The application of a high-density street-level air temperature observation network (HiSAN): Dynamic variation characteristics of urban heat island in Tainan, Taiwan.

The effects of urban heat island (UHI) have recently become a crucial issue. This study utilized a high-density street-level air temperature observation network (HiSAN) to understand the UHI characteristics in Tainan City. A total of 100 measurement points were established throughout the city. The average distance between two neighboring measuring points was 1.9 km in rural areas and 0.8 km in metropolitan areas. The UHI caused a temperature differences of at least 3 °C in each month over the study period, and the UHI's centric point moved from west to east during the day and from east to west at night, mainly because of the physical effects of the different urban environment including location and the impermeable surface area (ISA), total floor area, and sky view factor in urban areas. The results also indicated that factors such as ISA and distance to the coast had the strongest influence on thermal conditions at various times, especially in the areas far from the coast during the hot season. This was mainly because of differences in how heat was retained over the study area. The HiSAN method can be used by urban planners, architects, and policymakers to mitigate the thermal stresses caused by complex urban environments.