Examining the Sensitivity and Vulnerability to Summer Extreme Heat in Major Cities of the United States

Many cities are experiencing more and more frequent extreme heat events in hot summer because of the warming global temperature and urban heat island effects. The land surface temperature (LST) derived from remotely sensed thermal imageries has been widely used in understanding the spatial distribution of urban heat. However, the coarse resolution LST that indicates the surface temperature of building roofs and treetops, cannot fully indicate human heat stress levels. In this study, we applied urban microclimate modeling to map human heat stress indicator of Universal Thermal Climate Index (UTCI) at unprecedentedly fine spatial resolution level (1 m) and examined the human heat stress levels across different socioeconomic and racial/ethnic groups in 14 major cities in the United States. This study further investigated the sensitivity of human heat stress level to air temperature increase by modeling and mapping the UTCI in the scenarios of 1 ºC higher air temperature. Results show that there is no nationally consistent pattern between the association of social statuses and the heat stress level across cities, while generally, people with higher income tend to live in neighborhoods with less heat stress level. The sensitivity analysis results show that 1 ºC increase in air temperature would impact human heat stress level significantly, while the impacts are different for different cities. The results of this study will help us to better evaluate the impact of extreme heat on urban residents and provide reference for building more resilient cities to extreme heat.