Amplified Increases of Compound Hot Extremes Over Urban Land in China

Abstract

Abstract Consecutive hot periods without nighttime heat relief significantly increase mortality and morbidity rates. Using the Geophysical Fluid Dynamics Laboratory land model coupled with a newly developed and validated urban canopy model, changes in three types of summertime hot extremes, that is, independent hot days, independent hot nights, and compound hot events (CHEs), in the 21st century are quantified in China. Results indicate that all three types of hot extremes become more frequent, and CHEs are projected to be the dominant type at the end of this century under the representative concentration pathway 8.5 scenario. Furthermore, compared to the rural land, the urban land experiences even stronger increases in CHEs in terms of frequency, duration, and intensity. These faster increases of CHEs in urban areas highlight the urgency of developing and implementing mitigation and adaptation strategies to combat the adverse health effects of global warming and urban heat islands.