Effects of urbanization on extreme precipitation based on Weather Research and Forecasting model: A case study of heavy rainfall in Beijing

Study Region: Beijing Study focus: Urbanization has altered the processes of the hydrological cycle in cities, further affecting their precipitation extremes. This study utilizes Weather Research and Forecasting model (WRF) to investigate the sensitivity of extreme precipitation to urbanization, exemplified by analyzing the "23.7" extraordinary rainstorm in Beijing.Two comparative urban development scenarios (1980 and 2020) were designed, using the real underlying surface as the static geographic data for the WRF model. Furthermore, the reliability of the model results was validated through an analysis of the extreme precipitation event that occurred in July 2021, reinforcing the findings of this study. New Hydrological Insights for the Region: The simulated precipitation is well represented by using the underlying surface data post-urbanization. Furthermore, the study reveals that urbanization has augmented the total rainfall of two extreme precipitation events in Beijing: the "23.7" event and the event on July 12, 2021. Specifically, there was an increase of 19.1 mm and 7.1 mm, respectively, in the rainfall within the core urban area during these two extreme precipitation events, when comparing the underlying surface scenarios from 1980 to 2020. Analyzing the impact mechanism, weakened horizontal winds in the urban core prolong water vapor residence, altering land surface energy balance to boost temperature and convection, both contributing to urban-induced precipitation increase.