Urban Climatic Map Studies: a Review
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INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. (2010) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/joc.2237 Urban climatic map studies: a review Ren Chao,a* Ng Edward Yan-yunga and Katzschner Lutzb a School of Architecture, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong b Department of Landscape and Urban Planning, University Kassel, Kassel, Germany ABSTRACT: Since their introduction 40 years ago, worldwide interest in urban climatic map (UCMap) studies has grown. Today, there are over 15 countries around the world processing their own climatic maps, developing urban climatic guidelines, and implementing mitigation measures for local planning practices. Facing the global issue of climate change, it is also necessary to include the changing climatic considerations holistically and strategically in the planning process, and to update city plans. This paper reviews progress in UCMap studies. The latest concepts, key methodologies, selected parameters, map structure, and the procedures of making UCMaps are described in the paper. The mitigation measures inspired by these studies and the associated urban climatic planning recommendations are also examined. More than 30 relevant studies around the world have been cited, and both significant developments and existing problems are discussed. The thermal environment and air ventilation condition within the urban canopy layer (UCL) of the city are important in the analytical processes of the climatic-environmental evaluation. Possible mitigation measures and planned actions include decreasing anthropogenic heat release, improving air ventilation at the pedestrian level, providing more shaded areas, increasing greenery, creating air paths, and controlling building morphologies. Further developments have and will continue to focus on the spatial analysis of human thermal comfort in urban outdoor environments and on the impacts and adaptations of climate change. Mapmakers must continue to share lessons and experiences with city planners and policy makers, especially in the rapidly expanding cities of developing countries and regions. Copyright 2010 Royal Meteorological Society KEY WORDS urban climate; climatopes; thermal environment; air ventilation; urban planning; urban climatic map Received 10 November 2009; Revised 11 August 2010; Accepted 31 August 2010 1. Introduction However, urban climatic consideration has thus far had a low impact on planning (Schiller and Evans, 1990/1991; More than half of the world population now lives in Eliasson, 2000). There is a need to bridge the gap between urban areas (UNFPA, 2007). By 2030, nearly 60% of urban climatology and town planning and urban design, the humanity will be urban dwellers (UN, 2008). The and to transfer the climatic knowledge into planning rapid urbanization in the past half a century has not only languages (Schiller and Evans, 1990/1991; Eliasson, brought new immigrants into the urban areas but has also 2000; Alcoforado et al., 2009). One important link is gradually changed the physical urban environment. Both to create an information platform for interdisciplinary the landscape transformation and the associated activities of urban areas have modified the city’s meteorology and communication and collaboration. urban climate (Esser, 1989; Lambin et al., 1999; Zhou The urban climatic map (UCMap) is an information et al., 2004; Lam, 2006; He et al., 2007), especially the and evaluation tool to integrate urban climatic factors climate below the rooftops of buildings or the urban and town planning considerations by presenting climatic canopy layer (UCL)(Oke, 1987; Mills, 1997; AMS, phenomena and problems into two-dimensional spatial 2010). In this layer, the climate is dominated by micro- maps (Baumuller¨ et al., 1992; VDI, 1997; Scherer et al., scale processes and exchanges, which are highly relevant 1999). It has two major components: the urban climatic to human comfort and the environmental health of the analysis map (or synthetic climate function map) (UC- city (Leung et al., 2008; Jendritzky et al., 2009). There AnMap) and the urban climatic planning recommenda- has been a worldwide vision to design cities that are tion map (UC-ReMap). This concept of UCMapping was sustainable, healthy, comfortable, and even enjoyable first developed by German researchers in the late 1970s (UN, 2008). To achieve this goal, it is necessary to (Matzarakis, 2005). To date, there are over 15 countries understand and apply urban climatic information in the around the world processing their own UCMap, apply- urban planning and design process (Cleugh et al., 2009). ing climatic measures and guidelines to local planning practices. In order to further develop our knowledge and to * Correspondence to: Ren Chao, School of Architecture, Room 514, Wong Foo Yuan Building, The Chinese University of Hong Kong, plan project studies concerning urban climatic planning Shatin, New Territory, Hong Kong SAR. E-mail: [email protected] strategies and application, it is useful to study past Copyright 2010 Royal Meteorological Society R. CHAO et al. developments and projects of UCMap. This paper is on the urban climate and air quality of study areas. Anal- the first review of the development of the UCMap tool. ysis of the thermal image and meteorological data was More than 30 relevant studies in the world are cited, conducted, and the car traverse measurement was also and both significant developments and existing problems carried out for examining the air temperature profile of are discussed. Selected examples of UCMap studies urban areas. A geographical distribution of topography, from different countries are compared and summarized. aerial views, thermal image, real land use, and urban air Secondly, the structure and the map-making procedure of paths were synergized and mapped with a grid resolution the UCMap are described by citing key examples. The of 250 m × 250 m with map drawings done manually analytical aspects and consideration parameters, as well (Mayer, 1988; Matzarakis, 2005; Matzarakis and Mayer, as any planning instructions and climatic considerations 2008). in planning, are elaborated. Thirdly, the advantages and In the 1990s, after the re-unification of Germany, sev- limitations of UCMap studies are discussed critically. eral cities in the northern part of the country conducted Finally, the review delineates the opinions of the authors synthetic climate function mapping (VDI, 1988; Helbig on the future of UCMap research and application. There et al., 1999; Matzarakis, 2005). Since 1992, the Section is still the need to apply and to refine the methodology, of Urban Climatology of the Office for Environmental and it is important to continue the communication and Protection in Stuttgart has conducted a series of cli- implementation of results in collaboration with city mate analysis studies, consequently providing a set of planners. climatic atlases for Neighborhood Association Stuttgart (Klimaatlas Nachbarschaftsverband Stuttgart), including synoptic maps, thermal maps, emission maps, climatic 2. Review of the development of UCMap study analysis map, and UC-ReMap in the geographic infor- mation system (GIS) (Klimaatlas, 1992). Thus, local In the field of UCMap study, German researcher Prof. planners could easily assess various climatic information Knoch (1951, 1963) first proposed a climate-mapping and evaluation results using the Stuttgart UCMap. The system for planning purposes. He suggested a series of project ‘STUTTGART 21’ developed over one hundred UCMapping with different scales in his publication Die climatic map layers at diverse scales that could be imple- Landesklima-aufanhme, which should be fitted into the mented at regional, city, and district planning levels. In local planning system. Since the 1970s, West Germany Berlin, another project titled ‘Berlin Digital Environmen- has intensified its geoscientific activities in presenting tal Atlas’ has been conducted since 1995. The UCMap, as maps relevant to planning (Luttig,¨ 1972, 1978a, 1978b). one of its eight environmental topics, has been produced Stuttgart climatologists led by Dr Baumuller¨ were the first for planning purposes to assist the design of settlement to conduct UCMap studies for mitigating air pollution areas, green and open space, to control traffic-related problems under weak wind conditions, and to apply air pollution, and to improve the air exchange of the the climatic knowledge into land use planning and urban areas (Berlin Government, 2008). For guiding prac- environmental planning (Baumuller¨ and Reuter, 1999; tice in Germany, the National Guideline-VDI 3787: Part Baumuller,¨ 2006). 1, namely, Environmental Meteorology Climate and Air In the 1980s, with the aim to control heavy metal pol- Pollution Maps for Cities and Regions, was published lution in the old industrial areas of the Ruhr, the Associ- in 1993 by the workgroup of UCMap at the German ation of Local Authorities of Ruhr Areas (Kommunalver- National Committee of Applied Urban Climatology. It ban Ruhrgebiet: KVR, 1992) implemented clean air man- aimed to define the symbols and representations used in agement programs using the UC-AnMap to differentiate UCMap studies to recommend methods of developing the areas according to their different climatic functions urban climatic and air pollution maps, and to create a and characteristics. More than 25 cities in the Ruhr Areas standard for their application. Thus, this Guideline-VDI were involved in this project;