The Urban Heat Island (UHI) is a phenomenon in which the urban temperature is higher than that of the non-urban areas. Previous studies from other countries showed that an UHI phenomenon exists in urbanized cities. In Hong Kong, instead of only few study using fixed stationary stations on UHI analysis, past effort have been concentrated on using traverse and remote sensing method to study the UHI. This dissertation therefore describes the annual, seasonal and diurnal UHI variability in Hong Kong based on hourly data of temperatures, wind speed and relative humidity from five selected fixed stations at urban and non-urban areas over the period 2001-2011. UHI intensity is calculated by the temperature difference between the urban and non-urban areas excluding the global warming factors and micro-climatic effects. The results showed that, although there is no significant increasing and decreasing trend in annual UHI variation, the maximum annual UHI intensity is increasing and the nocturnal UHI is proved significantly higher than that its daytime counterpart. The seasonal UHI variation is higher in summer or autumn and winter depends on the choice of non-urban stations due to different geographic settings and land use. The diurnal UHI variation revealed that the strongest UHI intensity was observed in late afternoon or early morning while the weakest one occurred in afternoon. Among the study groups, Hong Kong International Airport experiences the highest UHI intensity. It is probably due to the geographical settings, unique land use and significant anthropogenic heat. On the other hand, in using Ta Kwu Ling as non-urban stations, the wind speed showed a significant negative correlation with UHI intensity while the relative humidity showed a positive one in diurnal UHI variation. The results of the study indicated that the choice of non-urban station poses a significant impact to the UHI intensity calculation especially in seasonal and diurnal variations. Further study on choosing representative non-urban station for UHI intensity calculation is recommended. / published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Urbanization is known to cause significant changes to the properties of local climate. The Urban Heat Island (UHI) has been shown to add an additional burden to the impacts of global warming, impose risks on human health, and indirectly worsen air and water qualities. Studies have shown that urban areas, compared to rural areas with less artificial buildup, experience higher local temperatures as a result of UHI. Hong Kong is one of the most densely populated cities in the world with a high proportion of her population residing in urbanized areas. The hot and humid sub-tropical monsoon climate echoed with densely packed high-rise buildings and a high traffic volume can give rise to severe local thermal discomfort. To fully characterize the spatial and temporal aspects of UHI within Hong Kong’s urban areas, this study deployed 58 small, durable and low-cost logging sensors to measure road-side temperature/humidity measurements at 15-minute time intervals. The data collection was conducted over 17 consecutive days in the summer (September) and repeated in the winter (January) at two typical urban locations: Mong Kok and Causeway Bay. By employing the geographic information system (GIS) and global positioning system (GPS) software, the sampled data were mapped against urban structures and land uses to investigate the urban microclimate and the role of various environmental factors at the sampling locations. Official meteorological conditions for the duration of study were obtained from the Hong Kong Observatory to validate the sensors and to explore microclimate variations by comparing official (urban and rural monitoring stations) and sampled readings. Temporal variations of urban temperature were examined for daily, weekly and seasonal differences. Spatial and temporal variations were examined using spatial interpolation and hotspot analysis, as well as in a 3D representation with building models for better visualization. This empirical study establishes the methodological feasibility and reliability of employing small and inexpensive logging sensors for widespread deployment in places with hot and humid subtropical climates. The validation outcome indicated that road-side and control measurements were strongly correlated (r>0.81) and their average difference was well within the ±1 C measurement accuracy claimed by the manufacturer. Significant microclimate variations within the urban area were observed and characterized by five environmental settings: major road, secondary road, public activity area, green park and tunnel. Temporal variations of UHI were evident for all time scales, with the daily highest UHI at around midnight and daily lowest at around noon to early afternoon which also exhibited urban cool island (UCI) effects. A UHI Threat Rating was introduced for better understanding of microclimate variations and easier appreciation of hotspots. A 3D-GIS building model enhanced spatial-temporal analysis of UHI over a near “real” and 3D environment. The study and its methodology set a sound foundation and provide essential framework for future studies on microclimate variation and UHI effects. Given that modern cities have mixed land uses and are increasingly vertical, this micro-level study helps address local issues on human comfort and brings in the broader picture of environmental health in an urban setting. / published_or_final_version / Geography / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

abstract / Architecture / Doctoral / Doctor of Philosophy

Hui Shuk Ying. / Thesis submitted in: October 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 135-149). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.ii / ABSTRACT --- p.iii / 中文摘要 --- p.v / TABLE OF CONTENTS --- p.vi / LIST OF TABLES --- p.viii / LIST OF FIGURES --- p.ix / LIST OF SYMBOLS --- p.xii / Chapter CHAPTER I --- INTRODUCTION --- p.1 / Chapter 1.1. --- Background --- p.1 / Chapter 1.2. --- Situation in Hong Kong --- p.4 / Chapter 1.3. --- Physical setting of Hong Kong --- p.7 / Chapter 1.4. --- Climate of Hong Kong --- p.9 / Chapter 1.5. --- Objectives of the study --- p.12 / Chapter 1.6. --- Significance of the study --- p.12 / Chapter 1.7. --- Organization of the thesis --- p.13 / Chapter CHAPTER II --- LITERATURE REVIEW --- p.14 / Chapter 2.1. --- Introduction --- p.14 / Chapter 2.2. --- Nature of Urban Heat Island (UHI) --- p.15 / Chapter 2.3. --- Characterization of UHI --- p.16 / Chapter 2.3.1. --- Diurnal variation --- p.17 / Chapter 2.3.2. --- Seasonal variation --- p.19 / Chapter 2.3.3. --- Spatial distribution of UHI --- p.20 / Chapter 2.4. --- Effects of weather factors on UHI intensity --- p.22 / Chapter 2.5. --- Relationship between urban factors and UHI intensity --- p.27 / Chapter CHAPTER III --- WEATHER DATA AND METHODOLOGY --- p.34 / Chapter 3.1. --- Surface meteorological observation --- p.34 / Chapter 3.1.1. --- Meteorological stations --- p.35 / Chapter 3.1.2. --- Methods of observation --- p.40 / Chapter 3.2. --- Acquisition and processing of data --- p.42 / Chapter 3.3. --- Detection of urban heat island in Hong Kong --- p.46 / Chapter 3.4. --- "Characterization of UHI intensity, frequency and temporal patterns" --- p.48 / Chapter 3.5. --- Evaluation of relationship between UHI intensity and weather conditions --- p.49 / Chapter 3.6. --- Evaluation of correlation between UHI intensity and city growth --- p.51 / Chapter CHAPTER IV --- RESULTS AND DISCUSSION --- p.52 / Chapter 4.1. --- Temperature evolution in Hong Kong --- p.52 / Chapter 4.1.1. --- Urban center --- p.52 / Chapter 4.1.2. --- New town --- p.57 / Chapter 4.1.3. --- Rural areas --- p.64 / Chapter 4.1.4. --- Discussion of the temperature changes in Hong Kong --- p.68 / Chapter 4.2. --- Urban heat island in Hong Kong --- p.75 / Chapter 4.2.1. --- Basic characteristics of UHI --- p.75 / Chapter 4.2.2. --- Annual patterns of UHI --- p.83 / Chapter 4.2.3. --- Seasonal patterns of UHI --- p.87 / Chapter 4.2.4. --- Discussion of the UHI phenomenon --- p.96 / Chapter 4.3. --- Weather effect on UHI intensity --- p.102 / Chapter 4.3.1. --- UHI phenomena and weather conditions --- p.103 / Chapter 4.3.2. --- Relationship between UHI intensity and meteorological elements --- p.106 / Chapter 4.3.3. --- Discussion of weather effects on UHI intensity --- p.115 / Chapter 4.4. --- Correlation of urban indicators and UHI intensity --- p.121 / Chapter CHAPTER V --- CONCLUSIONS AND RECOMMENDATIONS --- p.128 / Chapter 5.1. --- Summary of findings --- p.128 / Chapter 5.2. --- Limitation of the research --- p.133 / Chapter 5.3. --- Prospects of the study --- p.134 / REFERENCES --- p.135

published_or_final_version / Geography / Master / Master of Philosophy

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Architecture / Doctoral / Doctor of Philosophy