the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Simulation of the heat mitigation potential of unsealing measures in cities by parameterizing grass grid pavers for urban microclimate modelling with ENVI-met (V5)
Abstract. Many urban areas are characterized by both a growing population and an intensification of summer heat events in the context of climate change. Thus, more and more people are exposed to heat stress and corresponding health consequences. Measures for climate change adaptation such as unsealing strategies are needed in the existing urban fabric to reduce sensible heat flux by increasing latent heat flux to cool down the urban environment without requiring additional space or changing the basic function of the area. Unsealing measures like grass grid pavers (GGPs) can also help to reduce flooding risks due to increased infiltration and water storage capacities. Up to now, a parameterization of GGPs for microclimatic simulations is not available. To fill this research gap, we here present a new GGP model parameterization developed for the fluid dynamics microclimate ENVI-met model based on field measurements with double-ring infiltrometers etc. To analyse the microclimatic effects and the cooling potential of this GGP parameterization, scenario analyses were performed using a validated ENVI-met model setup for an urban high-density study area in Cologne/Germany. An extreme scenario was designed to address the maximum cooling potential of the GGPs in comparison to the dominant sealed asphalt surfaces in the study area, and a more realistic scenario with a usage-compatible installation of GGPs in the model domain only in side streets and inner courtyards while main streets remain sealed We found a maximum cooling potential of up to -20.1 K for ground surface temperature and up to -7.1 K for air temperature in 1 m above ground level for a simulated 3-day heat wave in summer 2022 which represents a 20-year heat event in Cologne. On spatial average, a decrease of up to -11.1 K for surface temperature and up to -2.9 K for air temperature was determined. On temporal average for the 3-day heat event, statistically significant mean temperature differences of -5.8 K for surface temperature and -1.1 K for air temperature were simulated. Cooling effects are more pronounced during daytime for surface temperature especially on unshaded areas, while cooling effects for air temperature are strongest during nighttime. Model results also show that the entire air volume in the study area is cooled down due to this adaptation measure, even in areas of the domain where no surfaces have been unsealed in the scenario design. The more realistic GGP scenario shows cooling effects of a comparable magnitude as the extreme GGP scenario. Thus, even partial GGP unsealing is an effective adaptation measure for reducing extreme temperatures in cities if water availability is not limited.
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RC1: 'Comment on egusphere-2024-697', Anonymous Referee #1, 25 Jul 2024
- Scientific significance (2)
The paper addresses an actual urban microclimate issue an adds significant information to the knowledge about colling the city by vegetation and specifically by grass grid pavers.
- Scientific quality (2)
The approach to the research is well substantiated.
The results provide a good basis for much additional research, for example the relationship with the albedo of surface materials. More suggestion for further research would be desirable.
- Scientific reproductibility (2)
The methodology description is sufficiently complete to allow reproduction.
- Presentation quality (3)
The description is sometimes redundant, the authors should scan the paper and reduce repetitions, it would improve the quality of the presentation.
Citation: https://doi.org/10.5194/egusphere-2024-697-RC1 -
AC1: 'Reply on RC1', Nils Eingrüber, 29 Jul 2024
Thank you very much for your valuable feedback. We will deal with this and we are happy to add additional suggestions for further research, especially with regard to other full unsealing measures, combinations with other technical- and/or nature-based solutions as well as surface albedo effects.
Citation: https://doi.org/10.5194/egusphere-2024-697-AC1
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RC2: 'Comment on egusphere-2024-697', Anonymous Referee #2, 13 Aug 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-697/egusphere-2024-697-RC2-supplement.pdf
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AC3: 'Reply on RC2', Nils Eingrüber, 02 Oct 2024
Thank you very much for your valuable feedback and recommendations. We will address your comments in detail in the upcoming version and specify the corresponding descriptions and evaluations more precisely, clearify the structure and deviations like between Ta and Ts, as well as refine the drawn conclusions. We are also happy to add information on the overall thermal effects for the entire neighborhood as well as list all the test results etc.
Citation: https://doi.org/10.5194/egusphere-2024-697-AC3
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AC3: 'Reply on RC2', Nils Eingrüber, 02 Oct 2024
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RC3: 'Comment on egusphere-2024-697', Anonymous Referee #3, 02 Sep 2024
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AC2: 'Reply on RC3', Nils Eingrüber, 02 Oct 2024
Thank you very much for your valuable feedback. We are happy to address your aspects in the upcoming version and will discuss, review and intercompare the cooling effects and parameterization in more detail, as well as outline the development contribution in a more specific way.
Citation: https://doi.org/10.5194/egusphere-2024-697-AC2
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AC2: 'Reply on RC3', Nils Eingrüber, 02 Oct 2024
Status: closed
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RC1: 'Comment on egusphere-2024-697', Anonymous Referee #1, 25 Jul 2024
- Scientific significance (2)
The paper addresses an actual urban microclimate issue an adds significant information to the knowledge about colling the city by vegetation and specifically by grass grid pavers.
- Scientific quality (2)
The approach to the research is well substantiated.
The results provide a good basis for much additional research, for example the relationship with the albedo of surface materials. More suggestion for further research would be desirable.
- Scientific reproductibility (2)
The methodology description is sufficiently complete to allow reproduction.
- Presentation quality (3)
The description is sometimes redundant, the authors should scan the paper and reduce repetitions, it would improve the quality of the presentation.
Citation: https://doi.org/10.5194/egusphere-2024-697-RC1 -
AC1: 'Reply on RC1', Nils Eingrüber, 29 Jul 2024
Thank you very much for your valuable feedback. We will deal with this and we are happy to add additional suggestions for further research, especially with regard to other full unsealing measures, combinations with other technical- and/or nature-based solutions as well as surface albedo effects.
Citation: https://doi.org/10.5194/egusphere-2024-697-AC1
-
RC2: 'Comment on egusphere-2024-697', Anonymous Referee #2, 13 Aug 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-697/egusphere-2024-697-RC2-supplement.pdf
-
AC3: 'Reply on RC2', Nils Eingrüber, 02 Oct 2024
Thank you very much for your valuable feedback and recommendations. We will address your comments in detail in the upcoming version and specify the corresponding descriptions and evaluations more precisely, clearify the structure and deviations like between Ta and Ts, as well as refine the drawn conclusions. We are also happy to add information on the overall thermal effects for the entire neighborhood as well as list all the test results etc.
Citation: https://doi.org/10.5194/egusphere-2024-697-AC3
-
AC3: 'Reply on RC2', Nils Eingrüber, 02 Oct 2024
-
RC3: 'Comment on egusphere-2024-697', Anonymous Referee #3, 02 Sep 2024
-
AC2: 'Reply on RC3', Nils Eingrüber, 02 Oct 2024
Thank you very much for your valuable feedback. We are happy to address your aspects in the upcoming version and will discuss, review and intercompare the cooling effects and parameterization in more detail, as well as outline the development contribution in a more specific way.
Citation: https://doi.org/10.5194/egusphere-2024-697-AC2
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AC2: 'Reply on RC3', Nils Eingrüber, 02 Oct 2024
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