The application of a high-density street-level air temperature observation network (HiSAN): The relationship between air temperature, urban development, and geographic features.

The urban heat island effect in cities has become an important problem in relation to not only urban climate but also public health and urban planning. Tainan, which located in Southern Taiwan, is a compact city with intense development. Therefore, this study investigated the urban thermal condition by employing a high-density street-level air temperature observation network (HiSAN). A total of 100 measurement points were set in various urban development areas. The geographic factors in Tainan can be used for indicating the relationship between thermal conditions and urban built environments to comprehensively compare the approaches, such as conducting traverse measurement and utilizing only a single datum or a small amount of weather station data. Buffer zone analysis was used in this study for zones of different sizes, and it was determined that a 300-m scale is optimal to illustrate the effects of land features on microclimate. The results revealed that the thermal condition in Tainan is influenced by urban development factors, such as the floor area and land cover area, and by geographic factors, such as the distance to the sea. A better cooling effect can be obtained from a vegetation area during the night time and from a water body during the daytime. Moreover, different cooling effects are observed based on the distance to the sea. Through these results, a model for predicting the thermal condition for different periods can be established using a multiple regression model. Urban planners and architects can proffer design and planning suggestions for different areas based on the findings of this study to reduce thermal stress in urban areas.