Edward Ng

The Chinese University of Hong Kong | CUHK · School of Architecture

In the humid subtropics, rising temperatures can cause higher humidity via enhanced evaporation which exacerbates heat-related health problems. This study uses multi-station observational data to reveal the spatial-temporal changes of compound temperature-humidity extreme events in Hong Kong during 1961–2020. Based on the 90th and 10th percentiles...

Breezeways are crucial for horizontal urban ventilation. However, their morphologies, which are highly irregular, still lack investigation. This study aims to gain a categorical understanding of how irregular breezeway morphologies affect pedestrian-level wind performance in high-density cities. Firstly, we extracted breezeway areas and centerlines...

The vertical wind speed profile is crucial to urban ventilation assessment and urban planning/design. This study uses Light Detection and Ranging (LiDAR) observation as benchmark to evaluate accuracy of wind profiles estimated by conventional methods. The conventional methods include Boundary Layer Wind Tunnel (BLWT), Regional Atmospheric Modeling...

The land surface temperature (LST)—based surface urban heat island (SUHI) is suitable for exploring thermal environments at large scales. Despite a few studies focused on the intra-urban SUHI intensity (SUHII) of a single city or cities with similar climates by adopting the local climate zone (LCZ) scheme, exploration of the spatial-temporal charac...

Pedestrian spaces in cities allow a large number of outdoor activities. However, they are vulnerable to vehicular pollutants. This study aims to investigate how pedestrian spaces should be linked to optimize wind conditions and air quality in tropical cities. Numerical simulations are conducted to evaluate various upwind-to-downwind linking pattern...

To tackle urban overheating induced by the combined effect of global warming and intensive urbanization, researchers have recommended assimilating microclimate-related strategies into urban design practices. Field measurements, playing a central role in urban climatology, have been widely applied worldwide. Reviewing the last five years' field meas...

Climate warming, rapid economic development, and urbanisation in (sub)tropical regions lead to increasing electricity demand for building air-conditioning that could jeopardise the efforts of decarbonisation required to meet the climate change mitigation goals. This study investigates two strategies to reduce building energy consumption due to air-...

Climate change and heatwaves challenge urban dwellers’ thermal comfort and health. In Hong Kong, more frequent and intensive extreme heat has been observed recently. This study uses Light Detection and Ranging (LiDAR) to observe vertical wind profiles and calibrate numerical simulation methods for urban ventilation assessment in nighttime extreme h...

Mean radiant temperature (MRT) is a significant variable for outdoor thermal comfort studies. Two measurement-based methods can estimate MRT, one is globe thermometer – cheap, easily-applied but relatively inaccurate, another is integral radiation measurement method (also known as the six-directional method) - accurate but expensive. Due to low-cos...

Recent advances in numerical tools and data for the study of urban microclimates have helped to evaluate countermeasures for urban heat in heterogeneous and high-rise cities such as Hong Kong. Thus, two ventilation strategy designs, point ('oases') and linear ('corridors') features, were numerically simulated during a typical heatwave using the mul...

Microclimate knowledge has been intensively integrated into urban planning and design to improve the buildings’ energy performance and outdoor thermal comfort. To assess the climatic mitigation strategies, numerical modeling is gaining higher relevance. ENVI-met, a microclimate model to simulate the complex surface-vegetation-atmosphere interaction...

The high-density urban boundary layer (UBL) is one of the most complex atmospheric conditions, while the field data of UBL is limited due to the lack of suitable measurement methods. To better understand the UBL structures in high-density cities, a pioneering investigation is conducted in Hong Kong by Doppler wind LiDAR. Vertical wind speed profile...

Anthropogenic modification of the natural environment has caused significant impacts on the local atmosphere and far-reaching changes to the global climate. Taking Hong Kong as a case study, high-resolution (250 m) mesoscale simulations are conducted using Meso-NH coupled with the multi-layer Town Energy Balance to investigate the effects of past (...

Urban green and blue infrastructures (GBI) are considered an effective tool for mitigating urban heat stress and improving human thermal comfort. Many studies have investigated the thermal effects of main GBI types, including trees, green roofs, vertical greenings, and water bodies. Their physical characteristics, planting designs, and the surround...

Data-driven methods, such as artificial neural networks (ANNs), support vector regression (SVM), Gaussian process regression (GPR), multiple linear regression (MLR), decision trees (DTs), and gradient boosting decision trees (GBDTs), are the most popular and advanced methods for energy demand prediction. However, these methods have not been cross c...

A failure to consider extreme weather conditions in building design can lead to poor resilience and low passive survivability of buildings. Several approaches exist to construct extreme weather files for building performance assessments. Since literature comparing such extreme weather datasets is limited, this study aims to examine the applicabilit...

Researchers have made immense progress in understanding the urban-induced microclimate by numerical modelling. It has been around two decades since urban canopy models now commonly employed in mesoscale atmospheric models for operational and applied research purposes have emerged. To drive further advancement, it is timely to conduct a review of th...

Greenery infrastructure (GI) is an important design strategy for sustainable cities and communities’ development, as it brings multiple benefits including mitigating urban heat island. Based on the implementation locations, three typical GI typologies, namely green roof, green wall, and ground tree, are widely adopted in urban communities. As previ...

The application of passive design strategies is crucial at the early architectural design stage for building energy use minimization. However, the time-varying effectiveness of passive design strategies in responding to future climate change in hot and humid climates are rather limited in the literature. This paper aims to examine the dynamic effec...

Background This study aimed to quantify the mortality burden attributable to non-optimal cold and hot conditions from moderate and extreme temperatures in Hong Kong during 2006-2016. Methods The association between mortality and daily mean temperature was assessed using a distributed lag non-linear model (DLNM) integrated with a quasi-Poisson mode...

The WUDAPT (World Urban Database and Access Portal Tools project goal is to generate consistent information on urban form and function for cities worldwide that can support a wide range of “fit for purpose” urban weather, climate, hydrology and air quality analyses and modeling on a variety of scales. The latest developments are designed to generat...

Local climate zone (LCZ) maps that describe the urban surface structure and cover with consistency and comparability across cities are gaining applications in studies of urban heat waves, sustainable urbanization and urban energy balance. Following the standard World Urban Database and Access Portal Tools (WUDAPT) method, we generated LCZ maps for...

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 desig...

Doppler wind LiDAR (Light Detection And Ranging) makes use of the principle of optical Doppler shift between the reference and backscattered radiations to measure radial velocities at distances up to several kilometers above the ground. Such instruments promise some advantages, including its large scan volume, movability and provision of 3-dimensio...

Particulate matter that <2.5 µm in aerodynamic diameter (PM2.5) has been recognized as one of the principal pollutants that degrades air quality and increases health burdens. In this study, we employ the MLR and GWR modelling method to obtain estimation models for PM2.5 with a set of land use/landscape metrics as predictor variables. The study focu...

Background The impact of heatwaves on public health has led to an urgent need to describe extremely hot weather events (EHWEs) and evaluate their health impacts. Methods In Hong Kong, a very hot day (VHD) can be defined when the daily maximum temperature ≥ 33 °C, and a hot night (HN) can be identified if the daily minimum temperature ≥ 28 °C. Thre...

In face of the warming climate, proper building designs are necessary to combat the ever-increasing energy demands, especially in high-density built environments. Shading is a common practice in subtropical cities owing to its effectiveness and feasibility. However, window shading alone is insufficient for achieving a satisfying energy performance...

To better understand the relationship between energy consumption, and prevailing climatic condition, the present study uses Hong Kong’s observed air temperature records, end-use electricity consumption, and population datasets to: (a) investigate the spatial pattern of cooling energy requirement i.e. cooling degree days on a typical normal and extr...

This study examines the spatial-temporal changes of land cover and the surface urban heat island (SUHI) effect in the Pearl River Delta (PRD) region from 2000 to 2015. The Local Climate Zone (LCZ) concept is used, given its standard but comprehensive classification scheme designed for urban climate studies. Firstly, historical LCZ maps of the PRD r...

本书简介 有关香港可持续城市规划与发展的信息，往往散见于不同的杂志期刊。而有关香港城市规划的读本，比如1986年由香港政府屋宇地政署出版的《香港城市规划》、1997年由三联书店出版的《香港城市规划导论》，1999年香港大学出版社出版的《Town Planning in Hong Kong: A review of planning appeals》, 1991年出版的《城市规划条例全面检讨：摘要、咨询文件》， 2000年香港大学出版社出版的《Planning Buildings for a High-Rise Environment in Hong Kong: A review of building appeal decisions》。这些书大多出版于2000年以前，主要介绍香港城市规划...

Urban greenery is a natural solution to cool cities and provide comfort, clean air and significant social, health and economic benefits. This paper aims to present the latest progress on the field of greenery urban mitigation techniques including aspects related to the theoretical and experimental assessment of the greenery cooling potential, the i...

The comfort and health of building occupants are significantly affected by the indoor thermal environment, which can be improved by building envelopes with a good façade design. This study aims to explore the impact of façade shading on the indoor thermal comfort by adding external shading panels on a typical public rental housing building in Hong...

In recent years, urban ventilation assessment and urban ventilation corridor plan have been conducted and adopted in the urban planning of Chinese cities in response to the national call from the Central Government of China as well as the public concern on the quality of living environment. Therefore, a national technical guide is needed to provide...

This study presents a method for calculating solar irradiance of street canyons using Google Street View (GSV) images and investigates its spatiotemporal patterns in a high-density urban environment. In this method, GSV images provide a unique way to characterize the street morphology from which the diurnal solar path and solar radiation exposure c...

High-density urban areas are often associated with limited outdoor natural ventilation. Given the growing call for more vegetation in the cities, it is important to study the wind resistant of urban trees in order to address outdoor natural ventilation problem in the landscape planning. Currently, Computational Fluid Dynamics (CFD) simulation and w...

Research on the experiences of the recent tremendous rural construction and restructuring in China show that the social dimension of sustainability is crucial for the success of rural development. However, most conventional built environmental sustainability assessment tools (BESATs) are mainly focussed on environmental sustainability and building...

Urban heat island (UHI) has been identified as a threat to urban living quality in the context of climate change. As awareness of the impacts of urban expansion on local climate increases, urban planners/decision makers attempt to incorporate climatic considerations into the planning process. An increasingly-used urban climatic analysis scheme— Loc...

This 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 i...

Full report accessible at the Planning Department, HKSAR Government, Air Ventilation Assessment Register - https://www.pland.gov.hk/pland_en/info_serv/ava_register/ProjInfo/AVRG124_FinalReport.pdf

Using a validated ENVI-met model, a parametric study was conducted to investigate the thermal and energy saving benefits in a selected neighbourhood with its current greenery coverage ratio (GCR) of 7.2%, compared to the recommended 30%. To provide information for efficient tree species selection, nine scenarios were tested for the case of 30% GCR....

The World Urban Database and Access Portal Tools (WUDAPT) is an international community-based initiative to acquire and disseminate climate relevant data on the physical geographies of cities for modeling and analysis purposes. The current lacuna of globally consistent information on cities is a major impediment to urban climate science toward info...

In most current air ventilation assessment (AVA) studies, a simple neutral assumption that does not consider thermal effects is adopted, particularly for numerical simulation practices. With statistics of daytime observations during summer in Hong Kong as an example, this study demonstrates that neutral atmospheric boundary conditions occur with a...

Computational fluid dynamics (CFD) techniques, such as large-eddy simulation (LES), are widely used in urban ventilation studies. Unfortunately, realistic building data required in CFD studies are not always available. In this study, LES of urban ventilation is used to assess building height extraction from different satellite images. As a case stu...

Realistic digital elevations of urban areas are required in urban studies but are not always available. There is a need to extract urban information from satellite images that can be used for, but not limited to, studies of the urban wind environment. This study evaluates urban geometries, including building heights and building footprints, extract...

Combined effects of climate change and rapid urbanisation make buildings in high-density cities vulnerable to overheating, and thus induce high cooling energy demand, especially during the more frequently occurring near-extreme conditions in summer. It is necessary to minimise building energy consumption without compromising the comfort of occupant...

The exchange of radiant fluxes between different surfaces in an outdoor environment can be described with an enclosure theory. It provides a physical understanding of the relationship between different surfaces and consequent radiant fluxes within an enclosure, which is constructed by including surfaces of building façades and an imaginary surface...

Although projected precipitation increases in East Asia due to future climate change have aroused concern, less attention has been paid by the scientific community and public to the potential long-term increase in precipitation due to rapid urbanization. A ten-year precipitation dataset was analysed for both a rapidly urbanized megacity and nearby...

In high-density cities, optimization of their compact urban forms is important for the enhancement of pollution dispersion, improvement of the air quality, and healthy urban living. This study aims to identify critical building morphological design factors and provide a scientific basis for urban planning optimization. Through a long-term mobile mo...

The regenerative design framework aims to ‘engage a broader range of possibilities by moving beyond the immediate building and site boundaries’. It implies that the environmental performance of buildings requires a revised definition so that it considers not only the building itself, but also its contribution beyond its own boundary, i.e. neighbour...

Urban morphology information is an important indicator in urban planning, information management, and urban climatic applications. However, the problem of urban morphological data harmonization, quality, and availability are well-known, especially in developing countries. In this study, a novel satellite-based approach was proposed to extract 3D ur...

Extreme hot weather events are likely to increase under future climate change, and it is exacerbated in urban areas due to the complex urban settings. It causes excess mortality due to prolonged exposure to such extreme heat. However, there is lack of universal definition of prolonged heat or heat wave, which leads to inadequacies of associated ris...

To improve outdoor thermal environment and reduce indoor energy use, passive techniques including façade greenery have been suggested. In high-density cities like Hong Kong, buildings' surface area is much greater than the roof and ground surface areas combined, offering a huge vertical surface platform for greening. However, scientific evidence to...

Urban heat island (UHI) effect significantly raises the health burden and building energy consumption in the high-density urban environment of Hong Kong. A better understanding of the spatiotemporal pattern of UHI is essential to health risk assessments and energy consumption management but challenging in a high-density environment due to the spars...

Outdoor thermal comfort studies have proved that urban design has a great influence on pedestrians’ thermal comfort and its assessment helps to understand the quality and usage of the pedestrian environment. However, the majority of outdoor thermal comfort studies perceive pedestrian thermal comfort as “static”. The dynamic multiple-use of urban sp...

Ventilation in cities is crucial for the well being of their inhabitants. Therefore, local governments require air ventilation assessments (AVAs) prior to the construction of new buildings. In a standard AVA, however, only neutral stratification is considered, although diabatic and particularly unstable conditions may be observed more frequently in...

Particulate matters (PM) at the pedestrian level significantly raises the health impacts in the compact urban environment of Hong Kong. A detailed investigation of the fine-scale spatial variation of pedestrian-level PM is necessary to assess the health risk to pedestrians in the outdoor environment. However, the collection of PM data is difficult...

Extended Abstract Indoor thermal comfort and building energy performance are crucial for evaluating the sustainability and quality of urban living environments, especially for high-density cities with hot and humid summers. Studies show that climate change and urbanisation have contributed to the rise in urban air temperatures, resulting in advers...

Building performance evaluation is crucial for sustainable urban developments. In high-density cities, occupants suffer from poor living conditions due to building overheating, especially during increasingly frequent near-extreme summer conditions caused by climate change. To represent this situation, the summer reference year weather data was empl...

Previous studies found a relationship between geriatric depression and social deprivation. However, most studies did not include environmental factors in the statistical models, introducing a bias to estimate geriatric depression risk because the urban environment was found to have significant associations with mental health. We developed a cross-s...

Ventilation in cities is crucial for the well being of their inhabitants. Therefore, local governments require air ventilation assessments (AVAs) prior to the construction of new buildings. In a standard AVA, however, only neutral stratification is considered, although diabatic and particularly unstable conditions may be observed more frequently in...

Urban air quality serves as an important function of the quality of urban life. Land use regression (LUR) modelling of air quality is essential for conducting health impacts assessment but more challenging in mountainous high-density urban scenario due to the complexities of the urban environment. In this study, a total of 21 LUR models are develop...

Since the conclusion of the 2014 Climate Summit in New York and the 21st Conference of the Parties (COP21) in Paris, China has been actively advancing its national policies on climate change mitigation and adaptation since more unpredictable extreme weather events are expected, which may incur a heavy cost in terms of economics and public health. S...

Worldwide sustainable development advocates sustainable living for all. The increasing architectural construction in China has become an irreversible force in rural development. Judging and conducting architectural practice based on analysis of living sustainably in rural China is urgently needed. The developing of rurality should show sustainabili...

This study investigates ventilation performance in parametric urban scenarios using a large-eddy simulation (LES) model called the Parallelized LES Model (PALM). With various combinations of planning parameters, air flows and pedestrian-level velocity ratios in a total of 48 scenarios are investigated. Major findings and recommendations are: First,...

This study aims to develop a Local Climate Zone (LCZ) classification map and establish the associated urban morphology database as a cross-discipline information platform for climate research and planning decision making in Hong Kong. Geographic information system (GIS) was applied to synergize various kinds of planning data, and classify land surf...

Hot summers in the subtropics cause thermal discomfort, which is intensified by the urban heat island effect in heavily built-up areas. Use of urban greenery has been proposed as a mechanism for microclimate regulation. In this study, the microclimatic effect of urban trees was investigated in the context of high-density cities in subtropical hot a...

The local climate zone (LCZ) scheme provides a standard method to conduct urban heat island studies, in which urban landscapes are classified into different LCZs according to urban structures, land cover, and construction materials. Based on the LCZ classification scheme, the World Urban Database and Access Portal Tools (WUDAPT) is a new initiative...

This paper presents a parametric study on the effect of four green-roof types on outdoor/indoor temperature and cooling demand under four different climates and three urban densities using co-simulation approach with ENVI-met and EnergyPlus. Results reveal an outdoor nighttime warming effect of not more 0.2 °C which is most obvious with the semi-ex...

Due to limited land resources and hilly topographical condition, Hong Kong has focused on compact high density urban development and planning since the 1950s. High rise and vertical urban development and mixed land use mode have made high efficient and convince to citizens and created diversified and dynamic urban space. But at the same time, it al...

This study investigates ventilation performance in parametric urban scenarios using a large-eddy simulation (LES) model. The LES codes are first validated using computational fluid dynamics (CFD) guidelines for building simulations, and then utilized in the simulations of parametric-designed urban configurations. With various combinations of planni...

High-density urban environment affects urban microclimate, and thermal comfort of outdoor spaces. Shading by urban structure is the primary measure to reduce daytime mean radiant temperature (MRT) by blocking direct solar radiation. However, it is believed that overly-restricted Sky View Factor (SVF) limits the radiative cooling by the sky of lower...

Building performance simulation requires representative weather data of specific locations. Test Reference Year (TRY) and Typical Meteorological Year (TMY) are common hourly dataset for typical year conditions. In sub-tropical climates, overheating is very common in buildings due to high temperature and intense solar radiation. However, there are n...

The process of urbanization has changed the surface properties and spatial structures of urban areas, and accordingly, induced urban climate change. A warming trend has been observed in many cities of China, associated with severe heat events in summer. Previous studies have found that improving air ventilation in one of the most effective methods...

Hong Kong is an ageing society. According to the World Health Organization, an estimated 22% of its residents will be 65 years old or above by the year 2030. Physical activities provide an important way for older people to stay healthy. Green space is recognized as an important environmental setting for physical activity. Therefore, improving elder...

Urban heat islands (UHIs), usually defined as temperature differences between urban areas and their surrounding rural areas, are one of the most significant anthropogenic modifications to the Earth’s climate. This study applies the extreme value theory to model and detect trends in extreme UHI events in Hong Kong, which have rarely been documented....

Computational fluid dynamics (CFD) techniques, such as the Reynolds-averaged Navier-Stokes (RANS) model and large-eddy simulations (LES), are widely used in urban ventilation studies. Unfortunately, realistic digital elevations of urban areas required in CFD studies are not always available. Therefore, there is a need to extract urban information f...

The building facade not only serves as the outer surface of building itself, but also defines the boundaries of outdoor urban environment. This enclosure entraps more shortwave radiation from the sun due to its complex geometry and thermo-physical properties when compared with an unobstructed flat area. Building surface reflects and absorbs shortwa...

The exchange of radiant fluxes between different surfaces in outdoor urban environment can be described based on the theoretical framework of enclosure theory (or net-radiation method) in order to have a general understanding of the relation between different surfaces and consequent radiant fluxes and hence the Tmrt within the enclosure. To apply t...

Building performance simulation requires weather data that are representative of the climatic conditions of specific locations. Test Reference Years (TRY) and Typical Meteorological Year (TMY) are common hourly data set for typical year conditions. In sub-tropical high-density cities, overheating is very common in buildings due to the high air temp...

Physical activities provide an important way for elderly people to stay healthy. It is widely documented that the environment in which older people live plays an important role in promoting or inhibiting physical activity. In particular, green space has been recognized as an important behaviour setting for physical activity. The aim of this study...

Monitoring street-level particulates is essential to air quality management but challenging in high-density Hong Kong due to limitations in local monitoring network and the complexities of street environment. By employing vehicle-based mobile measurements, Land Use Regression (LUR) models are developed to estimate the spatial variation of PM2.5 and...

The Urban Heat Island (UHI) is a hot topic, especially in Asian cities, because their booming economics and rapid urbanization have intensified the UHI effect. The Local Climate Zone (LCZ) scheme was developed by Stewart and Oke to provide researchers worldwide with a standard way to conduct urban heat island studies. Recently, the World Urban Data...

Urbanization in China has been rapid since the 1990s. According to the latest report from the National Bureau of Statistics, it has been found that the urbanization rate reached 54.77% in 2014. This has led to a series of urban environmental problems and has changed urban climatic conditions, e.g. intensified urban heat island (UHI) effect. There i...

Rapid global urbanization means that most people will experience the effects of climate change in cities. These effects are augmented by local warming. Much of theis current urban growth is in the warm, humid tropics of Asia and Latin America. This three-part book explores the unique local climate consequences of urban growth trajectories of tropi...