Sustainable Urban Development for Heat Adaptation of Small and Medium Sized Communities

Round 1

Reviewer 1 Report

The article titled “Sustainable Urban Development for Heat Adaptation of Small and Medium Sized Communities” by Wollshläger, Zinck and Schlink. Presents a  a new online tool to simulate the effect of different biophysical processes on Surface Temperature changes during heat wave events. I believe the tool is useful for the research community and urban designers interested in urban heat mitigation or extreme heat events mitigation.  I recommend the paper to be published in the journal “Land” after minor corrections and editions here described.

 Line 27: …of higher temperatures….. add “in urban areas” as the definition of UHI indicates that urban areas are warmer than its urban surroundings.

Figure 1. I would recommend to add a panel to the figure with the location of Naumburg within Germany

Table 2: “Szenario” change to its English equivalent

I would recommend to start section 3.1 with the link to the tool developed by the authors as this is a major contribution of your paper. Also, if it has a name (XXX), it could be added in the first line. For example, The developed XXXX (available in https://.........) is a user friendly……..

Please check all references because in some you used the journal’s name abbreviation such as in reference 3 and in others you used the full name of the journal (for example, reference 4). Please use consistently the required format by this journal (Land).

Some references have the first part of the URL repeated, for example, reference 7, : https://doi.org/https://doi.org......... Please fix this problem in all of the references.

Finally, please revise reference 13 as the name of the authors and the title of the paper are unreadable.

Author Response

Reply: We would like to thank the reviewers for their thoughtful comments and efforts towards improving our manuscript.  We have taken the comments on board to improve and clarify the manuscript. Please find below a detailed point-by-point response to all comments (reviewers’ comments in black, our replies in blue, see also the attached pdf file).

Reviewer #1:

The article titled “Sustainable Urban Development for Heat Adaptation of Small and Medium Sized Communities” by Wollshläger, Zinck and Schlink. Presents a new online tool to simulate the effect of different biophysical processes on Surface Temperature changes during heat wave events. I believe the tool is useful for the research community and urban designers interested in urban heat mitigation or extreme heat events mitigation.  I recommend the paper to be published in the journal “Land” after minor corrections and editions here described.

Thank you for reviewing our submitted manuscript. In the following we address the comments you listed. These were very useful and helped us to improve our manuscript.

Line 27: …of higher temperatures….. add “in urban areas” as the definition of UHI indicates that urban areas are warmer than its urban surroundings.

We changed the definition of the UHI according to your suggestion to: “As a result, phenomena like the urban heat island (UHI) effect arise, which describes the occurrence of higher temperatures in urban areas.”

Figure 1. I would recommend to add a panel to the figure with the location of Naumburg within Germany

Many thanks for the recommendation. We have added a panel with the borders of Germany to the corresponding image and marked the location of Naumburg.

Table 2: “Szenario” change to its English equivalent

Thank you for pointing this out. We changed this.

I would recommend to start section 3.1 with the link to the tool developed by the authors as this is a major contribution of your paper. Also, if it has a name (XXX), it could be added in the first line. For example, The developed XXXX (available in https://.........) is a user friendly……..

Thank you very much for this advice. Yes, the online tool is the main contribution to our article. However, since we have already provided the link to the online tool in the methods and the captions, we would prefer to leave it as it is.

Please check all references because in some you used the journal’s name abbreviation such as in reference 3 and in others you used the full name of the journal (for example, reference 4). Please use consistently the required format by this journal (Land).

Some references have the first part of the URL repeated, for example, reference 7, : https://doi.org/https://doi.org......... Please fix this problem in all of the references.

Finally, please revise reference 13 as the name of the authors and the title of the paper are unreadable.

We revised the formatting of the references.

Author Response File: Author Response.pdf

Reviewer 2 Report

Article presented the online tool to estimate different urban climate approaches using the ENVI-Met model application for the small German city Naumburg. The study is completed on the high scientific level, there are different experiments conducted, interesting and topical results obtained and the online system is created. The study gives a notable contribution to the current knowledge about local climate adaptation opportunities and challenges. However, there are some questions and remarks listed below.

1.    Authors stated in the Introduction that small and medium-sized cities in Germany have also some significant urban climate features including the UHI getting it more vulnerable during heat waves, etc. In my opinion, this should be accompanied by references to confirm the presence of significant UHI features within small and medium sized cities.

2.    Authors have chosen the Naumburg city center as a model object in this study. However, some information about reasons for this choice should be provided including city’s spatial size, population and its typicality among other similar cities.

3.    Sources of the 3d-city model and a land-use plan should be provided, if any.

4.    Authors provided information about median tree parameters used in the ENVI-met model, however, it would be useful to specify the tree species utilized in this study.

5.    Quite more information about experiment design is needed: total grid cells number in each direction, the upper vertical level of the model domain, time step of model integration.

6.    Authors suggested the Scenario 2 with increased street albedo from 0.2 up to 0.6. Please provide some examples of materials, which could be substituted in reality?

7.    Formula 2 presents the sensible heat flux calculation. In my opinion, the height difference between surface and air temperature levels (i.e., the height of air temperature measurements) is absent. Please clarify this issue.

8.    Authors assumed the reference height as 30 m. Please explain in more details, why this value was taken, or/and provide any appropriate reference.

9.    Authors based their decomposition algorithm on the sensible heat flux equation and Bowen ratio. However, the question is how the Bowen ration, latent heat and ground heat fluxes are calculated via ENVI-met model. Please clarify these issues in the text.

10.    Authors analyzed the PET values from their experiments. However, how these values were calculated? Using the RayMan tool, or some others? Which individual parameters were used for calculations? Please specify this in the text. One more question is why do not to use the mPET, modified and more advanced version of PET?

11.    Authors presented the online tool and specified the date of experiments as 2015-07-03 with weather station data usage as input. However, if the system is really online, the model calculations should use updating operational station data each day at 00 h local time to simulate high-resolution conditions. Does this operational system implemented, or not – please, specify this.

12.    Authors labeled radiation, ventilation, evapotranspiration, and heat storage processes as biophysical processes. In my opinion, it is incorrect term, more precise one would be energy fluxes.

13.    In conclusion, Authors are recommended to provide quite more information about future perspectives of presented online tool development based on limitations pointed out in 4.3.

14.    There are also some typos. Figures should be placed mostly after the first mention in the text. Line 99: ‘of of’; line 106: ‘othphotos’ (‘orthophotos’); line 123: ‘(scenario 1)’ – is missed; lines 281, 283, 288, 298, 304, 312, 326 – there are duplicated closing brackets; Table 2: ‘szenario’ (‘scenario’); number 43 in reference contains error in Author’s Name; and maybe some others.

The given questions and remarks recommended to be answered and/or included in text. However, these issues are not crucial for results, therefore, I recommend this manuscript to minor revision.

Author Response

Reply: We would like to thank the reviewers for their thoughtful comments and efforts towards improving our manuscript.  We have taken the comments on board to improve and clarify the manuscript. Please find below a detailed point-by-point response to all comments (reviewers’ comments in black, our replies in blue; see also the attached pdf file).

Reviewer #2:

Article presented the online tool to estimate different urban climate approaches using the ENVI-Met model application for the small German city Naumburg. The study is completed on the high scientific level, there are different experiments conducted, interesting and topical results obtained and the online system is created. The study gives a notable contribution to the current knowledge about local climate adaptation opportunities and challenges. However, there are some questions and remarks listed below.

Thank you for reviewing our submitted manuscript. In the following we address the comments you listed. These were very useful and helped us to improve our manuscript.

1. Authors stated in the Introduction that small and medium-sized cities in Germany have also some significant urban climate features including the UHI getting it more vulnerable during heat waves, etc. In my opinion, this should be accompanied by references to confirm the presence of significant UHI features within small and medium sized cities.

Thank you for the comment. We agree urban climate effects like the UHI are notably less pronounced compared with larger cities. However, we mainly attribute the vulnerability of the urban population of such small and medium-sized communities during heat wave events to the age distribution as more elderly people are living there. To make this clear, we added a line break in line 33.

2. Authors have chosen the Naumburg city center as a model object in this study. However, some information about reasons for this choice should be provided including city’s spatial size, population and its typicality among other similar cities.

This study was funded as part of the KlimaKonform project (mentioned in the acknowledgements), which deals with the climate adaptation of small and medium-sized municipalities in the German low mountain regions. Interviews with local city councils showed increased vulnerability and awareness of heat perception in Naumburg. Therefore, we took the opportunity to work closely with local actors. We have added information about the spatial size and population in our article (section 2.2).

3. Sources of the 3d-city model and a land-use plan should be provided, if any.

We followed your suggestion and provided information concerning the source of the data in section 2.3.

4. Authors provided information about median tree parameters used in the ENVI-met model, however, it would be useful to specify the tree species utilized in this study.

Our model tree would correspond to a rather typical Field Maple (Acer Campestre). We added this information to our article in section 2.3.

5. Quite more information about experiment design is needed: total grid cells number in each direction, the upper vertical level of the model domain, time step of model integration.

For the resolution of the model, a compromise had to be made between sufficient spatial accuracy and a reasonable computation time for the simulations. The horizontal resolution was therefore set to 3 x 3 m and the vertical grid cell size to 2 m.

The simulated model results of the first 24 hours and of the outermost 20 grid cells in the horizontal domain were not taken into account in the evaluation in order to exclude the effects of initial conditions and the boundary effects of the model from the evaluation.

The total number of grid cells was 288 x 288 x 22.  We added the information to Table 1.

6. Authors suggested the Scenario 2 with increased street albedo from 0.2 up to 0.6. Please provide some examples of materials, which could be substituted in reality?

We selected a rather high albedo value for scenario 2 to gain visibly pronounced effects. According to Santamouris (2013), very high albedo values of 0.8-0.9 can be achieved using highly reflective paints applied on the surface. However, albedo values of such highly reflective materials may also be lower due to the impact of the local weather (i.e. dust, ultraviolet radiation, acid rain, biomass accumulation, etc.) (Santamouris (2014)). Thus, our selected albedo value may represent such highly reflected paint that was already exposed to weathering. We added a respective reference in section 2.4.

7. Formula 2 presents the sensible heat flux calculation. In my opinion, the height difference between surface and air temperature levels (i.e., the height of air temperature measurements) is absent. Please clarify this issue.

Thank you for pointing this out. We included the height dependence of the sensible heat flux in the respective definition.

8. Authors assumed the reference height as 30 m. Please explain in more details, why this value was taken, or/and provide any appropriate reference.

Within the decomposition algorithm, a reference height of 30 m was assumed, as suggested by Hertel et al. (2018), since temperatures at this altitude are not affected by the respective climate adaptation scenarios. Actually, this height is variable under the assumption that air temperatures of the climate adaptation scenario and reference scenario are equal. This assumption was valid in our simulations at a height level of 30 m.

9. Authors based their decomposition algorithm on the sensible heat flux equation and Bowen ratio. However, the question is how the Bowen ration, latent heat and ground heat fluxes are calculated via ENVI-met model. Please clarify these issues in the text.

Following this suggestion, in section 2.5 we specified the approaches integrated in the ENVI-met model for the calculation of the energy fluxes:

“The micrometeorological model ENVI-met is based on the SEB, wherein the turbulent fluxes (QH and QE) are determined using E-ε 1.5-order model which is a good compromise between the convenient K theory and the numerically complex closure of the second-order and allows to appropriately consideration of urban structures as well as advection while heat ground heat fluxes are determined using Fourier’s law [37, 38].”

10. Authors analyzed the PET values from their experiments. However, how these values were calculated? Using the RayMan tool, or some others? Which individual parameters were used for calculations? Please specify this in the text. One more question is why do not to use the mPET, modified and more advanced version of PET?

Based on the ENVI-met simulation output, we calculated PET using the integrated tool Biomet. In the process, we used the usual default settings for body and clothing characteristics and the metabolic rate of a reference person. We supplemented this information in section 3.2.

Besides PET there are several other measures of thermal comfort, such as the mentioned mPET, PMV, UTCI, and PPD. However, PET is the most basic and widely used measure and therefore we decided to present the PET results here. This was sufficient to illustrate the effects of the adaptation scenarios. Extending our tool by additional thermal comfort measures is straightforward.

11. Authors presented the online tool and specified the date of experiments as 2015-07-03 with weather station data usage as input. However, if the system is really online, the model calculations should use updating operational station data each day at 00 h local time to simulate high-resolution conditions. Does this operational system implemented, or not – please, specify this.

This is a very interesting idea. At this stage, the online tool is only able to visualize and analyze urban climate data that has already been simulated in advance. Our simulations each had a calculation time of about 2 weeks. Thus, an updating according to the current weather data is not feasible and we can only consider such an exemplary case as it was performed in our study. The calculation times may be significantly reduced using high-performance computer networks while our online tool could serve as a suitable framework for an appropriate online presentation of the results. However, setting up such a workflow is beyond the scope of this study.

12. Authors labeled radiation, ventilation, evapotranspiration, and heat storage processes as biophysical processes. In my opinion, it is incorrect term, more precise one would be energy fluxes.

Thank you for this remark that indicates an important aspect: The biophysical processes (radiation, ventilation, evapotranspiration, heat storage) contribute to the surface energy balance in terms of energy fluxes. However, these energy fluxes manifest themselves in different temperature increases, depending on the local climate sensitivity of the surfaces. This is expressed in Eq. (8-10) and the following text; see also the text after Eq.(5).

13. In conclusion, Authors are recommended to provide quite more information about future perspectives of presented online tool development based on limitations pointed out in 4.3.

The online tool allows the identification of urban structures exhibiting an unfavourable partition of the biophysical processes leading to strong warming and are, therefore, particularly vulnerable to urban heat. Nevertheless, our study is restricted to an example situation (heat wave event with southern wind direction). As already responded to your comment 11, we consider the online tool as the basis for additional simulations since the online tool can be easily extended to the simulation output of other regions (see end of section 3.1).

14. There are also some typos. Figures should be placed mostly after the first mention in the text. Line 99: ‘of of’; line 106: ‘othphotos’ (‘orthophotos’); line 123: ‘(scenario 1)’ – is missed; lines 281, 283, 288, 298, 304, 312, 326 – there are duplicated closing brackets; Table 2: ‘szenario’ (‘scenario’); number 43 in reference contains error in Author’s Name; and maybe some others.

Thank you for pointing out these typos. We have revised them. 

The given questions and remarks recommended to be answered and/or included in text. However, these issues are not crucial for results, therefore, I recommend this manuscript to minor revision.

References:

Santamouris, M. Cooling the cities – A review of reflective and green roof mitigation technologies to fight heat island and improve comfort in urban environments. Solar Energy 2014, 103, 682–703. https://doi.org/10.1016/j.solener.2012.07.003.

Santamouris, M. Using cool pavements as a mitigation strategy to fight urban heat island—A review of the actual developments. Renewable and Sustainable Energy Reviews 2013, 26, 224–240. https://doi.org/10.1016/j.rser.2013.05.047

Hertel, D.; Schlink, U. Decomposition of urban temperatures for targeted climate change adaptation. Environmental Modelling & Software 2018, 113. https://doi.org/10.1016/j.envsoft.2018.11.015

Author Response File: Author Response.pdf

Reviewer 3 Report

It is a well-written article that addresses a addresses a very significant aspect of climate change adaptation in the urban areas. The results of different climate change adaptation scenarios are evaluated through digital tools that can be used by stakeholders to prepare for the changing climate. The manuscript is clear and presented in a well-structured manner. The digital tool is an asset that will provide real-time effects of adaptation measures to assist in decision making.The figures are clear and explained well. The conclusions should be improved by summarising important factors from the findings. Some typo errors can be found and hence proofreading is requires. Examples of typos are on line 99, Table 2, line 361 etc.  

Author Response

Reply: We would like to thank the reviewers for their thoughtful comments and efforts towards improving our manuscript.  We have taken the comments on board to improve and clarify the manuscript. Please find below a detailed point-by-point response to all comments (reviewers’ comments in black, our replies in blue; see also the attached pdf file).

Reviewer #3:

It is a well-written article that addresses a very significant aspect of climate change adaptation in the urban areas. The results of different climate change adaptation scenarios are evaluated through digital tools that can be used by stakeholders to prepare for the changing climate. The manuscript is clear and presented in a well-structured manner. The digital tool is an asset that will provide real-time effects of adaptation measures to assist in decision making. The figures are clear and explained well. The conclusions should be improved by summarising important factors from the findings. Some typo errors can be found and hence proofreading is requires. Examples of typos are on line 99, Table 2, line 361 etc.

Thank you for reviewing our article and for your positive feedback. We corrected the typos. In addition, we extended the conclusions section by the sentence:

As was shown in our discussion, the selection of the most suitable approach for urban climate adaptation varies with time as well as the site characteristics and a generalization is not possible. For that reason, the presented software is a useful tool for climate adaptation of cities.

 

Author Response File: Author Response.pdf