The Influence of Land Use on the Urban Heat Island in Singapore

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Habitat Habitat Internatio International nal 31 (2007) 232–242 www.elsevier.com/locate/habitatint

The influence of land use on the urban heat island in Singapore Steve Kardinal Jusuf Ã, N.H. Wong, Emlyn Hagen, Roni Anggoro, Yan Hong Department Department of Building, Building, School of Design Design and Environmen Environment, t, National National University University of Singapore, Singapore, 4 Architecture Drive, Singapore 117566, Singapore

Abstract

The urban air temperature is gradually rising in all cities in the world. One of the possible causes is the drastic drastic reduction in the greenery area in cities. It means that land use planning becomes critical in determining the environment quality. This study tries to investigate and identify land use types which have the most influence to the increase of ambient temperature temperature in Singapore. Singapore. The main tools are remote sensing data and geographical geographical information information system (GIS) to obtain a macro view of Singapore Singapore and carry out comprehensive comprehensive analysis at the same time. The data were analyzed by utilizing both qualitative qualitative and quantitative quantitative methods. Both the qualitative and quantitative analysis results show that the land usage will influence urban temperature. In the daytime, the order of surface temperature in different land use types is industrial, commercial, airport, residential, and park respectively. respectively. However, during the night time, the order is commercial, residential, residential, park, industrial, industrial, and airport. Therefore, with appropriate land use planning, the urban heat island (UHI) could be mitigated. r 2007 Elsevier Ltd. All rights reserved. Keywords: Influence; Land use; Urban heat island; Temperature; Singapore; GIS; Remote sensing

Background

The urban air temperature is gradually rising in all cities in the world. Several factors become the cause of it, such as diminishing of green area, low wind velocity due to high-building density and change of street surface coating materials (Takahashi, (Takahashi, Yoshida, Tanaka, Aotake, & Wang, 2004). 2004). This may lead to overheating by human energy release and absorption of solar radiation on dark surfaces and buildings. This problem will be further aggravated by increasing demand on air conditioning, which will again lead to further heating and CO2 release (Crutzen, (Crutzen, 2004). 2004). The change of land use from green area to new built structures results in changes of the natural surface of  the earth. The changes of materials that cover the earth’s surface affect the absorption of solar energy, and the changes of the shapes of the earth’s surface, that is manmade uneven ground, affect the airflow (Ojima, ( Ojima, 1990/ 1991). 1991 ). Abbreverations: GIS, Geographical information system; NUS, National University of Singapore; UHI, Urban heat island; URA, Urban and redevelopment authority à Correspo Correspondin nding g author. author. Tel.: +65 6516 4691. E-mail address: [email protected] (S. Kardinal Jusuf). 0197-3975/$0197-3975/$- see front front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.habitatint.2007.02.006 doi:10.1016/j.habitatint.2007.02.006

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Singapore is an interesting place to study the urban heat island (UHI) since it can be considered as a small developed country. It has no distinction between urban and rural, thus analysis on the land use is suitable to study the trend in increase of temperature in Singapore. Literature Literature review

An UHI is the name given to describe the characteristic warmth of both the atmosphere and surfaces in cities (urban areas) compared to their (nonurbanized) surroundings ( Voogt, 2005). 2005 ). Heat islands are caused by urbanization, when buildings, roads and paved surfaces store the heat during the day and then release it slowly during the evening keeping urban lands hotter than surrounding areas. Artificial heats released by combustive proces processes ses from from vehicle vehicless and indust industria riall activi activitie ties, s, and heat heat escapi escaping ng from from commer commercia ciall and domest domestic ic air conditioning, also contribute to higher air and surface temperatures within the city. Heat islands affect urban climate, energy use and habitability of cities. Higher temperatures affect cooling energy use and accelerate urban smog formation. Urban trees can offset or even reverse the heat island effect by transpiring water and shading surfaces. According to previous studies (Akbari ( Akbari et al., 1992), 1992), large number of trees and urban parks reduce local air temperature by 0.5–5 C. Each 1 C drop in air temperature could lower the peak electric demand by 2–4%. Cooling energy savings and smog reduction are other potential benefits. There were some studies conducted to investigate the Singapore UHI. The first Singapore UHI study was conducted by Niewolt in 1964, city area compared with airport area (represented as rural area). It was found that there was 3.5 C temperature difference between city area and airport area. It was believed that the city rura rurall temp temper erat atur uree diff differ eren ence cess were were due due to the the grea greater ter abso absorp rpti tion on of sola solarr radi radiat atio ion n and and to redu reduce ced d evapotranspiration in the city. The measurements were conducted with nine points of spot measurement in the city compared with the temperature data recorded by Paya Lebar station. The study did not consider night time, time, and also carried carried inherent inherent errors errors due to time time differ differenc ences es in travel travelling ling from one locati location on to anoth another er (Nieuwolt, 1966). 1966). Chia (1970) also conducted a similar study as Niewolt and considered the effect of variations in cloud patterns on the microclimate. Chia found out that a combination of low solar radiation receipts and low wind speed together with a low cloud ceiling reduced the city rural temperature and relative humidity differences. Nicholl (199 Nicho (1994) 4) presented UHI in Singapore through the remote sensing technology. Roughly over 4 C difference was observed from the satellite image of Singapore. The observation of UHI in Singapore provides evidence that the local buildings do have the great impact on the local climate. The most recent study done in Singapore is the exploration conducted by Roth (2002), (2002) , which explores the UHI dynamics in Singapore. Preliminary results based on traverse observations conducted in spring and summer of year 2001 have shown that night time heat island magnitudes of up to 4 C with lowest temperatures observed in densely vegetated areas. Wong and Chen (2003) investigated the severity and impact of UHI on the environmental conditions and identified the possible causes by using thermal satellite image and mobile survey. He also explored the various potential measures that could be implemented to minimize the impact. Satellite images and geographical information system (GIS) are also used for UHI study besides using field measurement method. One of the examples is UHI study in Rhode Island ( Brown University, 2004). 2004). The study focused on Providence city. By analyzing thermal data obtained with ETM+ onboard Landsat 7 on July 2001 and the land land use/la use/land nd cover cover classi classifica fication tion from Rhode Rhode island island GIS, GIS, the spatia spatiall distri distribut bution ion of land land uses, uses, vegeta vegetativ tivee cover, cover, and and the daytim daytimee land land surfac surfacee temper temperatu ature re in Provid Providenc encee was was identi identified fied.. The densel densely y populated residential districts, commercial and industrial areas represent urban heat islands, with the surface temperature as high as 43 C in summer days. On an average, the summertime land surface temperature is 20 C higher than in the surrounding suburban areas and 13 C higher than in treed neighborhoods. The highest level of mean land surface temperature of 32.5 C is observed in mixed industrial areas, followed by industrial area and commercial with the range of 31–32 C. The maximum mean land surface temperature in high-density residential areas amounts to 28 C. Another study on UHI by means of field measurement and GIS has also been done in Vancouver, Canada (Ao & Ngo, 2000). 2000). Its objective is to identify the relationship between design characteristics of urban land use 1

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and surface thermal emissions within the City of Vancouver. The analysis seeks to quantify the influence of  land use characteristics such as impervious surfaces, vegetation, density of the built environment, and street geometr geometry y on the release release of therma thermall energy energy.. The study identified identified that areas areas with with high high densit density, y, like like the downtown downtown core, have highest highest temperatu temperature re which is related related to the thermal thermal properties properties of the existing structures structures and the street geometry. The relatively coolest intersection in the city was found to be closest to vegetation. In Japan, Kinya and Koumura (2003) was using ADS40 image and GIS to analyse the greenery effect in Tokyo. The green places from ADS40 image was extracted to get the current greenery distribution and GIS played as analysis tool to find the size of potential space to increase green. Then the extracted data was superimposed on building data using the GIS software ArcView3 in order to get rooftop greening areas. Objectives

In Singapore, with the projection of 5.5 million people in the next 40–50 years ( URA, 2001), 2001), the demand for housing and infrastructure is also increasing. It leads to the changing of land use type from green to hard surfa surface ce buildin building g blocks blocks or indust industrie ries. s. Previo Previous us resear research ch on the UHI of Singap Singapore ore (Wong Wong,, 2004 2004)) has not discussed yet which land use type has more obvious influence on the temperature build up and its possible cause. This study has the following objectives: (a) to investigate the influence of various land use types on the urban heat island; (b) to identify land use types which have obvious impact on the urban temperature; (c) to study the temperature distribution across the different land use types. Methodology

The main tools for the analysis of this study are remote sensing data and GIS to obtain a macro view of  Singapore and carry out comprehensive analysis at the same time. In this study, both qualitative analysis and quantitative analysis are used. Each analysis consists of daytime and night time temperature analysis. The overall methodology is summarized in Fig. 1. 1.1 Qualitative analysis Qualitative analysis is used to get the indication of the land use types which cause the increase of urban temperature and its possible causes. For daytime daytime anal analysis ysis,, the satellite satellite image, image, land land use map and thermal thermal satelli satellite te image image of Singap Singapore ore were superimposed and zoomed into a particular area, especially the hot spots by means of Google Earth software (Google, 2007). 2007). Thermal satellite image uses different colors to represent different temperatures, which range from red (hot) to blue (cool). It can be expected that areas with high building density will have more reddish color; on the contrary, those with large proportion of dense plants should be more greenish. For night time analysis, analysis, isopleths map produced by ArcGIS (ESRI, (ESRI, 2007) 2007) from the night time mobile survey measurements is overlaid to satellite image by means of Google Earth software. The temperature distribution is analyzed and zoomed in to the same location with the daytime analysis. Thus, the difference with daytime temperatu temperature re distributio distribution n can be identified. identified. Quantitative analysis Quantitative analysis was carried out to investigate the influence of various land use types on the UHI in daytime as well as at night time. For better reference, two different land use data sources were used. One is a SPOT image (taken on 25 October, 2004), which was only used to highlight the differences in temperature 1

The figures in the printed version of this paper are in black and white. The original color versions of the figures are presented in the on-line version of the paper, which can be accessed at www.sciencedirect.com www.sciencedirect.com..

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Fig. 1. Diagram Diagram of methodolo methodology. gy.

between vegetation (surfaces that contain chlorophyll, water) and urban structures. The other is Master Plan 2003 where temperature and the intended purpose of a certain area were compared. Both night time and daytime thermal data was loaded in ArcGIS and analyzed with spatial analyst zonal statistics module. The land use layer was used to obtain thermal statistics of each individual land use type. However, since these results were not accurate enough for our needs, the data were loaded in ENVI (2006) to compute the statistics for each temperature class. Thus, for each land use type the total surface area can be known known,, and theref therefore ore in combin combinati ation on with with the tempera temperatur turee classe classes, s, obtain obtain detail detailed ed inform informati ation on on the percentage of each temperature class per land use type. For daytime analysis, analysis, daytime surface temperature distribution across different land use types was studied through comparison of land usage with the Singapore thermal satellite image taken by Landsat 7 ETM+ thermal band on 11 October 2002 at 11.09AM. The thermal image has nine spectral bands, as shown in Fig. 2. 2. The eighth band is a 15 m resolution panchroma panchromatic tic image, and bands 1–5 and 7 contain contain 30 m resolution resolution within the visible and infrared infrared spectrum. Band six consists out of a low and high gain 60 m resolution resolution thermal band (8–12 mm). An approx approxima imate te surfac surfacee temper temperat ature ure could could be extrac extracted ted from from the later. later. The extrac extractio tion n of the temperature data from the high-gain band was used as it had a less stripped texture and a wider range of record recorded ed val values ues digita digitall number number (DN) (DN) value values. s. The techni technique que develo developed ped by the Land Landsat sat Scien Scientific tific team (2006) was was chos chosen en for for the the conve convers rsion ion.. Wi With th the the imag imagee proc proces essi sing ng soft softwa ware re ENVI, ENVI, the the ther therma mall imag imagee

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Fig. 2. Daytime surface temperature temperature conversion.

Fig. 3. Interpola Interpolation tion of night night time ambient temperatur temperature. e.

‘‘L71125059_05920021011_B62’’, which is the high-gain band six of the Landsat 7 ETM+ data, calculations on each pixel were performed. The Master Plan 2003 land use map was used to extract the land use in a supervised classification. This was done by a supervised Mahalanobis Distance classification, followed by a majority/minority analysis to clean up the data—furthermore, the data underwent several clumped and sieved processes. Only the seven major land use types were then further analyzed with the thermal image. Other land use types were either to small or were due to contextual reasons cannot be processed, e.g. military areas have dense jungle as well as airfields and buildings. A green, green, red, and near infrare infrared d (NIR) (NIR) band of a 20 m resolu resolutio tion n SPOT SPOT image image of Singap Singapore ore was used used to classify either human built structures (roads, airports, buildings) or vegetation (parks, natural grass sport fields, jungle). For night time analysis, analysis, two methods were used to analyse the night time ambient temperature distribution across different land use types. Firstly, the land use map was prepared from Master Plan 2003 using the polygon in ArcMap. Then night time ambient temperature data were plotted in point form from the study of  Wong (200 (2004) 4) using using ArcMap ArcMap.. Descrip Descriptiv tivee summar summary y and 3D gra graph ph repres represent entati ation on of night night time time ambien ambientt temperature were generated using ArcMap and ArcScene after over lapping land use and temperature map.

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Secondly the interpolation of the night time mobile survey data. The night time survey temperature isopleths were acquired by creating a minimum distance interpolation, using the outline of the main Singapore Island as a boundary, in ArcGIS. However, the results from this survey must be treated quite carefully on the different land use types. The heavy industrial areas in the west were also left out in the data acquirement due to access rights, but business and residential areas will perform quite well, as these results are similar to those of other residential areas. The interpolated night time temperatures, are shown in Fig. 3 was thereafter, overlaid with the different types of land use from the land use Master Plan 2003 and with the previously described SPOT vegetation map. By using ArcGIS 3D analyst, a 3D profile that ranges from the industrial zone in the west, over the CBD and the airport in the East was created. The profile shows the temperature range of the slice of land. Discussion and findings

Qualitative analysis—daytime The first focus is the western part of the Singapore island, Jurong industrial area. From the thermal image in Fig. 2, 2, large spread of red color can be seen which means that the area has a high surface temperature. The hot surface area spreads exactly in the industrial land use zone. There are two different characteristics causing the high high surfac surfacee temper temperatu atures res.. Firstl Firstly, y, in the Jurong Jurong island area, it has the character characterist istic ic of a lar large ge expose exposed d concrete surface area. The industrial buildings are arranged far apart from one to another with no greenery in between. Another characteristic is industrial buildings which were designed with combination of metal pitched roofs roofs and concre concretete-flat flatted ted roofs roofs and there there is a tremen tremendou douss therma thermall distri distribut bution ion in reddis reddish h color. color. Both Both characteristics contribute to the increase of temperature because of the extensive use of concrete and other heat absorbing surfaces, by decreasing of surface moisture available for evapotranspiration. Furthermore, more solar radiation is absorbed and reradiated as heat because dry surfaces have higher absorbtivity. So, the latent heat flux is very small compared with the sensible heat in these areas. In the eastern part, very high surface temperature happens at Changi airport. This is because of a very large concrete area of runways and airport buildings. The absence of plantation creates a large area of hot spot in Changi airport, which have a reduction of evaporating surfaces. This is because it puts more energy into sensible heat and less into latent heat too. It also impacts the environment nearby by reradiating the absorbed heat from the large area of concrete surfaces. Similar condition happens also in the west coast container harbor. Another identified hot spot area is in the East Coast. In this area, most of the land use is for residential purpose. The hot spot characteristic of this area is different from the industrial and airport purpose. In the residential area, it usually has open space of greenery area for community parks and sport field. Thus, in the image it shows that in between the red color there is yellowish and green color. It means that the greenery area has the impact on the surrounding buildings. And also most of the residential buildings are using roof tiles which have a better thermal performance than the bare concrete roof. Similar appearance can be seen also in the CBD area where a lot of high-rise commercial buildings consist. The thermal image shows that it does not exhibit a high temperature. As mentioned before, this thermal image was taken during daytime. Thus, due to the shading from the buildings, the roads and space between the towers are appears yellowish color, even it does not have the greenery. The large green area in Singapore Island is found in Central Natural reserve. Due to the shading provided by trees and the evapotranspiration process of the trees, the deep blue and green color distribution in surface temperature can be seen obviously at central part of dense greenery area. As mentioned earlier on, it is believed that this environmental condition has impacts on the other zones. The buildings surrounded by or at the perimeter of the greenery area have better thermal distribution than other buildings apart from it. It appears as yellowish in color so it can be concluded that a building near or surrounded by the park has better ambient temperature than the one apart from the park. Qualitative Qualitative analysis—night analysis—night time In Jurong industrial area, the condition is reverse as compared with the daytime temperature (Fig. ( Fig. 3), 3), when industrial area is higher than the residential area. It is because the industrial area mostly consists of low-rise

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buildings using metal roof. Meanwhile, the residential area consists of high-rise buildings using bare concrete flat roof. Thus, industrial buildings can release heat faster during night time as compared with residential building, where heat is trapped inside. The next point of interest is Changi airport. It also has a lower temperature than the residential area. It is because the large open asphalt surface releases heat faster than the buildings. The heat exchange with the air is much faster in an open area. Building can act as a thermal storage. The bigger of the volume, the bigger the capacity is to storage heat. CBD and east coast residential area seems to have the similar ambient temperature condition. This may be because they have similarity in the form of tower buildings. Quantitative analysis—daytime surface temperature distribution across different land use types A 3D temperature profile (Fig. (Fig. 4) 4) of daytime surface temperature distribution in Singapore were generated using using ArcMap ArcMap.. The analys analysis is result resultss reveal reveal that that indust industria riall area area and air airpor portt have have higher higher daytim daytimee surfac surfacee temperatu temperature re than residential residential and commercial areas, which support the hypothesis hypothesis.. However, However, against against the hypothesis, the daytime surface temperature is higher in residential area than in commercial area. This may be explained that residential area normally has more green areas surrounding the buildings, as compared to the shortage of open space to promote evaporation in the commercial and business areas where high-rise buildings are congested. For the weighted average temperature of every land use type, as expected, the quantitative analysis results reflect reflect that that human human struct structure ure area area has has much much higher higher daytime daytime mean mean surfac surfacee temper temperatu ature re (38.39 (38.39 C) than than vegetation area (34.17 C) (Fig. 5). 5). The analysis results also partly support the hypothesis that industrial area has the highest daytime mean surface temperature 39.69 C, while the park area has the lowest daytime mean surface temperature 34.29 C. However, the analysis results reveal that commercial area (38.3 C) and business area (37.41 C) have higher daytime mean surface temperature than airport (37.34 C). This may be explained by the shortage of open space to promote evaporation in the commercial and business areas. As shown in Fig. 6, 6, residential area is the second coolest land use type among the analyzed seven land use types (36.51 C), which may be due to the neighborhood green areas surrounding residential buildings. The industrial land use type has the most obvious influence on the daytime urban surface temperature. The dayti daytime me surfac surfacee temper temperatu ature re distri distribut bution ionss of five land land use types types (commer (commercia ciall and residen residentia tial, l, busine business, ss, commercial, residential, and park) concentrate within relatively narrow ranges compared to that of the other two land use types (industrial and airport) which have much wider ranges. This may be caused by the relatively uniform land feature and building density within the first five land use types compared to the variety of land feature and density in the other two especially airport. 1

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Fig. 4. 3D temperature temperature profile of daytime daytime surface surface temperature temperature distribut distribution ion from west to east of Singapore Singapore..

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Comparison of Daytime Temperature in Human Structure and Vegetation Areas

40    )   n   C 38   a   e   (   m  e   r    d   t   u 36   e    t   a    h   r   e   g   p    i   e   m    W   e 34    t

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Comparison of Daytime Tem Temperature perature in Different Land Use Areas    ) 40    C    (   e   r   u 38    t   a   r   e   p   m   e 36    t   n   a   e   m    d 34   e    t    h   g    i   e    W 32             °

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Land use type Fig. 6. Compariso Comparison n of daytime mean surface temperatur temperaturee in seven land use areas.

Quantitative analysis—night time ambient temperature distribution across different land use types Firstl Firstly, y, analys analysis is of overla overlayin ying g land land use and mobile survey survey maps maps was done. Mean Mean night night time time ambien ambientt temperature distribution in different land use types are generated using ArcMap. The descriptive summary result resultss reveal reveal that that at night night time, time, commerc commercial ial area area (27.78 (27.78 C) has higher higher mean mean ambien ambientt temper temperatu ature re than than residential residential area (27.18 (27.18 C), and these these two land land use areas areas exhibi exhibitt higher higher mean mean ambien ambientt temper temperatu ature re than than industrial area (the Business 1 (27.32 C) and Business 2 (27.18 C) are industrial areas) and airport (the Port (27.32 C) is airport area. The night time ambient temperature is higher in the CBD, east coast and west coast areas where the main land uses are commercial and residential than in the northern part where the main land uses are residential and park. The areas with lowest night time ambient temperature are found in northwest and central parts where the land use type is park. Secondly is the analysis using interpolation of the night time mobile survey data. A temperature profile (Fig. 7) 7) of night time ambient temperature distribution in Singapore was generated using ArcGIS Spatial Analys Analyst. t. The analys analysis is result resultss suppor supportt the hypoth hypothesis esis that that at night night time, time, commer commercia ciall area area has the highes highestt ambient temperature, while industrial area and airport have the lowest ambient temperature among the four land land use types types (comme (commercia rcial, l, reside residenti ntial, al, indust industria rial, l, and airpor airport). t). The night night time time ambien ambientt temper temperatu ature re in 1

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Fig. 7. 3D temperature temperature profile of daytime daytime surface surface temperature temperature distribut distribution ion from west to east of Singapore Singapore..

Comparison of Night Time Temperature in Human Structure and Vegetation Areas

28    )   n   C 27.5   a   e   (   m  e   r    d   t   u 27   e    t   a    h  r   g  e    i   p   e  m    W   e 26.5    t

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residential area is lower than that in commercial area and higher than that in industrial area and airport. This is because that in commercial areas with highly congested high rise buildings, the heat absorbed in daytime release much slower at night time than that in residential area where buildings are normally surrounded by greenery and in low-rise industrial area and airport which have more open space to promote heat releasing. As shown in Fig. 8, 8, human structure structure area has higher night time mean ambient ambient temperature temperature (27.16 (27.16 C) than vegetation area (26.65 C). The analysis results indicate that at night time, the commercial (27.79 C) and business (27.34 C) areas exhibits a higher mean ambient temperature compared with industrial (27.04 C) and airport airport (26.84 (26.84 C) areas (Fig. ( Fig. 9). 9). This is because the heat is trapped inside the urban canyon and slowly released to the environment. The analysis results also reveal that commercial and business areas have higher night time mean ambient temperature than residential area (27.21 C). 1

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Conclusion

From the qualitative analysis, some patterns of temperature profile for different land use types can be observed. For industrial area, during daytime, it has a very high surface temperature due to a large open

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Comparison of Night Time Temperature in Different Land Use Areas 28   e   r   u    t   a   r   e 27.5   p   m   e    t    )   n   C 27   a   e   (   m    d   e    t 26.5    h   g    i   e    W 26

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concrete surface area and high-dense metal and concrete roof buildings. In the airport/port area, high surface temperature is mainly due to a large open concrete area. Combination of yellowish/greenish color and red color appears in both residential and CBD area. In residential area, the yellowish/greenish colors is mainly the presence of greenery, meanwhile in the CBD, it is mainly due to the shading from the high-rise buildings. At night time, the condition turns the other way around. Industrial area and Changi airport seem to have a lower ambient temperature as compared with CBD and residential area. It is because the industrial area consists of  low-rise building and airport mainly consists of open large asphalt surface, which have lower thermal capacity as compared with high-rise buildings. Quanti Quantitat tative ive analys analysis is result resultss reveal reveal that that during during daytim daytime, e, the indust industria riall area area exhibit exhibit a higher higher surfac surfacee temperature than commercial and business areas, and park area has the lowest surface temperature. However, at night night time, time, on the contra contrary, ry, the commer commercia ciall and business business areas areas exhibi exhibitt a higher higher ambient ambient temperat temperature ure compared with industrial and airport areas. This is due to the heat trapped inside the urban canyon releasing slowly to the environment. The analysis results also reflect that in daytime, human structure area has much higher surface temperature than vegetation area, while the raise of ambient temperature is minor at night. Both Both the qualit qualitat ative ive and quanti quantitat tative ive analys analysis is results results show show that that the land land usage usage will will influen influence ce urban urban temperature. In the daytime, the sequence of surface temperature in different land use type areas is industrial, commercial, airport, residential and park, respectively. At night time, the sequence of ambient temperature in different land use type areas is commercial, residential, park, industrial and airport, respectively. Therefore, with appropriate land use planning, the UHI could be mitigated. One of the limitations is that the mobile survey did not cover all the land use types, neither the Jurong Island which is the industrial area. Therefore, the descriptive summary and 3D representation do not include night time ambient temperature in all the land use types neither the Jurong Island. Another limitation is that all the measurements were taken on roads, and although some of these roads traverse through nature reserve sites, there is the impression when compared with the daytime thermal image, that the results cannot fully account for vegetated areas such as parks. In the future, the study can be done by using thermal image of the nighttime temperature. Acknowledgment

We would like to express our sincere thanks to Associate Professor Han Sun Sheng, National University of  Singapore for the tremendously benefit of his feedback and suggestions on GIS application. References Akbari, H., et al. (1992). Cooling our communities—A guidebook on tree planting and light colored surfacing. surfacing. US Environmental protection Agency. Office of Policy Analysis, Climate Change Division.

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