Abstract
This study took Chiayi City—a tropical, medium-sized city—as an example to investigate the urban heat island (UHI) effect using mobile transects and built environment characteristics in 2018. The findings were compared to those from a study in 1999 to explore the spatiotemporal changes in the built environment characteristics and UHI phenomenon. The result for the UHI intensity (UHII) during the day was approximately 4.1 °C and at midnight was approximately 2.5 °C. Compared with the survey in 1999, the UHII during the day increased by approximately 1.3 °C, and the UHII at midnight decreased by approximately 1.2 °C. The trend of the spatial distribution of the increasing artificial area ratio (AAR) proved the importance of urban land use expansion on UHI. The results of the air temperature survey were incorporated with the nesting space in GIS to explore the role of built environment characteristics in UHI effects. The higher the population density (PD) and artificial area ratio (AAR) were, the closer the proximity was to the downtown area. The green area ratio (GAR) was less than 0.2 in the downtown area and increased closer to the rural areas. The built environment factors were analyzed in detail and correlated with the UHI effect. The air temperature in the daytime increased with the population density (PD) and artificial area ratio (AAR), but decreased with the green area ratio (GAR) (r = ±0.3–0.4). The result showed good agreement with previous studies.
Highlights
Rapid social and economic growth and prosperity have affected the urban thermal environment and caused changes in the local climate, environment, and quality of life of residents
The effects were investigated of urban development in a tropical area on urban sprawl, the urban heat island (UHI) effect, and metropolitan weather phenomena that are related to the quality of urban life in the Hanoi metropolitan area in Vietnam
The daytime and nighttime measurement periods were from 12:00 to 14:00 and from 2:00 to 4:00, respectively, and the time synchronization point was 14:00 and 2:00, respectively [24,25]. This allowed us to compare these data in detail to those of the present work to understand the spatiotemporal changes in the built environment characteristics and UHI
Summary
Rapid social and economic growth and prosperity have affected the urban thermal environment and caused changes in the local climate, environment, and quality of life of residents. The urban heat island intensity (UHII), which is the maximum temperature difference between the urban and rural areas, is usually used to measure the severity of UHI [2]. From the 2000–2015 Bangkok survey, it was found that urban physical characteristics have a significant impact on the UHI magnitude, the floor area ratio (FAR) and building coverage ratio (BCR), in which temperature levels at 10 p.m. and the thermal cooling rate between 4 and 10 p.m. had a correlation value (r) of over 0.50 [11]. In the city of Bogotá, Colombia, the relationship between the UHI and population size was studied while considering population density and urban form parameters of different neighborhoods.
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