Simulation and Assessment of Extreme Precipitation in the Pearl River Delta Based on the WRF-UCM Model

The impact of urbanization on the spatial distribution of extreme precipitation has become a major topic in the field of urban hydrology. This study used an urban canopy model (UCM) coupled with a Weather Research and Forecasting model (WRF) to analyze two extreme precipitation events experienced by the Pearl River Delta on 12–13 June (monsoon rainstorm) and 16–17 September (typhoon rainstorm) in 2018. The results showed that both experiments, considering UCM and not considering UCM, can effectively simulate the spatial distribution of two precipitation events in Pearl River Delta urban agglomeration. The root mean square errors of simulation and observation data of the two precipitation events by the UCM scheme were 14.6 mm and 16.7 mm, respectively, indicating relatively high simulation accuracy. The simulated precipitation amounts for the two rainfall events were increased by 2.3 mm and 3.0 mm, respectively. The simulation results of the two precipitation events showed that compared to agricultural land, urban and built-up land have experienced temperature increases of approximately 0.7 °C and 1 °C, respectively. The air-specific humidity of the two precipitation events increased by approximately 0.5 g/kg and 1.2 g/kg, respectively. These differences between UCM and NON simulations confirm that the increase in near-surface air humidity and temperature significantly enhances the intensity of extreme precipitation in the Pearl River Delta urban agglomeration.