On the Relationship between Urbanization and Extreme Rainfall in a Warming Climate

More than half of the global population now resides in urban areas, and that number is expected to increase to 60% by 2030 and 70% by 2050. Under the warming climate, extreme precipitation, short-term extreme precipitation in particular, tends to increase, leading to a higher risk of flood disasters in urban areas and posing greater challenges to urban construction and social emergency management. Cities themselves can affect the dynamic and thermodynamic structure of the atmosphere through, e.g., the urban heat island effect, increased surface friction, and anthropogenic aerosol emissions, which then influence the evolution of convection and the associated precipitation. The related nonlinear physical processes are very complex. This five-part talk will mainly present our recent studies on the relationship between urbanization and extreme precipitation in China. First, a background on changes of urban extreme precipitation worldwide. Second, the physical processes producing extreme hourly precipitation in the two major coastal urban agglomerations in China (i.e., the Pearl River Delta and the Yangtze River Delta), focusing on the collective roles played by multiple cities, coastlines and topography. Third, the possible impact of urbanization on the disastrous extreme rainfall event in Zhengzhou, the capital city of Henan Province in central China on July 20, 2022. Fourth, the high uncertainty of modeling urban extreme precipitation at monsoon coast (South China) using an advanced regional earth system model at convection-permitting resolutions. Finally, concluding remarks.