Urban vegetation provides essential shade that reduces heat stress in cities. However, there are nuances in shade provisioning and how that affects thermal comfort at the pedestrian scale. While overstory vegetation like trees intercepts direct solar radiation, understory vegetation—shrubs and grass—could serve as a crucial secondary buffer, reducing surface temperatures and long-wave emissions. However, the complex interplay of radiative transfers between the different vegetation layers still is insufficiently understood and inadequately quantified. Despite extensive research establishing the importance of factors such as surface type, canopy coverage, and leaf area index, we lack a comprehensive understanding of how diverse vegetation structures collectively influence pedestrian thermal comfort. This knowledge gap has significant practical implications, as landscape architects must make evidence-based decisions between various configurations, from simple grass lawns to complex multi-layered vegetation systems. Through empirical studies conducted in several public squares in Munich, Germany, we investigate the structural diversity of urban vegetation and its impact on thermal comfort, quantified through Physiological Equivalent Temperature (PET). Our results show that sites with high vegetation structural complexity achieved significantly greater cooling on hot summer days (ΔPET = -5.2 ± 0.08°C) compared to sites with low structural complexity (ΔPET = -1.7 ± 0.13°C). This difference highlights how multiple vegetation layers work synergistically to enhance cooling effects. Additionally, low and medium-height trees (5m to 15m) demonstrated stronger cooling effects (Correlation coefficient r = -0.53 and -0.51, respectively) than tall trees (>15m) (r = -0.39). Among understory vegetation, shrubs exhibited moderate cooling potential (r = -0.28), while grass showed limited effects (r = -0.11), primarily influenced by soil moisture conditions. These findings provide urban decision-makers with evidence-based insights into the relative cooling effectiveness of different vegetation structures and demonstrate how both horizontal and vertical vegetation structural diversity can be leveraged for enhanced urban heat mitigation.

How to cite: Pattnaik, N., Rahman, M. A., and Pauleit, S.: From Ground to Crown: Analyzing shade provision and thermal comfort benefits of multilayered vegetation structures, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-598, https://doi.org/10.5194/icuc12-598, 2025.

Trees in urban areas are important for their ecological functions as well as for their aesthetic characteristics. They provide shade, which is welcome in hot weather and lowers pedestrian heat stress. They may also lower air temperature: the magnitude of the cooling has been variously claimed to be as much as 6^oC, while other studies report a negligible effect. This disparity may be due to different circumstances, but may also be an artifact of insufficient sheltering of the sensors from radiant fluxes. A systematic field study was performed in hot, dry conditions to assess the effect of trees, comparing air temperature in 10 pairs of adjacent exposed sites and sites shaded by adult trees of 8 different species. Measurements at each site made at 10-second intervals included air DBT by four different methods, humidity, wind speed and direction, net and global solar radiation, and gray bulb temperature, as well as the sky view factor and IR images. Temperature variations due to the properties of the sensor-shield combinations – over 1°C – were similar in magnitude to the cooling effect of the trees. A linear mixed effect model developed to assess the effect of the environmental conditions and tree type on air temperature yielded a correlation of R²=0.54 and RMSE=0.67^oC, with wind speed having the greatest impact. Evapotranspiration from the trees had a minimal effect on humidity below the canopy, probably because the local species are adapted to water scarcity. The contribution of trees to human thermal comfort was substantial, with differences of up to 10 degrees in the PET index between shaded and adjacent non-shaded areas, but these were due primarily to shade. The study confirms the beneficial effect of trees on thermal comfort but reiterates that the focus in many studies on temperature reduction by evapotranspiration may be misplaced.

How to cite: Blank, T. and Erell, E.: Measuring the impact of trees on localized air temperature in the city, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-223, https://doi.org/10.5194/icuc12-223, 2025.

By the end of the 21^st Century heat waves are expected to increase in frequency, duration and intensity due to climate change. Therefore, cities must find solutions to limit heat-related health impacts on their population. Many ways to mitigate the effects of heat waves exist, such as urban greening or cool pavements.

Since 2013, the City of Paris has been experimenting pavement-watering using its non-potable water network. The results of these experiments have shown that this cooling strategy allows a reduction of up to 2 to 3°C UTCI-equivalent temperature.

Since 2017, the Cool & Low Noise Asphalt project, co-funded by the European Union's Life program, aims to study the thermal performance of three innovative pavements compared to traditional asphalt concrete, as well as their acoustic performance. These pavements have been developed to optimize the effects of pavement-watering thanks to their surface texture and porosity that is expected to offer greater water retention and longer pavement-watering cooling effects.

Three experimental sites are divided into three portions: innovative portion (innovative pavement) and traditional portion (repaved with standard asphalt), which are both watered, and a control portion (original pavement) that isn’t watered. Each of the portions are equipped with a weather station to monitor a multitude of meteorological parameters to evaluate the effectiveness of the innovative pavement and pavement-watering.

Based on the temperature and heat flux measurements conducted 5 cm deep in the pavement, the thermal analysis shows a positive impact of watering. From the analysis of the heat flux hysteresis, the surface cooling flux and evaporation rate are estimated. The differences in observations are discussed in light of street orientation and pavement materials.

How to cite: Chanial, M., Parison, S., Hendel, M., and Royon, L.: Thermal Behaviour of Innovative Acoustic Pavements for the Life Cool & Low Noise Asphalt Project, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-948, https://doi.org/10.5194/icuc12-948, 2025.

The urban heat island (UHI) effect arises when urban areas experience higher temperatures than their rural surroundings due to the prevalence of man-made materials. These surfaces modify the surface energy balance, leading to a net heat gain in cities. This increase in urban temperatures can have a range of consequences, such as greater risks of heat-related fatalities. In response, many cities have sought strategies to mitigate extreme heat. One solution is the application of reflective pavements, which enhance surface albedo to redirect more incoming solar radiation away from the ground. While most studies on reflective pavements have been conducted in controlled settings a few pilot programs have been emerging to assess this strategy in the field. 

This presentation outlines a multifaceted evaluation of a reflective pavement pilot project in Austin, Texas. In June 2024, the City of Austin installed 6.4 lane miles of reflective pavement in a southeast Austin neighborhood. To assess its effectiveness, in situ air temperature sensors were deployed for continuous monitoring in both the treated neighborhood and a nearby reference neighborhood to the south. Additionally, surface temperature measurements were collected.

Beyond physical measurements, this study incorporates a novel social science approach to evaluate how these pavements influence human thermal perception. Two primary methods were used: first, a survey was distributed to residents of both the treated and reference neighborhoods to gauge their perceptions of the pavement and its impact on their daily lives. Second, a blind study was conducted in which participants unfamiliar with either neighborhood walked across different pavement surfaces and provided feedback on whether they could detect a thermal difference. This research is ongoing, with data collection and monitoring set to continue through the summer of 2025.

How to cite: Brooks, T., Sudharsan, N., Miniard, D., Bixler, P., and Niyogi, D.: Assessing Reflective Pavements Through a Multilayered Approach: Lessons from a Pilot Study in Austin, Texas, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-968, https://doi.org/10.5194/icuc12-968, 2025.

As urban heat stress affects both the physiological and psychological health of people, many city administrations are planning to implement heat mitigation strategies that include built and green infrastructure as a part of their action plan. Using Austin, TX, as a representative metropolitan area, this study explored the potential for realistically reducing 2-meter air temperature (T_2M) and the Universal Thermal Climate Index (UTCI) in cities through heat mitigation strategies (HMS) implemented in the Weather Research and Forecasting model coupled with urban physics (WRF-Urban). We tested cool roofs, green roofs, and solar photovoltaics under two scenarios: full rooftop coverage and a more realistic implementation based on available flat roofs. In addition to rooftop-based HMS, we also evaluated the effectiveness of urban gardens and street trees in reducing T_2M and UTCI. All experiments, including the control scenario (without any HMS applied), were conducted during clear-sky days in August 2020, which is one of the hottest months.      For the simulation of realistic rooftop-based HMS, we introduced a new I/O feature in the building effect parameterization model within WRF-Urban to handle 2-D fields specifying the fractional rooftop areas available. Results showed that while cool and green roofs are effective in some neighborhoods, their realistic implementation led to negligible changes in city-wide T_2M. Combining rooftop-based HMS with gardens and trees also showed similar results and had limited impact. Further, HMS had a minimal impact on reducing the city-wide UTCI. Based on these findings, we argue that heat mitigation strategies must be hyper-locally targeted to areas with high heat risk (e.g., streets or playgrounds), as mitigating heat risk at the city scale may be extremely challenging and costly.

How to cite: Kamath, H., Lin, T.-S., Sudarshan, N., Fung, K. Y., Zonato, A., Singh, M., He, C., Yang, Z.-L., and Niyogi, D.: Urban Heat Mitigation Under Realistic Constraints: A Case Study in Austin, TX, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-1105, https://doi.org/10.5194/icuc12-1105, 2025.

In 2023, the residential sector was the second-largest energy end-user in Ireland, accounting for approximately 22.5% of the country's final energy consumption. In Dublin's city center, 65% of buildings were constructed before 1970, which falls below modern energy standards. Combined with Ireland's long and windy winters, these substandard buildings exacerbate heating demand. A key challenge in renovating Dublin's building stock is reducing heat loss due to infiltration, which occurs through gaps in building envelopes and is exacerbated by ambient wind. While building upgrades can address the former, the high costs of these improvements present additional challenges. However, urban design offers a potential solution, mitigating wind-driven heat loss through effective wind sheltering.

This study examines the impact of urban trees on the heating demand of typical residential building archetypes in Dublin, focusing on how their wind-sheltering effects reduce heat loss via infiltration. By generating localized climate data across various tree layouts and simulating building energy use, this research provides a comprehensive assessment of how urban evergreen vegetation can reduce heating demand. The findings show that urban trees, particularly street trees, can decrease wind-driven heat loss by up to 6.15%. These results highlight the value of urban evergreen trees in enhancing residential energy efficiency. This study offers insights that can inform urban planning and retrofitting strategies in cities with similar climates, contributing to global efforts toward energy sustainability and climate resilience.

How to cite: Ren, Z., Nikolopoulou, M., Mills, G., and Pilla, F.: Effects of urban tree sheltering on the heating demand in residential building: A case study in Dublin, Ireland, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-953, https://doi.org/10.5194/icuc12-953, 2025.

In many countries, so-called 'green building' building codes are adopted that aim, inter alia, to reduce energy consumption for heating and cooling. Separately, local initiatives promote green infrastructure and increase the vegetated fraction of the surface as a response to climate change and global warming. The compound effect of both strategies was examined in a simulation study of an urban neighborhood in Tel Aviv. Using the CAT model, modified TMY files were generated that account for the urban effects of location, surface cover, and density in different building configurations. These files were then used to assess the climatic cooling potential (CCP) by night ventilation and as inputs for detailed computer simulation of building energy performance. Model outputs indicate that the nocturnal urban heat island will increase demand for summer cooling relative to the reference rural site, but this penalty will be more than offset by reduced winter heating, resulting in an overall annual saving of nearly 7% in a standard urban building. However, because the urban heat island will reduce the potential for cooling by night ventilation in summer, the prevalence of air conditioning use will increase. Peak electricity loads will be higher and buildings may be more vulnerable to potential loss of electric power during episodes of extreme heat. 'Green' buildings are more efficient than standard ones, but the shading effect of adjacent buildings in dense urban locations reduces their advantage. Implementing a strategy of extensive planting, so that a green surface fraction of 0.5 is obtained, results in a mean annual temperature reduction of about 0.3^oC and an energy saving relative to the current condition of about 2-3% in both standard and 'green' buildings. The study highlights the importance of comprehensive analysis of the complex interactions between neighborhood-scale modifications of the microclimate and upgrades to individual buildings.

How to cite: Erell, E. and Zhou, B.: Are building upgrades and neighborhood-scale microclimate modifications complementary?, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-368, https://doi.org/10.5194/icuc12-368, 2025.

Urban growth patterns significantly influence a city's environmental impact and its resilience to climate change. This study analyzes the distinct urbanization pathways of two medium-sized cities in Buenos Aires Province, Argentina: Tandil, situated in a hilly region, and Bahía Blanca, located in an estuary. Both cities share a temperate climate but present unique topographical characteristics.

The World Urban Database and Access Portal Tools methodology was employed to generate Local Climate Zone (LCZ) maps for 2003, 2013, and 2023 for both cities. These maps, combined with population data, provide insights into urbanization patterns and their socio-economic implications. Statistical analysis of LCZ class transitions quantifies changes in impervious and pervious surfaces, enabling an assessment of ecosystem service loss and its impact on the cities' resilience to extreme events such as heat waves and floods. Finally, the potential of Nature-Based Solutions (NbS) for enhancing urban resilience and informing climate change adaptation plans is explored.

Results reveal rapid expansion in both cities, with land consumption outpacing population growth. This indicates a decline in ecosystem services, notably the loss of hill cover in Tandil and the degradation of estuary and riparian areas in Bahía Blanca. The conversion of natural LCZs (e.g., forests, grasslands) to built-up LCZs (e.g., compact and open low-rise) has increased impervious surfaces and reduced pervious surfaces, exacerbating the urban heat island effect and diminishing the cities' natural capacity for rainwater absorption. Consequently, both cities face increased vulnerability to heat waves and flooding, posing risks to the urban population and environment.

The study identifies specific NbS interventions tailored to each city's unique context to enhance resilience to future hazards. These interventions are integrated into proposed climate change adaptation plans, offering pathways towards more sustainable urban development.

How to cite: Picone, N.: Urbanizations pathways and climate impacts in two cities of Argentina: how to address enviromental impacts in city rapidly growing?, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-430, https://doi.org/10.5194/icuc12-430, 2025.

Rapid urbanization has intensified ecological challenges, including urban heat islands, energy consumption, significantly impacting socioeconomic outcomes. Greenery strategies, such as tree and grass integration, can enhance cooling effects, improve thermal comfort, and reduce energy consumption, effectively mitigating urban environmental issues. Therefore, optimizing and quantitatively integrating greening strategies under limited land resources is crucial. This study develops a multi-objective optimization model and an integrated assessment framework for urban greening strategies in hot and humid climates. The framework considers three key indicators: environmental performance, energy efficiency, and economic benefits, aiming to identify the optimal greening configurations over its lifecycle and assess its holistic impact on high-density city. The study employs ENVI-met for simulating vegetation-induced thermal effects, EnergyPlus for building energy performance analysis, and NSGA-2 for multi-objective optimization. A multi-criteria decision-making approach is used to determine the optimal design scheme. The proposed framework was applied to a high-density residential community in Singapore. Results indicate that different green configurations and layouts result in performance deviations ranging from -8.34% to +22.17%.Morris sensitivity analysis identifies GCR (Green Coverage Ratio) and LAI (Leaf Area Index) as the most influential factors affecting greening performance. The optimized design favors larger tree canopies, higher LAI values, and an orientation from south to southwest. Compared to the baseline model, the optimized scheme achieves a 38.57% reduction in outdoor thermal discomfort and a 12.34% reduction in energy consumption while maintaining economic feasibility. This framework provides practical guidance and a decision-making tool for optimizing urban ecological design, assisting urban planners in balancing environmental and economic benefits. Furthermore, it highlights the critical role of greening strategies in addressing rapid urbanization and climate change challenges.

How to cite: Mingqi, W.: Multi-Objective Optimization of Urban Greening Strategies in Hot Climates: An Integrated Framework for Environment, Energy, and Economy, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-945, https://doi.org/10.5194/icuc12-945, 2025.

Globally, cities face increasing extreme heat, impacting comfort, health and energy consumption. Infrastructure-based heat adaptation strategies can improve these outcomes, but each strategy has a unique mix of benefits, co-benefits, costs, and externalities. Studies to date examine insufficiently diverse outcomes and use  inconsistent methodologies, limiting quantitative comparison between adaptation strategies and hindering our ability to assess optimal combinations of heat adaptation infrastructure in cities.

To assess the impact of urban heat infrastructures in a rigorous, comprehensive framework, we apply an urbanized meteorological model (WRF) with the newly integrated multi-layer BEP-Tree street tree model to dynamically downscale Earth system model projections, and a 3-D microclimate model (TUF-Pedestrian) to simulate the street-scale radiative environment impacting pedestrians. We evaluate the performance of five heat adaptation strategies (street trees, cool roofs, green roofs, rooftop photovoltaics, and reflective pavements) during extreme heat events in three cities with contrasting background climates (Toronto, Phoenix, and Miami), under contemporary and end-of-century projected climates, based on three metrics: outdoor heat stress, air conditioning energy use, and ventilation of vehicular air pollution.

No single adaptation strategy improves all three outcomes. While street trees inhibit ventilation, they reduce outdoor heat stress four times more effectively than the next best strategy through shade, fully offsetting heat stress increases in all cities studied, even under a high-emissions end-of-century climate scenario. Cool and green roofs moderately reduce heat stress and energy use. Alternatively, rooftop photovoltaics with energy storage can generate sufficient power for space cooling but have marginal effects on heat stress. Reflective pavements are the least effective across metrics. Where the ventilation of street-level emissions is of less concern, our results clearly support the combination of street trees and rooftop photovoltaics as a highly complementary and effective means of adaptive mitigation across different climates and neighbourhood densities.

How to cite: Jiang, T., Krayenhoff, S., Martilli, A., Nazarian, N., Stone, Jr., B., and Voogt, J.: Prioritizing urban heat adaptation infrastructure based on multiple outcomes: Comfort, health and energy, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-328, https://doi.org/10.5194/icuc12-328, 2025.