Development of a micro-scale heat island (MHI) model to assess the thermal environment in urban street canyons

Abstract

The urban thermal environment has a direct impact on the outdoor thermal comfort of city dwellers and pedestrians, which can have negative effects on their health and overall quality of life. Therefore, it is crucial to estimate the influence of the thermal environment in micro-scale urban spaces. Previous studies have used estimation models that only consider a limited number of meteorological elements and urban geometry. This study developed a new model that incorporates the concept of micro-scale heat islands (MHIs) using field measurements to estimate the micro-scale thermal environment in urban spaces. The study found that factors such as sky view factor (SVF), floor area ratio (FAR), and building coverage ratio (BCR) have a significant impact on the thermal environment of urban street canyons. Based on these results, an MHI model was developed and tested. In this process, the aspect ratio (H/W) concept was extended to a three-dimensional perspective and used to calculate the amount of heat contained in the air volume in a street canyon. This study applied a method of maximizing the use of data collected in the study area using a mobile weather station. SVF, air temperature, and surface temperature were reflected in calculating the net radiation and sensible heat flux. The MHI model showed 86.19% explanatory power in estimating the thermal environment of urban canyons. The model would benefit from further refinement by incorporating data from various cities and reflecting the characteristics of different climatic regions and urban forms.