Urban overheating poses a significant risk to most cities worldwide. To support effective heat mitigation decision-making, we propose a mitigation-centered machine learning model. A feature classification framework based on the scale at which physical processes or urban characteristics influence urban climate is introduced. Specifically, physcial processes primarily governed by background climate are classified as driving climates (DC), while those exhibiting two-way couplings with urban areas are categorized as local climates (LC). Meanwhile, urban morphologies, materials, and landscaping that not only have strong heat mitigation potential but are also manageable are classified as urban attributes (UA). This model enables the assessment of the most effective mitigation strategies because the effectiveness of multiple potential mitigation measures-i.e. the impact of urban attributes-can be evaluated through their respective weights. This is crucial, as some high-ranking urban climate drivers in conventional models, such as urban boundary layer height, may be less practical for direct mitigation efforts, as discussed in our perspective article [1].

As an initial case, we applied our model to Zurich, Switzerland, using Weather Research and Forecasting (WRF) simulations for the summers of 2017 and 2019, covering both heatwave and non-heatwave periods. Our model outperformed a reference model that lacked the classification of influencing factors. Additionally, incorporating historical heatwave data further improved model performance. Our findings suggest that increasing leaf area intensity (LAI) is the most effective strategy for reducing pedestrian-level air temperatures in Zurich, outperforming other heat mitigation interventions. Our model offers a practical framework to support urban heat mitigation, particularly in scenarios where multiple measures need to be assessed, prioritized, and implemented.

Reference

[1] Prioritizing Nature-Based Solutions and Technological Innovations to Accelerate Urban Heat Mitigation Pathways. Y Zhao, J Carmeliet, R Hamdi, C Yuan, X Ding, D Derome, Y Fan, S Jiang, J Peng. Annual Review Environment Resources, 2025.

How to cite: Tschan, D., Wang, Z., Carmeliet, J., and Zhao, Y.: Cooling Cities Through Data-Driven Insights: Distinguishing and Weighting Driving Climates, Urban Attributes, and Local Climates, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-301, https://doi.org/10.5194/icuc12-301, 2025.

Urban climate mitigation strategies, such as increasing vegetation and enhancing surface reflectivity, are widely studied with numerical weather models. However, mesoscale models like the Weather Research and Forecasting (WRF) model typically apply these strategies across all urban areas within the domain, which is neither practical nor reflective of real-world implementations. In reality, mitigation efforts are usually local, incremental, spatially disjointed, or targeted toward the most vulnerable areas. This highlights the need for more flexible modeling approaches that better represent the scale at which urban climate mitigation occurs.

In this study, we introduce a novel method for implementing local urban climate mitigation strategies in WRF. Our approach modifies land use classifications and urban parameterization tables, allowing mitigation strategies to be applied at individual gridcells rather than across the entire domain. This enables more precise testing of interventions and aligns simulations with how cities actually deploy mitigation efforts.

We demonstrate this method in a series of WRF simulations over Baltimore, Maryland, examining the effects of urban greening and surface albedo modifications under different spatial scenarios, including targeted mitigation within select neighborhoods, implementation in low-income communities, and focused interventions in the city's warmest areas. Results highlight how the spatial configuration of mitigation strategies influences urban temperatures and atmospheric conditions. By enabling neighborhood-scale intervention testing, this method bridges the gap between mesoscale climate modeling and real-world urban planning.

How to cite: Foust, W., Davis, K., Hadjimichael, A., Różański, M., Zaitchik, B., Eyni, A., and Waugh, D.: A Realistic Approach to Urban Climate Mitigation with WRF: Modeling Local and Practical Solutions, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-543, https://doi.org/10.5194/icuc12-543, 2025.

As cities grow and face increasing ecological and social challenges, integrating urban green-blue infrastructure (uGBI) is essential for enhancing resilience and quality of life. However, despite its proven benefits, the adaptive capacity of uGBI depends mainly on contextual aspects. Among these are morphological and climate aspects, governance challenges, land-use regulations, and socio-cultural factors. Developing global knowledge for these locally embedded policies is sometimes successful, but it might also lead to pitfalls and trade-offs, particularly in low-middle-income countries (LMICs). Improving international cooperation and knowledge exchange on the science-policy interface could enhance the effectiveness of these policies.

Recently, different mapping methodologies have been proposed to bridge local and global knowledge to arrive at better-informed uGBI policies. In this paper, we will compare ecosystem, heritage, and landscape approaches to uGBI to identify how mapping methodologies can contribute to more balanced and sustainable urban development. These methodologies will be compared by reviewing their theoretical focus and research objectives, use of data (qualitative or quantitative), relationship to everyday practices, and connection to planning institutions. Their application in LMICs is of specific interest here.

This research contributes to the ongoing discourse on sustainable urban development by clarifying the critical obstacles that hinder uGBI implementation. The paper will contribute to RUGBIS research, a collaboration of PBL, TUD, and VU.

How to cite: Peters, B., Bijlsma, L., Huang, X., and van Rijn, F.: Between Global Data and Local Living Quality: Risks and possibilities for improving uGBI, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-1039, https://doi.org/10.5194/icuc12-1039, 2025.

The intensification of urban heat due to climate change poses risks to both human populations and biodiversity. Urban green spaces (UGS), such as parks and gardens, have been demonstrated to be cooler than surrounding areas. However, in a future hotter climate, it is unclear whether UGS will maintain sufficiently cool conditions to support both species and human tolerances. The study aims to investigate how climate change will affect the microclimate conditions of UGS and evaluate the effectiveness of different strategies to maintain their cooling benefits. We applied a microclimate model (UT&C) to simulate air temperature, thermal comfort and other relevant variables within 15 urban green spaces across three Swiss cities (Zurich, Geneva and Lugano) under historical and future climate conditions. All models show good predictive performance for air and surface temperatures (R² = 0.61–0.97). Future climate data for the 2080 decade was obtained from the COSMO-CLM convection permitting model under RCP 8.5 and bias-corrected to the station scale. Scenarios incorporating these vegetation parameters most relevant to thermal comfort were developed and assessed for their effectiveness in mitigating temperature increases in a future climate.

Preliminary results for Zurich show that the thermal comfort within UGS, as represented by Universal Thermal Climate Index (UTCI), is expected to increase by an average of 2.2°C by 2080 if the existing vegetation configuration in urban green spaces remains unchanged. Increasing the fraction of ground vegetation is the most effective solution, further cooling by up to 0.8 °C, although unable to offset the negative impact on thermal comfort due to climate change. Future work will confirm the generalizability of these findings with a comparison across all UGS and cities. Overall, this study provides insights into the adaptive management of green infrastructure in cities for both humans and biodiversity in the face of climate change.

How to cite: Yin, Y., Manoli, G., and Cook, L.: Cooling down urban green spaces in a future climate, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-253, https://doi.org/10.5194/icuc12-253, 2025.

Nature based solutions have a critical role in climate mitigation and adaptation in cities. Recently, urban vegetation has gained attention in cities’ climate action plans as a vital strategy for enhancing carbon sequestration from the atmosphere. To support the cities, a detailed knowledge of the strength and variability of urban biogenic carbon sinks and their dependencies on environmental conditions in changing climate is critical. In this study we harness the intensive eco-physiological observations made in parks, gardens, forests and street trees in the Helsinki in 2020—2022 and land surface modelling (LSM) to examine our current capabilities in simulating urban biogenic carbon sinks and the magnitude and variability of these sinks in different urban vegetation types and in changing climate.

We see how different urban green infrastructure types, from urban forests to lawns, can act as carbon sinks. The three tested LSMs (JSBACH, LPJ-GUESS and SUEWS) effectively simulated seasonal and annual variations, as well as the impacts of weather events on carbon fluxes and related factors in both irrigated and non-irrigated lawns, park trees, and urban forests. Irrigation as key management practise emerged as a key factor often improving carbon sequestration. Tree-covered areas demonstrated greater carbon sequestration rates compared with lawns on an annual scale. Meadows are not better carbon sinks than lawns under typical summer conditions, but their drought resilience is better maintaining their capacity to uptake carbon also during drier periods contrary to lawns. In Helsinki, the city-level biogenic carbon sinks are expected to increase with climate change by 11% mainly due to the longer growing season whereas carbon sinks in forested areas decreased due to increased environmental stress. This research emphasizes the importance of integrating diverse vegetation types and impacts of irrigation into urban carbon modelling efforts to inform sustainable urban planning and climate change mitigation strategies.

How to cite: Järvi, L., Thölix, L., Havu, M., Backman, L., and Kulmala, L.: Advancing our understanding on the climate mitigation potential of urban green infrastructure   , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-219, https://doi.org/10.5194/icuc12-219, 2025.

Urban trees are increasingly recognized as a vital urban planning strategy for mitigating heat stress in cities facing climate risks worldwide. To improve the effectiveness of tree planning, it is essential to evaluate how their cooling effects vary depending on urban contexts. The effectiveness of urban trees in reducing temperature and climate risks (e.g., health risks, energy consumption) is influenced by various factors, including building morphology, location, and climate zone. However, a comprehensive comparison of urban tree effects across various global cities using urban climate models remains unstudied.

In this study, we simulated the cooling effect of urban trees in diverse cities with different climate zones and built environments, including Tokyo (Japan), Baltimore and Phoenix (US), and Telok Kurau (Thailand). Many urban climate models have simplified the cooling effects of trees, making it challenging to accurately estimate their impact. The CM-BEM (one-dimensional Climate Model and Building Energy Model) employs a mosaic of non-urban tiles to represent green spaces but does not account for interactions between urban trees and other urban elements. However, CM-BEM incorporates anthropogenic heat from buildings by simulating air conditioning use, providing a useful framework for comparing adaptation strategies between air conditioning and urban trees, which remains our future work.

To enhance the capability of CM-BEM in representing urban tree effects, we integrated a multi-layer tree canopy structure and simulated radiation and heat flux interactions between trees and urban structures. Our findings indicate that the cooling effects of urban trees vary across cities, with greater temperature reduction observed in densely built environments and drier climate regions.  

How to cite: Park, C., Takane, Y., Kondo, H., Nakajima, K., and Lee, D.-K.: Different cooling effect of urban tree in global cities, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-520, https://doi.org/10.5194/icuc12-520, 2025.

Blue-Green Infrastructure (BGI), as a Nature-Based Solution, is one of the key approaches to addressing climate change impacts and urbanization challenges. By enhancing urban resilience through sustainable stormwater management and flood risk mitigation, BGI also delivers diverse ecosystem services. However, despite its multiple benefits and co-benefits, BGI still remains far from mainstream adoption.

We adopted Socio-Technical Transition (STT) as the theoretical framework of our research to investigate the barriers to BGI adoption and to explore the transition pathways to it. Using Sydney as a case study, we designed and facilitated two focus groups involving planners, decision-makers, stakeholders, developers, and engineers from various entities such as state and local governments, agencies, councils, and corporations. Thematic and content analysis of the focus group data was conducted and synthesized with existing published literature.

Building on these findings, we argue that this is a wicked problem and a complex situation that requires a Systems Thinking approach to holistically integrate all the findings into designing transition pathways to facilitate mainstreaming BGI.

The results indicate that transitions to BGI depend on regime shifts in five key domains: (1) Governance, institutional organisation and collaboration, (2) Economics and finance, (3) Knowledge, expertise and technical aspects, (4) Socio-cultural Attitudes, and (5) The planning regime. Acknowledging the complexity of this process, it should be approached as an iterative, continual learning experience—an "infinite loop" of probing, sensing, and responding. This research underscores the necessity of adopting STT through systemic interventions to overcome practical barriers and facilitate the widespread uptake of BGI in urban environments.

How to cite: Sadegh Koohestani, S., Mukheibir, P., Wakefield-Rann, R., and Santamouris, M.: Transition Pathways Towards Blue-Green Infrastructure: Adopting a System’s Approach, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-19, https://doi.org/10.5194/icuc12-19, 2025.

Due to the projected impacts of climate change, there is increasing urgency to investigate how to adapt to potential increases of extreme temperatures, especially in cities. Several possible adaptation strategies already exist, but their complex impacts on urban temperatures remain largely uncertain. In our study, we investigate the reduction in temperature by different adaptation strategies and study the spatial variations in heat exposure across different Belgian cities. By using a multi-model approach, we aim to quantify the uncertainties related to the reduction of heat by different adaptation strategies and using different models.

The focus of our study is the extreme heatwave of July 2019, where temperatures reached 40°C in Belgium. We use a mini-ensemble of three urban climate models: the urban boundary layer model UrbClim at 100m horizontal resolution, WRF with the multi-layer BEP/BEM at 1km and COSMO-CLM with bulk urban land-surface scheme TERRA_URB at 2.8km. Three adaptation strategies are implemented across the three models: increasing vegetation fraction by decreasing built-up coverage, implementing cool roofs by increasing roof albedo, and a combination of both. This mini-ensemble allows us to characterize spatial variations in heat exposure across the city and to investigate the possible reduction of heat exposure by certain adaptation strategies.  Our model intercomparison improves our understanding of how different model parameterizations simulate the impact of different heat adaptation strategies and why each intervention may have different impacts in the different models. Lastly, we quantify the potential heat-reduction effects of the adaptations for local populations.

How to cite: Serras, F., Vanderkelen, I., Brousse, O., Simpson, C., Lauwaet, D., Demoury, C., van Lipzig, N. P. M., and Heaviside, C.: Quantifying  the uncertainty of urban heat adaptation impacts through a multi-model approach, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-669, https://doi.org/10.5194/icuc12-669, 2025.

Heat poses a significant risk to human health in cities due to the urban heat island (UHI) effect. Understanding the diverse impacts of heat across different neighbourhoods is essential, as is recognising the potential of urban vegetation to mitigate temperatures. This study focuses on Paris and its green spaces, where the limited observational data make numerical modelling necessary to estimate the cooling capacity of urban green areas.

The primary aim of this research is to examine the role of parks and urban forests in reducing air temperatures during the summer. Simulations were carried out for 2022 and 2023 using the Meso-NH model, a non-hydrostatic atmospheric research model. Meso-NH is driven by atmospheric boundary conditions from the French convective-scale operational Numerical Weather Prediction model AROME-France. The model is coupled with the land surface model SURFace EXternalised (SURFEX), which incorporates the Town Energy Balance (TEB) model for urban elements, supported by a high-resolution surface database. The simulations use three nested domains with grid resolutions of 1200 m, 300 m (covering the Paris region), and 100 m (over the city of Paris). Model validation of 2-m air temperature was performed using data from the PANAME intensive measurement campaign.

Previous studies have shown, through local observations, that different weather types produce contrasting UHI regimes, leading to varying cooling capacities of parks. This study demonstrates that hectometric-scale modelling successfully replicates these observed patterns. Furthermore, we explore the potential of parks to cool surrounding neighbourhoods under varying turbulent mixing conditions.

This research offers valuable insights into the role of urban green spaces in mitigating the urban heat island effect, providing potential strategies to enhance urban resilience against heatwaves.

How to cite: Havu, M., Nagel, T., Wurtz, J., Masson, V., Haeffelin, M., Ribaud, J.-F., Kotthaus, S., Dupont, J.-C., and Lemonsu, A.: Hectometric-scale modelling of Parisian green spaces’ cooling capacity, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-360, https://doi.org/10.5194/icuc12-360, 2025.

Since more extreme heat events occur and will occur under climate change, it is important to adapt urban environments in such a way that the population is safeguarded from extreme heat stress as much as possible. It is however unclear how green, blue and brown infrastructures perform in real urban redevelopments. The redevelopment of the main square of the city of Genk (Belgium) was therefore studied with in situ observations and microclimate modelling. Three weather stations were placed onsite, each capturing a different micro-environment both before and after redevelopment and an additional station served as a reference by maintaining the same micro-environment before, during and after the redevelopment. During August 2023 and 2024 the stations measured 2 m-air temperature, black globe temperature, relative humidity, wind speed and direction, making it possible to derive outdoor thermal comfort indices. This data is used to validate the ENVI-met microclimate model, which in turn is employed to model the complete local environment. This allows us to identify the microclimate and thermal comfort impact of persisting, new and removed green, blue and brown infrastructures in their specific environments. The model approach allows us to evaluate the effects of these nature-based adaptation measures under different climate scenarios and regional development scenarios. Such knowledge can be directly translated into practical appliances, mainly allowing urban planners and architects to better design climate proof living environments. A similar observation and model strategy will be employed in six other Belgian cities to verify the outcomes.

How to cite: Puynen, S., Caluwaerts, S., Top, S., Verdonck, P., and Hamdi, R.: Modelling and observations of green and blue adaptation measures, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-464, https://doi.org/10.5194/icuc12-464, 2025.

Exposure to elevated temperatures in heavily built-up environments, largely caused by impermeable surfaces, artificial heat exhaust, and reduced green spaces, poses serious challenges to urban sustainability and public health. While urban green spaces are recognized for their potential to mitigate such heat island effects through shading, evapotranspiration, and airflow improvement, existing studies often lack systematic quantification of these cooling effects and fail to contextualize them within specific urban environments. This study investigates the contribution of green spaces to lowering the high heat exposure in urban areas, where a neighborhood in Brooklyn, New York, was used as the lab to carry out measurements and simulations of the constructed and natural environment. Computational simulations were conducted to replicate the urban landscape, including buildings, streets, and vegetation, and to model the effects of vegetation, particularly evapotranspiration, on temperature. Summer temperature, wind speed, and humidity were simulated at a high spatial resolution, and the results were compared with measured data for verification. This approach contributes to the reliability of the predictions and provides localized insights into the cooling potential of green spaces. By addressing gaps in research in this area, the results of this study area aim to inform planning strategies to support climate-resilient urban development.

How to cite: Yamada, S., Ghandehari, M., and Fitzky, M.: Multi-Physics Analysis of Cooling Effects of Green Spaces: Case Study in Brooklyn, New York, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-545, https://doi.org/10.5194/icuc12-545, 2025.

How to cite: Karvonen, A., Havu, M., Grange, S., Ponomarev, N., Stagakis, S., Molinier, B., Kljun, N., Brunner, D., Emmenegger, L., and Järvi, L.: Utilizing urban land surface model SUEWS to estimate effects of green infrastructures to carbon and heat balances in Zürich, Switzerland , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-358, https://doi.org/10.5194/icuc12-358, 2025.

Abstract:

As the climate crisis intensifies, urban areas worldwide are experiencing rising temperatures and more frequent heat waves, exacerbating thermal discomfort and straining urban ecosystems. One prominent manifestation of this phenomenon is the exacerbation of the urban heat island (UHI) effect, in which built-up environments retain more heat than surrounding rural areas due to land cover modifications and anthropogenic activities.

This study leverages satellite remote sensing (RS) techniques and the World Urban Database and Access Portal Tools (WUDAPT) framework to classify Local Climate Zones (LCZs) and assess UHI dynamics in Wilmington, USA, and Amsterdam, Netherlands. Using multi-temporal Landsat imagery and machine learning-based classification in SAGA GIS, we analyze spatial patterns of UHI intensity and their relationship with green-blue space (GBS) connectivity.

Our spatial regression and correlation analyses reveal that areas with lower GBS coverage exhibit significantly higher UHI intensity, with temperature differences averaging +3.5°C. Conversely, regions with greater GBS density—particularly in Amsterdam—demonstrate a measurable cooling effect of up to 2.8°C. These findings underscore the critical role of GBS in mitigating urban heat stress and highlight the necessity of integrating climate-responsive strategies into urban planning.

This study utilizes WUDAPT’s standardized LCZ classification to provide a scalable and replicable framework for assessing urban climate resilience. The insights generated will support equitable cooling infrastructure development, inform heat adaptation policies, and advance sustainable urban design. This research further demonstrates the potential of RS and LCZ-based methodologies to guide climate adaptation planning at multiple urban scales.

Keywords:

Climate Crisis, RS, Urban Heat Island (UHI), WUDAPT, Green-Blue Spaces, Remote Sensing, Urban Resilience

How to cite: Farahbakhshy, M., Naghibi, M., and Veron, D.: Understanding and Mitigating Urban Heat Islands: A Satellite Remote Sensing and Local Climate Zone Approach to Green-Blue Space Connectivity for Urban Planning, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-844, https://doi.org/10.5194/icuc12-844, 2025.

In the context of climate change, it is crucial to develop methods for assessing the impact of green infrastructures on urban climates through a co-constructive process with local planners. The study proposes a methodological framework for modelling geoprospective greening scenarios in collaboration with the metropolitan services of Dijon (eastern France, 260 000 inhabitants).

A sensitivity analysis confirms the suitability of the Town Energy Balance (TEB) model coupled with Méso-NH for simulating the effects of tall and short vegetation on the UHI. It also highlights the need for detailed vegetation databases to ensure research remains aligned with local conditions, which is especially important in action research.

The collaborative development of vegetation scenarios is anchored in the theoretical framework of geoprospective. This approach yields contrasting scenarios tailored to local contexts and leads to realistic greening guidelines derived from urban planning documents. These scenarios address a wide range of concerns raised by local planners, validating geoprospective as an effective tool for informing institutional decision-making. One scenario in particular stands out: it prioritizes the greening of available spaces in the city. It leads to add more than 100 000 trees and the equivalent of 4000 football fields. A dedicated QGIS plug-in was developed to support this scenario, paving the way for broader applications of scenario-based planning tools.

This scenario focuses largely on greening private gardens and commercial/industrial areas. Results shows a reduction of the intensity (by a mean of 2°C) and spatial extent of UHI, prompting further consideration of the role of private garden greening.

Overall, these findings highlight the need for an interdisciplinary methodological framework that integrates land-use planning, geomatics, and climate modelling. They also underscore the importance of combining action research with the translation of urban planning documents into scenarios, a strategy that could ultimately lead to the development of robust decision-support and urban planning tools.

How to cite: Poupelin, M., Pergaud, J., Thévenin, T., and Richard, Y.: Modelling co-designed geoprospective scenarios to assess greening adaptation strategies at the metropolitan scale, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-304, https://doi.org/10.5194/icuc12-304, 2025.

Extreme weather events and the occurrence of hydrological disasters have intensified and grown into environmental challenges in many Brazilian cities. Given the current climate crisis scenario and the escalating frequency and magnitude of extreme events, it is imperative to not only implement prevention and mitigation measures but also to embrace strategies for disaster adaptation. This article aims to explore green infrastructure solutions that can mitigate flooding impacts in the Iguaçu-Sarapuí river basin, situated in the Metropolitan Region of Rio de Janeiro state, Brazil. To achieve this, we analyzed precipitation thresholds for the basin over each decade (from 1980 to 2020) using boxplots and quantile techniques, and assessed the impacts based on Civil Defense data from cities within the basin - institutions which are fundamental to disaster risks management. Additionally, we utilized Landsat data to map land cover, focusing on detecting changes in wetlands and flooded areas of the basin to identify correlations between these changes, the intensification of extremes, and the severity of impacts. Preliminary analysis of the study area revealed that extreme rainfall events and land use characteristics have contributed to flooding, leading to a range of environmental and social consequences including loss of life, economic damage, and displacement of populations. The expansion of urbanized areas and reduction of green spaces have notably decreased infiltration zones capable of capturing rainwater, consequently increasing surface runoff within the basin. Over the decades, local governments have predominantly favored gray infrastructure measures in the basin, leading to significant growth in paved and impermeable surfaces. Despite the implementation of flood control measures, the issue persists nowadays.

How to cite: da Costa, M. and Oscar Júnior, A.: Green infrastructure measures as a strategy to adaptation of flooding risks in the Iguaçu-Sarapuí river basin, Rio de Janeiro, Brazil, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-530, https://doi.org/10.5194/icuc12-530, 2025.

Children spend approximately 1,300 hours annually in schools, making air quality in these environments crucial for their health and development. This study analyzes outdoor air pollution exposure around 844 schools in the Brussels Capital Region (BCR) using high-spatial-resolution NO₂ data from the Curieuzenair citizen science project (September–October 2021). The project collected measurements at 2,483 locations across BCR, with dataset validation against IRCELINE governmental data.

The research analyzed three categories of indicators within multiple buffer zones (150, 300, 600, and 800 meters) around schools: green infrastructure (vegetation and tree canopy density), brown infrastructure (building and street surface density), and contextual factors (vehicles per household and altitude). Analysis of 150-meter buffer zones revealed that 390 of 844 schools exceed the WHO NO₂ daily limit(25 µg/m³) based on Curieuzenair data, while 841 schools exceed the WHO annual limit(10 µg/m³) according to IRCELINE data. Results demonstrate that building density significantly correlates positively with NO₂ concentrations, while both vegetation density and vehicles per household show significant negative correlations. A key finding reveals that tree canopy, while beneficial, has less effect on NO₂ concentrations than overall vegetation. Clustering analysis reveals distinct spatial patterns, with central districts showing highest NO₂ levels due to dense brown infrastructure and limited green spaces.

To the authors' knowledge, this is the first study in BCR to comprehensively analyze the relationship between urban green-brown infrastructure and air quality across all school environments. The findings underscore the potential of integrating regulatory data with citizen science to inform urban planning strategies, specifically helping identify school environments where increasing ventilation and vegetation density would most effectively reduce air pollution exposure and promote healthier learning spaces.

How to cite: Aydin, N., Irajpour, A., and Llaguno-Munitxa, M.: Examining Urban Green and Brown Infrastructure's Impact on Air Pollution: A Spatial Analysis of School Environments in the Brussels Capital Region, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-442, https://doi.org/10.5194/icuc12-442, 2025.

As urban populations grow and built infrastructure ages, climate change impacts are increasingly pronounced in urban environments. Cities face more temperature and hydroclimatic extremes, increasing human livability concerns. Green stormwater infrastructure (GSI) installation is one possible adaptation tactic to combat effects of urbanization and climate change while increasing resilience and livability. However, GSI is not always a suitable solution everywhere due to prevailing weather patterns, soil type, and other factors, in addition to typically being designed primarily for a hydrologic purpose (e.g., runoff reduction). We utilize the Community Land Model Urban (CLMU) to simulate the temperature and humidity impacts from installation of rain gardens, a form of ground-based vegetated GSI, across urban areas in the contiguous United States. With a previously-developed rain garden parameterization within CLMU, we bridge microscale vegetation modeling and macroscale climate modeling. We completed two 10-year (2006-2015) simulations at a 10-km resolution: 1) a control run with CLMU defaults, and 2) a GSI run reflecting our implemented rain garden parameterization. Results demonstrate potential for GSI to provide air temperature cooling effects, while also quantifying the relationship between cooling and humidity changes due to enhanced evapotranspiration and impacts to human perceived comfort. This approach helps assess the possible co-benefits of local thermodynamic effects associated with vegetated GSI implementation throughout cities in different climates and regions.

How to cite: Gray, L., Zhao, L., and Stillwell, A.: Local Temperature and Humidity Impacts from Rain Garden Implementation in Contiguous U.S. Cities Using Urban Climate Modeling, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-485, https://doi.org/10.5194/icuc12-485, 2025.

The thermal performance of vertical greenery systems (VGSs) in indoor/outdoor environments has been extensively studied; nevertheless, spatiotemporal observational experiments of VGSs at block-scale are scarce, with the evapotranspiration and cooling potential of VGSs in response to urban morphology remaining unclear. Therefore, scaled outdoor experiments were conducted to investigate the effects of VGSs on the wind, radiation, and thermal parameters in urban blocks with plan area index (λ_p) of 11% and 25% in the temperate region of Xingtai, China. VGSs reduce wind speed in the crossroads by 26% in the block with λ_p=25%, but no significant effect for λ_p=11%. Compared with non-VGS cases, VGS cases have more net radiation capture and lower albedo. VGS cases experience significant temperature reductions in wall (T_w), indoor, canyon air (T_a), and ground (T_g), as well as mean radiant temperature (T_mrt) and physiological equivalent temperature (PET). The south walls in blocks with λ_p=11% and 25% exhibit the best cooling effect, with maximum reductions of 22.2 and 18.4 °C at 0.1 m height, respectively, while the north walls show weaker cooling. The east and south streets experience better air and ground cooing than the crossroads. In the south street of blocks with λ_p=11% and 25%, the maximum reductions of T_a are 1.5 and 3.9 °C, respectively. VGSs in urban block with λ_p=11% have a greater evapotranspiration rate than that with λ_p=25%. Thus, block with λ_p=11% achieve more pronounced cooling effects on walls and indoor air, whereas block with λ_p=25% exhibit better air and ground cooling due to lower wind speed. Moreover, the reductions in T_mrt and PET in block with λ_p=25% are 36.7 and 20.2 °C, respectively, significantly higher than those with λ_p=11%.

How to cite: Zheng, X. and Hang, J.: Effects of vertical greenery systems on microclimate in urban blocks with different plan area indices: Scaled outdoor experiments, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-744, https://doi.org/10.5194/icuc12-744, 2025.

Urban trees are a defining element of the cityscape. In addition to their aesthetic value, further ecosystem services they provide, such as cooling, shading, air purification and runoff reduction, are currently the subject of research for climate-adapted cities. In times of climate change with frequent drought events and global warming, these are important elements for sustainable urban planning and climate protection in cities. However, the ecosystem services provided are directly related to the tree structures and size dimensions, the tree species, vitality and the site climate. In this study, more than 6,500 tree individuals of 26 common urban tree species in 17 cities worldwide were analyzed. Allometric growth relationships of tree dimensions (trunk diameter, height, crown dimensions, leaf area) were determined and tested for significant differences between species, climate of a city and growth types. A cluster analysis was used to evaluate allometric growth types based on the correlations between heights and crown growth with stem diameter, with which the species can be assigned to different growth types (e.g. Picea glauca as a species with small crown size but steep slope and Quercus robur as a species with large crown size and medium slope). The CityTree model was used to calculate and compare the ecosystem services provided by selected tree species in terms of CO₂ storage, runoff reduction and cooling through shading and transpiration. The results show that species characteristics (growth rate, drought strategy, crown density, light requirements) and location (i.e. urban climate and local site conditions and soil sealing) directly influence growth and ecosystem service provision. Our findings are of relevance for the sustainable planning and management of urban tree populations, particularly under climate change. The presented evaluations provide a simple determination of the expected tree dimensions and ecosystem services for individual tree species in cities.

How to cite: Moser-Reischl, A., Franceschi, E., Rahman, M. A., and Rötzer, T.: Worldwide comparison of the growth and ecosystem services of urban trees influenced by species traits and climate, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-359, https://doi.org/10.5194/icuc12-359, 2025.

As cities grow, rising temperatures and reduced green spaces contribute to more urban heat stress. Numerous studies confirm that urban tree cover increases Outdoor Thermal Comfort (OTC). However, there are fewer studies available, which confirm the optimal percentage of tree cover in the cities for built-up local climate zones. This study aims to observe and understand how different levels of tree cover (0%, 10%, 20%, 30%, existing tree cover) influence Outdoor Thermal Comfort (OTC) in two local climate zones common in Europe. Kassel, Germany, was selected as a representative mid-sized European city, with LCZ 5 (open mid-rise) and LCZ 6 (open low-rise) as its most frequent built-up local climate zones. We used the ENVI-met microclimate model to simulate temperature conditions for UTCI under the four different tree-cover scenarios to identify optimal tree-cover percentages for reducing heat stress. Since each Local Climate Zone (LCZ) has different layouts, including green space distribution, building shapes, and street arrangements, we selected three representative structures from each LCZ. In the presentation, we will discuss the main difference between the two LCZ types and approach a statement on balancing tree cover and OTC. The findings will help to understand how urban heat stress and thermal comfort are affected by different LCZ layouts and vegetation patterns.

How to cite: Patel, N. and Jänicke, B.: Assessing the effect of tree cover on Outdoor Thermal Comfort: A Comparative Study for two Local Climate Zones common in Europe, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-960, https://doi.org/10.5194/icuc12-960, 2025.

Trees and green infrastructures are recognized as essential to help adapt cities to deal with urban heat extremes. But while it is common knowledge that trees contribute to cooling through shade and evapotranspiration, it remains unclear what the relationship is between these mechanisms and the various thermal metrics used in the built environment. A comprehensive and reliable approach to equipment and protocols to measure the various tree cooling performances is by extension, also lacking. Accurate data on the performances of different tree species in relation to different thermal metrics is an expected outcome of such an approach. This paper presents the results of a study addressing these questions. A protocol was developed outlining the relevant metrics to measure, the selection and calibration of relevant instruments and equipment, the locations in and around trees for the placement of instruments, the minimum climatic conditions needed for measurement campaigns, and procedures for the setup, duration and validation of measurements. Relevant metrics to measure include Mean Radiant Temperature (MRT), Physiological Equivalent Temperature (PET) and Air Temperature. Five tree architecture traits impacting MRT were identified, expanding on current assumptions such as crown density, gap fraction and leaf area (index). Cooling performance values were generated for 69 tree species in all three metrics. The median difference in MRT between a reference point in the sun and beneath the trees ranged from -32.2°C to -22.5°C, illustrating the high impact on MRT but also the variability in cooling performance across different species and conditions. PET values under the analyzed trees ranged between 31°C and 45°C, demonstrating substantial differences in thermal comfort according to the tree species. The air-cooling performance of a tree was found to vary relative to the weather conditions, with cooling performance decreasing with the increase of atmospheric temperature.

How to cite: van der Velde, R., van Esch, M., Maiullari, D., and Pouderoijen, M.: Cool Tree Architecture and Measurement Protocols, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-1023, https://doi.org/10.5194/icuc12-1023, 2025.

Urban trees are key in heat resilient design strategies in cities. However, it remains unclear which trees are more effective in relation to human thermal comfort and what tree characteristics contribute most to cooling. These questions have been addressed with two measurement approaches in a Western European context. The first method consisted of three-hour long simultaneous measurements on multiple days on the same location. While the second method is based on short ten-minute serial measurements at varying times, days and locations. The cooling effect of the trees is expressed by the human thermal comfort indicator known as the Physiological Equivalent Temperature index (PET).

From the research we can draw two main conclusions: on the effect of trees and on the measuring methodology. The cooling effect of a tree is related to the amount of shade a tree provides, with crown density showing a significant relationship with cooling potential. Crown diameter, trunk circumference and tree height were of less importance. Even trees with a low crown density already show a significant reduction in PET values reducing the heat stress level by one class, meaning a 6 °C PET reduction. Whereas dense crowns can reduce heat stress by even three classes, up to 19 °C PET.

The main conclusion on the methodology is that simultaneous measurements are  needed to compare heat stress reduction by different tree traits because in serial measurements variation in meteorological and local conditions causes too much additional variation in the measurements. The serial measurements however do specify and amplify the cooling effectiveness of trees in order of magnitude.

The relationship of crown density with cooling potential shows the importance of healthy mature trees. A selection of trees for climate resilience should be focused on the most suitable species for the local growing conditions, such as drought resistance.

How to cite: Föllmi, D., Kleerekoper, L., Kluck, J., Hiemstra, J., and van der Sluis, B.: What make trees cool the environment? Two methodologies investigating the heat-stress reduction potential in relation to tree traits for the Western European climate, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-118, https://doi.org/10.5194/icuc12-118, 2025.

The urban microclimate model, urbanMicroclimateFoam developed by the authors, is used to simulate pedestrian thermal comfort in an urban park and adjacent building neighborhood in tropical Singapore during a hot and humid period. The thermal comfort is assessed using the Universal Thermal Climate Index (UTCI) which depends on air temperature, relative humidity, wind speed and mean radiant temperature.

Heat exposure of pedestrians is defined as the accumulated UTCI above a given threshold for a considered time, referred to as UTCI-degree hours. A weighting factor based on dynamic thermal sensation is introduced to account for higher heat exposure at high UTCI. This approach captures human thermal perception across varying periods, offering a comprehensive assessment of thermal stress. The cooling efficiency of vegetation as a heat mitigation measure is quantified as the ratio of heat exposure between a vegetated configuration and a reference non-vegetated configuration.

The study reveals that unshaded areas can experience heat exposure up to 700°C·h, while shaded zones exhibit significantly lower values around 450°C·h over a day. The present neighborhood configuration with trees in the park achieves cooling efficiencies of up to 40% in tree-covered areas. However, the results also highlight non-local effects, where unshaded zones in between the trees can heat up by as much as 25% due to the wind blocking and the increased humidity resultsing from the transpiration by trees. Among individual mitigation strategies, larger, densely placed trees, such as those in parks, are shown to be the most effective in improving cooling efficiency.

The study suggests that heat exposure and cooling efficiency metrics should incorporate activity maps to prioritize heat mitigation in high-activity zones while tolerating negative effects in less critical areas, enabling targeted urban cooling solutions.

How to cite: Derome, D., Nevers, C., Kubilay, A., and Carmeliet, J.: Assessment of heat exposure and cooling efficiency by trees in urban microclimate analysis, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-509, https://doi.org/10.5194/icuc12-509, 2025.

Rising extreme temperatures challenge outdoor activities, limiting urban mobility and reducing recreational opportunities in parks and public spaces. Climate change-driven heat stress increasingly affects urban livability, necessitating adaptation strategies to enhance outdoor thermal comfort. Green infrastructure, particularly urban trees, offers cooling benefits through evapotranspiration and shade. This study evaluates the cooling performance of four tree species from different plant families—Arecaceae, Fabaceae, Moraceae, and Tamaricaceae—at the King Abdullah University of Science and Technology (KAUST) campus in Saudi Arabia. Tree canopy characteristics are analyzed using the Leaf Area Index (LAI) for foliage density, Leaf Area Intensity for distribution, and Sky View Factor (SVF) for open sky exposure. Microclimate variations under the tree canopies are recorded using meteorological data, including air temperature, wind speed, relative humidity, and globe temperature. Additionally, physiological responses are assessed through skin temperature measurements, while psychological thermal comfort perceptions are gathered through surveys. Preliminary findings indicate that tree shade significantly enhances thermal comfort. The Universal Thermal Climate Index (UTCI), recorded in October, showed strong heat stress under shading (35.9°C) compared to very strong heat stress in direct sunlight (44.9°C). These results highlight the crucial role of tree canopies in mitigating outdoor heat stress. This study provides evidence-based recommendations for policymakers and urban planners to enhance urban resilience and outdoor thermal comfort through strategic tree planting in arid regions.

How to cite: Abuwaer, N., Azmeer, A., Tahir, F., and Al-Ghamdi, S.: Assessing the Cooling Benefits of Tree Canopies for Outdoor Thermal Comfort in Arid Climates , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-927, https://doi.org/10.5194/icuc12-927, 2025.

In the context of increasing frequency of heatwaves, growing urban populations, and the intensification of the urban heat island effect, green infrastructure has become a key focus of interest. Among these, urban trees deliver significant environmental services, particularly cooling, through the processes of transpiration and shading. However, their cooling capacity depends on their water status, as water stress limits transpiration. The impact of urban conditions, such as soil imperviousness, and the influence of tree species on water status remain understudied. This study aims to assess the water status of urban trees and identify the environmental and physiological factors that influence it. The work was carried out in the city of Dijon, eastern France, and focused on 2 tree species commonly found in urban environments in European cities: Acer platanoides and Tilia euchlora. First, 11 mature trees with different urban morphological conditions were equipped with micro-dendrometers (PépiPIAF system) to record the daily stem diameter variations during summer 2023 and spring 2024. From these measurements, dendrometric indicators such as the maximum daily shrinkage (MDS) and the tree water deficit (TWD) were calculated to provide insight into tree water status. Analyses show that dendrometric indicators are influenced by meteorological variables, soil imperviousness and tree species, especially in summer. Then, for each instrumented tree, the normalized vegetation index (NDVI) was calculated from several high spatial resolution SuperDove satellite images during summer 2023 and spring 2024.  While the correlation between NDVI and dendrometric indicators is moderate to weak, it remains significant. Additionally, soil imperviousness significantly affects NDVI values. The next step is to establish a model that combines satellite data and dendrometric indicators to assess tree water status. This, in turn, could contribute to a better understanding and improvement of urban tree management.

How to cite: Canovas, L., Martiny, N., Bur, T., Marilleau, N., and Hartmann, C.: Urban tree water status response to environmental and physiological factors using dendrometer measurements and high spatial resolution imagery: the case of Tilia euchlora and Acer platanoides in Dijon city, France, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-684, https://doi.org/10.5194/icuc12-684, 2025.

Isolated tree and permeable pavements are typical units for urban green infrastructure that contribute to stormwater management during rainy days through crown interception loss and enhancing infiltration by tree roots and permeable materials. Some rainwater is stored in tree crown, tree pits, and pavements, functioning as blue-green infrastructure for mitigating urban heat island on sunny days after rainfall. However, the interception and infiltration processes of isolated tree are simplified in the Storm Water Management Model (SWMM), potentially affecting the evaluation of synergistic benefits for tree and pavements. This study develops a field-measured and simulation-calibrated model to analyze the crown interception and root-influenced infiltration processes, aiming to assess surface runoff reduction and rainwater storage for an isolated tree combined with different pavement types. The crown interception processes were measured using a weighing lysimeter, revealing an interception loss of 11.2% of the target tree during 15 rainfall events. Meanwhile, the net rainfall (i.e., the rainfall amount reaching the ground surface beneath tree crown) variations were also obtained for rainfall-runoff analysis considering crown interception. Additionally, the root-influenced infiltration process was represented by an optimal set of parameters that was determined by parameter optimization and validated using experimental results from two irrigation-drainage events. The coefficient of determination (R²) between simulated and measured drainage and storage exceeded 0.9. According to the developed model, the rainfall-runoff processes of the target tree combined with impermeable, permeable, and water-retaining pavements during 15 rainfall events were analyzed. Surface runoff reduction and rainwater storage for different combinations were quantified, providing co-design recommendations for green, blue, and brown spaces in urban areas.

How to cite: Zhao, X. and Asawa, T.: Assessing rainfall-runoff processes of an urban isolated tree combined with different pavement types using a field-measured and simulation-calibrated model, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-823, https://doi.org/10.5194/icuc12-823, 2025.

Trees are vital to urban development, significantly reducing urban heat and capturing CO₂. As a crucial asset for enhancing human thermal comfort and improving CO₂ conditions in urban areas, the effectiveness of trees depends on factors like location, magnitude, and leaf area index (LAI). This study aims to: (1) analyze micrometeorological parameters - including air temperature, humidity, short- and long-wave radiation, wind speed, and wind direction - at pedestrian levels to quantify the cooling effects of trees from a human-biometeorological perspective; (2) examine CO₂ uptake through continuous measurement campaigns of two commonly used street trees, the evergreen broad-leaved Daphniphyllum macropodum and the broad-leaved Zelkova serrata, on the campus of Jeju National University in 2024-2025; and (3) evaluate the impact of street tree planting on reducing heat stress and CO₂ across various temporal scales (diurnal, seasonal, and annual) using the validated ENVI-met v5.7.1 model. Results from both measurements and simulations indicate that trees can reduce human heat stress, calculated by physiological equivalent temperature (PET), by up to 20 K under tree canopies in summer. While the evergreen broad-leaved tree demonstrates significant CO₂ absorption in both summer and winter, the broad-leaved tree compensates for reduced winter CO₂ uptake due to its leafless state, as evidenced by both measured and simulated outputs.

How to cite: Lee, H., Oh, S., Ko, Y., Park, S., and Mayer, H.: The role of street trees in enhancing human thermal comfort and CO2 absorption: A case study in Jeju, Republic of Korea, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-975, https://doi.org/10.5194/icuc12-975, 2025.

Green infrastructure in urban areas offers a significant opportunity to enhance environmental conditions and reduce CO2 emissions, paving the way for climate-neutral cities in the coming decades. The integration of vertical or horizontal green spaces in public areas can effectively improve microclimate conditions and outdoor thermal comfort, thereby contributing to energy savings for cooling buildings during the summer months.

The collaborative efforts of the Novi Sad Urban Climate Lab (NSUCL) at the University of Novi Sad, Faculty of Sciences, in partnership with architecture experts, have demonstrated that utilizing micrometeorological measurements alongside comprehensive datasets can effectively create the design of green infrastructure. This approach has shown promising results in mitigating the urban heat island effect and enhancing outdoor thermal comfort (OTC) in densely built urban settings. Notably, studies reveal that strategically placing additional trees—considering various crown shapes—can lower OTC values at specific locations by up to 6.11°C (UTCI), underscoring the critical importance of selecting optimal tree placements to maximize thermal comfort on hot summer days. The impact of additional trees on OTC conditions was assessed at three selected locations: Catholic Porta Square, Gymnasium Street (with a north-south orientation), and Laze Teleckog Street (with a southeast-northwest orientation). These locations represent densely built urban morphologies characterized as intensive pedestrian zones in downtown of Novi Sad city.

Finally, encouraging the adoption of these green concepts can lead to more sustainable urban environments, ultimately fostering healthier, more livable cities for current and future generations.

Acknowledgement: The research was supported by the project no. 003026234 2024 09418 003 000 000 001, funded by the Autonomous Province of Vojvodina (regional government).

How to cite: Savić, S., Bajšanski, I., Dunjić, J., Vasić, M., and Milošević, D.: Enhancing outdoor thermal comfort in densely built-up areas through green infrastructure, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-31, https://doi.org/10.5194/icuc12-31, 2025.

This study investigates the evolution of microclimatic benefits following de-sealing of a 64 m² patch (Oasis) inside a parking lot located in the suburbs of Angers, France. Vegetation (trees and herbaceous species) was introduced. We compared the microclimate in the Oasis with that of a neighboring asphalt area (negative control), a meadow area (positive control), and under a tree in a sealed area (Figure 1). This comparison was conducted using on-site meteorological stations. Over the two years following de-sealing, microclimate variables were monitored, and thermal comfort was evaluated using the Universal Thermal Climate Index (UTCI) as vegetation developed. The Oasis experienced a significant reduction in surface temperature compared to surrounding asphalted areas, with a maximum decrease of 18.4°C during the first summer and 23.0°C during the second one. This cooling effect was attributed to the development of the herbaceous layer, which covered 60% of the Oasis three months after sowing and exceeded 90% coverage from the second year. The reduction in surface temperature contributed to improved daytime thermal comfort. Tree shading further enhanced local cooling, reducing UTCI by up to 8°C in shaded areas. No evidence of lower nocturnal air temperature compared to sealed reference areas was observed, possibly due to the patch's small size and air mixing with the surroundings. This study highlights that small-scale de-sealing and revegetation initiatives can deliver notable microclimate benefits in urban environments from the first year, with even greater impacts as vegetation matures, supporting urban adaptation to climate change.

How to cite: Morel, A., Vidal-Beaudet, L., Brialix, L., Lemesle, D., Bulot, A., and Herpin, S.: Experimental study of microclimate benefits following de-sealing and revegetation in a parking lot., 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-847, https://doi.org/10.5194/icuc12-847, 2025.

Green infrastructure is increasingly recognized as a key factor in mitigating urban heat and enhancing thermal comfort, especially in cities experiencing rising temperatures due to climate change. The thermal conditions in urban parks are shaped by numerous factors, several of which are subject to seasonal fluctuations. Therefore, the study investigates how the heat exchanges between the thermal environment and the human body are influenced by spatial factors and their variation during different phases of the growing season.

The research was carried out based on measurement campaigns of the CLIMPARK project conducted in spring (2023, 2024), summer (2022, 2023) and autumn (2023) in Warsaw in 6 parks of various sizes, spatial development structures and vegetation. Weather conditions were measured at a height of 1.1 meters at 23 different locations, with measurements repeated across different seasons. After calculating the Universal Thermal Climate Index, the study tested which environmental elements had the greatest impact. Spatial indicators were calculated using data from OpenStreetMap, Bing Aerial and the topographic objects database (e.g., Ratio of Biologically Vital Area), hemispherical photos (Sky View Factor), the Tree Crown Map (tree cover), satellite products (e.g., Normalized Difference Vegetation Index, seasonal productivity) and a field inventory (vegetation types). The influence was tested for values measured at the monitoring site and within three buffers: 10, 50 and 100 meters.

The results primarily revealed the impact of direct solar radiation limitations within the park, as well as the heterogeneity of the surfaces on modifying the local bioclimate to varying degrees throughout the day. The study provides insights into the potential of green infrastructure to enhance thermal comfort in urban environments, thereby contributing to more sustainable and resilient urban planning strategies.

How to cite: Czarnecka, K., Kuchcik, M., Lindner-Cendrowska, K., Kowalska, A., Jarocińska, A., Derwisz, K., Słowińska, S., and Baranowski, J.: The influence of environmental factors on physiological comfort in urban green areas, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-277, https://doi.org/10.5194/icuc12-277, 2025.

'Water town', a city design idea featuring buildings sitting along rivers/lakes and their associated riparian vegetation, serves as an effective nature-based solution for citizens to escape the dual challenges of heatwaves and urban heat islands. We selected two Chinese megacities, i.e., Shanghai, a city encompassing rich river networks and Wuhan, a city of a hundred lakes as study areas and investigated the cooling potential of rivers and lakes via field monitoring, remote sensing and numerical modelling. It was found that the width of rivers, the confluence of river tributaries, coverage ratio, density, and morphology of river networks are key factors affecting the cooling potential of rivers. In contrast to rivers, lakes usually possess a relatively large surface area and can influence local and regional climate to a greater extent. Particularly, the temperature difference between built-up areas and lakes can induce wind circulation, i.e., the lake breeze circulation. Rivers were found to be all-day cool spots compared to adjacent city streets with greater daytime cooling intensity than at night, while lakes may induce daytime cooling and nighttime warming due to large thermal inertial. In addition, the combination of blue-green spaces and building forms in a neighborhood should be optimized to create a perfect 'water town' with good ventilation conditions, abundant tree shading effects, and effective evaporative cooling effects, so that the synergistic effect of urban heat and moisture islands can be mitigated. Our study can offer significant reference for the planning and design of water sensitive cities.

How to cite: Song, J., Shi, D., and Zhong, Q.: Cooling wisdom of 'water towns': How can urban river and lake networks shape city climate?, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-166, https://doi.org/10.5194/icuc12-166, 2025.

Souq Waqif, a historic marketplace in Doha, Qatar, is a prominent cultural and tourist destination that faces significant challenges in maintaining outdoor thermal comfort during the extreme summer months. This study investigates the potential of various heat mitigation strategies, focusing on the application of green and blue infrastructure, as well as complementary urban design interventions, to enhance the marketplace's thermal environment. A microclimate model of the marketplace was developed using ENVI-met V5.7.1, with the base case model validated spatially and temporally against field measurements. Various heat mitigation scenarios were then modeled, including: (1) green infrastructure, implementation of green roofs and the introduction of mature tree canopies; (2) blue infrastructure, addition of water misting systems and fountains; (3) adoption of cool materials for roofs and pavements; (4) adjustments to urban morphology, increasing the aspect ratio; and (5) the introduction of shading structures with openings for natural lighting across the alleys of the marketplace. Furthermore, several combinations of these heat mitigation scenarios were modeled and simulated to maximize cooling effects. The study evaluates the cooling potential of these strategies in improving outdoor thermal comfort. The findings demonstrate the effectiveness of integrated heat mitigation approaches in alleviating thermal stress, contributing to a more comfortable environment for visitors and residents, and ensuring the marketplace remains a viable and attractive destination even during peak summer months. This research provides a framework for climate-resilient urban design in hot arid regions, aligning with Qatar’s ambitions to host global events and sustain year-round tourism.

Acknowledgments:

Research reported in this work was supported by the Qatar Research Development and Innovation Council (Grant: ARG01-0503-230061). The content is solely the responsibility of the authors and does not necessarily represent the official views of Qatar Research Development and Innovation Council.

How to cite: Abedrabboh, O., Siddique, A., Moosakutty, S. P., Alfarra, M. R., and Fountoukis, C.: Enhancing outdoor thermal comfort in a historic marketplace: Integrating green, blue, and urban design strategies in hot arid climates, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-210, https://doi.org/10.5194/icuc12-210, 2025.

In recent years, many cities have experienced high summer temperatures, with the entailed impact on health and wellbeing. Implementing climate-sensitive strategies has become crucial to address this challenge and improve thermal comfort and quality of life in cities. Green spaces have emerged as a particularly effective solution, providing cooling and multiple other benefits such as improved drainage systems and biodiversity. However, the implementation of adaptation measures is still slow due to several factors, including the lack of practical tools to facilitate their application. This study presents the preliminary results of a research project supporting the Department of Urban Planning of the Municipality of Trento, Italy, to facilitate urban regeneration with climate-responsive solutions. Specifically, the focus is on summer outdoor thermal comfort using multiscale qualitative and quantitative approaches. This paper investigates the variability of cooling effects given by green elements depending on their type and size. Design scenarios with different Nature-based Solutions (NbS) are assessed in terms of thermal comfort predictors in two neighborhood typologies (LCZ 5 and LCZ 8). The process of configuring the scenarios (green roofs, tree lines and green elements in parking lots) included workshops with decision-makers, in order to select solutions that could be applicable in the context and integrated into existing urban morphologies. A comprehensive assessment of the cooling intensity and duration was carried out, encompassing a comparative analysis of microclimate parameters and Physiological Equivalent Temperature (PET) across diverse scenarios within the two study areas. This approach was undertaken to determine the most effective configuration for each neighborhood. The indices are calculated with the Envi-met software tool and simulate a hot summer day. The findings are strongly practice-oriented as they provide a practical guideline to understand suitable solutions for the context and give directions on the necessary updates in the urban planning tools.

How to cite: Codemo, A., Maracchini, G., Favargiotti, S., and Albatici, R.: Regenerating neighborhoods with nature-based solutions: assessment of pedestrian thermal comfort to support climate sensitive planning, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-412, https://doi.org/10.5194/icuc12-412, 2025.

Public green spaces play an increasingly important role in urban planning and public health, particularly for providing thermal comfort during hot days. Small green spaces enhance social equity by being more accessible and easier to integrate into existing urban structures across neighborhoods. The thermal regulation potential of green spaces generally increases with size but also largely depends on vegetation structure. To optimize the potential of small green spaces, it is essential to understand how their structural design and spatial configuration are linked to their local cooling effects. Based on field measurements on hot days in 2024, we modeled the modified physical equivalent temperature (mPET) across 12 small parks (0.25 - 2 ha) in the inner city of Munich, Germany, and in their urban surroundings. The structural composition of the park vegetation covered a gradient, ranging from sparse to forest-like. We recorded the vegetation structure using mobile laser scanning and derived the sky view factor from hemispherical photographs. Our results show that parks with high structural complexity reduced the mPET by up to 14 °C, whereas parks with low structural complexity provided only minimal cooling. According to a mixed-model analysis, the cooling effects of small green spaces were primarily influenced by the sky view factor and the tree canopy. Increased tree coverage and reduced visible sky correlated with greater cooling. However, high vegetation density negatively impacted cooling, likely due to restricted airflow, while subcanopy vegetation had little effect. We conclude that small green spaces with high canopy cover and large trees can mitigate extreme heat in cities. To increase the thermal regulation potential of parks during the hottest times of the day, particularly in summer months, it is critical to maintain and systematically increase high tree canopy coverage. 

How to cite: Arzberger, S., Burger, S., Egerer, M., Suda, M., and Annighöfer, P.: Thermal comfort on hot days in Munich, Germany: How does vegetation structure in small urban green spaces matter? , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-640, https://doi.org/10.5194/icuc12-640, 2025.

Evaporative misters are widely used in urban outdoor spaces for heat mitigation, yet their impacts on thermal stress and optimal operating conditions remain unclear. To address this, we developed a misting model and integrated it into the Princeton Urban Canopy Model (PUCM) to evaluate the influence of microclimate and system design on misting performance. The PUCM-mist simulates sensible-latent heat conversion during mist evaporation and predicts corresponding changes in canyon air temperature and humidity. Validation against in-situ measurements at five sites in Tempe, AZ, demonstrates the capability of the model in capturing mist-induced cooling and humidifying effects. By varying flow rates, wind speeds, and misted area ratios, we assessed the potential of misters to mitigate thermal stress and identified optimization strategies. In Phoenix, AZ, misters reduced maximum canyon air temperature by up to 17.5^°C and human skin temperature by 0.48^°C; in more humid cities such as Houston, TX, misters still mitigate thermal stress although the cooling benefits were halved due to higher ambient humidity. Wind speed emerged as a key factor, with intermediate speeds yielding optimal cooling. Higher flow rates (e.g., 1 L/min) require moderate breezes for full evaporation, whereas lower flow rates (e.g., 0.01 L/min) are more effective in calm conditions. We also compared misting with other water-based cooling strategies, such as irrigation and sprinkling. Under abundant water availability, sprinkling and misting were most effective, cooling air and surfaces rapidly during midday and late afternoon, respectively. For water-limited scenarios, we propose a thermostatic control scheme that can save at least 10.5 m³/day of water compared to continuous misting for a 100-m stretch of street; the savings are equivalent to the water demand of about 20 Phoenix residents.

How to cite: Huang, X., Bou-Zeid, E., Vanos, J., Middel, A., and Ramamurthy, P.: Misting as a key component of blue infrastructure for urban heat mitigation, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-316, https://doi.org/10.5194/icuc12-316, 2025.