169

Wind and Heat Environment in Densely Built Urban Areas in
Hong Kong
Edward NG
Department of Architecture, Chinese University of Hong Kong
Shatin, NT, Hong Konge-mail: edwardng@cuhk.edu.hk

Abstract
Global environmental changes, especially global warming, are becoming an issue for urban designers.
Coupled with that are the issues of life in mega- and high-density cities and the urban heat island effect.
Hong Kong is one of the world’s highest-density cities, with over sixty thousand persons per square kilometre in its urban areas. High-rise, bulky and closely packed buildings are the norm; and this increases theurban heat island intensity and reduces urban air ventilation. Given Hong Kong’s hot, humid tropical summers, high heat stress can be expected in the urban environment. Since 2003, the Hong Kong Government
has commissioned studies on this issue. An air ventilation assessment (AVA) study was carried out. In addition, an urban climatic map was drafted based on an evaluation of human thermal comfort. A study of
intra-urban temperature variations is underway and their possible implications to localised hot days and hot
spells is being investigated. The criticality of rising intra-urban temperature and decreased wind speed canbe established. This has provided objective input for planning actions in the form of urban climatic
recommendation maps. This work is on-going in Hong Kong. The present paper summarises some of theseprojects and documents the study process and rationale.
Key words: urban ventilation, city planning, human thermal comfort, wind tunnel tests, high density living

1. Introduction
Global environmental changes and global warming
have been an issue lately. In general, cities in tropicalregions will experience increased summer temperatures,
higher urban heat stress and higher frequencies andlonger durations of hot spells. In Hong Kong, based on
observed temperatures since 1885, the Hong Kong
Observatory has calculated an increase of 0.12°C per
decade (Leung et. al., 2004). More importantly, the data
indicate that the rate of increase has accelerated. The
average temperature rise from 1947 to 2002 was 0.17°C
per decade, but the rate of warming increased toward theend of that period, to 0.61°C per decade from 1989 to
2002. While the maximum temperature (56 years sincethe 2nd World War) has seen little change, the minimum
temperature has undergone a rising trend of 0.24°C per
decade. The observed temperature increase can also be
attributed to the rapid urbanisation of Hong Kong sincethe 2nd World War. In a comparison of the temperaturetime series at the Hong Kong Observatory Headquarters
with the global time series, scientists at the HKO havenoted that:
The global mean temperature dataset sourced
from the Climate Research Unit (CRU), University of
Global Environmental Research
13/2009: 169-178
printed in Japan

East Anglia, and the temperature at the Hong Kong
Observatory Headquarters both follow more or lessthe same trend as the global temperature during thepre-World War II period. In the post-war years, there
were two periods with notable temperature rises atthe Hong Kong Observatory Headquarters. The first
was from the mid-1950s to mid-1960s. The second
period of temperature rises began in the early 1980s,
which was in line with the global trend of significant
warming in the past two decades. A faster rate ofwarming at the Hong Kong Observatory Headquarters compared to the global trend since the early
1980s can be attributed to the effects of high-density
urban development.
Leung has concluded that there is an additional riseof 0.4°C per decade due to urbanisation. (Leung et. al.,2004)

2. Designing High Density Cities for Thermal
ComfortMore than 20 cities in the world are what are called“mega,” i.e., they have more than 10 million inhabitants.
High density city design is a topical issue. There is aneed to deal with land scarcity, to design a viable public©2009 AIRIES170

Edward NG

transport system and to re-build the communities of ourinner cities. The high-density city is iconic (Wolf, 2006).
High density living is increasing the number of issues
planners have to confront. Hong Kong is a high-density
city with a population of 8 million living on a piece ofland 1,000 square kilometres in area. The urban densityof Hong Kong is close to 60,000 persons per square
kilometre. Site development density can reach 3000 persons per hectare.
In 2003, the Hong Kong Government’s Team Clean
Report suggested that gradation of development heightprofiles, provision of breezeways, layout planning anddisposition of building blocks to allow for more open
spaces, greater building setbacks to facilitate air movement, reduced development intensity, increased open
space provisions especially in older districts and more
greenery are necessary to mitigate the ill effects of theurban heat island effect and weak urban ventilation.
The key concern of higher urban temperatures has
been the problem of urban thermal heat stress. Basedon comfort survey data (Givoni & Noguchi, 2004),
researchers in Hong Kong drew up the Hong Kong Outdoor Comfort Temperature Chart (Cheng & Ng, 2006).
The Hong Kong chart incorporates the average minimum, mean and average maximum summer temperatures of Hong Kong, at 26.4°C, 28.3°C and 31.3°C,
respectively (Fig. 1). It can be noted that in the shade(solar radiation of less than 100 W/m2), given an air
temperature of 28°C, there is a need for a wind speed ofapproximately 0.8 m/s for a person to remain comfortable thermally. Table 1 compares wind speed criteria

suggested by various studies at the same environmental
settings. Climatic adaptation exists; the Hong Kongchart generally agrees with the recommendations of
Macfarlane for a warm-humid climate, and is in areasonable range from the predictions of Nikolopoulou(Penwarden, 1973) and Nikolopoulou (Nikolopoulou &Steemers, 2003; Nikolopoulou et al. 2003).
The important point to note is that at an outdoor temperature of 30°C, the wind speed needs to exceed
2.5 m/s to provide thermal comfort. This is not feasible.
Hence, on the one hand, there is a need to allow wind
into the city; but on the other hand, there is a need not toallow the urban air temperature to rise too much beyond
the ambient air temperature. Hence, for high-density
city design, there is a need for allowing wind permeability with optimised urban morphological design, andurban heat island countermeasures with greenery, waterelements and cool materials.
Table 1 Comparison of wind speed criteria for pedestrian
comfort in the shade at a mean air temperature of 28oC.
Relative Comments
Humidity(%)

Researcher

PlaceStudied

Wind
Speed
(m/s)

Macfarlane

Warm-humid
regionGreeceDhaka,
Bangladesh
Japan

0.6

75

comfortable

1.5
0.0

75
75

neutralcomfortable

1.0-

neutral-0.8-

neutral

Nikolopoulou
Ahmed
Givoni
The HK Chart

Fig. 1 The Outdoor Comfort Temperature Chart of Hong Kong.

Wind and Heat Environment in Densely Built Urban Areas in Hong Kong

3. A Review of Existing Conditions
Since 2003, the Hong Kong Government has commissioned studies on Hong Kong’s urban air ventilation,
implemented some policies to mitigate the problem, andestablished guidelines to improve design and planning.
An air ventilation assessment (AVA) study was carriedout that led to the introduction of technical and planningguidelines (Ng, 2006). In addition, since 2006, an urban
climatic map has been drafted. Planning recommendations to optimise urban ventilation and to mitigate urban
heat island problems have been proposed.
A few studies on the urban heat island intensity ofHong Kong have been conducted (Ren et. al., 2008;
Fung and Lam, 2009; Nichol, 2005; Wu et. al. 2008).
The existing city conditions in Hong Kong were further
evaluated based on an expert qualitative evaluation byProfessors Baruch Givoni, Lutz Katzschner, Shuzo
Murakami and Mat Santamouris, and Dr. Wong Nyuk
Hien (Ng, 2009). With minor differences in their opinions, they made the following key comments.
Breezeways/air paths: As a general rule, the more air
ventilation to the streets the better for these dense urban
areas. The overall permeability of the district has to be
increased at the ground level. This is to ensure that theprevailing winds travelling along breezeways and majorroads can penetrate deep into the district. This can beachieved by properly linking open spaces, creating open
plazas at road junctions, maintaining low-rise structures
along prevailing wind direction routes, and widening theminor roads connected to major roads. It is also important to avoid obstructing sea breezes. Any localised
wind problem along the waterfront should be dealt withlocally and not affect the overall air ventilation of thecity.
Podiums/Site Coverage: The effect of building layout (especially in terms of building site coverage) has agreater impact than that of building height on the pedes-

171

trian wind environment (Fig. 2). Stepping buildingheights in rows would create better wind at higher levels
if the differences in building heights between rows are
significant. The “podium” structures commonly found inHong Kong are not desirable from the viewpoint of
maximizing wind availability to pedestrians. Podiums
with large site coverage not only block most of the wind
to pedestrians (affecting comfort and air quality), butalso minimize the “air volume” near the pedestrian level(affecting air quality).
Building Disposition: Proper orientation and layoutof buildings with adequate gaps between them areneeded. Stagger the arrangement of the blocks such thatthe blocks behind are able to receive the wind penetrating through the gaps between the blocks in the front row.
In the case of new development, to avoid obstruction of
the sea breeze, the axes of the buildings should be parallel to the prevailing wind. In order to maximize windavailability to pedestrians, towers should preferably abutthe podium edge that faces the main pedestrian area/
street so as to enable most of the downwash wind toreach the street level.
Building Heights: Vary the heights of the blocks withdecreasing heights towards the direction from which theprevailing winds come. If that is not possible, it is betterto have varying heights rather than similar or uniform
height. Given the extremely high density of the urban
fabric and narrow streets, a probable strategy for improving air ventilation is to vary building heights inorder to divert winds to the lower levels. Nonetheless,assessment will be required to further quantify the actual
performance of such potential in view of the deep urban
canyon profiles common in Hong Kong.
Building permeability: The provision of permeability
or gaps nearer to the pedestrian level is far more important than that at high levels. Create permeability in housing blocks. Try to create voids at ground level toimprove ventilation for pedestrians. This will improve

Fig. 2 A typical building morphology in Hong Kong: tower blocks sitting on a podiumthat occupies the entire site. When such podiums are very close together, theysignificantly reduce the air space at pedestrian levels.

172

Edward NG

not only the air movement at the ground level (thusimproving pedestrian comfort), but also help to remove
the pollutants and heat generated at the ground level.
The channelling effect created by the void also helps toimprove the ventilation performance for those residential units at lower floors. Creation of openings in thebuilding blocks to increase their permeability may be
combined with appropriate wing walls that contribute topressure differences across building facades and thus
facilitate airflow through the openings of the buildings.
The wing walls have to be designed according to the
known standards. For very deep canyons or very tallbuilding blocks, mid-level permeability may be required
to improve the ventilation performance for those occupants situated at mid-floors.
The more the better: It was the general opinion that
unlike most cities in the world, Hong Kong may findwind gusts not to be a problem in most areas. On thecontrary, wind stagnation and blockage is the main problem. For the tropical climatic conditions of Hong Kong,
where winds in the summer are a welcoming quantity,
the five experts opined unanimously that “the more thebetter” should be the guiding spirit. That is to say, designs and development should focus on facilitating theincoming wind, as well as minimising stagnant zones atthe pedestrian levels.
In a nutshell, the evaluation indicates two very
important urban morphological parameters that need to
be optimised for the design of high density cities. On the
one hand, it points to the issue of building volume, andhence the density of the city. On the other hand, it also
points to the issue of how the buildings occupy theground and their permeability from an urban design
point of view, especially at the near ground, or pedestrian, level.

4. Field Case Studies of Intra-Urban
Temperatures
Given the high-density environment of Hong Kong,a number of case-based field studies have been conducted during the summer months in Hong Kong. Oneof the studies focused on a commercial city area call
Tsim Sha Tsui, relying on handheld mobile measurement equipment for assessing temperature, humidity,
globe temperature and wind speed. Teams of researchers
traversed the area starting from the waterfront, working
their way into the city and returning. At each measurement point, the researchers stationed their equipment forthree minutes. Simultaneously to the ground measurements, a wind mast at the top of a building tower monitored the upper urban canopy layer. Readings fromnearby meteorological stations were also downloaded.
The case study was conducted in the afternoon (1-3 pm)in the summer months under calm-wind conditions. One
example of intra-urban temperature (Tiu) elevation isexpressed by the contour lines in Fig. 3. A difference of
3°C to 4°C can be noted from the seafront to the highdensity inner core of the city.
To further understand the basis of the intra-urban
temperature gain, area average sky view factors (SVF)
were calculated using urban morphological data of
Hong Kong (Fig. 4). A linear relationship between SVF
and temperature variation has been adopted, as shown in

Fig. 3 Intra-urban temperature variations as shown with contour lines. The legend denotes an urban climaticclassification based on building heights and volumes, and the resulting sky view factor. The two match well.

Wind and Heat Environment in Densely Built Urban Areas in Hong Kong

Equation 1 (Oke, 1981; Svensson, 2004; Yamashita
et al., 1986; Grimmond, 2001; Eliasson, 1990). It
reveals a logarithmic relationship between building
volume and temperature.

∆T = c * BV α

(1)When the two sets of data (Figs. 3 and 4) are superimposed, a close correlation is found (Table 2). That is
to say, areas with higher building volume, and hence
higher density, are warmer than open areas or areas withhigh SVF. The relationship is logarithmic. As such, it ispossible to predict intra-urban temperature differentials
based on urban morphological information for the entire
city. Combining the building volume data with an173

assessment of altitude and greenery, a thermal load mapof Hong Kong can be evaluated (Fig. 5). The legend
indicates the predicted temperature attenuation, fromminus 2°C to plus 3°C. Data from the mobile traverse
further validate the thermal load layer of the Hong Kongurban climatic map (Chen & Ng, 2008). Given Hong
Kong’s average air temperature of 28°C, an intra-urban
temperature increase would bring this to 30°C or 31°C.
Table 2 T-SVF-Building Volume relationship for selected
points in the field measurement.
T (°C)
28.2
29.2
30.7
31.8

SVF
0.59
0.33
0.22
0.07

Building Volume (%)
2.0
6.0
12.8
21.6
Tref = 28 °C

Fig. 4 Areal Sky View Factor map of the study areas.

Fig. 5 The Thermal Load layer of Hong Kong’s Urban Climatic Map. Six classes of intra-urban
temperature differentials are indicated. Class 0 indicates neutral ambient air temperature at sea
level, each positive class (say +1) indicates approximately 0.5°C rise above the ambient
temperature. Likewise, each negative class (say –1) indicates approximately 0.5°C rise below
the ambient temperature. The map predicts an intra-urban temperature rise of 2°C to 3°C fromthe ambient air temperature. Areas of higher altitude (200m+ above sea level) can experience a
negative intra-urban temperature differential of 1°C to 2°C. It is not without reason that thesecooler areas are also the more expensive and sought after residential areas of the city.

174

Edward NG

5. Implications of Intra-Urban Temperature –Hot Days and Hot Spells
Bio-meteorological indicators like “hot days,” “hotnights,” “very hot days” and “very hot nights” havebeen used (Hajat et. al., 2002; Masumoto, 2008; Diazet al., 1986; Leung et. al., 2008). They are known tocorrelate to health impacts on city dwellers. Various
definitions of these terms exist, for example, the Japan
Meteorology Agency defines “very hot days” as days on
which the maximum air temperature (Ta max) exceeds
or equals 30°C; whereas the Hong Kong Observatory
defines them as days on which Ta max >= 33°C. Thishas to do with the differences between the climaticconditions of the two cities. For this study, the following
definitions will be adopted.
Very hot day
Hot day
Very hot night
Hot night

Ta max >= 33°C
Ta max >= 30°C
Ta min >= 28°C
Ta min >= 25°C

The Hong Kong Observatory has observed theoccurrence of very hot days and very hot nights since1885. The data was trend analyzed (11-year runningaverage) and the results as shown in Figs. 6 and 7; towhich regression equations (2, 3 and 4) have been fitted,
are given by:
For very hot days

y = 0.097( x − 1890) + 0.997
r = 0.844

For very hot nights
step 1: 1890-1980
y = 0.059( x − 1890) + 0.201
step 2: 1970-2003
y = 0.502( x − 1970) + 5.231(2)

r = 0.733(3)

r = 0.970(4)

To promote further understanding, the Hong Kong
Observatory (HKO) publishes a summary of meteorological observations in Hong Kong annually. It contains
tables of Daily Mean Temperature (°C), Daily Maximum Temperature (°C), and Daily Minimum Temperature (°C) at the HKO. For this study, published data of
the nine year from 1998 to 2007 have been used. The
data tabulation is as shown in Table 3. For example, in
2007, there were 25 very hot days and 117 hot days.
More importantly, there were six very hot days that werepreceded by at least six other consecutive very hot days
(Table 4) – known as “long very hot days” in this paper.
Likewise, when very hot nights were preceded by atleast six consecutive very hot nights they were known as“long very hot nights” in this paper (Table 5).
Based on the tabulated data of Tables 4 and 5, given
an intra-urban temperature (Tiu) rise of 1°C, 2°C or 3°C,
it can be seen that both the number of long hot days andthe number of long hot nights increase exponentially, as
shown in Equations 6 and 7. That is to say, the impact of
any intra-urban temperature rise due to the urban heatisland effect can be serious.
Table 3 An overview of the hot days and nights of
1998-2007.

Fig. 6 Linear relationship between the year and the 11-year
running average of number of very hot days.

Table 4 Occurrences of long very hot days in 1998-2007.

Fig. 7 Linear relationship between the year and the 11-year
running average of number of hot nights, in two steps:
1890-1980 and 1970-2003.

Wind and Heat Environment in Densely Built Urban Areas in Hong Kong

Based on the tabulated data of Tables 4 and 5, given
an intra-urban temperature rise of 1, 2 or 3°C, it can beseen that both the number of long hot days and the number of long hot nights increase exponentially, as shownin Equations 6 and 7. That is to say, the impact of any
intra-urban temperature rise due to the urban heat islandeffect can be serious.
Episodes of long very hot days = 1.2516e1.2407(Tiu)
R2 = 0.920
Episodes of long very hot nights = 1.274e1.4617(Tiu)
R2 = 0.935

(6)
(7)

Table 5 Occurrences of long very hot nights in 1998-2007.

Table 6 NET and PET under various climatic conditions in
the hot summer months of Hong Kong.

175

The seriousness of this increase in number of episodes can be seen against the predicted mortality rate
due to heat stress. Leung, using Kong Kong’s
meteorological and health data found that the meanmortality associated with heat strokes would double perunit rise in the NET (Net Effective Temperature, whichtakes into account air temperature, relative humidity andwind speed) beyond 26 (Table 6).
Under the average summer air temperature in thesummer months of 28°C, even given good urban
ventilation with a mean wind speed of 1 m/s, the NET is
25.9°C. However, when taking into account an
intra-urban temperature rise of 3°C, the NET will be
28.4°C. This means a four-fold increase in the meanmortality. Based on Leung’s study, the normalisedmortality increases from 0.000 when the NET is 26 to,alarmingly, 0.015 when the NET is 29. The catch of thisevaluation is that for Hong Kong a temperature increaseof three degrees, due to global warming and intra-urban
temperature elevation, means episodes of hot spells canincrease from once a year to 38 times a year; and when
this happens, one would expect the morality rate toincrease very rapidly.

6. Field Case Studies of Intra-Urban Wind
FieldsAt the same time air temperature case studies wereconducted, as mentioned above, in which urban ventilation was also measured, using a hot ball anemometer.
The normalised wind velocity ratio is presented in Fig. 8.
Zoning contours were also added. The air circulation
pattern under moderate easterly incoming winds (theprevailing wind direction of the study area) was evaluated. In Fig. 8, zones of low wind velocity ratios arenoted in areas where the ground coverage of buildings is

Fig. 8 Wind velocity ratios and zoning contours of the study area.

176

Edward NG

high. This coincides with recent wind tunnel test findings (Yoshie et. al., 2008). Hence, based on the urban
morphological understanding of ground cover, adynamic potential map of Hong Kong can be generated(Fig. 9). This is further calibrated using wind tunnel
tests.

7. Physiological Equivalent Temperature(PET) & Urban Climatic Maps
Bio-climatically based on Table 6, both NET and
PET serve as indicators of human thermal comfort basedon a combined consideration of air temperature andwind speed. Using a PET formulation for urban thermal

Fig. 9 A dynamic potential map of Hong Kong indicating areas of high roughness andweak urban ventilation performance. Legend 0 and -1 indicates urban areas ofbaseline dynamic potentials. A difference of minus one class is roughly equal toan increase in dynamic potential of about 0.5 m/s above the baseline.

Fig. 10 Hong Kong Urban Climatic Analysis Map. An eight-class differential has been categorised. A one
class differential is approximately equal to a one-degree difference in PET. Class 4 has beencalibrated to represent the baseline ambient PET condition. Hence, areas of Class 7 and 8 is predicted
to have an intra-urban PET increase of 3°C to 4°C.

Wind and Heat Environment in Densely Built Urban Areas in Hong Kong

comfort, it can be calculated that at low wind speeds of
0.5 to 2 m/s, every 1 m/s increase in air wind can mitigate a two-degree rise in air temperature. Hence it ispossible to combine understanding of thermal load withthat of dynamic potential, which was illustrated earlier.
This helped in producing the Hong Kong Urban
Climatic Analysis Map (Ng et al., 2008) (Fig. 10). The
urban climatic map thus created was further validated byfield measurements based on figures obtained in studiesof another area in Hong Kong and by wind tunnel tests.
The Urban Climatic Analysis Map provides a spatial
understanding of the PET distribution in the urban areas.
For example, in the metro core areas of the inner city ofHong Kong on both sides of Victoria Habour, it can be
expected that the intra-urban temperature difference
between the waterfront and inland areas on a typicalsummer afternoon in Hong Kong can be on the order of
3°C to 4°C. That is to say, given the average summer
temperature of 28°C, the inner urban areas can experience air temperatures of 31°C to 33°C. Coupling thatwith a decrease in the available wind, the PET can
increase by 4°C to 7°C. This creates spatially localised“hot days” and “hot spells” not conducive to healthy
human living in built-up urban areas.
Based on the Urban Climatic Analysis Map and thepossible implications to human thermal comfort, it ispossible to draft up an Urban Climatic Recommendation
Map with planners so that strategic planning actions canbe developed. This work is currently underway in HongKong.

8. Conclusions
For cities located in the tropics and sub-tropics withhot, humid summers, the risk of global warming and theurban heat island effect due to buildings contributing to
the already hot, humid thermal comfort conditions has
been delineated. Field and data studies have establishedits criticality. An exponential increase in the numbers of
hot days and hot spells can be expected for each degree
rise in urban temperature. This is not conducive to urban
living and can be dangerous to human health. It is possible to summarise the urban effects of an increase in
intra-urban air temperature and decrease in wind andurban air ventilation using Geographic Information
Mapping techniques. Urban climatic maps can be
drafted for spatial understanding of the issue. With theinformation, strategic planning actions can be developedin the form of an urban climatic recommendation map.
This can provide planners and designers an objective
evaluation tool for mitigation actions. Measures can be
implemented such as greenery, open spaces, shadingwith trees, well spaced buildings carefully positioned,
reduction of ground coverage and building density andso on.
It is not possible to eliminate the ill environmental
effects of cities and high-density cities completely.
However, it is possible to design a city with well distributed pockets and routes of quality spaces and urban

177streets and roads so that pedestrians can have a diversified urban landscape to engage in and explore (Steane &Steemers, 2004). The task for planners is to utilise theavailable urban climatic information to make good decisions.

Acknowledgment
The author would like to thank the Planning Department and the Hong Kong Observatory for the information they supplied, which was used in this paper. Thanks
are also due to many students helping, especially Ms.
Ren Chao.
References
Chen, L. and E. Ng (2008) Sky view factor analysis of street
canyons and its implication for Hong Kong's urban heat island
intensity: a GIS-based methodology. Special Reports of
the Meteorological Institute, Albert-Ludwigs-University ofFreiburg, 5th Japanese-German Meeting on Urban Climatology,
6-11 October 2008, Freiburg, Germany.
Cheng, V. and E. Ng (2006) Thermal comfort in urban open
spaces for Hong Kong. Architectural Science Review(Australia), 49(3): 236-242.
Díaz, J., R. García, F. Velázquez de Castro, E. Hernández, C.
López and A. Otero (1986) Effects of extremely hot days on
people older than 65 years in Seville (Spain) from 1986 to 1997.
International Journal of Biometeorology, 46:145-149
Eliasson, I. (1990) Urban Geometry, surface temperature and airtemperature, Energy and Buildings, 15(1-2): 141-145.
Fung, W.Y. and K.S. Lam (2009) Derivation of nighttime urban
air temperatures using a satellite thermal image, Journal ofApplied Meteorology and Climatology.
Givoni, B. and M. Noguchi (2004) Outdoor comfort responses ofJapanese persons. Proceedings of the American Solar Energy
Society: National Solar Energy Conference 2004, 9-14 July,
Portland, Oregon.
Grimmond, C.S.B., S.K. Potter, H.N. Zutter and C. South (2001)
Rapid methods to estimate sky view factors applied to urban
areas. Int. J. Climatol., 21: 903-913.
Hajat, S., R.S. Kovats, R.W. Atkinson and A. Haines (2002)
Impact of hot temperatures on death in London: a time series
approach. Journal of Epidemiology and Community Health, 56:
367-372.
Leung Y.K., K.H. Yeung, E.W.L. Ginn and W.M. Leung (2004)
Climate change in Hong Kong. Technical Note, No. 107, Hong
Kong Observatory, Hong Kong.
Leung, Y.K., K.M. Yip and K.H. Yeung (2008) Relationshipbetween thermal index and mortality in Hong Kong, Meteorol.
Appl. 15: 399-409.
Masumoto, K. (2008) Urban heat island in Osaka city distributionof air temperature and west bulb globe temperature. The
seventh International Conference on Urban Climate, 29 June 3 July 2009, Yokohama, Japan.
Ng, E., C. Ren and L. Katzschner (2008) Urban climatic studies
for hot and humid tropical coastal city of Hong Kong. Special
Reports of the Meteorological Institute, Albert-LudwigsUniversity of Freiburg, 5th Japanese-German Meeting on
Urban Climatology, 6-11 October 2008, Freiburg, Germany.
Ng, E. (2006) Air ventilation assessment system for high density
planning and design. Proceedings of Passive Low Energy
Architecture (PLEA) International Conference 2006, Geneva,
Switzerland, 6-8 Sept 2006, 1-323.
Ng, E. (2009) Policies and Technical Guidelines for Urban

178

Edward NG

Planning of High Density Cities – Air Ventilation Assessment(AVA) of Hong Kong, Building and Environment 44;
1478-1488.
Nichol, J.E. (2005) Remote sensing of urban heat islands by day
and night. Photogramm. Eng. Remote Sens., 71; 613-621.
Nikolopoulou, M. and K. Steemers (2003) Thermal comfort andpsychological adaptation as a guide for designing urban spaces.
Energy and Buildings, 35: 95-101.
Nikolopoulou, M., S. Lykodis and M. Kikira (2003) Thermal
comfort in outdoor spaces: field studies in Greece. Proceedingsof the Fifth International Conference on Urban Climate, 1-5
September 2003, Lodz, Poland.
Oke, T. R. (1981) Canyon geometry and the nocturnal urban hestisland: comparison of scale model and field observations.
Journal of Climatology, 1: 237-254.
Oke, TR. 1987. Boundary Layer Climates (2nd edn). Routledge,
London.
Penwarden, A. D. (1973) Acceptable wind speeds in towns. Building Science, 8(3): 259-267.
Ren, C., E. Ng and X. P. An (2008) Review of urban heat island
research in Hong Kong. Special Reports of the Meteorological
Institute, Albert-Ludwigs-University of Freiburg, 5th JapaneseGerman Meeting on Urban Climatology, 6-11 October 2008,
Freiburg, Germany.
Steane M. A. and K. Steemers, eds. (2004) Environmental Diversity in Architecture, Routledge, London.
Svensson, M.K. (2004) Sky view factor analysis – implications
for urban air temperature differences Meteorol. Appl., 11:201-211.
Wolf, M. (2006) www.photomichaelwolf.com/hongkongarchitec
ture/Wu, M.C., W.M. Leung, W.M. Lui and T.C. Lee (2008) A study
on the difference between urban and rural climate in Hong
Kong, Hong Kong Observatory Reprint, 745, Hong Kong.

Yamashita, S., K. Sekine, M. Shoda, K. Yamashita and Y. Hara
(1986) On relationships between heat island and sky view
factor in the cities of Tama River basin, Japan, Atmospheric
Environment, 29(4): 681-686.
Yoshie, R., H. Tanaka, T. Shirasawa and T. Kobayashi (2008)
Experimental Study on Air Ventilation in a Built-up Area with
Closely-Packed High-Rise Building, Journal of Environmental
Engineering, 627: 661-667, (in Japanese).

Edward NG
Edward Ng is an Architect and a Professor
at the Chinese University of Hong Kong
(CUHK). He has been practising as anarchitect and lecturing in various universities around the world. His specialty isin Environmental and Sustainable Design.
He is the Director of the M.Sc. Sustainable and Environmental Design Programme at CUHK. As an environmental
consultant to the Hong Kong SAR Government, he developed performance-based daylight design building regulations and Air Ventilation
Assessment (AVA) Guidelines. He is currently drafting an Urban Climatic
Map for Planning in Hong Kong. Prof. Ng is a daylight and solar energy
expert advisor to the Chinese Government. As a visiting professor of Xian
Jiaotong University, China, he is designing ecological schools andbuilding sustainable projects in China.

(Received 30 September 2009, Accepted 20 November 2009)