Urban-canopy airflow dynamics: A numerical investigation of drag forces and distribution for generic neighborhoods, and their relationships with breathability

Thorough investigations of urban-canopy drag primarily stemming from pressure drag on building surfaces are necessary given the turbulent flows within complex urban areas. Moreover, a gap persists regarding the relationships between canopy drag and breathability. Therefore, this work delves into the canopy-layer airflow dynamics for generic urban neighborhoods by performing three-dimensional Reynolds-Averaged Navier-Stokes simulations. A total of 32 subcases are examined, encompassing uniform- and varying-height and diverse plan area densities (λp, categorized into groups of sparse: 0.0625/0.067, medium: 0.23/0.25, and dense: 0.53/0.56). Results for the drag distribution highlight the windward-row shelter effect for the medium and the dense, local shelter by taller buildings, and distinct shapes of sectional drag forces (F⁎Z). Local velocity and mean age of air are found strongly positively and negatively correlated to F⁎Z, respectively, with distinct slopes in relation to λp. For the uniform-height, the normalized bulk drag (F⁎bulk, referred to as drag coefficient in literature) peaks for the medium with wake-interference regime; F⁎bulk demonstrates a maximum increase of over two times with height variation; moreover, F⁎bulk for varying-height groups exhibits a marked increase from the sparse to the medium, while remaining comparable values for the dense. The frontal area averaged drag (FAf,ave) exhibits a decreasing trend against λp across all cases. Further, FAf,ave exhibits strong correlations with λp and porosity, and with bulk ventilation indices such as spatially averaged velocity, air change rate, and normalized net escape velocity. Throughout the 'suburban-urban-suburban' canopy, medium neighborhoods exerting larger drag cause greater streamwise outdoor pressure drops and flow reductions compared to the sparse. However, dense neighborhoods with lower drag exhibit even larger pressure losses, which should be carefully scrutinized. The findings can inform urban planners in designing more aerodynamically efficient neighborhoods and guide strategies for improving air quality within urban environments.

Spatiotemporal patterns and drivers of the urban air pollution island effect for 2273 cities in China

Air pollution levels tend to be higher in urban areas than in surrounding rural areas, and this air pollution has a negative effect on human health. However, the spatiotemporal patterns of urban-rural air pollution differences and the determinants of these differences remain unclear. Here, we calculate the Urban Air Pollution Island (UAPI) intensity for PM2.5 and PM10 on a monthly, seasonal, and annual scale for 2273 cities in China from 2000 to 2020. Subsequently, we analyze the influence of urban characteristics using a combined approach of a two-way fixed effects model and a spatial Durbin model. Results show a strong downward trend in the UAPI intensity since 2013, with reductions ranging from 42 % to 61 % until 2020, for both pollutants and in summer as well as winter. Consistently, the proportion of the cities experiencing the UAPI phenomenon decreased from 94.5 % to 77.3 % for both PM2.5 and PM10. We find a significant influence of urban morphology on UAPI. Specifically, urban sprawl, polycentric development, and an increase in urban green spaces are associated with a reduction in UAPI, while dense urban areas intensify it. Our study also reveals a robust inverted U-shaped relationship between stages of economic development and UAPI. Moreover, economic development and air pollution itself show spillover effects that oppose their direct impacts. These results suggest that urban and regional planning and more ambitious climate change mitigation policies could be more effective strategies for mitigating air pollution in cities than end-of-pipe control.

Turbulent flow modification in the atmospheric surface layer over a dense city

Winds in the atmospheric surface layer (ASL) over distinctive urban morphology are investigated by building-resolved large-eddy simulation (LES). The exponential law is applied to urban canopy layers (UCLs) unprecedentedly to parameterize vertical profiles of mean-wind-speed u¯z and examine the influence of morphological factors. The skewness of streamwise velocity Su is peaked at the zero-plane displacement d (drag center) where flows decelerate mostly. The dynamics and intermittency in roughness sublayers (RSLs) are further contrasted. It helps determine the critical strength of the organized structures (ejection, Q2 and sweep Q4) in their contributions to the average momentum transport (i.e., 3 to 5). Two key factors of the local-scale dynamics are revealed - building heterogeneity and upstream giant wakes that could amplify turbulence kinetic energy (TKE) and energetic intermittent Q4 by different mechanisms. The former is conductive for large-eddy generation that promotes vertical fluctuating velocity w", stimulating intermittent, energetic Q2 and Q4. The latter, whose footprints are identified by the two-point correlation of streamwise velocity Ruu with specific size and inclination, facilitates intermittent, fast streamwise fluctuating velocity u", forming vigorous Q4. Nevertheless, excessive planar density λp (≈ 0.7) is detrimental to both transport processes. These findings contribute to the theoretical and empirical wall models of large-scale roughness that help urban planners and policymakers to improve air quality.

The effects of city morphology on airborne transmission of COVID-19. Case study: Port Said City, Egypt

Looking beyond COVID-19 outbreak, Scholars continue to develop innovative approaches to bring the city on to health and safety. Recent studies have indicated that urban spaces could produce or propagate pathogens, which is an urgent topic at the city level. However, there is a dearth of studies investigating the interrelationship between urban morphology and pandemics outbreak at the neighborhood level. Accordingly, this research will trace the effect of cities morphologies on the rate of spread of COVID-19 through a simulation study held on five areas that form the urban morphology of Port Said City, using Envi-met software. Results are explored based on the degree of concentration and rate of diffusion of coronavirus particles. It was observed on a regular basis that wind speed has a directly proportional relationship with the diffusion of the particles and an inversely proportional relationship with the concentration of the particles. However, certain urban characteristics led to inconsistent and opposing results like wind tunnels, shaded arcades, height variance, and spacious in-between spaces. Moreover, it is obvious that the city morphology is being transformed over time toward safer conditions; urban areas constructed recently have low vulnerability to respiratory pandemics outbreak compared to older areas.

Environmental determinants of access to shared sanitation in informal settlements: a cross-sectional study in Abidjan and Nairobi

BACKGROUND

Universal access to basic sanitation remains a global challenge, particularly in low- and middle-income countries. Efforts are underway to improve access to sanitation in informal settlements, often through shared facilities. However, access to these facilities and their potential health gains-notably, the prevention of diarrheal diseases-may be hampered by contextual aspects related to the physical environment. This study explored associations between the built environment and perceived safety to access toilets, and associations between the latter and diarrheal infections.

METHODS

A cross-sectional study was carried out between July 2021 and February 2022, including 1714 households in two informal settlements in Abidjan (Côte d'Ivoire) and two in Nairobi (Kenya). We employed adjusted odds ratios (aORs) obtained from multiple logistic regressions (MLRs) to test whether the location of the most frequently used toilet was associated with a perceived lack of safety to use the facility at any time, and whether this perceived insecurity was associated with a higher risk of diarrhea. The MLRs included several exposure and control variables, being stratified by city and age groups. We employed bivariate logistic regressions to test whether the perceived insecurity was associated with settlement morphology indicators derived from the built environment.

RESULTS

Using a toilet outside the premises was associated with a perceived insecurity both in Abidjan [aOR = 3.14, 95% confidence interval (CI): 1.13-8.70] and in Nairobi (aOR = 57.97, 95% CI: 35.93-93.53). Perceived insecurity to access toilets was associated with diarrheal infections in the general population (aOR = 1.90, 95% CI: 1.29-2.79 in Abidjan, aOR = 1.69, 95% CI: 1.22-2.34 in Nairobi), but not in children below the age of 5 years. Several settlement morphology features were associated with perceived insecurity, namely, buildings' compactness, the proportion of occupied land, and angular deviation between neighboring structures.

CONCLUSIONS

Toilet location was a critical determinant of perceived security, and hence, must be adequately addressed when building new facilities. The sole availability of facilities may be insufficient to prevent diarrheal infections. People must also be safe to use them. Further attention should be directed toward how the built environment affects safety.

Nonlinear forces in urban thermal environment using Bayesian optimization-based ensemble learning

Urbanization witnessed unprecedented development globally, which causes citizens and urban temperature to become increasingly intertwined. Although researchers were interested in the field, most studies focused on holistic linear links between the characteristics of the urban built-up environment and temperature. The study used Bayesian optimization ensemble learning and Shapley value to decouple the urban thermal environment by Landsat satellite data. This work's novelties reveal the specific driving effect of different value ranges of urban features in the overall process on the urban thermal environment and advancing an optimum observation buffer zone of the urban surface temperature. The study's results were only for daytime and Beijing scope. The following are the main findings: (1) The 2 km observation buffer zone is best to analyze the urban thermal environment for this dataset. (2) The ecological environment factors have a more significant effect on the urban temperature than the urban morphology factors. (3) In summer, when the vegetation coverage exceeds 58.1%, every 10% increase could reduce the temperature by 0.84 °C. In contrast to summer, when vegetation coverage exceeds 64.7% and 73.2%, respectively, in spring and fall, there will be a significant marginal utility. (4) The effect of the building height has seasonal variations. It has the greatest cooling effect in the spring when the height is between 18 m and 75 m, and the daytime surface temperature at the time of Landsat overpass will drop by 1.25 °C. These findings will aid in understanding how building construction influences urban surface temperature and provide statistical support for planners.

Combining computational fluid dynamics and neural networks to characterize microclimate extremes: Learning the complex interactions between meso-climate and urban morphology

The urban form and extreme microclimate events can have an important impact on the energy performance of buildings, urban comfort and human health. State-of-the-art building energy simulations require information on the urban microclimate, but typically rely on ad-hoc numerical simulations, expensive in-situ measurements, or data from nearby weather stations. As such, they do not account for the full range of possible urban microclimate variability and findings cannot be generalized across urban morphologies. To bridge this knowledge gap, this study proposes two data-driven models to downscale climate variables from the meso to the micro scale in arbitrary urban morphologies, with a focus on extreme climate conditions. The models are based on a feedforward and a deep neural network (NN) architecture, and are trained using results from computational fluid dynamics (CFD) simulations of flow over a series of idealized but representative urban environments, spanning a realistic range of urban morphologies. Both models feature a relatively good agreement with corresponding CFD training data, with a coefficient of determination R² = 0.91 (R² = 0.89) and R² = 0.94 (R² = 0.92) for spatially-distributed wind magnitude and air temperature for the deep NN (feedforward NN). The models generalize well for unseen urban morphologies and mesoscale input data that are within the training bounds in the parameter space, with a R² = 0.74 (R² = 0.69) and R² = 0.81 (R² = 0.74) for wind magnitude and air temperature for the deep NN (feedforward NN). The accuracy and efficiency of the proposed CFD-NN models makes them well suited for the design of climate-resilient buildings at the early design stage.

Impact of the COVID-19 pandemic on the energy performance of residential neighborhoods and their occupancy behavior

Several contrasting effects are reported in the existing literature concerning the impact assessment of the COVID-19 outbreak on the use of energy in buildings. Following an in-depth literature review, we here propose a GIS-based approach, based on pre-pandemic, partial, and full lockdown scenarios, using a bottom-up engineering model to quantify these impacts. The model has been verified against measured energy data from a total number of 451 buildings in three urban neighborhoods in the Canton of Geneva, Switzerland. The accuracy of the engineering model in predicting the energy demand has been improved by 10%, in terms of the mean absolute percentage error, as a result of adopting a data-driven correction with a random forest algorithm. The obtained results show that the energy demand for space heating and cooling tended to increase by 8% and 17%, respectively, during the partial lockdown, while these numbers rose to 13% and 28% in the case of the full lockdown. The study also reveals that the introduced detailed occupancy scenarios are the key to improving the accuracy of urban building energy models (UBEMs). Finally, it is shown that the proposed GIS-based approach can be used to mitigate the expected impacts of any possible future pandemic in urban neighborhoods.

Influence of urban form on air quality: The combined effect of block typology and urban planning indices on city breathability

Urban morphology affects airflow, causing pollutant accumulation within the urban canopy. Urban planning can regulate urban form by applying such strategies as defining urban block typology and stipulating urban indices. Consequently, urban planning can contribute to a healthy environment. In this context, modeling pollutant dispersion can assist urban planning decisions. Nonetheless, there is a lack of studies investigating the combined impact of urban block typology and urban indices on air quality. Therefore, this study aims to analyze the impact of these combined strategies on pollutant dispersion. Using computational fluid dynamics techniques, we investigated three combinations of urban indices (floor area ratio, surface coverage, and height) for three urban block typologies (single-block, detached building, and central courtyard). A total of nine urban configurations were distributed into three sets of urban index values for the three block typologies, namely "basic cases," "1-cases," and "2-cases." We used the Unsteady Reynolds-Averaged Navier-Stokes equations and the κ-ω SST turbulence model for the numerical simulations. The validation was conducted using wind tunnel experimental data. To assess city breathability at pedestrian height we used five parameters: pollutant concentration, the mean age of air, net escape velocity, and pollutant mass fluxes. The results showed that both strategies (i.e., block typology and urban indices) affect urban air quality. However, the performance of a block typology depends on the urban index values. For instance, in the "2-cases," decreasing the surface coverage by increasing the building's height improved ventilation efficiency in all typologies. Nonetheless, this strategy changed the performance ranking of the "basic cases." In "basic cases" the single-block typology had the best performance; in the "2-cases," the courtyard typology performed best. Although the courtyard typology improved air quality inside the patio, the outdoor areas displayed more pollutant concentration. Finally, general orientations to developing urban planning strategies were formulated.

Impact of morphological parameters on urban ventilation in compact cities: The case of the Tuscolano-Don Bosco district in Rome

Air pollution and heat stress are major concerns associated with the liveability, resilience and sustainability of cities. They directly affect health and comfort and are associated with augmented morbidity and mortality and an increase in the energy demand for building ventilation, air cleaning and cooling. Nevertheless, the detrimental effects of poor air quality may partly be mitigated by increased urban ventilation. This strategy is closely related to the level of urbanization and the urban morphology. Therefore, detailed investigations on the impact of different morphologies on urban ventilation are of paramount importance. Computational Fluid Dynamics simulations have been widely used during the last decades to investigate the effects of the urban morphology on the urban ventilation. However, most of these studies focused on idealized building arrangements, while detailed investigations about the role of real urban morphologies are scarce. This study investigates the ventilation in a compact area in the city of Rome, Italy. 3D steady-state Reynolds-averaged Navier-Stokes simulations are performed to analyze the impact of Morphological Parameters (MP) on the urban ventilation. The results show a considerable worsening of urban ventilation with increasing building density with a reduction in the mean wind velocity up to 62% experienced at the pedestrian level (z_p). Correlations between five MPs, e.g., plan area density, area-weighted mean building height, volume density, façade area density, and non-dimensional mean velocity at pedestrian level and at 10 m height are evaluated, and simple models are obtained using linear regression analysis. Among the selected MPs, the building façade area density shows a remarkable correlation with the non-dimensional mean velocity at z_p (R² = 0.82). Such correlations can be valuable tools for practitioners and urban designers, particularly during the first stage of planning, for highlighting areas potentially vulnerable to poor air conditions without running computationally expensive simulations.

The urban morphology on our planet - Global perspectives from space

Urbanization is the second largest mega-trend right after climate change. Accurate measurements of urban morphological and demographic figures are at the core of many international endeavors to address issues of urbanization, such as the United Nations' call for "Sustainable Cities and Communities". In many countries - particularly developing countries -, however, this database does not yet exist. Here, we demonstrate a novel deep learning and big data analytics approach to fuse freely available global radar and multi-spectral satellite data, acquired by the Sentinel-1 and Sentinel-2 satellites. Via this approach, we created the first-ever global and quality controlled urban local climate zones classification covering all cities across the globe with a population greater than 300,000 and made it available to the community (https://doi.org/10.14459/2021mp1633461). Statistical analysis of the data quantifies a global inequality problem: approximately 40% of the area defined as compact or light/large low-rise accommodates about 60% of the total population, whereas approximately 30% of the area defined as sparsely built accommodates only about 10% of the total population. Beyond, patterns of urban morphology were discovered from the global classification map, confirming a morphologic relationship to the geographical region and related cultural heritage. We expect the open access of our dataset to encourage research on the global change process of urbanization, as a multidisciplinary crowd of researchers will use this baseline for spatial perspective in their work. In addition, it can serve as a unique dataset for stakeholders such as the United Nations to improve their spatial assessments of urbanization.

GIS-based assessment for the potential of implementation of food-energy-water systems on building rooftops at the urban level

This research develops a bottom-up procedure to assess the potential of food-energy-water (FEW) systems on the rooftops of buildings in an urban district in Spain considering the urban morphology of the built environment and obtains accurate assessments of production and developmental patterns. A multicriteria decision-making technique implemented in a geographical information system (GIS) environment was used to extract suitable rooftop areas. To implement this method, the slope (tilt), aspect (azimuth), shading, and solar radiation of the rooftops were calculated using LiDAR (Light Detection and Ranging) data and building footprints. The potential of FEW system implementation was analysed at the building and morphology levels. The results showed several differences between residential and non-residential urban morphologies. Industrial areas contained the highest productivity for FEW systems. The production was 2.51 kg of tomatoes/m², 48 kWh of photovoltaic energy/m², and 0.16 l of rainwater/m². Regarding the residential urban morphologies, the more compact tents resulted in better performance. Among the FEW systems, although water could best benefit from the features of the entire roof surface, the best production results were achieved by energy. The food system is less efficient in the built environment since it requires flat roofs. The methodology presented can be applied in any city, and it is considered optimal in the European context for the development of self-production strategies for urban environments.

Impact of urban morphology on the spatial and temporal distribution of PM2.5 concentration: A numerical simulation with WRF/CMAQ model in Wuhan, China

The urban morphology can significantly change the urban microclimate, which in turn affects the diffusion of air pollutants. Urban planning is the most important means of shaping urban morphology. Therefore, this study takes Wuhan as an example and uses the method of WRF/CMAQ coupled UCM model to analyze the spatial and temporal distribution characteristics of PM_2.5 in the Wuhan metropolitan area in winter 2015. The six most important urban morphological indicators in urban planning: the floor area ratio and building height, building density and building width, vegetation coverage ratio, and urban fraction, are selected and classified into three groups. Studying their impact on the spatial and temporal distribution of PM_2.5 concentration provides support for urban planners to improve air quality. The results show that the maximum value of PM_2.5 concentration in Wuhan urban area occurs in the morning rush hour, and PM_2.5 is distributed concentrically in the downtown of the city (within the second ring highway) according to the highways around the city. The PM_2.5 concentration in the downtown area with the most extensive urban morphological index is the highest, and it decreases with increasing distance from the downtown. Among the six indicators, building density and urban fraction have the most significant impact on PM_2.5 concentration because they have the greatest impact on the wind speed at 10 m. The height of the planetary boundary layer is the key factors affect the vertical and horizontal diffusion of air pollutants. Except for the vegetation coverage ratio, the increase of other urban morphological indicators will lead to a decrease of PM_2.5 concentration in Wuhan urban area at night. During the daytime, increasing the floor area ratio and building height will cause an increasing of PM_2.5 concentration, but other indicators have the opposite effects.

Characteristics of noise complaints and the associations with urban morphology: A comparison across densities

This study aimed to characterise spatial-temporal distribution of noise complaints across urban areas with different densities and to analyse the associations between urban morphology and noise complaints. Taking New York City as the study area, crowdsourced noise complaint and urban morphology datasets from the government's open data source were statistically analysed. The results suggest that between boroughs the characteristics of noise complaints are different, in terms of their spatial-temporal distribution, their relation to transport network, land use, and building morphology. Noise complaints were clustered around the highest density area (Manhattan). The rate of noise complaints showed a year-on-year increase, peaking in autumn and spring. The rate of noise complaints is higher in areas with higher densities and roads that are 20-40 m wide, closer to road crossings, and in enclosed blocks. The relationships between noise complaints and urban morphology are weaker in high-density boroughs than in other boroughs.

Modelling Socio-Spatial Change: Istanbul, Kadıköy Case

This study aims to understand the relationship between social structure and morphological character based on a case area from Kadıköy, Istanbul, Turkey considering several independent (cultural diversity, family type, income level, ownership status) and dependent (land use type, land cover, building type, building layout, settlement type, settlement pattern, street pattern, commercial pattern) variables. Existing data is processed in two steps and analyzed by categorical regression. Results of the study show that urban character of the Kadıköy historical city center is closely related with family type, income level and cultural diversity. As this study has unique contributions in search for alternative methodologies to overcome limitations in the availability of data, it is expected to open new dimensions for further studies in social sciences and urban studies.

Urban heat island effects of various urban morphologies under regional climate conditions

Previous studies of the effects of regional climate conditions on urban heat islands (UHIs) focused mostly on surface UHIs, whereas few considered canopy layer UHIs. In the present study, a numerical modeling method is used to investigate the impacts of regional climate conditions on canopy layer UHIs at the district scale while controlling for the urban morphology. The urban morphology is classified according to the local climate zone (LCZ) system as LCZ1-LCZ6. Analysis of the spatial distribution of the urban heat island intensity (UHII) show that the nighttime and daytime UHII are most significantly correlated with the air temperature and wind speed, respectively. In five typical cities, LCZ1 has the most obvious urban heat island (UHI) effect, with an average annual UHII of 1-2.3 °C, which is about 1.5 times that for LCZ4. Reducing the building density has more significant influence on mitigating the UHI effect, where reducing the building height and building density reduce the heat island degree-hours (HIdh) by about 20% and 30%, respectively. The relationships between the UHII and meteorological conditions vary among different periods. For example, the correlation between UHII and average wind speed is more significant in the winter and at night. Our results help to understand the relationships between regional climate conditions and the canopy layer UHI at the district scale.

Statistical prediction of the nocturnal urban heat island intensity based on urban morphology and geographical factors - An investigation based on numerical model results for a large ensemble of French cities

Taking into account meteorological data in urban planning increases in relevance in the context of changing climate and enhanced urbanisation. The present article focusses on the nocturnal urban heat island intensity (UHII) simulated with a physically based atmospheric model for >200,000 Reference Spatial Units (RSU), which correspond to building patches delimited by roads or water bodies in 42 French urban agglomerations. First are investigated the statistical relationships between the UHII and six predictors: Local Climate Zone, distance to the agglomeration centre, population, distance to the coast, climatic region, and elevation differences. It is found that the maximum UHII of an agglomeration increases proportional to the logarithm of its population, decreases for cities closer than 10 km to the coast, and is shaped by the regional climate. Secondly, a Random Forest model and a regression-based model are developed to predict the UHII based on the predictors. The advantage of the regression-based model is that it is easier to understand than the black box Random Forest model. The Random Forest model is able to predict the UHII with <0.5 K absolute error for 54% of the RSU. The regression-based model performs slightly worse than the Random Forest model and predicts the UHII with <0.5 K absolute error for 52% of the RSU. A future challenge is to conduct a similar investigation at global scale, which is to date limited by the availability of a robust description of urban form and functioning.

Spatializing household energy consumption in the Netherlands: Socioeconomic, urban morphology, microclimate, land surface temperature and vegetation data

Household energy consumption (HEC) is affected by a variety of determinants. In addition to the level of HEC in 2612 residential zones in the Netherlands (the so-called wijk) in 2014, this dataset provides a geographically-referenced data of 11 determinants of HEC on: (1) socioeconomic characteristics - namely income per capita, household size, population density; (2) urban morphology -namely buildings' surface to volume ratio, building age; (3) microclimate factors -namely number of summer days, number of frost days, humidity, wind speed at 10 m height; (4) land surface temperature; (5) normalized difference vegetation index (NDVI). The dataset is initially prepared for an analysis titled as "Land surface temperature and households' energy consumption: who is affected and where?" [1].

Outdoor thermal comfort for pedestrians in movement: thermal walks in complex urban morphology

In the discussion of designing for a healthier city, people in movement between interconnected spaces perform a non-sedentary activity enhancing sustainability and well-being. However, adverse weather conditions may create uncomfortable thermal sensations that change or ruin the experience of people walking outdoors. This paper is presenting the findings of a 3-year study on the perceptual variation of thermo-spatial conditions and comfort state for pedestrians moving between interconnected spaces. Thermal walks were organised in two European pedestrian routes of 500-m length. The structured walks were conducted with simultaneous microclimatic monitoring and field surveys of thermal perception based on 314 questionnaires, with a focus on the variation of comfort states. The findings suggest that spaces in sequence do not affect significantly microclimatic variation but have a large impact on the dynamic thermal perception of pedestrians. Interconnected spaces of high density result in a differentiation of thermal pleasantness between streets and squares. The aspect of movement along with complexity in urban morphology along a sequence enhances diversity in thermal sensation. This understanding opens possibilities in developing a multisensory-centred urbanism, where the experience of the thermal environment plays an integral role for perception-driven and healthier urban design.

A new type of cities for liveable futures. Isobenefit Urbanism morphogenesis

Future cities? A morphogenetic code idea is presented. We need a conceptually different concept of cities which paradigmatically shifts their forms and structures toward more liveable future environments, both for us and our planet. The Isobenefit Urbanism is conceived within a medium-long term perspective mixing a macro top-down planning with a micro bottom-up spontaneous evolution in an attempt to moderate the human forces which typically induce agglomeration benefits and costs, maintaining the former while limiting the latter. It indicates a simple urban morphogenetic code to generate cities that are walkable, carless, low carbon, connected, compact, multifunctional settlements throughout nature, with unplanned forms and dinamically unlimitedly changeable/extendable, in which one can feel both urbanity and nature. By holding constant the number of inhabitants of a usual city/megacity, its Isobenefit city counterpart would enjoy the same (or greater) economies of scale benefits but without most of their costs. The Isobenefit Urbanism model might offer a potential solution to wild cementification, urban heat island effects, destruction of natural land and biodiversity, carbon emissions, congestion, air pollution, urbanicity and mental well-being, as well as provide a model to host the 3 billion new urban dwellers of the next few decades. Its ambition is to enjoy the economies of agglomeration without incurring to their diseconomies, manifested by sublinear and superlinear outputs scaling with city (population) size, typically infrastructural the former and socioeconomic the latter, without misusing lands and compromising daily rural/natural contacts.

Impact of urbanization-related land use land cover changes and urban morphology changes on the urban heat island phenomenon

Urban growth and development caused by urbanization influence the urban heat island (UHI) phenomenon. With the rapid development of urbanization, China's major cities are facing more serious climate change problems, especially the UHI phenomenon. Proper planning and urban design of compact cities may improve the ventilation of street canyons and change the heat balance in the urban canopy and thus mitigate the UHI phenomenon. The aim of this study is to evaluate and discuss the mitigation of UHI with different types of land-use and land-cover (LUCC), as well as different development patterns for compact cities. To this end, we applied the weather research and forecasting model (WRF) with urban canopy model (WRF/UCM) in this study. To evaluate the impact of LUCC changes on the UHI, we set 2 cases based on land use and land cover statistical data from 1965 and 2008 of Wuhan. Also, to evaluate the impact of urban morphology changes on the UHI, we designed 2 hypothetical cases based on 2 different urban developing patterns, one is high rise case and another is high density case, to simulate the impact of urban morphology on the UHI. As for the results of this study, with different LUCC of 1965 and 2008, UHI intensity of Wuhan increased by 0.2 °C-0.4 °C in average. Moreover, the critical wind speed which can mitigate UHI of case 1965 is much lower than case 2008. With different urban morphology, the high-rise case may lead to lower UHI intensity at the pedestrian level due to the shading effects of high-rise buildings. However, the critical value of wind speed in the high-rise case was almost 1.5-2 times greater than that of the high-density case, which illustrates the reduced possibility of mitigating the UHI phenomenon for high-rise buildings in Wuhan City.

Effects of atmospheric stability and urban morphology on daytime intra-urban temperature variability for Glasgow, UK

This study investigates the joint effect of atmospheric conditions and urban morphology, expressed as the Sky View Factor (SVF), on intra-urban variability. The study has been carried out in Glasgow, UK, a shrinking city with a maritime temperate climate type, and findings could guide future climate adaptation plans in terms of morphology and services provided by the municipality to overcome thermal discomfort in outdoor settings. In this case, SVF has been used as an indicator of urban morphology. The modified Pasquill-Gifford-Turner (PGT) classification system was adopted for classifying the temperature monitoring periods according to atmospheric stability conditions. Thirty two locations were selected on the basis of SVF with a wide variety of urban shapes (narrow streets, neighbourhood green spaces, urban parks, street canyons and public squares) and compared to a reference weather station during a total of twenty three transects during late spring and summer in 2013. Maximum daytime intra-urban temperature differences were found to be strongly correlated with atmospheric stability classes. Furthermore, differences in air temperature are noticeable in urban canyons, with a direct correlation to the site's SVF (or sky openness) and with an inverse trend under open-air conditions.

The relationship between urban form and air pollution depends on seasonality and city size

Understanding how urban form is related to air pollution is important to urban planning and sustainability, but the urban form-air pollution relationship is currently muddled by inconsistent findings. In this study, we investigated how the compositional and configurational attributes of urban form were related to different air pollution measures (PM_2.5, API, and exceedance) in 83 Chinese cities, with explicit consideration of city size and seasonality. Ten landscape metrics were selected to quantify urban form attributes, and Spearman's correlation was used to quantify the urban form-air pollution relationship. Our results show that the urban form and air pollution relationship was dominated by city size and moderated by seasonality. Specifically, urban air pollution levels increased consistently and substantially from small to medium, large, and megacities. The urban form-air pollution relationship depended greatly on seasonality and monsoons. That is, the relationship was more pronounced in spring and summer than fall and winter, as well as in cities affected by monsoons. Urban air pollution was correlated more strongly with landscape composition metrics than landscape configuration metrics which seemed to affect only PM_2.5 concentrations. Our study suggests that, to understand how air pollution levels are related to urban form, city size and seasonality must be explicitly considered (or controlled). Also, in order to mitigate urban air pollution problems, regional urban planning is needed to curb the spatial extent of built-up areas, reduce the degree of urban fragmentation, and increase urban compactness and contiguity, especially for large and megacities.

The application of a high-density street-level air temperature observation network (HiSAN): Dynamic variation characteristics of urban heat island in Tainan, Taiwan

The effects of urban heat island (UHI) have recently become a crucial issue. This study utilized a high-density street-level air temperature observation network (HiSAN) to understand the UHI characteristics in Tainan City. A total of 100 measurement points were established throughout the city. The average distance between two neighboring measuring points was 1.9 km in rural areas and 0.8 km in metropolitan areas. The UHI caused a temperature differences of at least 3 °C in each month over the study period, and the UHI's centric point moved from west to east during the day and from east to west at night, mainly because of the physical effects of the different urban environment including location and the impermeable surface area (ISA), total floor area, and sky view factor in urban areas. The results also indicated that factors such as ISA and distance to the coast had the strongest influence on thermal conditions at various times, especially in the areas far from the coast during the hot season. This was mainly because of differences in how heat was retained over the study area. The HiSAN method can be used by urban planners, architects, and policymakers to mitigate the thermal stresses caused by complex urban environments.

Identifying residential neighbourhood types from settlement points in a machine learning approach

Remote sensing techniques are now commonly applied to map and monitor urban land uses to measure growth and to assist with development and planning. Recent work in this area has highlighted the use of textures and other spatial features that can be measured in very high spatial resolution imagery. Far less attention has been given to using geospatial vector data (i.e. points, lines, polygons) to map land uses. This paper presents an approach to distinguish residential settlement types (regular vs. irregular) using an existing database of settlement points locating structures. Nine data features describing the density, distance, angles, and spacing of the settlement points are calculated at multiple spatial scales. These data are analysed alone and with five common remote sensing measures on elevation, slope, vegetation, and nighttime lights in a supervised machine learning approach to classify land use areas. The method was tested in seven provinces of Afghanistan (Balkh, Helmand, Herat, Kabul, Kandahar, Kunduz, Nangarhar). Overall accuracy ranged from 78% in Kandahar to 90% in Nangarhar. This research demonstrates the potential to accurately map land uses from even the simplest representation of structures.

Analysis of the relationships between environmental noise and urban morphology

Understanding the effects of urban morphology on urban environmental noise (UEN) at a regional scale is crucial for creating a pleasant urban acoustic environment. This study seeks to investigate how the urban morphology influences the UEN in the Shenzhen metropolitan region of China, by employing remote sensing and geographic information data. The UEN in this study consists of not only regional environmental noise (RN), but also traffic noise (TN). The experimental results reveal the following findings: 1) RN is positively correlated with the nighttime light intensity (NTL) and land surface temperature (LST) (p < 0.05). More interestingly, landscape composition and configuration can also significantly affect RN. For instance, urban vegetation can mitigate the RN (r = -0.411, p < 0.01). There is a reduced RN effect when fewer buildings exist in an urban landscape, in terms of the positive relationship between building density and RN (r = 0.188, p < 0.01). Given the same percentage of building area, buildings are more effective at reducing noise when they are distributed across the urban scenes, rather than being spatially concentrated (r = -0.205, p < 0.01). 2) TN positively relates to large (r = 0.520, p < 0.01) and small-medium (r = 0.508, p < 0.01) vehicle flow. In addition, vegetation along or near roads can alleviate the TN effect (r = -0.342, p < 0.01). TN can also become more severe in urban landscapes where there is higher road density (r = 0.307, p < 0.01). 3) Concerning the urban functional zones, traffic land is the greatest contributor to urban RN, followed by mixed residential and commercial land. The findings revealed by this research will indicate how to mitigate UEN.

Morphology of pedestrian roads and thermal responses during summer, in the urban area of Bucheon city, Korea

The purpose of this study was to elucidate the effect of urban morphology representing sky view factor (SVF) on urban microclimate and on human thermal responses. The physical environments and the changes in body temperatures as well as psychological responses were investigated in summer in Bucheon, Korea. The dry bulb temperature ranged from 31.5 °C at SVF 0.082 site to 35.7 °C at SVF 0.922 site. Most of the environmental elements were statistically correlated to the SVF: the dry bulb temperature R (2) = 0.602, UVB R (2) = 0.556 and the illumination level R (2) = 0.609. The mean skin temperature increased up to 36.0 °C at the SVF 0.940 site and decreased to 33.9 °C at the SVF 0.082 site. The mean skin temperature was statistically correlated to the SVF (p = 0.005). However, the core body temperature was not correlated to SVF because of time delay effect to the previously exposed thermal environment. In the investigation of thermal acceptability, only 5 % of subjects were dissatisfied with the road that was covered with plentiful trees; in contrast, approximately 50 % of subjects were dissatisfied with the road with poor solar obstacles in the summer. The thermal stress was affected by the urban morphology, and the plentiful urban greening improved thermal comfort.

Influence of urban morphology on total noise pollution: multifractal description

Exposure to ambient noise levels above 65 dB can cause public health problems. The spatial distribution of this kind of pollution is linked to various elements which make up the urban form, such as construction density, the existence of open spaces and the shape and physical position of buildings. Since urban morphology displays multifractal behaviour, the present research studies for the first time the relationship between total noise pollution and urban features, such as street width and building height by means of a joint multifractal spectrum in two neighbourhoods of the city of Cordoba (Andalusia, Spain). According to the results, the joint multifractal spectrum reveals a positive correlation between the total noise pollution and the street width to building height ratio, this being more evident when urban morphology is regular. The information provided by the multifractal analysis completes the description obtained by using urban indexes and landscape metrics and might be useful for urban planning once the linkage between both frameworks has been done.