Canopy-scale Built-environment Characteristics and Urban Heat Island Effect in a Tropical Medium-sized City

Abstract

Previous studies have found that built-environment characteristics in large cities produce important effects of the urban heat island (UHI) and know the horizontal space affected by the urban canopy microclimate ranges from about 30–200 m, but there are few studies in medium-sized cities. Therefore, this study investigates canopy-scale built-environment characteristics and their correlation with urban heat island (UHI) effects in Chiayi city, a tropical, medium-sized city. Under a 100 m buffer size, 2D and 3D built-environment factors such as the green coverage ratio (GCR), building coverage ratio (BCR), floor area ratio (FAR), and sky view factor (SVF) were first analyzed and then correlated with the UHI effect. The analyses were repeated on 200 and 1000 m scales and compared to previous studies. It was found that the built-environment factors were more strongly correlated with UHI under the 200 m buffer. Moreover, 2D factors such as the GCR and BCR had a higher correlation with UHI, especially in developing medium-sized cities. Regarding the GCR, BCR, and FAR, as expected, the correlation coefficients with UHI increased to 0.4 at 13:00 during the day and changed from 0.2 to 0.4 at 00:30 at night, whereas the correlation between the SVF and UHI was greatly different from the study area or calculation methods. The scale effect and SVF calculation methods are recommended for further study.

Advancing Urban Microclimate Monitoring: The Development of an Environmental Data Measurement Station Using a Low-Tech Approach

“…According to recent research, there are four different types of UHI: the surface heat island at the ground level, the canopy heat island that reaches up to the tallest buildings, the ground heat island that occurs within the soil [3], and the boundary layer heat island that occurs above the buildings and reaches the atmosphere [4,5]. There are two common ways to gather meteorological data on the UHI of the canopy layer: fixed measuring points through weather stations [6] and movable transects employing vehicles [7,8]. The main difficulty lies in balancing cost-effectiveness and spatial and temporal resolution, as each approach has distinct benefits and drawbacks [9].…”