Urban Physical Environments and the Duration of High Air Temperature: Focusing on Solar Radiation Trapping Effects

Abstract

Urban heat island effects, which are the phenomenon wherein higher ambient air temperatures are measured in cities than in rural areas, have worsened urban thermal environments over the past decades. This study aims to analyze the effects of urban physical environments on the duration of high air temperature, using climate data collected from 217 Automatic Weather Stations in Seoul, Korea. In order to specify radiation trapping effects, interaction effects between sky view factors (SVF) and albedo values were analyzed using multiple regression analysis. The results indicate that increases in commercial and traffic areas lead to longer durations of high air temperature and that high urban porosity shortens the duration of high air temperature by improving urban ventilation. This study also indicates that the duration of high air temperature has a negative association with SVF; however, an analysis of interaction effects indicates that high-albedo materials diminish the positive effects of high SVF largely because of radiation trapping effects. These findings suggest that urban ventilation paths, high SVF, and materials with an appropriate albedo value play important roles in improving thermal comfort conditions, such as the duration of high air temperature.

Quantifying Impacts of Urban Microclimate on a Building Energy Consumption—A Case Study

“…In the last two decades, numerous cities face serious problems of rapid urbanization [1,2], energy consumption [3][4][5][6][7], and climate change [8,9]. It is estimated more than 70% of people will reside in the built environment by 2050.…”

The Effects of the Layouts of Vegetation and Wind Flow in an Apartment Housing Complex to Mitigate Outdoor Microclimate Air Temperature

“…The report anticipates that this trend will continue to be exacerbated, by which many people in Seoul will be adversely affected [4]. To cope with this issue, the Seoul Metropolitan Government has implemented UHI mitigation strategies including the expansion of vegetated areas, open water surfaces, cool paving materials, and wind corridors [5]. These strategies help reduce air temperatures by increasing urban albedo reflecting solar radiation, evaporation absorbing heat, and air flow for ventilation.…”

“…These strategies help reduce air temperatures by increasing urban albedo reflecting solar radiation, evaporation absorbing heat, and air flow for ventilation. A number of previous studies have also broadly explored the roles of albedo [6,7], vegetation [8,9], and air flow [5,10] to moderate air temperature at the microclimate level, as well as in cases of the UHI effect.…”

“…Many studies also showed that increasing air flow mitigates air temperature. Choi et al [5] suggested wind corridors, which can mitigate urban heat by stimulating air flow or ventilation, leading to shorter durations of high air temperatures. They also demonstrated that urban porosity can increase urban ventilation performance by creating more spaces for wind corridors, which results in ameliorating pedestrian thermal discomfort [5].…”

“…Choi et al [5] suggested wind corridors, which can mitigate urban heat by stimulating air flow or ventilation, leading to shorter durations of high air temperatures. They also demonstrated that urban porosity can increase urban ventilation performance by creating more spaces for wind corridors, which results in ameliorating pedestrian thermal discomfort [5]. Bernard et al [15] considered vegetation and wind by suggesting design directions for a park and its surrounding urban morphology, in which parks in cities function as cool air drainage.…”