High-density Cities Research Articles

Identifying carbon emission reduction potentials of BIPV in high-density cities in Southeast Asia

We use life cycle analysis, urban building energy simulations and urban form generation to compare the operational carbon emissions of buildings with building-integrated photovoltaics (BIPV) in locations with different grid electricity mixes in Southeast Asia. Our results show that BIPV installations can reduce operational carbon emissions of buildings by up to ∼50%. The entire roofs and ∼40-100% of the facades should be activated for solar energy harvesting, depending on the context and urban form. Additionally, we prove that it is more effective to install BIPV in countries with high carbon intensive grid electricity mixes, independent of climate and urban form.

Designing Urban Green Spaces for Older Adults in Asian Cities.

Elderly populations in Asian countries are expected to increase rapidly in the next few decades. Older adults, particularly in high-density cities, spend a considerable amount of time in urban green spaces (UGSs). The World Health Organization noted that UGSs are key to improving the age-friendliness of neighborhoods. Thus, it is necessary to design UGSs for the promotion of healthy ageing to enhance preventive healthcare and relieve medical burdens. This study conducted interviews using a questionnaire with a sample size of 326 participants in the cities of Hong Kong (China) and Tainan (Taiwan region). The inter-relationships among the design of UGSs (e.g., spatial distribution and accessibility, characteristics of plants and UGSs), older adults’ perceptions on safety and aesthetics quality of UGSs, and their self-reported health conditions (assessed by the self-reported SF-12v2 Health Survey) were investigated with bivariate Spearman rank correlation tests. The results indicate that the duration of visits to UGSs was positively associated with mental health and social functioning, two subscales evaluating health-related quality of life in SF 12v2. The statistical model (moderation analysis) showed that such a correlation was especially significant in women and those with low social support and social capital. A positive relationship was found between the physical health subscale and perceived safety in UGSs. This relationship was stronger among older adults living alone (moderation analysis). Furthermore, the color of plants and maintenance condition of UGSs were significant aspects affecting the subjective assessment of aesthetic quality. This study provides useful information regarding how to plan and design urban green spaces with certain characteristics that could improve the accessibility and aesthetic quality, which are preferred by older adults.

The study of headway patterns and level of service in myBAS ridership

The challenge of increasing ridership in public transportation has never been easy. Private vehicles often provide a greater opportunity to travel in rural areas and small cities with low traffic density but not in high-density cities. This paper attempts to identify the factors that affect myBAS service operation in Perlis and provide ratings on its headway patterns. The study focuses on the passengers of myBAS in Perlis and the selected routes were T101, F101, and CF109, with the most access to popular cities. Atlas Ti. (Version 7.0) was used for data analysis and a group of 11 factors affecting service operation were identified. Subsequently, an observation was also made by comparing the schedules published by the operator. Based on United States Highway Capacity Manual 2010 (USHCM 2010), the findings revealed that LOS for headway pattern during peak hour on route T101, F101 and CF109 is in the range of E (30 min to 60 min) with 1 bus arriving per hour. The findings also show “Service available during hour” and by improving the LOS of bus headway, the operator may increase ridership among local citizens. This study will benefit the local authority in achieving the status of the sustainable city towards 2030 in line with the United Nation’s declaration which focuses on green and healthy cities by having good mobility management and promoting better transportation planning as well as increasing ridership among citizens.

Relationship between pedestrian-level outdoor thermal comfort and building morphology in a high-density city

Urban compact buildings impose large frictional drag on boundary-layer air flow and create stagnant air within the building environment. It results in exacerbating the street-level outdoor thermal comfort (OTC). It is common to perform in-situ measurements of the OTC in different urban forms and to study their relationship. However, it is impossible to do so from a planning perspective because of the absence of physical planned urban forms. Our objective was to quantify the thermal environment and OTC in different planned complex urban forms by well-validated numerical models. We coupled a computational fluid dynamics (CFD) model to an OTC (Rayman) model to study the OTC. The κ–ω SST turbulent model was adopted for the CFD simulations, with accuracy of the turbulent model validated by wind tunnel measurements. The highest calculated air temperature within the street canyon of a planned bulky urban form could reach more than 5 °C higher than the surrounding environment. Within the tested urban forms, our coupled model predicted mean radiant temperature comparable with measurements in the literature. The model also produced sensible street-level physiologically equivalent temperatures (PETs) when comparing with those listed in the human thermal sensation categories. In the morning, the predicted PETs within all the urban forms were lower than that in open areas, which indicated that the shading of buildings effectively reduced the PET increase due to solar irradiance. At noon, increases in PETs by more than 10 °C relative to the morning situation indicated that when the buildings acted as heat sources after insolation absorption, increase in the air temperature at the street intersection and in the street canyon made an important contribution to the receiver PETs. The reduction in building lengths and increase in the low-level porosity were the most effective ways to reduce the heat stress at the pedestrian-level.

The Transformation of Open Urban Space and Increasing Building Density in Hong Kong since the 1970s

The narrow concept of open space (OS) present in land-use statutes cannot cover all new kinds of open urban space (OUS), however they must take responsibility for various open spaces in real-life cities, especially in contemporary high-density built environments. Open urban spaces are inserted into buildings or their accessibility is controlled by gated systems. A systematic and comprehensive approach to studying and evaluating the way in which OUS is changing is still lacking — especially from an architectural perspective. We put forward the Level-Type (L-T) framework to analyse the OUS system in central area of the Wan Chai and Yau Tsim Mong Districts, according to an expanded concept of OUS. In this paper, we illustrate the empirical studies from the first level of our research, to demonstrate how to use the new approach to evaluate the impacts of increasing density in the pattern of OUS. This study is fundamentally a qualitative study, however some data analyses act as auxiliary references to interpret changes observed in spatial planes and models. Following a three-step comparison of the changes in spatial forms and relevant data available since 1975, we found that all types of OUS are influenced — to different extents — by increasing trends and the speed at which they occur. Four kinds of relationships between increasing density and the transformation observed in the pattern of OUS are revealed. Moreover, with exception to the fourth kind of relationship — in which the changes observed in OUS are hardly a result of increasing density or the rate at which it occurred — we extract three main characteristics of OUS transformation from the remaining three kinds of relationships, which increase in density respectively. Furthermore, these characteristics of transformation can also explain the current recognition conflicts surrounding OUS from different perspectives and scales. This study method and resultant findings could prove very useful for managing and analysing the OUS system in high-density cities.

Opportunities and risks of implementing zero-carbon building policy for cities: Hong Kong case

There is a worldwide policy agenda of reducing buildings’ carbon emissions. Zero-carbon building has emerged as an advanced model with policy support, but high-rise remains a knowledge gap. This paper aims to contribute a better understanding of the opportunities and risks of formulating and implementing a zero-carbon building policy, and identify recommendations for maximising the opportunities and minimising the risks. Hong Kong as a typical high-rise high-density city was considered as the case for study. The research was conducted through the combination of a policy review, a questionnaire survey, interviews and focus group meetings with several hundred professionals and stakeholders carefully selected using stratified sampling. Wide opportunities were identified, with most important ones including raising public awareness of sustainable living, reducing buildings’ energy use and carbon emissions, and promoting strategic urban planning. However, risks were found to co-exist, with most significant ones including geographical obstacles to domestic renewable energy generation, heavy reliance on fossil fuels, and resistance of practitioners to the policy. Nevertheless, the opportunities were considered to outweigh the risks. Recommendations were identified to mitigate the risks, which are centred on policy guidance, business strategy, stakeholder partnership, and government and client leadership. The findings reveal the complex, interactive, interchangeable and context-specific features of the opportunities and risks, which alert to reconstruct a dialectical system framework of implementing zero-carbon building policy for Hong Kong. The yielding policy implications and recommendations should shape the reconstruction of that framework for high-rise high-density cities.

Geographic Information System-assisted optimal design of renewable powered electric vehicle charging stations in high-density cities

The crowded urban environment and busy traffic lead to heavy roadside pollutions in high-density cities, thereby causing health damages to city pedestrians. Electric vehicle (EV) is considered as a promising solution to such street-level air pollutions. Currently, in high-density cities, the number of public charging stations is limited, and they are far from enough to form a complete charging network with a high coverage ratio that can provide easy and convenient charging services for EV users. Concerns and worries on being unable to find a charging port when needed become a major hurdle to EV practical applications. Meanwhile, greener and cheaper renewable energy is recommended to replace fossil fuel-based grid energy that is commonly used in existing charging stations. Thus, this study proposes a novel Geographic Information System (GIS) assisted optimal design method for renewable powered EV charging stations in high-density cities. By selecting the optimal locations and optimal number of the renewable powered charging stations with the considerations of the existing charging stations and renewable potentials, the proposed method is able to minimize the life cycle cost of the charging stations while satisfying a user defined area coverage ratio. Using Hong Kong as an example, case studies have been conducted to verify the proposed design method. The design method can be used in practice to help high-density cities build their public charging networks with cost-effectiveness, which will promote EV practical applications and thus alleviate the roadside air pollutions in high-density cities.

Reduction of urban heat island and associated greenhouse gas emissions

The reduction of urban heat island (UHI) and carbon emission is of great importance for thermal environment of urban residential areas. This paper aimed to establish a method to analyze the effect of different underlying surface layouts on the reduction of heat island intensity and carbon emission. Taking Tianjin, China, as a case study area, a computational fluid dynamics (CFD) model, satellite-based remote sensing retrieval technology, and orthogonal experimental design were performed to investigate and quantify the performance of mitigation strategies (i.e., urban green space or water body, cool/high reflectivity pavement, and reflective roofs and facades) on UHI. The results indicated that urban green space is the most natural and effective mitigation strategy, while the widespread application of cool/high reflectivity materials is suggested as a mitigation strategy for building height more than 10 m above the ground. Application of urban water body is the next preferred strategy for air at 1.5 m pedestrian level. Green roofs, rainwater gardens, and permeable brick pavements are also more feasible in high-density cities for mitigating the UHI effect. The above mitigation and adaptation strategies of community scale can be acted on UHI and as a global urban climate change response.

Data-driven model for cross ventilation potential in high-density cities based on coupled CFD simulation and machine learning

Effective urban ventilation through decent urban planning and building design can alleviate the deterioration of the urban built environment. However, natural ventilation requirements and guidelines in current building codes and standards are either qualitative or quantitative but subject to an absolute indoor airspeed threshold without considering the outdoor wind environment. To fill this gap, this paper develops an urban-scale coupled indoor and outdoor computational fluid dynamics (CFD) model and defines a novel ventilation index to assess natural ventilation potential. The index considers wind environments of both indoor and outdoor spaces. First, the coupled CFD model is developed to study wind-driven cross ventilation in high-density cities. A 3D isothermal CFD simulation is solved using the RNG k-ε turbulent model. The simulation results are compared with wind tunnel experiment data from literature. Second, six key design variables are used to generate 3840 parametric design variations for natural ventilation assessment. Third, a novel integrated index CIOIv (coupled indoor and outdoor interaction) is proposed to evaluate the wind speed ratio between the indoor area and outdoor reference area. For demonstration, CIOIv,F1 is used to represent CIOIv on the ground level. Data-driven CIOIv,F1 models are developed to predict indoor building ventilation potential for quick early design support. Compared with multivariate linear regression model, the Gradient Boosting non-linear model displays much higher prediction accuracy (mean absolute percentage error = 0.16 with R2 = 0.8). In early design stage, designers and engineers can skip the computational expensive CFD simulations and use this data-drive model to quickly check the building natural ventilation potentials of different design options in an urban environment.

Green façades: Their contribution to stress recovery and well-being in high-density cities

Rapid urbanization and the lack of green infrastructure threaten the health of urban dwellers. Green façades have been proposed as a green infrastructure solution to compensate for the loss of green spaces in dense city areas; however, as far as we know, there is inadequate evidence for associations between views of green façades and relaxation. This study aims to clarify the physiological and psychological relaxation effects of viewing a green façade landscape. Twenty-five Chinese females (23 ± 1.5 years) viewed a green façade landscape or a building-wall for 5 min. Data were generated using electroencephalographic, heart rate variability, and skin conductance physiological measures and psychological measures using a semantic differential questionnaire and a Profile of Mood State. Findings suggest that, compared to the viewing of the building wall, the viewing of the green façade resulted in a significant increase in alpha relative waves in the frontal and occipital lobes, a significant increase in parasympathetic activity, and a significant decrease in the skin conductance as well as a substantial increase in comfortable, relaxed, and natural feelings, and a significant improvement in mood state. The green façade appears to enhance human physiological and psychological relaxation compared to the building-wall.

3D built-environment attributes and household road traffic noise exposure in Hong Kong

Road traffic noise is an environmental health hazard in Hong Kong and other high-density cities. The dense built environment modifies noise propagation, reflects, absorbs or diffracts sound depending on building morphology, road configuration, and open space layout, etc. Mitigation of urban traffic noise is of growing concerns to planning and design practitioners. Existing assessment methods are limited in reliably accounting for localized variations in noise exposure associated with a high-density city. The aim of this research is to 1) develop a 3D database of road traffic noise exposure for a large number of households in a high-density city; 2) explore the linkages between built environment attributes and road traffic noise exposure. A 3D built environment database was constructed for Hong Kong using building geometries, topography and urban traffic noise data. Window coordinates for each household were extracted using address and building floor plans. Computer simulation was conducted to determine traffic noise exposure at window locations using CadnaA for a random sample of 8,158 households across the city. Results revealed that 76.3% of the households are exposed to excessive road traffic noise by WHO standards. Household traffic noise exposure are significantly associated with proximity to secondary road, story-level of the flat, and other urban form attributes. The 3D database is of value for public health research in relation to noise and urban noise mitigation measures. The next step is to develop an efficient and reliable simulation tool to support planning and design decisions in traffic noise mitigation.

The Cooling Efficiency of Urban Greenery Coverage in a High-density City

Urban greenery especially trees has been identified as one of the most effective measures for urban climate moderation through the mechanism of evaporative cooling and shading. For subtropical high-density cities like Hong Kong, intense heat stress arises from the compact urban form, poor ventilation, and the high percentage of impervious urban cover. Thus, concerted actions are being taken to harness the cooling potential of urban greenery for improved microclimate. However, the cooling effects of urban greenery vary based on multiple factors, including background climates, urban morphology, anthropogenic heat emission, vegetation types and quantity, etc. This study aims at quantifying and comparing the cooling efficiency of different urban greenery coverage for a typical residential neighbourhood in Hong Kong. The questions guiding our research are: what is the relationship between tree coverage and ambient environment, including air temperature and thermal comfort during a typical summer day in the selected neighbourhood? To achieve this objective, we employed a previously validated ENVImet model setting of a typical summer day to conducted parametric studies of cooling benefit of variable tree coverage ratio from 0 to 30% at the interval of 2% on a typical summer day. The results verified the greenery had a higher cooling potential during period of maximum temperature than the whole diurnal time, 1 °C and almost 0.8 °C respectively for air temperature. This study also showed that increasing greenery coverage indeed lowers diurnal temperatures, but this relationship is logarithmic instead of linear. The ratio of change in cooling effects to greenery increase and then decreased gradually. Between the coverage ratio of 8%-35%, the cooling potential would be underestimated in a linear relationship. Greenery measures may lead to ineffective results if greening principles have not been comprehensive understood, such as greenery abundance, composition and types. The present study allows urban planners and managers to understand more in greenery amount for urban micro-climate in high-density cities.

Simulation-Informed Urban Design: Improving Urban Microclimate in Real-World Practice in a High Density City.

In many dense cities, urban heat and the interaction of buildings with their immediate urban environment emerges as a pressing issue due to growing urban heat island effect and climate change. Informed evidence based design decisions to mitigate heat stress becomes a priority for urban planning and design practitioners. The aim of the study is to develop informed design and development decisions using computer simulation tools concerning urban microclimate performance. In this study, academic researchers have worked with industrial partners in an urban renewal project in Hong Kong’s high density urban area. In-house developed simulation software such as CityComfort+ and HTB2-Virvil were applied to assess urban microclimate conditions and risks of pedestrian thermal stress throughout key seasons. Simulation results were provided as feedback to project designers and managers at early stage, allowing timely design modification to improve performance while maintaining code compliance and design and fiscal priorities. The procedure is iterative until performance attributes converge. Preliminary results show that the informed design can deliver significant microclimate benefits compared with “business-as-usual scenarios”. By shaping building mass, orientation, and strategic placement of shading and vegetation, the improved design is expected to reduce summer-time outdoor heat stress by 1°C measured in UTCI equivalent temperature, thus bringing the average conditions for the hot season into the “comfort zone” for the local community. Energy simulation can predict overall energy demand and the potential for renewable energy supply at an urban scale. The simulation-designer workflow shows promising potentials to improve urban microclimate performance of design outcomes and the potential for zero carbon urban blocks. The early-stage action, forward-looking partnership, and computing efficiency of the simulation tools are the keys.

Shared landscapes increase condominium unit selling price in a high-density city

High-density buildings can benefit city sustainability by reducing expansion into biodiverse and often public natural ecosystems, reducing travel-time to work-and-play and improving energy efficiency. However, city densification can also remove vegetation which provides ecosystem services that enhance resident's wellbeing. Some architects design shared landscapes on and around large-scale buildings which are excludable to the public, like private gardens, but can be rivalrous between residents, like parks. This potentially mitigates public vegetation and subsequent ecosystem service loss. However, little evidence exists on whether condominium unit buyers pay more for shared landscapes. To address this knowledge gap, we used the hedonic pricing method to explain condominium unit resale value with unbuilt and vegetated space, accounting for other price determinants, spatial and temporal random effects using a robust regression. Leaf area above 184 m2 and unbuilt area (condominium estate area minus the building footprint) above 62.3 m2 per person had significant positive effects on condominium unit selling price. This provides evidence that economic returns can be gained by having vegetation in accessible landscapes on and around buildings, should they be provided above a certain quantity. When supplied at more abundant quantities condominium estate vegetation also had a bigger effect than nearby managed parks, suggesting condominium unit buyers see more economic value in having nearer more private vegetation. Planners and building developers should consider these effects when deciding whether to encourage vegetated landscapes at condominium estates, alongside how vegetation can provide other monetary and non-monetary ecosystem services.

Urban Design Factors Influencing Surface Urban Heat Island in the High-Density City of Guangzhou Based on the Local Climate Zone.

Surface urban heat island (SUHI) depicts the deteriorating thermal environment in high-density cities and local climate zone (LCZ) classification provides a universal protocol for SUHI identification. In this study, taking the central urbanized area of Guangzhou in the humid subtropical region of China as the study area, the maps or images of LCZ, land surface temperature, SUHI, and urban design factors were achieved using Landsat satellite data, GIS database, and a series of retrieval and classification algorithms, and the urban design factors influencing SUHI were investigated based on 625 samples of LCZs. The results show that on the 18 September 2016 at the local time of 10:51 a.m., the land surface temperature (LST) varied greatly from 26 °C to 40 °C and the SUHI changed with a wide range of −6 °C to 8 °C in the LCZs of the study area. Seven and five urban design factors influencing the summer daytime SUHI were identified for the two dominant LCZs of LCZs 1–5 (LCZ 1 to LCZ 5) and the mixed LCZ (containing at least three types of LCZs), respectively, in which vegetation cover ratio, floor area ratio, ground emissivity, and complete surface area ratio showed negative correlations and building density showed positive correlations. The summer daytime SUHI prediction models were obtained by using the step-wise multiple linear regression, with the performance of R2 of 0.774, RMSE of 0.95 °C, and the d value of 0.91 for the model of LCZs 1–5, and the values of 0.819, 0.81 °C, and 0.94 for the model of the mixed LCZ, indicating that the models can effectively predict the changes of SUHI with LCZs. This study presents a methodology to efficiently achieve a large sample of SUHI and urban design factors of LCZs, and provides information beneficial to the urban designs and regenerations in high-density cities.

Designing liveable urban open spaces in high density cities

Hong Kong is one of the densest cities compared to other metropolitan cities with population density in some districts exceeding 57,250 persons per sqkm. Hong Kong’s liveability has been affected by factors such as escalating urban density, lack of open spaces, congested living environments, air pollution concentration and high proneness to pandemics.Due to extremely high land premiums, some residents in Hong Kong live in nano flats small as 15sqm in high-rise towers. Given the congested nature of apartments, open spaces a play a vital role contributing to residents’ psychological and physical well-being. Due to peculiar topography and extreme high density, Hong Kong open space per capita is far from the WHO recommended standards of 9 sqm per person. Most urban open spaces are pocket spaces located among developments or adjacent to traffic roads with a high ratio of hardscape compared to vegetation. Due to challenging Summer conditions in Hong Kong with high temperature, humidity and stagnant wind most urban open spaces are underutilized.This research investigates the factors effecting enjoyment of open spaces and design factors that could contribute to improve their liveability as public amenities. Exploration is based on liveability parameters such as user comfort, user behaviour, and spatial attributes of urban open spaces. Field data was collected on seven urban open spaces within Tsuen Wan district during dry Summer days. Field data analysis was supplemented by simulation methods, photographic survey of users’ movement within open spaces and user interviews.All open spaces are located amidst of high-density urban environment facilitating easy access to residents in the neighbourhood proving sense of security. Findings indicate tendencies in using these open spaces in the afternoon after 4pm when these open spaces cool off from solar radiation. Majority of open spaces benefited from shading effect from surrounding buildings, however the seating arrangements have not benefited from the shading. Satisfactory wind speed could be observed in four open spaces out of the seven that benefited from South and SE wind directions providing desirable thermal comfort to users. The park that consisted of the highest ratio of greenery received the lowest wind speed due walled effect created by surrounding buildings. Ironically open spaces with high percentage of hardscape areas reported better wind performance indicating the possibility of high emissivity material creating low pressure pockets drawing winds in particularly in the afternoons.

Associations Between Latent Classes of Perceived Neighborhood Destination Accessibility and Walking Behaviors in Older Adults of a Low-Density and a High-Density City.

To examine associations between perceived destination accessibility within different distances from home and self-reported overall amounts of walking for different purposes among older adults (aged ≥ 65years) in Brisbane, Australia (N = 793) and Hong Kong, China (N = 484). Perceived neighborhood destination accessibility types were derived from latent class analysis using comparable measures of perceived distance to 12 destinations from epidemiological studies in the two cities. Associations of perceived destination accessibility with measures of within-neighborhood walking were also estimated in Hong Kong participants. Better perceived destination accessibility was positively associated with the likelihood of walking in Brisbane participants only. Perceived destination accessibility within a short distance from home (5-min walk) was negatively related to the amount of within-neighborhood walking for transport in Hong Kong residents who walked. Our findings suggest that providing moderate-to-high, but not extreme, levels of destination accessibility may be optimal for the promotion of walking in older community dwellers.

How short-term cycling training promotes cycling among schoolchildren in high-density cities

This study explores how short-term, school-based cycling training programs can promote cycling among schoolchildren in the high-density city of Hong Kong. The schoolchildren’s progression in cycling ability was monitored closely by professional cycling coaches. Fifty-two children (aged 8–17) at three schools participated. Before and after data on their cycling habits and perceptions of the children and their parents were collected. Children showed clear improvements in their cycling techniques and skills with each session of the cycling training. After the children’s training, parents readily felt that cycling training helped to protect cyclists’ safety, with three quarters of “yes” respondents, and children were in agreement to a lesser magnitude, at around 55%. Other perceptions of cycling and cycling training were explored as well, with varying results. 24% of children reported cycling more after training, the majority of those at the introductory level, who had hardly ever cycled prior to training. The results suggest that cycling training has improved schoolchildren’s cycling ability, while perceptions and habits of cycling have begun to change as well. These findings can inform future policy direction in the implementation of formalized cycling training for schools situated in high-density cities like Hong Kong primarily to promote cycling for recreation and further as a form of sustainable transport. This needs to go hand in hand with improving neighborhood environments so they become more amenable for active travel especially for vulnerable road users, such as child cyclists.

Comparative and combinative cooling effects of different spatial arrangements of buildings and trees on microclimate

The amounts and arrangements of buildings and trees are primarily responsible for controlling small-scale thermal environments. However, uncertainties exist about how such structures regulate microclimates in cities. We investigated the effects of three contributory factors on microclimates: building arrangement, amount of land covered by tree canopies, and the intensity of solar irradiation relative to latitude. We modeled microclimate with the high spatial and temporal resolution ENVI-met model and validated it with in situ measurements. We designed and modeled seventy-two idealized model scenarios to compare cooling effects of various combinations of the contributory factors to microclimate. We found that: (1) both building and tree arrangements influence thermal microclimates (i.e., high-rise developments provide more land for greenspace and lead to lower near-surface temperatures than low-rise developments), (2) more area of forested greenspace leads to a more significant cooling effects (but the cooling effect of forested greenspace is non-linear relative to area), and (3) intense solar irradiation suppresses the cooling effects of greenspaces. Our results underscore the practical implications of shading arrangements on the evolution of thermal environments in high-density cities, which is useful for planning and designing mitigation strategies in urban areas and developing action plans at the neighborhood scale.

Enhanced geographic information system-based mapping of local climate zones in Beijing, China

The vague urban-rural dichotomy severely restricts effective comparisons and communications among urban heat island studies. A local climate zone (LCZ) scheme has therefore been developed to classify urban and natural landscapes in a standardized and universal manner. Despite LCZ mapping efforts in worldwide cities, this study attempts to propose an enhanced geographic information system-based workflow to enable the hierarchical classification of LCZs with fewer indicators but higher accuracies while considering supplementary classes and subclasses. Specifically, five morphological and coverage indicators that were easily obtained and well differentiated among LCZs were derived from a city street map and satellite images, and 25 LCZs (including 16 standard, 3 supplementary, and 6 sub-classified zones) were determined at a block-level according to the indicator hierarchy and criteria. The method was performed over Beijing, China, and evaluations by field surveys and google earth images showed a high accuracy with little noise and sharp boundaries, outperforming the widely-used remote sensing-based method of the World Urban Database and Access Portal Tools, particularly in terms of building height and heavy industry. Results also demonstrate that the Beijing core was dominated by open (including extremely open) mid-rise buildings (28.7%) and open low-rise buildings (12.8%), forming an inner-low-middle-high-outer-low annular building-height pattern. Significant land surface temperature differences were detected among the LCZs, where the low-rise and compact LCZs had higher temperatures than the mid-/high-rise and open LCZs during daytime, and subclasses LCZ XB/C/D (LCZ XE/F) generated lower (higher) temperatures than their parent classes in May. This method was proposed to augment the LCZ mapping system and further support applications (e.g., urban planning/management and climate/weather modeling) in high-density cities similar to Beijing.