Critical evaluation of the spatiotemporal behavior of UHI, through correlation analyses based on multi-city heterogeneous dataset

This study utilizes year-round temperature data observed in 15 cities around the United States (U.S.) to investigate the relationships between UHI and urban design attributes, and answer the following questions: (1) Whether and to what extent these relationships vary with the diurnal cycle and across seasons?, (2) What is the spatial extent within which UHI is affected by different urban variables?, and (3) Which climatic factors determine the correlations between UHI and urban variables? Our analysis revealed that while surface reflectance, vegetation and building height are more influential on winter UHI, the effect of anthropogenic heat and building density is independent of the season. Also, tree canopy cover, impervious area and built-up area were more dominant on nighttime UHI, and albedo, surface reflectance, vegetation and building height had stronger influence on daytime UHI. With regards to the spatial extent, while the effect of 3D urban variables and imperviousness was prominent in the immediate vicinity (250 m–1 km), the effect of vegetation, surface reflectance and anthropogenic factors extend to a larger surrounding area (4 km–8 km). Lastly, the relationships between UHI and urban variables were noted to be strongly driven by humidity in each location.