Role of Structural Morphology in Urban Heat Islands at Night Time

We study the dependence of the intensity of the urban heat island (UHI) on urban geometry. UHI is a urban climate phenomenon referring to the air temperature difference between rural and urban areas. We use multi-year data for urban-rural temperature differences, combined with building footprint data and a simple heat radiation scaling model to demonstrate for more than 50 cities world-wide that structural morphology -- measured by a building distribution function and the sky view factor -- explains city-to-city variations in nocturnal UHI. Our results show that the relation between UHI and the morphology is significantly stronger than the one with population, which in the past has been considered as the dominant factor.