Urban Microclimate Research Articles

Case studies of the winds in the urban area of Hong Kong – Microclimate station observations and high resolution numerical simulations

Hong Kong, renowned for its densely packed urban areas, poses unique challenges for understanding the effects of buildings on local meteorological conditions. To address this, the Hong Kong Observatory has started building a network of urban meteorological monitoring stations since 2017 for monitoring, analysing and studying urban microclimate. This paper presents an observational and numerical study focusing on wind measurements obtained from wind sensors installed on two smart lampposts in Tsim Sha Tsui, a major urban area in Hong Kong. Two representative high wind conditions in Hong Kong, Super Typhoon Saola in 2023 and a strong monsoon case characterized by prevailing easterly winds, are considered. With the use of high resolution computational fluid dynamic simulations, major features of actual observations can be reproduced. This suggests that district scale or even street scale weather services could be possible in the future with sufficient computational power.

Nonlinear impacts of landscape and climatological interactions on urban thermal environment during a hot and rainy summer

Investigating the nonlinear impacts of urban landscape and climatic parameters on urban temperatures, a critical issue within urban climatology. Chengdu, characterized by its hot, rainy summers and rapid urban development, serves as an ideal model to illustrate these dynamics. Our investigation utilizes advanced analytical methods such as Random Forests (RF), SHapley additive explanation (SHAP), and Partial Dependence Plots (PDP) to analyze how landscape and climatic factors influence air temperature (AT) and land surface temperature (LST). Significant findings reveal profound thermal heterogeneity across Chengdu’s urban fabric, underscored by spatially distinct phenomena where some regions exhibit strong contrasts in temperature impacts due to varying climatic and landscape factors. The study identifies relative humidity and rainfall as key drivers of temperature variations during the summer months, reflecting Chengdu’s specific climatic idiosyncrasies. These insights are critical, as they highlight how urban planning and green infrastructure can be strategically used to mitigate adverse thermal effects. The research not only enhances understanding of the complex interplays within urban microclimates but also offers new perspectives on urban heat management. It contributes to the scientific community by providing evidence-based strategies for urban planners to counter the urban heat island effect and enhance urban resilience against climate change. This comprehensive analysis underscores the importance of incorporating multiple variables into urban climate models, lays the groundwork for more refined urban environmental policies and practices.

Urban Microclimate Impact on Vertical Building-Integrated Photovoltaic Panels

The ongoing climate crisis and turbulence on the world stage has highlighted the need for sustainability and resilience in the development and maintenance of urban areas regarding climate comfort and energy access. Local production of green energy increases both the sustainability and resilience of an area. Traditionally, photovoltaic (PV) panels are deployed wherever the amount of sunlight is highest but lowering costs for PV panels makes them cost-effective even in colder climates. Within the broader umbrella of positive energy districts, façade mounted building-integrated PV panels in urban areas additionally present unique opportunities and challenges, as factors such as wind, solar irradiance, or nearby obstructions can have either a positive or negative effect on the performance of the PV panels. In this article, we aimed to answer the question: What factors inform the optimization of vertical PV panels? To answer this, we developed a method for the optimization of placement of PV panels. By building upon readily available weather data, local panel conditions were examined, and field-driven aggregation algorithm used to guide panel placement. Performance of the resulting panel configurations were then compared to a baseline case. Results indicate that our developed method helped mitigate negative impacts of the aforementioned factors, and often improved performance over baseline.

Optimizing human thermal comfort and mitigating the urban heat island effect on public open spaces in Rome, Italy through sustainable design strategies

The climate affects how a city’s outdoor spaces are utilized. It is more likely that people will use and appreciate public areas designed for pedestrian use, such as parks, squares, streets, and foot-cycle pathways, when they provide a comfortable and healthy environment. A predicted increase in global temperature has made the climate uncomfortable, especially during the summer when heat stress is strengthened and anticipated. This phenomenon is more severe in urban areas, often affected by the Urban Heat Island (UHI) effect. Since the spatial characteristics of a city influence its climate, urban design can be deployed to mitigate the combined effects of climate change and UHI. This research is conducted to study the UHI effect on thermal comfort in an urban open space in Rome (Italy) and aims at identifying and implementing a methodology that urban designers can follow to reduce the impact of urban heat islands and increase thermal comfort in urban outdoor space. This study is based on an urban design concept adopting the Sustainable Development Goals as guidelines; it investigates how UHI’s effect affects the use of public space and examines the influence of urban microclimatic conditions on the thermal perception of users through PET, PMV and PPD values, that were assessed through simulations with ENVI-MET software. The study thus proposes a redesign for the site in Rome, with a masterplan based on sustainable design principles, aimed at improving the microclimatic conditions in the site. The design solution was then validated through ex post simulations.

Thermal regulation potential of urban green spaces in a changing climate: Winter insights

Global warming affects both summer and winter temperatures, altering the ecological and social dynamics of urban green spaces not only during the summer months but also during the winter. Strategies to mitigate climate change impacts often emphasize increasing urban vegetation cover, but the effectiveness of these green spaces in regulating the local microclimate depends on various factors, including the vegetation structure. These effects remain largely underexplored during the winter season. To investigate the thermal regulation capacity of urban green spaces we measured air temperature and humidity in 36 parks with different sizes and vegetation structures in Munich, Germany, in their non-green surroundings, as well as in a nearby forest during the 2022–23 winter. We then analyzed the relationship between the local microclimatic differences and the vegetation structure derived from mobile laser scans. In comparison with the nearby forest, we measured a winter urban heat island effect of 1.8 °C in Munich. The urban microclimates in winter were mainly influenced by the urban landscape of Munich, namely the distance to the city center with increasing air temperature closer to the center. Urban green spaces in Munich provided small but consistent local cooling and humidifying effects throughout the winter. These cooling effects largely depended on the green space size but partially also on the vegetation structure. We found a significant relationship between the microclimatic difference, the vegetation density, and the vertical homogeneity of vegetation. The canopy cover, however, could not significantly predict the cooling effect in winter. We conclude that increasing the structural complexity of urban green spaces through management decisions could improve their cooling effect and ecological value, even during winter months. To maximize the ecological and climatic benefits of urban green spaces, a nuanced understanding and management of urban microclimates is needed across all seasons.

Mapping pedestrian network level outdoor heat hazard distributions in Philadelphia

With the rise of global temperature, many cities are suffering from more and more frequent extreme heat in hot summers. Quantitative information on the spatial distributions of urban heat has become more and more important for extreme heat mitigation and adaptation in cities. This study first investigated the fine-level heat hazard distributions at the sidewalk and building block level from the pedestrian perspective in Philadelphia, Pennsylvania. The urban microclimate modeling based on a high-resolution urban geometrical model was used to generate the 1m resolution outdoor heat hazard map in the study area. The sidewalk map was overlaid on the generated high-resolution heat hazard map to estimate the sidewalk level heat hazard. Based on the sidewalk level heat hazard map, this study further calculated the heat hazard level in the 400m walkshed along sidewalks for each building block. The building level hazard data were then aggregated at the census tract level to compare with the socioeconomic and racial/ethnic variables. The result shows that neighborhoods with higher proportion of African Americans have a higher heat hazard level in Philadelphia. This study would provide new insights for developing more thermally comfortable and pedestrian-friendly neighborhoods in the context of climate change.

Sensitivity and vulnerability to summer heat extremes in major cities of the United States

Abstract Many cities are experiencing more frequent extreme heat events during summer because of the global temperature rise and the urban heat island effects. Yet, how the rising temperature impacts urban residents differently is still not clear. Here we leveraged urban microclimate modeling to map the Universal Thermal Climate Index (UTCI), a more complete indicator of human heat stress at an unprecedentedly fine spatial resolution (1 m) for 14 major cities in the United States. We examined the different heat exposure levels across different socioeconomic and racial/ethnic groups in these cities, finding that income level is most consistently associated with heat stress. We further conducted scenario simulations in a hypothetical 1 ºC increase of air temperature in all cities. Results show that a 1 ºC increase would have a substantial impact on human heat stress, with impacts that differ across cities. The results of this study can help us better evaluate the impact of extreme heat on urban residents.

On urban microclimate spatial-temporal dynamics: Evidence from the integration of fixed and wearable sensing and mapping techniques

Urban Heat Island (UHI) is acknowledged to generate harmful consequences on human health, and it is one of the main anthropogenic challenges to face in modern cities. Due to the urban dynamic complexity, a full microclimate decoding is required to design tailored mitigation strategies for reducing heat-related vulnerability. This study proposes a new method to assess intra-urban microclimate variability by combining for the first time two dedicated monitoring systems consisting of fixed and mobile techniques. Data from three fixed weather stations were used to analyze long-term trends, while mobile devices (a vehicle and a wearable) were used in short-term monitoring campaigns conducted in summer and winter to assess and geo-locate microclimate spatial variations. Additionally, data from mobile devices were used as input for Kriging interpolation in the urban area of Florence (Italy) as case study. Mobile monitoring sessions provided high-resolution spatial data, enabling the detection of hyperlocal variations in air temperature. The maximum air temperature amplitudes were verified with the wearable system: 3.3 °C in summer midday and 4.3 °C in winter morning. Physiological Equivalent Temperature (PET) demonstrated to be similar when comparing green areas and their adjacent built-up zone, showing up the microclimate mitigation contribution of greenery in its surrounding. Results also showed that mixing the two data acquisition and varied analysis techniques succeeded in investigating the UHI and the site-specific role of potential mitigation actions. Moreover, mobile dataset was reliable for elaborating maps by interpolating the monitored parameters. Interpolation results demonstrated the possibility of optimizing mobile monitoring campaigns by focusing on targeted streets and times of day since interpolation errors increased by 10% only with properly reduced and simplified input samples. This allowed an enhanced detection of the site-specific granularity, which is important for urban planning and policymaking, adaptation, and risk mitigation actions to overcome the UHI and anthropogenic climate change effects.

Harnessing Machine Learning Algorithms to Model the Association between Land Use/Land Cover Change and Heatwave Dynamics for Enhanced Environmental Management

As we navigate the fast-paced era of urban expansion, the integration of machine learning (ML) and remote sensing (RS) has become a cornerstone in environmental management. This research, focusing on Silchar City, a non-attainment city under the National Clean Air Program (NCAP), leverages these advanced technologies to understand the urban microclimate and its implications on the health, resilience, and sustainability of the built environment. The rise in land surface temperature (LST) and changes in land use and land cover (LULC) have been identified as key contributors to thermal dynamics, particularly focusing on the development of urban heat islands (UHIs). The Urban Thermal Field Variance Index (UTFVI) can assess the influence of UHIs, which is considered a parameter for ecological quality assessment. This research examines the interlinkages among urban expansion, LST, and thermal dynamics in Silchar City due to a substantial rise in air temperature, poor air quality, and particulate matter PM2.5. Using Landsat satellite imagery, LULC maps were derived for 2000, 2010, and 2020 by applying a supervised classification approach. LST was calculated by converting thermal band spectral radiance into brightness temperature. We utilized Cellular Automata (CA) and Artificial Neural Networks (ANNs) to project potential scenarios up to the year 2040. Over the two-decade period from 2000 to 2020, we observed a 21% expansion in built-up areas, primarily at the expense of vegetation and agricultural lands. This land transformation contributed to increased LST, with over 10% of the area exceeding 25 °C in 2020 compared with just 1% in 2000. The CA model predicts built-up areas will grow by an additional 26% by 2040, causing LST to rise by 4 °C. The UTFVI analysis reveals declining thermal comfort, with the worst affected zone projected to expand by 7 km2. The increase in PM2.5 and aerosol optical depth over the past two decades further indicates deteriorating air quality. This study underscores the potential of ML and RS in environmental management, providing valuable insights into urban expansion, thermal dynamics, and air quality that can guide policy formulation for sustainable urban planning.

Optimizing green infrastructure strategies for microclimate regulation and air quality improvement in urban environments: A case study

With an increasing global urban population andassociated health concerns, understanding the effects of urban microclimate and air quality is crucial. This study aims to assess the influence of different types and locations of greenery, along with building heights and wind orientation, on urban canyon microclimate and air quality. Focusing on PM10, PM2.5, and NOx concentrations in a hot-arid district, the research employs simulation-based analysis. Results indicate that stepped buildings with green walls exhibit the highest temperature (18.02°C), while scenarios featuring two rows of deciduous trees showcase the lowest temperature (17.56°C) but higher pollution levels. Notably, scenarios lacking trees exhibit elevated temperatures. The study introduces a novel ventilation design pattern for effective air pollutant removal and proposes a scenario with extensive green coverage on streets, walls, and rooftops, incorporating appropriate planting techniques and plant selection. The findings offer valuable insights for urban designers and architects seeking to create more sustainable and environmentally friendly cities.

The Relationship between Green Infrastructure and Air Pollution, History, Development, and Evolution: A Bibliometric Review

In response to the challenge of atmospheric pollution posed by growing environmental problems, this study reviews and analyzes the research status and development trends of green infrastructure (GI) in improving air pollution from 2014 to 2024. Using the CiteSpace tool, we explore research hotspots, disciplinary developments, significant contributors, and influential literature in this field, identifying current research gaps and predicting future trends. The findings indicate that GI significantly impacts the reduction of air pollution, the regulation of urban microclimates, and the enhancement of ecosystem services. However, existing studies often focus on isolated aspects and lack comprehensive assessments. Moreover, the research trajectory in this field shows a declining trend. Future research should emphasize interdisciplinary integration, combining ecology, urban planning, meteorology, and public health. By utilizing advanced technologies, such as drones, remote sensing, AI, and big data analysis, we can improve data accuracy and the generalizability of research findings. Additionally, it is crucial to consider the performance of GI under different climatic conditions and socio-economic contexts to comprehensively quantify its overall benefits in terms of air quality, urban thermal comfort, public health, and economic impact. This comprehensive approach will provide a scientific basis for policy-making and urban planning.

Urban agriculture as ecosystem services provider: A review

Background: Urban agriculture’s role in mitigating the urban environment deterioration as ecosystem services provider. Urban agriculture adds various functions to different landscape scales, providing numerous benefits if managed correctly. This paper aims to study the role of urban agriculture as ecosystem services provider in mitigating urban environment deterioration. Method: The method that will be used in this article is literature review from articles related to urban agriculture and ecosystem services from provisioning, regulating, services, and cultural. The review is compiled from urban agriculture’s function as ecosystem services provider, such as biodiversity conservation, microclimate regulation, aesthetic function, and food production. Result: In essence, urban agriculture is a diverse and vital solution for cities, and it takes various forms, from private gardens to community plots, addressing challenges like limited public funding and promoting greening initiatives. Urban agriculture plays a key role in biodiversity conservation, contributing to enhanced environmental benefits and the preservation of local habitats. Another crucial role in regulating the complex dynamics of the urban microclimate, offering ecological benefits such as reduced Urban Heat Island effects, wind protection, and pollutant absorption. Beyond its ecological impact, urban agriculture adds aesthetic value to urban spaces, creating visually appealing landscapes and promoting cultural integration. Moreover, it serves as a multifaceted strategy for sustainable urban development, addressing food security, resilience, and well-being. Conclusion: Amidst challenges, such as the threat to urban biodiversity and the need for proper green space management, urban agriculture emerges as a holistic approach, contributing to the visual, cultural, and environmental fabric of cities. Novelty/Originality of this article: This study offers a new perspective on urban agriculture as a multifunctional solution to address urban environmental degradation. By integrating agriculture into the urban landscape, the study reveals the transformative potential for creating greener, more resilient and sustainable cities.

Phenotypic plasticity as the main driver of alien plant trait variation in urban versus rural microclimate for the model species Veronica persica.

Urban environments are warmer than the rural surroundings, impacting plant phenotypic traits. When plants are present over areas with contrasted conditions such as along urbanization gradients, their phenotypes may differ, and these differencesdepend on different processes, including phenotypic plasticity, maternal environmental effects and genetic differentiation (local adaptation and/or genetic drift). Successful establishment of alien species along environmental gradients has been linked to high phenotypic plasticity and rapid evolutionary responses, which are easier to track for species with a known residence time. The mechanisms explaining trait variation in plants in urban versus rural microclimatic conditions have received little attention. Using the alien Veronica persica as model species, we measured leaf traits in urban and rural populations and performed a reciprocal common-garden experiment to study how germination, leaf, growth, and flowering traits varied in response to experimental microclimate (rural or urban) and population origin environment (rural or urban). Veronica persica displayed phenotypic plasticity in all measured traits, with reduced germination, development, and flowering under urban microclimate which suggests more stressful growing conditions in the urban than in the rural microclimate. No significant effect of the rural or urban origin environment was detected, providing no evidence for local adaptation to urban or rural environments. Additionally, we found limited signs of maternal environmental effects. We noted the importance of the mother plant and the population identities suggesting genetically based differences. Our results indicate that urban environments are more hostile than rural ones, and that V. persica does not show any adaptation to urban environments despite genetic differences between populations.

A novel approach to identify the microclimatic edge effect width of urban green spaces at the landscape level: A case study of Changsha, China

Microclimate (e.g., temperature and humidity) in urban green space (UGS) patches changes nonlinearly from the edge to the interior, displaying a microclimatic edge effect (MEE). Reducing the MEE width is an effective and practical strategy for UGS planning and management to enhance climatic benefits (e.g., cooling). However, cost-effective approaches are not available to quantify the MEE width, let alone explore its driving factors. This study proposes a novel and cost-effective method to quantify the MEE width, based on the relationship between climatic variables (e.g., temperature and humidity) and the percentage of remaining UGS after successive edge removals. The method was tested in the subtropical city of Changsha, China, considering air temperature (AT) and humidity. Its effectiveness was also tested using widely available land surface temperature (LST) datasets while considering different spatial resolutions of the UGS map (i.e., 1–10 m) and different analytical units (i.e., 1 km2 grid and township census tract). Finally, the generalizability of this method was validated with data on six other representative Chinese cities. The results show that: (1) The estimated MEE widths for temperature and humidity in Changsha are about 8 m and 6 m, respectively. (2) The approach obtains consistent MEE widths irrespective of temperature types and analytical units. (3) A high spatial resolution UGS map (i.e., 1 m) is recommended for higher accuracy. (4) This approach effectively identifies MEE width in six other representative Chinese cities (Beijing, Chengdu, Shanghai, Shenyang, Wuhan, Xi’an), demonstrating its generalizability. This novel approach provides an easy and fast method to identify the MEE width at the landscape scale, which can help (1) better understand the relationship between UGS fragmentation and the urban microclimate, and (2) better plan and manage UGS to improve the urban microclimate.

Large-Scale Solar Potential Analysis in a 3D CAD Framework as a Use Case of Urban Digital Twins

Solar radiation impacts diverse aspects of city life, such as harvesting energy with PV panels, passive heating of buildings in winter, cooling the loads of air-conditioning systems in summer, and the urban microclimate. Urban digital twins and 3D city models can support solar studies in the process of urban planning and provide valuable insights for data-driven decision support. This study examines the calculation of solar incident radiation at the city scale in Sofia using remote sensing data for the large shading context in a mountainous region and 3D building data. It aims to explore the methods of geometry optimisation, limitations, and performance issues of a 3D computer-aided design (CAD) tool dedicated to small-scale solar analysis and employed at the city scale. Two cases were considered at the city and district scales, respectively. The total face count of meshes for the simulations constituted approximately 2,000,000 faces. A total of 64,379 roofs for the whole city and 4796 buildings for one district were selected. All calculations were performed in one batch and visualised in a 3D web platform. The use of a 3D CAD environment establishes a seamless process of updating 3D models and simulations, while preprocessing in Geographic Information System (GIS) ensures working with large-scale datasets. The proposed method showed a moderate computation time for both cases and could be extended to include reflected radiation and dense photogrammetric meshes in the future.

Investigation of Density factor in Urban Morphology on Micro-Climate Parameters in Cold and Dry Areas (Case Study: Tabriz City, Iran)

In recent decades, in third world countries, especially in the Middle East, the concept of urban micro-climate has undergone many changes in the process of development and construction, leading to environmental crises and the discrete structure of energy consumption in urban blocks. The urban form, the product of morphological changes in recent periods, has had significant effects on the micro-climate of the city. The city of Tabriz in the cold and dry areas of Iran has suffered from the inadequacies of the urban form and adverse effects on the micro-climate of the city as a result of unbalanced development. The main aim of research as parametric study on the interactions between urban morphology and microclimate is to investigate density metric to analysis effect amount in micro-climates. The research is analytical-descriptive and method of collecting data in the form of documents includes literature review, modeling and simulation using Envi-met software and density metric explain modes of a hypothetical in 10 scenarios and are presented in the form of two groups. The construction parts of the hypothetical areas are located in the urban area of Tabriz city, Iran. All scenarios were assumed to be in the same area configuration, where buildings are located in 25 plots of 40 m x 40 m. The result shows Investigation the average ratings obtained from microclimatic simulation of the first group of scenarios shows that by keeping FAR constant and changing BSC, one cannot expect a specific sequence of changes in microclimatic parameters in the space around the buildings but in the case of the second scenario group which is presented with constant BSC and variable FAR, there is a significant sequence in the order of the obtained ranks and the change trend in the average parameters. The results show scenario A2 with FAR 1 and BSC 40% with the lowest average value (3.5) of the total of four parameters of simulating the hottest and coldest day has achieved the best result and is introduced as the best scenario. For future researches, it is possible to propose a more focused investigation on each of the mentioned parameters. DOI: https://doi.org/10.52783/pst.544

Urban land use, land cover change and urban microclimate dynamics in Addis Ababa, Ethiopia

Land surface temperature (LST) increases and urban heat island (UHI) variability are the major urban climatology problems arising in urban development. This study attempts to assess the effects of urban land use and land cover change on microclimate dynamics in Addis Ababa city. Three different sets of remotely sensed data from Landsat 5 TM (1990), Landsat 7 ETM+ (2005) and Landsat 8 OLI/TIRS (2021) were used for the study. LSTs were retrieved from Landsat5 TM and Landsat7 ETM+ using a mono window,and the thermal infrared band (TR-10) of Landsat–8 was used to retrieve LST. Regression and correlation analyses of the LST, normalized difference vegetation index (NDVI) and normalized difference built-up index (NDBI) were performed in SPSS V23. The study also examined the different residential urban morphology types (UMTs) of the LST and NDVI. The selected built-up blocks of UMTs included apartments, villas and mud houses. These UMTs are extracted by digitizing them from the Google Earth explorer. The results from this study showed that the proportion of urban green space (UGS) to other LULC types decreased from 120.4 km2 in 1990 to 76.26 km2 in 2021. However, the built-up area increased at a rate of 216.5 km2 (39.03%) from 1990 to 2021. The rapid expansion of built-up land in the study area was the main factor influencing the increase in LST. The residential UMTs exhibited significant differences in mean LSTs and NDVIs. The results indicate that UMT inhibited by Villia had the highest mean NDVI value and that the highest mean LST was observed in Apartment. The results of multiple linear regression analysis clearly indicate that built-up and green vegetation contributed 92.2% of the LST variations with R2 = 0.92 and VIF ≤ 10 in Addis Ababa city. The results of the study indicate that strengthening public participation in urban greening and optimizing the NDVI and NDBI are important strategies for mitigating the effects of microclimate change and that sustaining urban development and providing better quality of life for the urban population are important.

Strategic tree placement for urban cooling: A novel optimisation approach for desired microclimate outcomes

Trees are crucial elements for improving urban microclimates by providing cooling through shading, evapotranspiration, and windbreaks. To maximise their cooling effects, it is essential to strategically position the trees in optimal locations. However, research on optimising tree location and its impact on microclimates is limited owing to computational challenges and costs. This study introduces a novel method that employs three optimisation algorithms—i.e., Non-dominated Sorting Genetic Algorithm II (NSGA-II), Particle Swarm Optimisation (PSO), and Ant Colony Optimisation (ACO)—to identify the optimal locations for trees in urban environments to enhance urban thermal comfort. The research methodology involves simulating microclimate responses to tree placements optimised by each algorithm and assessing the results based on urban thermal comfort. The results underscore the efficacy of optimised tree locations, demonstrating that optimising tree locations can significantly reduce the Universal Thermal Comfort Index (UTCI) in urban areas. Furthermore, the findings suggest that the clustering of tree canopies has a compounding impact on these cooling benefits in urban areas. Notably, all three algorithms significantly improved UTCI. PSO demonstrated the rapid identification of effective tree configurations. However, ACO provided the most substantial reduction in air temperature, highlighting its potential as an effective tool for urban cooling. While efficient, NSGA-II plateaued earlier, suggesting its utility in scenarios where timely solutions are crucial.

The Application of Space Syntax to Enhance Sociability in Public Urban Spaces: A Systematic Review

Public urban spaces are vital settings for fostering social interaction among people. However, understanding how spatial layouts can promote positive social behaviors remains a critical and debated challenge for urban designers and planners aiming to create socially sustainable environments. Space syntax, a well-established theory and research method, explores the influence of spatial configurations on social aspects. Despite its significant contributions, there is a lack of comprehensive systematic reviews evaluating its effectiveness in enhancing social interaction within urban public spaces. This study aims to identify the existing scientific gaps in the domain of space syntax studies, with a primary focus on sociability in public urban spaces. Following the PRISMA framework, a thorough literature search was conducted in the Scopus database, yielding 1107 relevant articles. After applying screening and eligibility criteria, 26 articles were selected for in-depth review. This review adopted a novel approach to synthesizing and analyzing the findings for identifying underexplored scientific gaps. The findings suggested a wide variety of research gaps to address, encompassing evidence, knowledge, practical, methodological, empirical, theoretical, and target populations to provide a thorough overview of the current state of knowledge in this field. In conclusion, by exploring the interplay between space syntax and design elements such as the urban infrastructure, landscaping, and microclimate in these areas, future research can bridge this gap, particularly when considering a cross-cultural lens. This study underscores the importance of space syntax in promoting social interaction in urban public spaces, offering a robust foundation for future research and practical applications to create more socially engaging environments.

Quantifying City- and Street-Scale Urban Tree Phenology from Landsat-8, Sentinel-2, and PlanetScope Images: A Case Study in Downtown Beijing

Understanding the phenology of urban trees can help mitigate the heat island effect by strategically planting and managing trees to provide shade, reduce energy consumption, and improve urban microclimates. In this study, we carried out the first evaluation of high spatial resolution satellite images from Landsat-8, Sentinel-2, and PlanetScope images to quantify urban street tree phenology in downtown Beijing. The major research goals are to evaluate the consistency in pixel-level spring–summer growth period phenology and to investigate the capacity of high-resolution satellite observations to distinguish phenological transition dates of urban street trees. At the city scale, Landsat-8, Sentinel-2, and PlanetScope show similar temporal NDVI trends in general. The pixel-level analysis reveals that green-up date consistency is higher in areas with medium (NDVI > 0.5) to high (NDVI > 0.7) vegetation cover when the impacts of urban surfaces on vegetation reflectance are excluded. Similarly, maturity date consistency significantly increases in densely vegetated pixels with NDVI greater than 0.7. At the street scale, this study emphasizes the efficacy of NDVI time series derived from PlanetScope in quantifying the phenology of common street tree genera, including Poplars (Populus), Ginkgos (Ginkgo), Chinese Scholars (Styphnolobium), and Willows (Salix), in downtown Beijing to improve urban vegetation planning. Based on PlanetScope observations, we found that the four street tree genera have unique phenological patterns. Interestingly, we found that the trees along many major streets, where Chinese Scholars are the major tree genus, have later green-up dates than other areas in downtown Beijing. In conclusion, the three satellite observation datasets prove to be effective in monitoring street tree phenology during the spring–summer growth period in Beijing. PlanetScope is effective in monitoring tree phenology at the street scale; however, Landsat-8 may be affected by the mixture of land covers due to its relatively coarse spatial resolution.