อิทธิพลของโครงสร้างทางกายภาพต่อการแพร่กระจายความเย็นของพื้นที่สีเขียวเพื่อบรรเทาปรากฏการณ์เกาะความร้อนในเมืองเชียงใหม่

Abstract

The research aimed to study an influence of physical structure on cooling effect of green space for urban heat island mitigation in Chiang Mai city. The research itself had objectives as follows: 1.) to study the interrelated patterns of both time and spatial changes on heat island 2.) to analyze the spatial relationship between land-cover and surface temperature 3.) to analyze the relationship of the physical structure towards both surrounding temperature and wind flow speed respectively, at its different potentials 4.) to explore the possible ways to enhance the cooling effect efficiency of green spaces through collecting data both in the fieldwork survey and statistic collection, along with the data from Landsat 8’s satellite image interpretation. The result had found that the urban heat island in Chiang Mai has greatly changed over 15 years during 2002 – 2016. To explain, the rural representative station occupied higher temperature of heat island than that of the city representative station, specifically in 2009. This was due to the fact that an expansion of hard surface which is being considered an important factor of surface temperature increased. Still, the expansion of hard surface also made the pattern of heat island grow instantly in accordance with urban expansion. This was considered the changes in terms of time and space. Moreover, the analysis of the spatial relationship between landcover and temperature of Chiang Mai had revealed that the physical structure affected temperature significantly. This proved through the hard-characteristic land use, such as high crowded urban---- while soft-characteristic land use was exemplified by moderate crowded areas related to its temperature. To simplify, higher temperature had found in downtown or center of the city. On the other hand, the lower temperature had found in the area that consisted of green land use which was able to create a cool island (Park Cool Island) for its surrounding areas. This was a result of the cooling effects onto green spaces in public green areas at different potentials which were as follows: mini park, neighborhood park, and community park. The result of their efficiencies was revealed that the cooling effects of mini park is less efficiency than the community garden. The railway park (community garden) with its size at 60.5 rai had the distance of cooling effects of 75 - 100 meters, while Nong Buak Haad Health Park (neighborhood park) with its size at 12.42 rai had the distance of cooling effects of 25 - 75 meters. In addition, the cooling effects also further generated the cool island of its surroundings up to 200 meters away in the area around the Baan Den Health Park. However, the efficiency of cooling effects still depended on the physical structure of the green area which was comprised of physical factors, urban geometry, and land use. The proper physical structure of the green area was able to further enhance the efficiency of cooling effects. The results of the study could suggest possible ways to increase the efficiency of cooling effects of urban green spaces. For example, increasing the soft surfaces in the park at different levels, expanding an existing park to a level as same as the neighborhood park to have more green areas in order to increase the cooling effects, adding soft surfaces inside and around both public and private buildings, or even adding green roof areas that could help reduce the surface temperature and produced cooling effects to alleviate the urban heat island.