Temporal variation in the impact of urban morphology on outdoor air temperature in the tropics: A campus case study

Abstract

Due to climate change and urbanisation, Singapore is suffering from a worsening urban heat island effect. The rising air temperature has significantly increased the energy required for building cooling and reduced thermal comfort in the microclimate. Based on continuous field measurements obtained on the Kent Ridge Campus of the National University of Singapore, this work reveals a clear diurnal pattern of urban morphological impact on outdoor air temperature. Seven urban morphology variables were extracted from a Geographical Information System map, three-dimensional model and site survey, as follows: the sky view factor, building cover ratio, ratio of height to building cover ratio, building wall area, impervious ground surface fraction, the green plot ratio and ground albedo. Sky view factor was the dominant variable in the heating interval (07:00–11:59). Building wall area and impervious ground surface fraction affected air temperature most in the exchange interval (12:00–18:59), peaking at around 15:00. Ratio of height to building cover ratio and ground albedo were positively correlated with air temperature in the exchange interval, but negative correlations were observed in the other periods. The developed models provide more accurate planning suggestions for buildings with different operating schedules. Providing sufficient shading and maximizing plant cover are suggested for urban heat island mitigation.