Mean Building Height Research Articles

Impact of Urban Park Design on Microclimate in Cold Regions using newly developped prediction method

• The temperature distribution in the park was analyzed in different periods. • The temperature distribution in park was correlated with various morphology parameters. • The vegetation coverage and the average building height are the key factors. • Environmental evaluation and prediction method was developed and verified. With the acceleration of urbanization, the urban heat island phenomenon has attracted increasing attention. Urban parks play an important role for urban heat island mitigation. However, few studies were focusing on the impact of urban parks design on the urban microclimate. This research is based on the largest comprehensive park in Xi'an - Xingqing Palace Park. Measurement points in 20 locations with different urban morphological characteristics were selected to obtain typical summer weather characters (air temperature, relative humidity, wind speed, and wind direction). The value of the urban morphology parameters within different radii from the measuring points are measured to establish the relationship between urban planning and urban meteorology, and construct the prediction model using correlation analyses and regression analyses. The results showing that green coverage rate is an important factor affecting the urban microclimate. Meanwhile, building density and mean building height are affecting microclimate changes during nights, with a wide radius around the buildings. This research established a practical and feasible urban planning evaluation method by analyzing and selecting the urban morphology parameters that affecting urban microclimate for providing insights for mitigating the urban heat island effects and improving the urban microclimate.

Unravelling the multilevel and multi-dimensional impacts of building and tree on surface urban heat islands

The multilevel effects of landscape composition and configuration on daytime land surface temperature (LST) has been examined. However, how 2D and 3D characteristics of building and tree hierarchically interact to influence LST and how such effects vary diurnally were yet unknown. Using thermal satellite imagery, 2D and 3D characteristics of urban landscapes, and multilevel models (i.e. the random intercept model (RIM) and the random coefficient model (RCM)), we quantified the multi-dimensional and hierarchical effects of buildings and trees on LST as well as their diurnal contrast. Our results showed that combining landscape pattern and 3D urban morphology can capture more of the variation in diurnal LST than using them separately, regardless of single-level ordinary least squares (OLS) and multilevel models. Moreover, the multilevel models performed better than OLS models in explaining the impacts of landscape pattern and 3D urban morphology on LST for both day and night, and the RCM performed better than that the RIM. During the day, the standard deviations of the residual and autocorrelation in the residual for the RCM were 1.315 and 0.131, respectively, but 1.715 and 0.312 for OLS, respectively. Similarly, a smaller autocorrelation in the residual was produced by the RCM (0.155) than by OLS (0.366) at night. The spatial heterogeneity of LST was linked tightly to the percent cover of trees and the largest patch index of tree during the day, but was primarily dominated by the edge density of the buildings and the mean building height at night. Moreover, we found significant differences in the random effects of the composition and 3D urban morphology on the LST at the block level. The random impacts of the percent cover of buildings on both daytime and nighttime LSTs varied most across urban blocks. These findings provide urban planners and researchers a more thorough picture of LST-landscape associations from multi-dimensional and multilevel perspectives.

World Settlement Footprint 3D - A first three-dimensional survey of the global building stock

Settlements, and in particular cities, are at the center of key future challenges related to global change and sustainable development. Widely used indicators to assess the efficiency and sustainability of settlement development are the compactness and density of the built-up area. However, at global scale, a temporally consistent and spatially detailed survey of the distribution and concentration of the building stock – meaning the total area and volume of buildings within a defined spatial unit or settlement, commonly referred to as building density – does not yet exist. To fill this data and knowledge gap, an approach was developed to map key characteristics of the world's building stock in a so far unprecedented level of spatial detail for every single settlement on our planet. The resulting World Settlement Footprint 3D dataset quantifies the fraction, total area, average height, and total volume of buildings for a measuring grid with 90 m cell size. The World Settlement Footprint 3D is generated using a modified version of the World Settlement Footprint human settlements mask derived from Sentinel-1 and Sentinel-2 satellite imagery at 10 m spatial resolution, in combination with 12 m digital elevation data and radar imagery collected by the TanDEM-X mission. The underlying, automated processing framework includes three basic workflows: one estimating the mean building height based on an analysis of height differences along potential building edges, a second module determining the building fraction and total building area within each 90 m cell, and a third part combining the height information and building area in order to determine the average height and total built-up volume at 90 m gridding. Optionally, a simple 3D building model (level of detail 1) can be generated for regions where data on the building footprints is available. A comprehensive validation campaign based on 3D building models obtained for 19 regions (~86,000 km2) and street-view samples indicating the number of floors for >130,000 individual buildings in 15 additional cities documents that the novel World Settlement Footprint 3D data provides valuable and, for the first time, globally consistent information on key characteristics of the building stock in both, large urban agglomerations as well as small-scale rural settlements. Thus, the new dataset represents a promising baseline dataset for a wide range of previously impossible environmental, socioeconomic, and climatological studies worldwide.

Urban vertical profiles of three most urbanized Chinese cities and the spatial coupling with horizontal urban expansion

Earth has entered the century of city. Horizontal urban expansion has long been studied and is relatively well understood, but the knowledge of the vertical profiles of built structures remains limited. Here we propose a spatially explicit ensemble model and map the wall-to-wall building height of the three most urbanized Chinese cities in 2017 based on open-access Sentinel-1 SAR data, biophysical indices derived from Sentinel-2 multispectral imageries, and nighttime light (NTL) intensity. We further conduct a chronosequence analysis of the building height for these cities along with their horizontal urban expansion between 1985 and 2017. We show that our proposed method performs well in generating 1 km × 1 km building height maps in Beijing (R2 = 0.87, RMSE = 3.53 m), Shanghai (R2 = 0.82, RMSE = 4.21 m), and Shenzhen (R2 = 0.78, RMSE = 6.92 m). Shenzhen has the tallest (mean building height (MBH) = 37.63 m) and most diverse (coefficient of variation (CV) = 63.84%) vertical landscapes, followed by Shanghai (MBH = 29.86 m, CV= 51.14%). And the vertical profile is the lowest (MBH = 19.21 m) and relatively homogeneous (CV = 44.93%) in Beijing. We also find that vertical urban profiles are coupled with horizontal urban expansion, evidenced by an increase in building height along with the decreasing proximity to urban centers and the increasing urbanization intensity, and a clear imprint of urbanization age in all three cities. The specific characteristics vary among cities due primarily to local urbanization strategies. The knowledge of the vertical profiles of the three most urbanized Chinese cities complements the horizontal insights into urbanization and can assist sustainable land use and urban planning.

Understanding the effects of 2D/3D urban morphology on land surface temperature based on local climate zones

Summer increasingly gets hotter, which has become a common problem that threats human settlement environment and hinders urban sustainable development. The impacts of urban morphology on land surface temperature (LST) have been studied extensively, but the investigation from the local climate zones (LCZs) perspective is less concerned. We thus explored the relationship between 2D/3D urban morphology and spatial variation of LST across seasons based on LCZs by utilizing high-resolution remote sensing images and vector building data. The results showed that: (1) the spatial distributions of seasonal LSTs took a circle structure with three rings from the city center to the fringe area. In particular, the temperature showed a characteristic of “High-Low-High” in spring, autumn, and winter. However, the LSTs in the first ring were 1.4 °C and 2.2 °C higher than the second and third ring in summer, respectively. (2) The inter-LCZs differences of LST were consistent across seasons. In summer, the warmest zones were LCZ 2 and LCZ 3 with 2–3 °C higher than other built type LCZs, while the coldest zones were LCZ A and LCZ G with 4–6 °C lower than other land cover type LCZs. (3) The most influential 3D factor on LST was the mean building height with a significant cooling effect in LCZ 1, LCZ 3, and LCZ 4 in spring and autumn. Impervious surface fraction was the dominated 2D factor with a significant warming effect in all seven built type LCZs in summer.

Distributed urban drag parametrization for sub‐kilometre scale numerical weather prediction

AbstractA recently developed, height‐distributed urban drag parametrization is tested with the London Model, a sub‐kilometre resolution version of the Met Office Unified Model over Greater London. The distributed‐drag parametrization requires vertical morphology profiles in the form of height‐distributed frontal‐area functions, which capture the full extent and variability of building heights. London's morphology profiles are calculated and parametrized by an exponential distribution with the ratio of maximum to mean building height as the parameter. A case study evaluates the differences between the new distributed‐drag scheme and the current London Model setup using the MORUSES urban land‐surface model. The new drag parametrization shows increased horizontal spatial variability in total surface stress, identifying densely built‐up areas, high‐rise building clusters, parks, and the river. Effects on the wind speed in the lower levels include a lesser gradient and more heterogeneous wind profiles, extended wakes downwind of the city centre, and vertically growing perturbations that suggest the formation of internal boundary layers. The surface sensible heat fluxes are underpredicted, which is attributed to difficulties coupling the distributed momentum exchange with the surface‐based heat exchange.

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 (zp). 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 zp (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.

How Do Two- and Three-Dimensional Urban Structures Impact Seasonal Land Surface Temperatures at Various Spatial Scales? A Case Study for the Northern Part of Brooklyn, New York, USA

Identifying the driving factors of urban land surface temperatures (U-LSTs) is critical in improving urban thermal environments and in supporting the sustainable development of cities. Previous studies have demonstrated that two- and three-dimensional (2D and 3D) urban structure parameters (USPs) largely influence seasonal U-LSTs. However, the effects of 2D and 3D USPs on seasonal U-LSTs at different spatial scales still await a general explanation. In this study, we used very-high-resolution remotely sensed data to investigate how 2D and 3D USPs impact seasonal U-LSTs at different spatial scales (including pixel and city block scales). In addition, the influences of various functional zones on U-LSTs were analyzed. The results show that, (1) generally, the links between USPs and U-LSTs at the city block scale were more obvious than those at the pixel scale, e.g., the Pearson correlation coefficient (r) between U-LST and the mean building height at the city block scale (summer: r = −0.156) was higher than that at the pixel scale (summer: r = −0.081). Tree percentage yielded a considerable cooling effect on summer U-LSTs on both the pixel (r = −0.199) and city block (r = −0.369) scales, and the effect was more obvious in regions with tall trees. (2) The independently total explained variances (R2) of 3D USPs on seasonal U-LSTs were considerably higher than those of 2D USPs in most urban functional zones (UFZs), suggesting the distinctive roles of 3D USPs in U-LST regulation at the local scale. Three-dimensional USPs (R2 value = 0.66) yielded more decisive influences on summer U-LSTs than 2D USPs did (R2 value = 0.48). (3) Manufacturing zones yielded the highest U-LST, followed by residential and commercial zones. Notably, it is found that the explained variances of the total study area for seasonal U-LSTs were significantly lower than those of each UFZ, suggesting the different roles of 2D and 3D USPs played in various UFZs and that it is critical to explain U-LST variations by using UFZs.

Impacts of coexisting buildings and trees on the performance of rooftop wind turbines: An idealized numerical study

In response to the rapid growth of energy consumption in urban cities, rooftop wind turbines (RWT) have emerged as a powerful technique for providing sustainable energy and strategically minimizing the carbon footprint of buildings. However, significant knowledge gaps exist regarding how RWT respond to the complex urban environmental flows modified by the coexisting buildings and trees. This study conducts idealized numerical experiments using an open-source large-eddy simulation model to investigate the interactions between actuator-disc turbines, street trees and buildings. We found that trees taller than the mean building height modifies the existing roof-level strong shear layer by extracting energy from the mean momentum. A significant change in the mean kinetic energy budget is induced, drastically increasing turbulence production of the flow, which leads to lower power output of RWT. Trees lower than the buildings hardly alter the mean flow field but they reduce turbulence production near the roof level. As a result, improved power output (16%) and decreased normalized power fluctuation (5.2%) are observed compared to the control case without trees. The results highlight that it is important to assess effects of different street tree morphologies on the performance of RWT in their design and implementation processes.

Effects of neighbourhood morphological characteristics on outdoor daylight and insights for sustainable urban design

ABSTRACT Urban daylight significantly affects the physical and mental health of urban residents. Many previous studies focused on how outdoor daylight conditions affect indoor daylighting of buildings, whereas the design of outdoor daylighting conditions, which also exerted an equally significant part, was relatively overlooked. There are also few studies empirically explored the outdoor daylight in various forms of mature urban neighbourhoods. Through investigating the outdoor pedestrian daylight performances of 11 representative open urban neighbourhood units in inner-city Shenzhen, this study aims to identify the influence of urban design factors. Through field investigation, mapping and on-site measurement, this study explored and analysed the horizontal illuminance level and site illuminance uniformity of 84 outdoor spaces. As the results revealed, urban morphological characteristics significantly affected the daytime pedestrian illumination. Specifically, the high-density mid-rise urban villages and the urban park demonstrated the best daytime outdoor visual comfort conditions. The multivariate regression test demonstrated that sky view factor exerted the greatest influence on the daytime outdoor illumination, followed by the mean building height, ground surface albedo and vertical uniformity. Hence, urban morphological patterns have great potential in optimizing urban design for outdoor daylighting behaviours and energy use, which is of great reference value in setting specific standards to achieve the goals of the initiatives of “Healthy Cities.”

Air Quality and Key Variables in High-Density Housing

The high-rise and high-density housing development in nearby industry relocations is a general urban sprawl phenomenon in fast-growing cities in Southern China. Aside from the low price, the improved air quality in the suburban area is always a reason for home buyers, but the consistent monitoring of air quality and knowledge about how to plan housing estates are lacking. This paper investigates the relationship between the housing morphology and the air quality in three housing estates in Shenzhen. This research utilizes on-site monitoring equipment to examine negative air ions (NAIs) and fine particulate matter (PM2.5) and the Computational Fluid Dynamics (CFD) simulation to examine the air flow. This study reveals the effect of the urban form on the concentration of NAIs and PM2.5 in spatial variation. A correlation study between the configuration variables of the urban form and the CFD air flow pattern helps to identify the key variables influencing the air quality. This study concludes that in housing estates with good air quality of surroundings, the building density has no remarkable effect. However, the footprint of buildings, the layout of podiums, the roughness length of the building, the distance between buildings, the open space aspect ratio and the mean building height may have a remarkable impact on the air flow and quality. These findings may encourage high-density housing development and provide planning guidance for the configuration of housing forms in Southern China and subtropical climate regions around the world.

Gustiness in thermally-stratified urban turbulent boundary-layer flows and the influence of surface roughness

Gustiness is examined for the wind speed, fluctuations, turbulence intensities and fluxes for a real urban topography. Using large-eddy simulation (LES) and an ensemble sampling approach, which allows a more comprehensive characterisation of the urban morphological features, a wide range of boundary-layer stabilities is considered: the bulk Richardson number, Rb ​∈ ​[−0.41, 0.82]. Ratios of the proposed gustiness statistics, G, over the conventional time-averaged flow and turbulence statistics are maximised for z/Have ​≲ ​1 (where Have is the mean building height). The strong linear scaling of G with the plan-area index (λp) for neutral stratification is found to persist for stably- and unstably-stratified flows (R2 ~ 0.8). By contrast, the non-dimensionalised building-height variability, σH/Have, and the effective frontal-area index, λf^≡λfHave/σH, are argued to be of more appropriateness as scaling parameters for G compared to their original forms, σH and λf. While the sensitivity of G to Rb is well defined at greater heights, the influence of surface inhomogeneity may be strong enough to oppose the effect of thermal stratification in the lower surface layers. Qualitative differences in the sensitivities to the boundary-layer stability are narrowly distinguishable amongst the zeroth-, first- and second-order gustiness statistics. The results are relevant to the understanding of urban wind hazards in thermally-stratified boundary layers.

Characteristic Scales for Turbulent Exchange Processes in a Real Urban Canopy

An experimental field campaign is designed to unveil mechanisms responsible for turbulent exchange processes when mechanical and thermal effects are entwined. The focus is an urban street canyon with a mean aspect ratio H/W of 1.65 in the business centre of a mid-size Italian city (H is the mean building height and W is the mean canyon width). The exchange processes can be characterized by time scales and time-scale ratios specific to either mechanical or thermal process. Time scales describe the mixing caused by momentum and heat exchange within different canyon layers, while their rates are surrogates of their efficacy. Given that homogeneous mixing does not always occur within the canyon, several time scales are estimated at different levels, showing that mechanical and thermal processes may both contribute to enhance mixing. By computing mechanical time scales, it is found that the fastest mixing occurs at the canyon rooftop level for perpendicular or oblique wind directions, while slow mixing occurs for parallel directions. Thermal processes are faster than the mechanical ones and are particularly efficient for perpendicular wind directions. By calculating the time-scale ratios, exchange processes are found to facilitate mixing for most wind directions and to regulate the pollutant-concentration variability in the canyon. This variability can be associated with the local-circulation regime, demarcated as thermally driven or inertially driven using a buoyancy parameter, i.e., the ratio between thermal and inertial forcings. Using this approach, a generalization of the results is proposed, enabling the extension of the current investigation to different street-canyon aspect ratios.

IMPACT OF URBAN FORMS ON 3D BUILT-UP INTENSITY EXPANSION RATE FROM AERIAL STEREO-IMAGERY

Abstract. Urban areas have been cited to be contributors to changing climatic conditions. Conversion of vegetated areas to impervious surfaces causes an alteration of surface temperatures, where impervious surfaces absorb and store incoming radiation during the day, releasing it slowly at night. This causes the urban heat island effect where temperatures in urban areas are higher than rural areas during night. Extreme weather conditions experienced in urban areas include heat waves, intense rainfall resulting to flash floods, destruction of infrastructure facilities. The research involved the use of time-series of stereo-aerial images acquired in 1978, 2000 and 2017. Building footprints were digitized and using digital elevation models, building heights were derived and volumes calculated. Road volumes were calculated using minimum standards of road construction and the total built-up volume was determined. The ground coverage ratio (GCR) and built-up volume densities (BVD) of the built-up areas was calculated from area and volumes from road and building values. Results indicate the mean GCR and BVD in Upper Hill is within the low density range. Mean building height from 1978 to 2017 are in the low-rise range with significant rise in building height and volumes between 1998 and 2017. The 3D built-up intensity expansion rate ranged between −4.28% to 56.80% per annum with a mean of 19.6% per annum. Roads and pavements also have a significant influence on the built-up density and should therefore be considered in planning policies.

Local-Scale Urban Energy Balance Observation under Various Sky Conditions in a Humid Subtropical Region

AbstractThe present study presents local-scale urban energy balance observations under various sky conditions in a humid subtropical region. The study site is a typical urban residential area in Guangzhou in which building density is 38%, vegetation coverage is 36%, and mean building height is 21 m. The observation was conducted at a 110-m-high tower using the eddy covariance technique from September to November 2016. The median diurnal pattern and daily maxima were achieved for all radiation components and turbulent fluxes. The Bowen ratio (β) results indicated a predominant role for sensible heat flux (QH) in the daytime and latent heat flux (QE) at night. The sky conditions played a significant part in the urban surface energy exchanges, showing that the median daily maxima of net radiation (Q*), QH, storage heat flux (ΔQS), surface albedo, and β all present a consistent order from large to small for clear, cloudy, and rainy days and a different order of rainy, clear, and cloudy days for QE. The mean daytime QH/Q*, QE/Q*, ΔQS/Q*, and β changed with urban density, while QE/Q* and β also varied with vegetation fraction. Furthermore, the adaptability of net all-wave radiation parameterization (NARP), objective hysteresis model (OHM), and local-scale urban meteorological parameterization scheme (LUMPS) were validated, given the index of agreements of 0.998 and 0.951 for Q* and ΔQS and the reasonable RMSEs for QH and QE. The present study helps to verify and improve the parameterizations of energy exchange over an urban surface in the humid subtropical region.

Influence of urban form on the cooling effect of a small urban river

Urban warming due to increased urbanization is becoming a serious environmental problem, requiring urban planners to consider heat mitigation strategies that reduce urban air temperature. Urban rivers play an important role in reducing urban heat through evaporation and transfer of sensible heat, known as the river cooling effect (RCE). We used detailed field measurements to calculate the river cooling intensity (RCI) and river cooling distance (RCD) for the Cheonggye River in Seoul, Korea in order to determine the relationship between RCE and urban form at different times of day during summer. Our results showed that the Cheonggye River had a mean RCI of 0.46 °C and a mean RCD of 32.7 m at 2 p.m. and a mean RCI of 0.37 °C and a mean RCD of 37.2 m at 10 p.m. Spatial variations in RCE were negatively correlated with street width and mean building height at 2 p.m., indicating that narrower streets and lower buildings would improve the RCE. In addition, temporal variations in RCE were related to changes wind speed at similar humidity levels. Our results show that the urban form surrounding a river can affect the local RCE, suggesting that landscape and urban planners should consider urban form as a variable affecting urban heat and RCE.

Comparison between local climate zones maps derived from administrative datasets and satellite observations

This paper proposes a method for generating maps of Local Climate Zones (LCZs) within a GIS using administrative and 2.5D building databases. The LCZs are computed from morphological indicators and building typology, on vector reference spatial units that correspond to urban islets, i.e. blocks of buildings surrounded by nearby roads. The main originality is that, while mean building height criteria correspond exactly to the LCZ classification, a k-means statistical method is used to determine, for each city, the limits between compact and open (and sparsely built) LCZs for high-, mid- and low-rise LCZs, respectively. For example, in SO12 LCZ look-up tables and the WUDAPT-L0 mapping approach, “compact” LCZs correspond to a building density of over 40%. The resulting groups for Nantes, Toulouse and Paris for mid-height, treated with the proposed statistical method, are 36%, 37% and 33.8% respectively. The LCZ maps for these three cities are compared to the WUDAPT LCZ maps, the latter being obtained from satellite imagery at a resolution of 100 m. MApUCE LCZ maps show more spatial details, due to their finer resolution, and more variety in urban LCZs within each conurbation. This is very important for modeling micro-climatic effects on town peripheries.

Large-eddy simulations of air ventilation in parametric scenarios: comparative studies of urban form and wind direction

ABSTRACTThis study evaluates effects of building form and wind direction on urban ventilation using a large-eddy simulation (LES) model. Numerical simulations of air flow in 80 sets of parametric scenarios are conducted and the results are cross-compared. Main findings and potential recommendations for urban planning are: First, high mean building height is generally not good for ventilation, as vertical momentum is prevented from penetrating inside the street canyon. Second, inhomogeneous building heights tend to decrease the variance of site-averaged velocity ratios compared to homogeneous scenarios. Horizontal ventilation is moderated by the vertical momentum generated by inhomogeneous building heights. Third, rectangular (1:2 horizontal size) building arrays may allow better ventilation than square (1:1 horizontal size) building arrays. Moreover, given a moderate ground coverage ratio in square building arrays, 45° wind input allows better ventilation than 0° wind input. Finally, in cases of square arrays, higher ground coverage ratios result in lower site-averaged velocity ratios. But in the case of rectangular arrays, this negative relationship may be reversed.

Do water bodies play an important role in the relationship between urban form and land surface temperature?

Water bodies are considered an effective factor in mitigating urban heat island (UHI) effects in large cities. In Chongqing, the largest city in western China, using Landsat 8 data obtained in the daytime during the summer, we analyzed the potential influence of the cooling effects of water bodies on the urban land surface temperature (LST) based on the gradient of the distance to the water bodies (DIST). The results indicate that the cooling effect of water bodies can reach one kilometer (horizontal distance) and have a great impact on the relationship between the urban form factors and LST, particularly at a DIST less than 500 m. The sampling was performed in a 250 m × 250 m grid size, and correlations between four urban form factors (i.e., sky view factor, building density, mean building height and floor area ratio) and the LST gradually increased as the DIST increased. According to the multiple linear regression model, the DIST is an important independent variable at a DIST less than 500 m. This study may help researchers better understand the influence of urban form factors on thermal comfort considering water bodies.

How to Design a Park and Its Surrounding Urban Morphology to Optimize the Spreading of Cool Air?

Green areas induce smaller increases in the air temperature than built-up areas. They can offer a solution to mitigating the urban heat island impacts during heat waves, since the cool air generated by a park is diffused into its immediate surroundings through forced or natural convection. The purpose of this study is to characterize the effect of several variables (park size, morphology of surrounding urban area, and wind speed) on the spreading of cool air. A parametric study is performed to run computational fluid dynamics simulations. The air temperature entering the computational domain was set at 35 °C, and the 2-m high surface included within the 34 °C isotherm was defined as an indicator of cool air spreading. The effects of park shape and orientation were negligible in comparison with size effects. The number of buildings was better correlated with the cooled surface area than the typical urban parameters identified in the literature (i.e., building density, aspect ratio, or mean building height). Since the number of buildings is obviously related to the number of streets, this result suggests that the greater the number of streets around a park, the wider the area that cool air spreads.