Impacts of urban configuration on urban heat island: An empirical study in China mega-cities

Abstract

Urban configuration can influence the local thermal environment by altering energy balances. However, previous studies have found that either sprawling urban or compact urban development could intensify urban heat island (UHI) intensity. How urban configurations can mitigate the UHI intensity has drawn full attention. In this study, we quantified the diurnal and seasonal UHI intensities in 36 cities in China and investigated their response to urban configurations. In each city, urban land cover maps were classified from Landsat 8 and UHIs were quantified using Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST). Results show that the average UHI intensities of 36 cities vary temporally with a sequence of summer day > summer night > winter night > winter day. Moreover, whether the daytime UHI is higher or lower than the nighttime UHI significantly depends on climatic zones and seasons. Besides, we found that UHIs significantly correlate with urban configurations in two ways. First, for the spatial structure among built-up patches, a lower UHI located in the smaller built-up area with dispersed distribution when compared to the larger built-up patches, if the total built-up area holds constant. Second, for the spatial structure of a single patch, the single patch with more complex shape would mitigate the UHI intensities. Overall, urban configuration and other control variables (e.g., urban characteristics and climatic condition) can explain 41% and 51% of the variance in UHI in summer day and night, respectively. Therefore, the design of urban configuration can serve as an essential practice to mitigate UHI intensity. Considering the difficulties of altering the urban configuration in the urbanized area, planting vegetation might be a great choice to change the urban contiguity and shape complexity with providing an extra cooling effect.