The surface urban heat island response to urban expansion: A panel analysis for the conterminous United States

Abstract Urban heat island(UHI), the phenomenon that urban areasexperience higher temperatures compared to their surrounding rural areas, has significant socioeconomic and environmental impacts. With current and anticipated rapid urbanization, improved understanding of the response of UHI to urbanizationis important for developing effective adaptation measures and mitigation strategies. Current studies mainly focus on a single or a few big cities and knowledge on the response of UHI to urbanizationfor large areas is limited. As a major indicator of urbanization, urban areasize lends itself well for representation in prognostic models. However, we have little knowledge on how UHI responds to urban areasize increase and its spatial and temporal variation over large areas. In this study, we investigated the relationship between surface UHI (SUHI) and urban areasize in the climate and ecological context, and its spatial and temporal variations, based on a panel analysisof about 5000 urban areasof 10 km 2 or larger, in the conterminous U.S. We found statistically significant positive relationship between SUHI and urban areasize, and doubling the urban areasize led to a SUHI increase as high as 0.7 °C. The response of SUHI to the increase of urban areasize shows spatial and temporal variations, with stronger SUHI increase in Northern U.S., and during daytime and summer. Urban areasize alone can explain as much as 87% of the variance of SUHI among cities studied, but with large spatial and temporal variations. Urban areasize shows higher association with SUHI in regions where the thermal characteristics of land cover surrounding the urban areaare more homogeneous, such as in Eastern U.S., and in the summer months. This study provides a practical approach for large-scale assessment and modeling of the impact of urbanizationon SUHI, both spatially and temporally.