- Email: [email protected]
The tropical urban climate experiment (TRUCE)
Energy and Buildings, 15 - 16 (1990/91) 67 - 73
67
The Tropical Urban Climate Experiment (TRUCE) OKE Atmospheric Science Programme, Department of Geography, University of British Columbia, Vancouver, B.C. (Canada)
T. R.
ROGER TAESLER
SMHI, Norrk6ping, and Royal Institute of Technology, Stockholm (Sweden) LARS E. OLSSON
Applications Division, World Climate Programme, World Meteorological Organization, Geneva (Switzerland)
ABSTRACT
Tropical cities face an enormous expansion in population and probable degradation in environmental quality, including aspects of urban climate such as air pollution, heat stress and flash-floods with significant negative implications for health, safety, productivity and conservation. It is therefore distressing to note that we know relatively little about the climate of tropical cities. In order to address these problems, the World Meteorological Organization (WMO) is launching a major research, training and education i n i t i a t i v e - The TRopical Urban Climate E_xperiment (TRUCE). The purpose is to improve our understanding of the mechanisms controlling the modification of the atmospheres of tropical cities and to provide a better basis for urban environmental planning and forecasting. T R U C E will include both observations and modelling, involving contributions from many research and operational groups and organizations, and is expected to extend until the end of the century. The rationale and proposed scope, objectives and organization of T R U C E are outlined and an invitation to plan and participate is extended to all members of the urban climate community.
1. INTRODUCTION This is the first formal indication in the open l i t er atu r e of a major i n t e r n a t i o n a l research u n d e r t a k i n g which is being planned in the field of u r b an climatology and meteorology. 0378-7788/91/$3.50
The project is named TRUCE, an acronym of TRopical U rban Climate Experiment. In fact, and in common with many similar international collaborative meteorological projects, it is not an experiment in a strict sense (i.e., it is not the test of an hypothesis under controlled conditions). Rat her it is a set of observation, analysis and model studies designed to discover much more about the n a t u r e of the atmosphere in tropical cities and to use t hat information both to improve the living environm ent and to inform future research efforts. This paper states the rationale, purposes and objectives of TRUCE, followed by an outline of how the project will be organized, and invites those interested to consider orienting their research towards TRUCE and becoming involved in its development and implementation.
2. RATIONALE It is nat ural and appropriate to ask, "Why is the tropical city the focus of TRUCE?" There are at least four main reasons why we think urban climatologists and meteorologists should t urn at t ent i on to this topic.
2.1. Climate-related problems of urban growth in the tropics Although it is not easy to forecast accurately, there is no doubt t h a t tropical cities of the 'less developed world' are already experiencing or are on the verge of explosive growth in population: see for example, Tables 1 and 2 [ 1 - 3]. The statistics are so dramatic it is hard to conceive of the magnitude of the prospect ((~)Elsevier Sequoia/Printed in The Netherlands
68 TABLE l Population living in urban areas, 1950-2000 [3} Region
1950
World total More developed regions Less developed regions Africa Latin America Asia
1985
2000
(%)
(million)
(%)
(million)
(%)
(million)
29.2 53.8 17.0 15.7 41.0 16.4
734.2 447.3 286.8 35.2 67.6 225.8
41.0 71.5 31.2 29.7 69.0 28.1
1982.8 838.8 1144.0 164.5 279.3 791.1
46.6 74.4 39.3 39.0 76.8 35.0
2853.6 949.9 1903.7 340.0 419.7 1242.4
TABLE 2 Examples of rapid population growth in Third World cities (in million) [3] City
1950
UN Project 2000
Mexico City Sao Paulo Bombay Delhi Cairo Jakarta Manila Bogota Lagos Nairobi
3.1 2.7 3.0 1.4 2.5 1.5 1.8 0.6 0.3 0.1
26.3 24.0 16.0 13.3 13.2 12.8 11.1 9.6 8.3 5.3
t h a t , in t h e p e r i o d 1 9 8 6 - 2000, cities in the less d e v e l o p e d w o r l d will g r o w by 750 million i n h a b i t a n t s . A t t h a t time, t h r e e of the w o r l d ' s five cities of o v e r 20 million i n h a b i t a n t s , a n d 17 of the 26 cities of o v e r 10 million will be l o c a t e d in t r o p i c a l climates. In the Asia Pacific r e g i o n alone, the n u m b e r of cities w i t h one million i n h a b i t a n t s h a s g r o w n f r o m 26 in 1950 to a p r o j e c t e d 180 in 2000 [2]. M a n y of t h e s e people will be a d d e d to cities w h o s e i n f r a s t r u c t u r e is o f t e n a l r e a d y a t or b e y o n d its limit a n d w h e r e e n v i r o n m e n t a l issues are tert i a r y c o m p a r e d to t h o s e t h a t a r e e s s e n t i a l in the e v e r y d a y s t r u g g l e for existence. As a result t h e r e is a n i n e v i t a b l e decline in the quality of life a n d the u r b a n e n v i r o n m e n t [3, 4]. S e v e r a l of t h e s e p r o b l e m s are d i r e c t l y or indir e c t l y r e l a t e d to the c l i m a t e of t h e s e cities. A l t h o u g h the less d e v e l o p e d w o r l d m i g h t be c o n s i d e r e d less industrialized, m a n y cities contain very concentrated industrial areas sited w i t h little r e g a r d to d o w n s t r e a m i m p a c t on r e s i d e n t i a l d i s t r i c t s a n d often o p e r a t i n g w i t h little or no e m i s s i o n c o n t r o l s a n d s u b j e c t
to lax e n f o r c e m e n t . T r a n s p o r t a t i o n s y s t e m s are o u t d a t e d a n d o v e r l o a d e d , cars are poorly m a i n t a i n e d , r o a d s m a y be dusty, a n d t h e r e is little c u r b on d o m e s t i c burning. To this nightm a r e of e m i s s i o n f a c t o r s m u s t be added the fact t h a t m a n y cities in the t r o p i c s e x p e r i e n c e v e r y w e a k v e n t i l a t i o n giving p o o r dispersion; t h e i r a t m o s p h e r e s are a l w a y s hot, t h e r e b y increasing the r e a c t i v i t y of p o l l u t a n t s leading to the r a p i d d e v e l o p m e n t of s e c o n d a r y products, a n d some are v e r y moist, l e a d i n g to a v e r y hazy a t m o s p h e r e . S u c h c o n d i t i o n s are p a r t l y responsible for the fact t h a t r e s p i r a t o r y , c a r d i o v a s c u lar a n d c a n c e r o u s diseases are r e p l a c i n g infectious a n d p a r a s i t i c diseases as the prim a r y c a u s e of d e a t h in m a n y t r o p i c a l cities [5]. L u n g c a n c e r m o r t a l i t y is four to s e v e n times h i g h e r in Chinese cities t h a n in the n a t i o n as a w h o l e [6], 60% of C a l c u t t a ' s p o p u l a t i o n suffer from p n e u m o n i a , b r o n c h i t i s a n d o t h e r r e s p i r a t o r y diseases [7], a n d a i r b o r n e o r g a n i c p a r t i c l e s are r e s p o n s i b l e for some p a r a s i t i c , e n t e r i c a n d r e s p i r a t o r y diseases i n c l u d i n g b r o n c h i a l a s t h m a in M e x i c o City [8]. O u t s i d e the tropics, h e a t stress d u r i n g summ e r c a n r e s u l t in i n c r e a s e d m o r b i d i t y a n d loss of p r o d u c t i v i t y , a n d in e x t r e m e cases d e a t h from h e a t s t r o k e or f a t a l a g g r a v a t i o n of underlying c a r d i o v a s c u l a r w e a k n e s s (e.g., see Fig. 1). D e s p i t e h e a t t o l e r a n c e by i n h a b i t a n t s of the tropics, s i m i l a r p r o b l e m s a r e experienced, a n d the e x t r a stress c o n t r i b u t e d by the h e a t island g r o w t h of l a r g e cities is seen as a t h r e a t . In p a r t i c u l a r the n o c t u r n a l h e a t island m a y c a u s e the t o l e r a b l e limit for r e c u p e r a t i o n to be exceeded; this t o g e t h e r w i t h the o t h e r m u l t i p l e stresses of u r b a n living in t r o p i c a l cities reduces the ability of people to cope w i t h h e a t so t h a t t h e y m o r e r e a d i l y s u c c u m b to c a r d i o v a s c u l a r a i l m e n t s [5]. U r b a n h e a t m a y also inc r e a s e the i n c i d e n c e of h o m i c i d e a n d suicide,
69 5000
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70
4000
60
40
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TEMPERATURE, ( Cl
Fig. 1. Heat deaths in St. Louis, MO, in July 1966, as a function of average daily temperature (lagged by one day). Solid dots indicate average temperature is warmer than the previous day, open circles that it is cooler [9].
a g g r a v a t e d by alcohol c o n s u m p t i o n in the 2 0 - 4 5 age group, as has been observed in several cities [10]. As t r o p i c a l cities e x p a n d into megacities, t h e i r v u l n e r a b i l i t y to n a t u r a l hazards increases. M a n y of the m a j o r cities are located on coasts and e s t u a r i e s and are open to the d a n g e r s of high winds and flooding associated with t r o p i c a l storms. F o r example, K a r a c h i , J a k a r t a , C a l c u t t a , Delhi, D a c c a and S h a n g h a i are all disaster-prone cities whose p o p u l a t i o n s are p r o j e c t e d to be b e t w e e n 20 and 30 million people by the y e a r 2025. P o p u l a t i o n densities in such cities can be v e r y h i g h (10 b persons per km 2) m a k i n g e v a c u a t i o n e x t r e m e l y difficult and the poor who are least able to fend for t h e m s e l v e s are the most v u l n e r a b l e because t h e y o c c u p y the most u n s a f e areas (flood plains and u n s t a b l e slopelands) [11]. Flood h a z a r d due to c o n v e c t i v e or f r o n t a l rainfall is g r e a t in b o t h the dry and wet tropics and is e x a c e r b a t e d in cities due to the modification of the surface h y d r o l o g i c c h a r a c t e r i s t i c s , the i n t e n s i t y of t r o p i c a l rainfall, and the vast a m o u n t s of sedim e n t c o n t r i b u t e d by u n p a v e d roads and poorly designed c o n s t r u c t i o n sites [12]. P o t e n t i a l clim a t e c h a n g e m a y alter the frequencies and intensities of disastrous w e a t h e r - r e l a t e d p h e n o m e n a and an improved u n d e r s t a n d i n g of h o w these impacts m a y c h a n g e could help save life and p r o p e r t y . This is especially emphasized in the I n t e r n a t i o n a l F r a m e w o r k of A c t i o n for the I n t e r n a t i o n a l D e c a d e for N a t u r a l Disaster R e d u c t i o n (IDNDR). A m a j o r problem for the economies of m a n y less developed t r o p i c a l c o u n t r i e s is the expen-
100CI0
ll5
2L0
215
3J0
35
AVERAGE DAILY TEMPERATURE. ( C~
Fig. 2. The relation between electricity power load at 16:00 and average daily temperature in Los Angeles for each day in 1986 [13]. The upper more-dense population of points is for weekdays and the lower for weekends. At higher values, where there is a clear temperature dependence, the slope is approximately 3.6% increase in load for each degree Celsius. Given typical unit electricity rates and 1500 hours of cooling demand per year, this means each degree of extra warmth costs the city about $20.25 million per year. Note that this is the case of a coastal city outside the tropics proper. d i t u r e on imported e n e r g y supplies. An increasing d e m a n d t h a t c r e a t e s this d r a i n is the need for power to r u n a i r - c o n d i t i o n i n g equipment. As cities and t h e i r h e a t islands grow the d e m a n d spirals. The examples provided by the cities of the hot climates of the U n i t e d States of A m e r i c a are not a good model to follow. As can be seen in Fig. 2, for e v e r y degree Celsius rise in the a v e r a g e daily t e m p e r a t u r e of Los Angeles t h e r e is a b o u t a $20M/year i n c r e a s e in the cost of air-conditioning. F u r t h e r this p o w e r p r o d u c t i o n also c o n t r i b u t e s to problems of c a r b o n dioxide and p o l l u t a n t release and p r o b a b l y the depletion of a n o n - r e n e w a b l e resource. The c o n c e r n is sufficient t h a t the U.S. D e p a r t m e n t of E n e r g y has commissioned a m a n u a l to show how h e a t islands can be mitigated t h r o u g h a p p r o a c h e s such as the planting of v e g e t a t i o n and the use of light-coloured surfaces. Only the more affluent sectors of tropical n a t i o n s use a i r - c o n d i t i o n i n g but, w h e r e practicable, n e w e r buildings show a t e n d e n c y to move away from t r a d i t i o n a l passive m e a n s of cooling and t o w a r d s a r e l i a n c e on e n e r g y - i n t e n s i v e systems. As always, w a t e r is a c e n t r a l b u t multif a c e t t e d element. Its p r e s e n c e or absence helps define the n a t u r e of the t r o p i c a l climate, its o v e r a b u n d a n c e is a hazard, its u n d e r s u p p l y can be l i f e - t h r e a t e n i n g and it forms one of the most powerful and flexible tools for ameliorat-
70 ing thermal climate. Urban growth brings all of these aspects into even sharper focus. Although the tropical regions are projected to experience the least dramatic climatic changes resulting from trace gas warming, they may well experience very serious impacts. Any increase in temperature will exacerbate all of the previously outlined problematic features of urban warmth, and the flooding associated with sea-level rise may be devastating to deltaic, island and low-lying coastal communities.
2.2. Poor state of tropical urban climate knowledge Every major review of the field of urban climatology has commented upon the lack of a proper scientific base of knowledge of tropical urban climates [8, 14-18]. Whilst some progress is being made, tropical work occupies less than 10% of t hat published in urban climatology [8]. Perhaps more importantly, the nature of the work does not hold the promise of gaining rapid insight into the system. The necessary descriptive base is largely unstructured and highly specific to the city involved. Most of the work is based upon data from standard stations which are rarely ideal to monitor the urban system. There is very little information concerning the state of the atmosphere above roof level and there is almost no work into the underlying atmospheric processes. The reasons for this state of affairs are many but most can be traced to the relatively poor base of meteorological resources available to research workers. These include insufficient numbers of trained personnel, lack of research funding, inappropriate or no equipment and the lack of computer facilities or expertise. Anot her contributing factor is the fact that there is little demand or requirement for information for urban planning or environmental management. 2.3. The challenge of a new frontier No urban atmospheric research scientist should be short of topics for study. The field is young and immature and the ar r ay of problems is almost as large as it is perplexing in its complexity. But the opportunity to investigate tropical urban atmospheres will open up a whole range of new possibilities for many because tropical systems present a new set of
boundary conditions and a forum in which to test the transferability of our much larger temperate latitude knowledge and experience [19]. In addition to questions of similarity or difference from the temperate case, we want to find out why cool r a t h e r than heat islands characterize some tropical cities for long periods, why most studies suggest smaller heat islands than expected, if cities produce an enhancement of warm rain, what are the implications of smaller Coriolis forces for circulation systems, is vegetation a universal panacea for thermal and comfort conditions or are there problems to be avoided, etc. Some questions are driven by purely scholarly interest, others by pragmatism; there is room and need for both in TRUCE.
2.4. Indigenous support The idea of focusing international research effort on improving understanding of the urban climate and meteorology of tropical cities was first recommended as a conclusion by participants at the WMO Technical Conference in Mexico City in 1984 [20]. It was repeated by those attending the WHO/PAHO Regional Seminar in Sao Paulo in 1987, the WMO Regional Seminar in Kuala Lumpur in 1989, and the IFHP/WMO/CIB/IGU Conference in Kyoto in 1989. The delegates to these meetings came from many tropical countries, thus we can conclude that there is strong support for such a programme from the regions involved.
3. PURPOSES OF TRUCE The two central purposes of TRUCE are simply: - - to improve scientific understanding of urban climates in tropical areas, and --- to improve the basis of decisions regarding urban design and environmental management, especially in the light of potential impacts of climate variability and change, and the need to establish disaster-preparedness programmes. The actual plans for the programme remain to be detailed by the interested community. It is anticipated that TRUCE will have a number of very important by-products which further deepen the purpose of the project: (a) To spur urban climate research in general. The field is in need of a heightened profile
71
in the scientific research community and the provision of extra funds. (b) TRUCE will provide a much needed focus for research in the field. Urban climatology, meteorology and hydrology and their use in urban design, management and engineering cover a wide range of disciplines and organizations. As a result there is a tendency for the impact of the work and its dissemination to be blunted by the fact that it is presented at a wide variety of conferences and is published in different journals. TRUCE can help draw the community together physically and intellectually. (c) The project can help facilitate the transfer of expertise and technology in general and especially from those areas where the field is more advanced and better funded to those less well endowed. In particular it can move the state of knowledge, training and interest in tropical areas far ahead of its present position. In so doing it will increase international cooperation, contacts and opportunities. (d) TRUCE can generate an informed, comprehensive and high quality set of tropical urban climate data rapidly. Such a database is necessary if we are to judge the validity of the existing scant information from tropical cities and to assess the transferability of temperate climate concepts, results and models. It is certain that this will allow the present knowledge gap to be narrowed quickly. (e) The impetus provided by the need to generate a coordinated set of data may be used to encourage the development of better observing practices in urban areas. For example it will be necessary to issue recommendations for the choice of urban sites and the exposure of instruments so that they appropriately reflect urban conditions of relevance to urban concerns. (f) By combining talents and experience, and through the use of demonstration projects and commissioned publications or competitions, it should be possible to develop, test and publish appropriate and relevant guidelines for design in different tropical climates.
4. TENTATIVE PLANS AND TIMETABLE TO IMPLEMENT TRUCE
TRUCE is at a very young stage and its shape is open to the input of interested parties
(individual scientists, meteorological services, government, private, professional and scientific organizations, countries and cities). TRUCE has already been formally adopted by WMO and a small start-up budget is available. At the IFHP/WMO/CIB/IGU meeting in Kyoto where this paper was originally presented, the conference unanimously adopted the following statement: "Concern for the environment of rapidly growing tropical cities is stressed by the conference. It is agreed t h a t TRUCE as presently conceived provides an important focus for the research necessary to improve understanding of the climate system of tropical cities and thereby lay a firm foundation for the development of practical measures to address associated problems. The three co-sponsoring organizations (IFHP, CIB and IGU) express interest in aligning their activities with the TRUCE programme and pledge to collaborate with WMO in its development and implementation. As a result, they strongly urge WMO to press ahead with TRUCE and request t h a t they be kept informed and involved with its preparation."
Individuals and other groups can make their interest known by contacting Dr. Olsson at the WMO Secretariat in Geneva. It is hoped that a separate TRUCE secretariat can be established. At least two phases of TRUCE are anticipated. A first phase which might extend up to about 1993 involves careful preparation for TRUCE, and a second phase extending until the end of the century in which the research and application programmes are run. The first stage is just beginning and will involve an inventory of present knowledge of tropical urban climates and an assessment of the gaps in that knowledge. With that as background and input, a draft scientific plan for TRUCE will be developed for discussion, refinement and adoption by those interested. Preliminary discussions were undertaken at the end of November 1990 in Guadalajara, Mexico. The initial period will also be characterized by encouragement to develop new methods (e.g., new instrument packages to be deployed, new data management systems to interface with the WMO CLICOM computerized climate archival and analysis system which is already in place in many tropical countries) and to foster cooperation between all those interested in the project. By the end of this initial phase the participants and sites for TRUCE will be selected. The second phase will include several longterm (multi-year) and short-term (months)
72
projects, observational programmes and modelling studies. An example of the long-term type of project might involve the establishment of a tropical city observing network to monitor the exact nature of urban climates. Many cities would be encouraged and assisted to establish urban climate stations and urban-rural (or the equivalent to rural) station pairs. The choice of cities would reflect local interest and need, together with the scientific goals of TRUCE including the need to sample an appropriate range of geographic site and climatic types (coastal, inland, island, highland, hot/humid, hot/dry, etc.) throughout the tropical world. Prior to installation each city would be surveyed with mobile equipment to establish the appropriate locations for sites. Instrument and archival systems would be selected and installed and the local personnel would be instructed and helped where necessary. In this manner a coordinated, comprehensive and high-quality network of urban climate stations could be rapidly established so as to generate data to meet both general TRUCE and local goals. A central archive could ensure quality control and analysis and the data could be made available to a wide range of interested individuals and groups in the research and user communities. Bulletins and conference sessions could be devoted to the results of this TRUCE network. An example of a short-term project may look very much like many previous boundary layer observational programmes organized on an international basis such as FIFE, HAPEXMOBILHY, LOWTRAN, etc., except that it will be held in and near a tropical city. It would involve coordinated measurement programmes conducted by individual research groups both local and foreign using their own equipment. Such a project may concentrate work in a period of say two months in a host city chosen with the same criteria used to select the long-term sites plus the existence of especially pressing or interesting atmospheric or design problems, the presence of an indigenous research capability and a clear indication that the city and country is interested to assist the participation of the international research community. Again, the results of these studies would be a focus for conferences and provide ongoing feedback to inform and inspire the succeeding projects.
The observation programmes would be run in tandem with modelling studies so that the field data can be used as realistic input to the models and form a dataset against which to test the output. Equally the output of models should be used to instruct the design of TRUCE field projects. Both field and model components can be brought to bear on the question of infusing climatically sensitive design principles into tropical cities. However, it is important to keep a sense of perspective here because it is a depressing fact that much of the expansion of large tropical cities occurs as illegal settlement in which planning plays no role. But where opportunities for demonstration projects allow, it will be very important to show how climate can be improved, to quantify the impacts of design strategies and to inform and validate design guidelines for making cities more healthy, safe, efficient, pleasant and sustainable. TRUCE will be a multi-lateral effort and will require a multi-facetted steering mechanism to successfully coordinate the overall programme because it will include many disciplines, organizations, nations, objectives, locations and funding agencies. It will also require the commitment of many within the urban climate community to devote a portion of their research effort to participation within the TRUCE framework. This is a challenge which can serve to demonstrate the excitement and value of our field and also to bring our wideranging interests into a common focus.
REFERENCES 1 J. Peterson, Global population projections through the 21st century, Ambio, 13 (1984) 134- 141. 2 ESCAP, Human Settlements Atlas for Asia and the Pacific, Part III Urbanization and City Profiles, Publ. No. ST/ESCAP/354, United Nations, New York, 1986. 3 World Commission on Environment and Development, Our Common Future, Oxford University Press, Oxford, 1987. 4 J. E. Hardoy and D. Satterthwaite, Third World cities and the environment of poverty, Geoforum, 15 (1984) 307 - 333. 5 W. H. Weihe, Life expectancy in tropical climates and urbanization, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 313- 353. 6 V. Smil, The Bad Earth: Environmental Degradation in China, Zed Press, London, 1986.
73 7 Centre for Science and Environment, State of India's Environment: A Citizen's Report, New Delhi, 1983. 8 E. Jauregui, Urban climatology in the tropics, Report of First Session of CCl Working Group on Climate and Urban Areas including Building and other Aspects, WCAP-8, WMO/TD-No. 287, World Meteorological Organization, Geneva, pp. 13- 19. 9 J. F. Clarke and W, Bach, Comparison of the comfort conditions in different urban and suburban microenvi. ronments, Int. J. Biometeorol., 15 (1971) 41-54. 10 PAHO, Patterns of Urban Mortality, Sci. Publ. No. 151, Pan American Health Organization, Washington, DC, 1967. 11 I. R. Davis, The planning and maintenance of urban settlements to resist extreme climatic forces, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 277312. 12 T. Dunne, Urban hydrology in the tropics: problems, solutions, data collection and analysis, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 405434. 13 H. Akbari, R. Rosenfeld and H. Taha, Recent develop. ments in heat island studies: technical and policy, in K. Garbesi, H. Akbari and P. Martien (eds.), Con-
14
15
16 17
18
19
20
trolling Summer Heat Islands, Lawrence Berkeley Laboratory, Berkeley, 1989, pp. 14-30. T. J. Chandler, Urban climatology: Summary and Conclusions of the Symposium, Tech. Note No. 108, Publ. No. 254, World Meteorological Organization, Geneva, 1970, pp. 375-379. T. R. Oke, Towards a prescription for the greater use of climatic principles in settlement planning, Energy Build., 7(1984) 1 - 10. D. O. Lee, Urban climates, Prog. Phys. Geography, 8 (1984) 1- 31. E. Jauregui, Tropical urban climates: review and assessment, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 26- 45. S. Sham, Urbanization and the Atmospheric Environment in the Low Tropics, Penerbit Universiti Kebangsaan Malaysia, Bangi, 1987. T. R. Oke, Urban climatology and the tropical city: an introduction, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 1 - 25. T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986.
67
The Tropical Urban Climate Experiment (TRUCE) OKE Atmospheric Science Programme, Department of Geography, University of British Columbia, Vancouver, B.C. (Canada)
T. R.
ROGER TAESLER
SMHI, Norrk6ping, and Royal Institute of Technology, Stockholm (Sweden) LARS E. OLSSON
Applications Division, World Climate Programme, World Meteorological Organization, Geneva (Switzerland)
ABSTRACT
Tropical cities face an enormous expansion in population and probable degradation in environmental quality, including aspects of urban climate such as air pollution, heat stress and flash-floods with significant negative implications for health, safety, productivity and conservation. It is therefore distressing to note that we know relatively little about the climate of tropical cities. In order to address these problems, the World Meteorological Organization (WMO) is launching a major research, training and education i n i t i a t i v e - The TRopical Urban Climate E_xperiment (TRUCE). The purpose is to improve our understanding of the mechanisms controlling the modification of the atmospheres of tropical cities and to provide a better basis for urban environmental planning and forecasting. T R U C E will include both observations and modelling, involving contributions from many research and operational groups and organizations, and is expected to extend until the end of the century. The rationale and proposed scope, objectives and organization of T R U C E are outlined and an invitation to plan and participate is extended to all members of the urban climate community.
1. INTRODUCTION This is the first formal indication in the open l i t er atu r e of a major i n t e r n a t i o n a l research u n d e r t a k i n g which is being planned in the field of u r b an climatology and meteorology. 0378-7788/91/$3.50
The project is named TRUCE, an acronym of TRopical U rban Climate Experiment. In fact, and in common with many similar international collaborative meteorological projects, it is not an experiment in a strict sense (i.e., it is not the test of an hypothesis under controlled conditions). Rat her it is a set of observation, analysis and model studies designed to discover much more about the n a t u r e of the atmosphere in tropical cities and to use t hat information both to improve the living environm ent and to inform future research efforts. This paper states the rationale, purposes and objectives of TRUCE, followed by an outline of how the project will be organized, and invites those interested to consider orienting their research towards TRUCE and becoming involved in its development and implementation.
2. RATIONALE It is nat ural and appropriate to ask, "Why is the tropical city the focus of TRUCE?" There are at least four main reasons why we think urban climatologists and meteorologists should t urn at t ent i on to this topic.
2.1. Climate-related problems of urban growth in the tropics Although it is not easy to forecast accurately, there is no doubt t h a t tropical cities of the 'less developed world' are already experiencing or are on the verge of explosive growth in population: see for example, Tables 1 and 2 [ 1 - 3]. The statistics are so dramatic it is hard to conceive of the magnitude of the prospect ((~)Elsevier Sequoia/Printed in The Netherlands
68 TABLE l Population living in urban areas, 1950-2000 [3} Region
1950
World total More developed regions Less developed regions Africa Latin America Asia
1985
2000
(%)
(million)
(%)
(million)
(%)
(million)
29.2 53.8 17.0 15.7 41.0 16.4
734.2 447.3 286.8 35.2 67.6 225.8
41.0 71.5 31.2 29.7 69.0 28.1
1982.8 838.8 1144.0 164.5 279.3 791.1
46.6 74.4 39.3 39.0 76.8 35.0
2853.6 949.9 1903.7 340.0 419.7 1242.4
TABLE 2 Examples of rapid population growth in Third World cities (in million) [3] City
1950
UN Project 2000
Mexico City Sao Paulo Bombay Delhi Cairo Jakarta Manila Bogota Lagos Nairobi
3.1 2.7 3.0 1.4 2.5 1.5 1.8 0.6 0.3 0.1
26.3 24.0 16.0 13.3 13.2 12.8 11.1 9.6 8.3 5.3
t h a t , in t h e p e r i o d 1 9 8 6 - 2000, cities in the less d e v e l o p e d w o r l d will g r o w by 750 million i n h a b i t a n t s . A t t h a t time, t h r e e of the w o r l d ' s five cities of o v e r 20 million i n h a b i t a n t s , a n d 17 of the 26 cities of o v e r 10 million will be l o c a t e d in t r o p i c a l climates. In the Asia Pacific r e g i o n alone, the n u m b e r of cities w i t h one million i n h a b i t a n t s h a s g r o w n f r o m 26 in 1950 to a p r o j e c t e d 180 in 2000 [2]. M a n y of t h e s e people will be a d d e d to cities w h o s e i n f r a s t r u c t u r e is o f t e n a l r e a d y a t or b e y o n d its limit a n d w h e r e e n v i r o n m e n t a l issues are tert i a r y c o m p a r e d to t h o s e t h a t a r e e s s e n t i a l in the e v e r y d a y s t r u g g l e for existence. As a result t h e r e is a n i n e v i t a b l e decline in the quality of life a n d the u r b a n e n v i r o n m e n t [3, 4]. S e v e r a l of t h e s e p r o b l e m s are d i r e c t l y or indir e c t l y r e l a t e d to the c l i m a t e of t h e s e cities. A l t h o u g h the less d e v e l o p e d w o r l d m i g h t be c o n s i d e r e d less industrialized, m a n y cities contain very concentrated industrial areas sited w i t h little r e g a r d to d o w n s t r e a m i m p a c t on r e s i d e n t i a l d i s t r i c t s a n d often o p e r a t i n g w i t h little or no e m i s s i o n c o n t r o l s a n d s u b j e c t
to lax e n f o r c e m e n t . T r a n s p o r t a t i o n s y s t e m s are o u t d a t e d a n d o v e r l o a d e d , cars are poorly m a i n t a i n e d , r o a d s m a y be dusty, a n d t h e r e is little c u r b on d o m e s t i c burning. To this nightm a r e of e m i s s i o n f a c t o r s m u s t be added the fact t h a t m a n y cities in the t r o p i c s e x p e r i e n c e v e r y w e a k v e n t i l a t i o n giving p o o r dispersion; t h e i r a t m o s p h e r e s are a l w a y s hot, t h e r e b y increasing the r e a c t i v i t y of p o l l u t a n t s leading to the r a p i d d e v e l o p m e n t of s e c o n d a r y products, a n d some are v e r y moist, l e a d i n g to a v e r y hazy a t m o s p h e r e . S u c h c o n d i t i o n s are p a r t l y responsible for the fact t h a t r e s p i r a t o r y , c a r d i o v a s c u lar a n d c a n c e r o u s diseases are r e p l a c i n g infectious a n d p a r a s i t i c diseases as the prim a r y c a u s e of d e a t h in m a n y t r o p i c a l cities [5]. L u n g c a n c e r m o r t a l i t y is four to s e v e n times h i g h e r in Chinese cities t h a n in the n a t i o n as a w h o l e [6], 60% of C a l c u t t a ' s p o p u l a t i o n suffer from p n e u m o n i a , b r o n c h i t i s a n d o t h e r r e s p i r a t o r y diseases [7], a n d a i r b o r n e o r g a n i c p a r t i c l e s are r e s p o n s i b l e for some p a r a s i t i c , e n t e r i c a n d r e s p i r a t o r y diseases i n c l u d i n g b r o n c h i a l a s t h m a in M e x i c o City [8]. O u t s i d e the tropics, h e a t stress d u r i n g summ e r c a n r e s u l t in i n c r e a s e d m o r b i d i t y a n d loss of p r o d u c t i v i t y , a n d in e x t r e m e cases d e a t h from h e a t s t r o k e or f a t a l a g g r a v a t i o n of underlying c a r d i o v a s c u l a r w e a k n e s s (e.g., see Fig. 1). D e s p i t e h e a t t o l e r a n c e by i n h a b i t a n t s of the tropics, s i m i l a r p r o b l e m s a r e experienced, a n d the e x t r a stress c o n t r i b u t e d by the h e a t island g r o w t h of l a r g e cities is seen as a t h r e a t . In p a r t i c u l a r the n o c t u r n a l h e a t island m a y c a u s e the t o l e r a b l e limit for r e c u p e r a t i o n to be exceeded; this t o g e t h e r w i t h the o t h e r m u l t i p l e stresses of u r b a n living in t r o p i c a l cities reduces the ability of people to cope w i t h h e a t so t h a t t h e y m o r e r e a d i l y s u c c u m b to c a r d i o v a s c u l a r a i l m e n t s [5]. U r b a n h e a t m a y also inc r e a s e the i n c i d e n c e of h o m i c i d e a n d suicide,
69 5000
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TEMPERATURE, ( Cl
Fig. 1. Heat deaths in St. Louis, MO, in July 1966, as a function of average daily temperature (lagged by one day). Solid dots indicate average temperature is warmer than the previous day, open circles that it is cooler [9].
a g g r a v a t e d by alcohol c o n s u m p t i o n in the 2 0 - 4 5 age group, as has been observed in several cities [10]. As t r o p i c a l cities e x p a n d into megacities, t h e i r v u l n e r a b i l i t y to n a t u r a l hazards increases. M a n y of the m a j o r cities are located on coasts and e s t u a r i e s and are open to the d a n g e r s of high winds and flooding associated with t r o p i c a l storms. F o r example, K a r a c h i , J a k a r t a , C a l c u t t a , Delhi, D a c c a and S h a n g h a i are all disaster-prone cities whose p o p u l a t i o n s are p r o j e c t e d to be b e t w e e n 20 and 30 million people by the y e a r 2025. P o p u l a t i o n densities in such cities can be v e r y h i g h (10 b persons per km 2) m a k i n g e v a c u a t i o n e x t r e m e l y difficult and the poor who are least able to fend for t h e m s e l v e s are the most v u l n e r a b l e because t h e y o c c u p y the most u n s a f e areas (flood plains and u n s t a b l e slopelands) [11]. Flood h a z a r d due to c o n v e c t i v e or f r o n t a l rainfall is g r e a t in b o t h the dry and wet tropics and is e x a c e r b a t e d in cities due to the modification of the surface h y d r o l o g i c c h a r a c t e r i s t i c s , the i n t e n s i t y of t r o p i c a l rainfall, and the vast a m o u n t s of sedim e n t c o n t r i b u t e d by u n p a v e d roads and poorly designed c o n s t r u c t i o n sites [12]. P o t e n t i a l clim a t e c h a n g e m a y alter the frequencies and intensities of disastrous w e a t h e r - r e l a t e d p h e n o m e n a and an improved u n d e r s t a n d i n g of h o w these impacts m a y c h a n g e could help save life and p r o p e r t y . This is especially emphasized in the I n t e r n a t i o n a l F r a m e w o r k of A c t i o n for the I n t e r n a t i o n a l D e c a d e for N a t u r a l Disaster R e d u c t i o n (IDNDR). A m a j o r problem for the economies of m a n y less developed t r o p i c a l c o u n t r i e s is the expen-
100CI0
ll5
2L0
215
3J0
35
AVERAGE DAILY TEMPERATURE. ( C~
Fig. 2. The relation between electricity power load at 16:00 and average daily temperature in Los Angeles for each day in 1986 [13]. The upper more-dense population of points is for weekdays and the lower for weekends. At higher values, where there is a clear temperature dependence, the slope is approximately 3.6% increase in load for each degree Celsius. Given typical unit electricity rates and 1500 hours of cooling demand per year, this means each degree of extra warmth costs the city about $20.25 million per year. Note that this is the case of a coastal city outside the tropics proper. d i t u r e on imported e n e r g y supplies. An increasing d e m a n d t h a t c r e a t e s this d r a i n is the need for power to r u n a i r - c o n d i t i o n i n g equipment. As cities and t h e i r h e a t islands grow the d e m a n d spirals. The examples provided by the cities of the hot climates of the U n i t e d States of A m e r i c a are not a good model to follow. As can be seen in Fig. 2, for e v e r y degree Celsius rise in the a v e r a g e daily t e m p e r a t u r e of Los Angeles t h e r e is a b o u t a $20M/year i n c r e a s e in the cost of air-conditioning. F u r t h e r this p o w e r p r o d u c t i o n also c o n t r i b u t e s to problems of c a r b o n dioxide and p o l l u t a n t release and p r o b a b l y the depletion of a n o n - r e n e w a b l e resource. The c o n c e r n is sufficient t h a t the U.S. D e p a r t m e n t of E n e r g y has commissioned a m a n u a l to show how h e a t islands can be mitigated t h r o u g h a p p r o a c h e s such as the planting of v e g e t a t i o n and the use of light-coloured surfaces. Only the more affluent sectors of tropical n a t i o n s use a i r - c o n d i t i o n i n g but, w h e r e practicable, n e w e r buildings show a t e n d e n c y to move away from t r a d i t i o n a l passive m e a n s of cooling and t o w a r d s a r e l i a n c e on e n e r g y - i n t e n s i v e systems. As always, w a t e r is a c e n t r a l b u t multif a c e t t e d element. Its p r e s e n c e or absence helps define the n a t u r e of the t r o p i c a l climate, its o v e r a b u n d a n c e is a hazard, its u n d e r s u p p l y can be l i f e - t h r e a t e n i n g and it forms one of the most powerful and flexible tools for ameliorat-
70 ing thermal climate. Urban growth brings all of these aspects into even sharper focus. Although the tropical regions are projected to experience the least dramatic climatic changes resulting from trace gas warming, they may well experience very serious impacts. Any increase in temperature will exacerbate all of the previously outlined problematic features of urban warmth, and the flooding associated with sea-level rise may be devastating to deltaic, island and low-lying coastal communities.
2.2. Poor state of tropical urban climate knowledge Every major review of the field of urban climatology has commented upon the lack of a proper scientific base of knowledge of tropical urban climates [8, 14-18]. Whilst some progress is being made, tropical work occupies less than 10% of t hat published in urban climatology [8]. Perhaps more importantly, the nature of the work does not hold the promise of gaining rapid insight into the system. The necessary descriptive base is largely unstructured and highly specific to the city involved. Most of the work is based upon data from standard stations which are rarely ideal to monitor the urban system. There is very little information concerning the state of the atmosphere above roof level and there is almost no work into the underlying atmospheric processes. The reasons for this state of affairs are many but most can be traced to the relatively poor base of meteorological resources available to research workers. These include insufficient numbers of trained personnel, lack of research funding, inappropriate or no equipment and the lack of computer facilities or expertise. Anot her contributing factor is the fact that there is little demand or requirement for information for urban planning or environmental management. 2.3. The challenge of a new frontier No urban atmospheric research scientist should be short of topics for study. The field is young and immature and the ar r ay of problems is almost as large as it is perplexing in its complexity. But the opportunity to investigate tropical urban atmospheres will open up a whole range of new possibilities for many because tropical systems present a new set of
boundary conditions and a forum in which to test the transferability of our much larger temperate latitude knowledge and experience [19]. In addition to questions of similarity or difference from the temperate case, we want to find out why cool r a t h e r than heat islands characterize some tropical cities for long periods, why most studies suggest smaller heat islands than expected, if cities produce an enhancement of warm rain, what are the implications of smaller Coriolis forces for circulation systems, is vegetation a universal panacea for thermal and comfort conditions or are there problems to be avoided, etc. Some questions are driven by purely scholarly interest, others by pragmatism; there is room and need for both in TRUCE.
2.4. Indigenous support The idea of focusing international research effort on improving understanding of the urban climate and meteorology of tropical cities was first recommended as a conclusion by participants at the WMO Technical Conference in Mexico City in 1984 [20]. It was repeated by those attending the WHO/PAHO Regional Seminar in Sao Paulo in 1987, the WMO Regional Seminar in Kuala Lumpur in 1989, and the IFHP/WMO/CIB/IGU Conference in Kyoto in 1989. The delegates to these meetings came from many tropical countries, thus we can conclude that there is strong support for such a programme from the regions involved.
3. PURPOSES OF TRUCE The two central purposes of TRUCE are simply: - - to improve scientific understanding of urban climates in tropical areas, and --- to improve the basis of decisions regarding urban design and environmental management, especially in the light of potential impacts of climate variability and change, and the need to establish disaster-preparedness programmes. The actual plans for the programme remain to be detailed by the interested community. It is anticipated that TRUCE will have a number of very important by-products which further deepen the purpose of the project: (a) To spur urban climate research in general. The field is in need of a heightened profile
71
in the scientific research community and the provision of extra funds. (b) TRUCE will provide a much needed focus for research in the field. Urban climatology, meteorology and hydrology and their use in urban design, management and engineering cover a wide range of disciplines and organizations. As a result there is a tendency for the impact of the work and its dissemination to be blunted by the fact that it is presented at a wide variety of conferences and is published in different journals. TRUCE can help draw the community together physically and intellectually. (c) The project can help facilitate the transfer of expertise and technology in general and especially from those areas where the field is more advanced and better funded to those less well endowed. In particular it can move the state of knowledge, training and interest in tropical areas far ahead of its present position. In so doing it will increase international cooperation, contacts and opportunities. (d) TRUCE can generate an informed, comprehensive and high quality set of tropical urban climate data rapidly. Such a database is necessary if we are to judge the validity of the existing scant information from tropical cities and to assess the transferability of temperate climate concepts, results and models. It is certain that this will allow the present knowledge gap to be narrowed quickly. (e) The impetus provided by the need to generate a coordinated set of data may be used to encourage the development of better observing practices in urban areas. For example it will be necessary to issue recommendations for the choice of urban sites and the exposure of instruments so that they appropriately reflect urban conditions of relevance to urban concerns. (f) By combining talents and experience, and through the use of demonstration projects and commissioned publications or competitions, it should be possible to develop, test and publish appropriate and relevant guidelines for design in different tropical climates.
4. TENTATIVE PLANS AND TIMETABLE TO IMPLEMENT TRUCE
TRUCE is at a very young stage and its shape is open to the input of interested parties
(individual scientists, meteorological services, government, private, professional and scientific organizations, countries and cities). TRUCE has already been formally adopted by WMO and a small start-up budget is available. At the IFHP/WMO/CIB/IGU meeting in Kyoto where this paper was originally presented, the conference unanimously adopted the following statement: "Concern for the environment of rapidly growing tropical cities is stressed by the conference. It is agreed t h a t TRUCE as presently conceived provides an important focus for the research necessary to improve understanding of the climate system of tropical cities and thereby lay a firm foundation for the development of practical measures to address associated problems. The three co-sponsoring organizations (IFHP, CIB and IGU) express interest in aligning their activities with the TRUCE programme and pledge to collaborate with WMO in its development and implementation. As a result, they strongly urge WMO to press ahead with TRUCE and request t h a t they be kept informed and involved with its preparation."
Individuals and other groups can make their interest known by contacting Dr. Olsson at the WMO Secretariat in Geneva. It is hoped that a separate TRUCE secretariat can be established. At least two phases of TRUCE are anticipated. A first phase which might extend up to about 1993 involves careful preparation for TRUCE, and a second phase extending until the end of the century in which the research and application programmes are run. The first stage is just beginning and will involve an inventory of present knowledge of tropical urban climates and an assessment of the gaps in that knowledge. With that as background and input, a draft scientific plan for TRUCE will be developed for discussion, refinement and adoption by those interested. Preliminary discussions were undertaken at the end of November 1990 in Guadalajara, Mexico. The initial period will also be characterized by encouragement to develop new methods (e.g., new instrument packages to be deployed, new data management systems to interface with the WMO CLICOM computerized climate archival and analysis system which is already in place in many tropical countries) and to foster cooperation between all those interested in the project. By the end of this initial phase the participants and sites for TRUCE will be selected. The second phase will include several longterm (multi-year) and short-term (months)
72
projects, observational programmes and modelling studies. An example of the long-term type of project might involve the establishment of a tropical city observing network to monitor the exact nature of urban climates. Many cities would be encouraged and assisted to establish urban climate stations and urban-rural (or the equivalent to rural) station pairs. The choice of cities would reflect local interest and need, together with the scientific goals of TRUCE including the need to sample an appropriate range of geographic site and climatic types (coastal, inland, island, highland, hot/humid, hot/dry, etc.) throughout the tropical world. Prior to installation each city would be surveyed with mobile equipment to establish the appropriate locations for sites. Instrument and archival systems would be selected and installed and the local personnel would be instructed and helped where necessary. In this manner a coordinated, comprehensive and high-quality network of urban climate stations could be rapidly established so as to generate data to meet both general TRUCE and local goals. A central archive could ensure quality control and analysis and the data could be made available to a wide range of interested individuals and groups in the research and user communities. Bulletins and conference sessions could be devoted to the results of this TRUCE network. An example of a short-term project may look very much like many previous boundary layer observational programmes organized on an international basis such as FIFE, HAPEXMOBILHY, LOWTRAN, etc., except that it will be held in and near a tropical city. It would involve coordinated measurement programmes conducted by individual research groups both local and foreign using their own equipment. Such a project may concentrate work in a period of say two months in a host city chosen with the same criteria used to select the long-term sites plus the existence of especially pressing or interesting atmospheric or design problems, the presence of an indigenous research capability and a clear indication that the city and country is interested to assist the participation of the international research community. Again, the results of these studies would be a focus for conferences and provide ongoing feedback to inform and inspire the succeeding projects.
The observation programmes would be run in tandem with modelling studies so that the field data can be used as realistic input to the models and form a dataset against which to test the output. Equally the output of models should be used to instruct the design of TRUCE field projects. Both field and model components can be brought to bear on the question of infusing climatically sensitive design principles into tropical cities. However, it is important to keep a sense of perspective here because it is a depressing fact that much of the expansion of large tropical cities occurs as illegal settlement in which planning plays no role. But where opportunities for demonstration projects allow, it will be very important to show how climate can be improved, to quantify the impacts of design strategies and to inform and validate design guidelines for making cities more healthy, safe, efficient, pleasant and sustainable. TRUCE will be a multi-lateral effort and will require a multi-facetted steering mechanism to successfully coordinate the overall programme because it will include many disciplines, organizations, nations, objectives, locations and funding agencies. It will also require the commitment of many within the urban climate community to devote a portion of their research effort to participation within the TRUCE framework. This is a challenge which can serve to demonstrate the excitement and value of our field and also to bring our wideranging interests into a common focus.
REFERENCES 1 J. Peterson, Global population projections through the 21st century, Ambio, 13 (1984) 134- 141. 2 ESCAP, Human Settlements Atlas for Asia and the Pacific, Part III Urbanization and City Profiles, Publ. No. ST/ESCAP/354, United Nations, New York, 1986. 3 World Commission on Environment and Development, Our Common Future, Oxford University Press, Oxford, 1987. 4 J. E. Hardoy and D. Satterthwaite, Third World cities and the environment of poverty, Geoforum, 15 (1984) 307 - 333. 5 W. H. Weihe, Life expectancy in tropical climates and urbanization, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 313- 353. 6 V. Smil, The Bad Earth: Environmental Degradation in China, Zed Press, London, 1986.
73 7 Centre for Science and Environment, State of India's Environment: A Citizen's Report, New Delhi, 1983. 8 E. Jauregui, Urban climatology in the tropics, Report of First Session of CCl Working Group on Climate and Urban Areas including Building and other Aspects, WCAP-8, WMO/TD-No. 287, World Meteorological Organization, Geneva, pp. 13- 19. 9 J. F. Clarke and W, Bach, Comparison of the comfort conditions in different urban and suburban microenvi. ronments, Int. J. Biometeorol., 15 (1971) 41-54. 10 PAHO, Patterns of Urban Mortality, Sci. Publ. No. 151, Pan American Health Organization, Washington, DC, 1967. 11 I. R. Davis, The planning and maintenance of urban settlements to resist extreme climatic forces, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 277312. 12 T. Dunne, Urban hydrology in the tropics: problems, solutions, data collection and analysis, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 405434. 13 H. Akbari, R. Rosenfeld and H. Taha, Recent develop. ments in heat island studies: technical and policy, in K. Garbesi, H. Akbari and P. Martien (eds.), Con-
14
15
16 17
18
19
20
trolling Summer Heat Islands, Lawrence Berkeley Laboratory, Berkeley, 1989, pp. 14-30. T. J. Chandler, Urban climatology: Summary and Conclusions of the Symposium, Tech. Note No. 108, Publ. No. 254, World Meteorological Organization, Geneva, 1970, pp. 375-379. T. R. Oke, Towards a prescription for the greater use of climatic principles in settlement planning, Energy Build., 7(1984) 1 - 10. D. O. Lee, Urban climates, Prog. Phys. Geography, 8 (1984) 1- 31. E. Jauregui, Tropical urban climates: review and assessment, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 26- 45. S. Sham, Urbanization and the Atmospheric Environment in the Low Tropics, Penerbit Universiti Kebangsaan Malaysia, Bangi, 1987. T. R. Oke, Urban climatology and the tropical city: an introduction, in T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986, pp. 1 - 25. T. R. Oke (ed.), Urban Climatology and its Applications with Special Regard to Tropical Areas, Publ. No. 652, World Meteorological Organization, Geneva, 1986.