipelago [21] and the original heat island concept [19]; such as the Ruhr region in which Bochum is located. Using the LST method described here and the PET break point agglomeration, we observed a central island in the urban core with ultra-heated islands and an archepelligo of smaller heat islands, where highly sealed industrial land and an absence of GV. This finding is both promising and vexing at the same time in terms of spatial planning solutions. On the one hand, high temperatures in industrial areas without living quarters do not impact residential populations. On the other hand, heat stress on workers can occur in industrial building houses during heat waves. Given the intensive mix of land uses in tight spatial proximity within German land use planning, it is still possible for industrial heat islands to impact surrounding areas with latent heat outflow and reduced evapotranspiration cooling.  Thereby indirectly affecting residential quarters that tend to be directly adjacent to industrial areas.

Lines 559-571. Overall, the text is hard to read it. It needs some rephrasing.

Unlike UHIs, we find that GV is spatially constrained and scattered across Bochum and can be described as spotty, patchy, or discontinuous. Also, while we found an area of increased LST surrounding many industrial heat islands (Figure 9) where latent heat outflow influences adjacent areas, we do not observe such an area surrounding large GV areas. Therefore, we can conclude that the heat islands increase temperatures in surrounding areas more than forest does in reducing them. Following this conclusion, it is reasonable for future spatial plans to consider increasing green volumes in residential areas directly adjacent to UHIs to buffer residential areas from unrestrained latent heat outflow from UHIs. Here, the conceptual framework from landscape ecology [71] of diverse boundary conditions of natural habitats to increase edge diversity might be a reasonable cross-disciplinary concept. In this case, diverse widths, thickness, and types of GV retrofits can be applied to residential areas adjacent to UHIs to improve spatio-thermal control of the UHI edge.

Lines 584-598. Suggestion

When we look at the historic socio-demographic properties of Bochum, one of the strongest single indicators is the German highway A40 which bisects the north and south districts of Bochum and other Ruhr cities [72] in two halves. The northern half of Bochum (Wattenscheid, Mitte, Nord, Ost) is where coal mining, steel production, and the automobile industry have historically been located and where urban heat islands and reduced green volume exist. Whereas south of A40 (Süd, Südost), few, if any, coal mines or industrial areas exist. Thereby lower income worker population has historically settled adjacent to these industry areas, resulting in the average income per inhabitant north of A40 being 80% of the Bochum-wide average. 

Conversely, south Bochum is traditionally where wealthier families have settled to distance themselves from the noise and air pollution of the industrialized north. Correspondingly, in the south, we find that the average income per inhabitant is 120% of the Bochum-wide average [72] (p 6). Here, we conclude that the environmental burden of heat islands in Bochum is spatially distributed to lower average-income areas in the north. In contrast, the more affluent south Bochum area significantly reduces UHI burdens.

Lines 600-612. Suggestion

 

LST is not air temperature; this could introduce inaccuracy to the precise degrees Celsius people experience as ambient temperature. While urban surface heating is still a primary driver in the formation of UHIs, it could mean that the PET categories might be one category level less than we conclude here. This is because the ambient air temperature is usually less than the surface temperature. For this reason, we also refrained from trying to link GV increases directly to LST decreases.

We do not have GV data for Wattenscheid, and although we see a lot of area 606 above 35°C, we cannot conclude anything about this area in our correlation or about average LST values. It is possible that more observations could improve the strength of the correlation (i.e., the inclusion of Wattenscheid). Still, the lack of this area in the analysis likely would not have changed the correlation direction. If any factor can increase the strength of the correlation, it is not the object of this study.

Lines 614-620. Suggestion

 

Regarding the current practice in Germany for estimating urban heat islands, the temperature-specific LST approach holds promise for future studies to relate temperature and GV more directly via more advanced inferential statistics. Future studies should seek to link LST and GV more directly to statistically model resultant LST reductions in °C derived from GV increases. This approach could allow future urban planning retrofits to design with specific LST load reductions in °C related to GV increases.

 

Comments for author File: Comments.pdf

Author Response

Thank you very much for your insightful comments and also the tremendous effort to help improve the grammar and conciseness of the text.  I believe your comments were critical in improving the manuscript and am very thankful.

Responses to your comments are listed on the attached word document.

Author Response File: Author Response.pdf

Reviewer 4 Report

This manuscript presents an interesting study of “Association between land surface temperature and green volume in Bochum, Germany”.

Overall, it combines a nice array of data sources to present how the green volume impact the land surface temperature in Bochum, Germany. The paper clearly presents its objectives and can make an important contribution to planners. Furthermore, the materials and methods are detailed and allow such procedures to be applied in other areas of interest. The maps are carefully presented, containing all the basic cartographic conventions. Similarly, the results are detailed and consistent with the procedures used.

However, there are some aspects of the manuscript that I believe should be addressed by the authors before publication. Firstly, the text needs extensive editing to correct typographical, grammatical and spelling mistakes. Examples are too many to be included in this report, but I could select a few just from the manuscript:

1.     The key-words should be alphabetically arranged.

2.     Updated reference needs to be added in the manuscript. For example, this sentence need reference “On the one hand, due to the increased population density in cities, there is statistically also a higher number of vulnerable groups, which can be particularly affected by negative climatic impacts due to their physical or mental constitution”. I suggest adding the updated references here (Sultan et al., 2022) (P 12).

·       Sultan H, Zhan J, Rashid W, Chu X, Bohnett E. 2022. Systematic Review of Multi-Dimensional Vulnerabilities in the Himalayas. International Journal of Environmental Research and Public Health 19:12177. https://doi.org/10.3390/ijerph191912177.

3.     Please check abbreviations such as NDVI, GV etc that should be written in full at first appearance, then followed by abbreviated form throughout the manuscript. However, currently they are used interchangeably in full and abbreviations at different locations of the manuscript.

4.     In the figure 6, Please add northern arrow to the map.

5.     Please reference this sentence “Heat stress in larger cities is therefore already considered problematic today and is expected to worsen due to the projected increase in annual mean global temperatures and urban population growth”.

6.     The references should follow a uniform pattern. Additionally, some of the journals names are written in abbreviated form while others are mentioned with full names.

7.     Please add a reference to this sentence “With an increase in the global average temperature,” [Sultan et al 2022] (P 7).

·       Sultan, H.; Rashid, W.; Shi, J.; Rahim, I. u.; Nafees, M.; Bohnett, E.; Rashid, S.; Khan, M. T.; Shah, I. A.; Han, H.; Ariza-Montes, A., Horizon Scan of Transboundary Concerns Impacting Snow Leopard Landscapes in Asia. Land 2022, 11, (2), 248-269. https://doi.org/10.3390/land11020248

8.     Line # 119-120, Please explain the abbreviation of NRW used in this sentence “This is particularly critical in Germany because five million people in NRW are already affected by adverse thermal situations as of 2018 [10] (p 1)”

9.     Please correct this sentence “This reduced absorption of shortwave radiationy results in lighter surfaces heating up less”

10.  Please replace the figure 3 with a higher resolution image.

11.  Line # 175-177 “GV thus provides information about the volume of "[...] of all plants standing on a green space" [32] (p 1). Please complete this sentence.

12.  As mentinoed above, the temperate climate of Central Europe -and thus also the climate in Bochum- is subject to increasingly strong climate change-related fluctuations [39] (p 5). Please correct the spelling mistake and improve this sentence.

13.  Line # 232-233 Please explain the abbreviation of “nDOM” in this sentences.

14.  Please check the caption of the figure 5, “Figure 5. Flow chart for calculation of LST (own representation after [47])..”

15.  The references are written as [61, [62]”. Please combine it like this [61, 62].

16.  Please improve the resolution of the Figure 15.

17.  Line # 526 -528, please check the spelling mistake in this sentence, “In light of our primary research question regarding the associatino of GV and LST in Bochum, we can conclude that increases in GV result in a borderline moderate statistical reduction of LST.

18.  Line # 550 -551, please check the spelling mistake in this sentence, “This finding is both promising and vexxing at the same time in terms of spatial planning solutions”.

19.  Line # 554-558 please check the spelling mistake in this sentence, “Given the intensive mix of land uses in tight spatial proximity within German land use plnning, it is still possible for industrial heat islands to impact surrounding areas with latent heat outflow and reduced evapotranspirative cooling, thereby indirectly affecting residential quarters that tend to be directly adjacent to industrial areas.

20.  Line # 614-615, please check the spelling mistake in this sentence,  Regarding the current practice in Germny of estimating areas of urban heat island using land cover or land sealing percentages that are not directly tied to temperature [24].

 

Comments for author File: Comments.pdf

Author Response

Thank you very much for these insightful comments.  I have accepted almost every one of them and where I did not it is noted why on the point by point reviewer response form attached.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Thank you for the revisions and improvements. But there are some grammar and format mistakes in the revised manuscript. Please carefully check the manuscript for final publication.