Megacity effects on rainfall induced by Typhoon Nida

Megacities, with their unique land cover and high pollutant emissions, may influence the outer rainband of approaching typhoons. Here we demonstrate, through numerical simulations and sensitivity experiments, that the Pearl River Delta megacity enhanced convection and precipitation during Typhoon Nida in 2016 offering insights into how urbanization influences precipitation processes. We find that the impact of urban land and anthropogenic heat is more pronounced than that of anthropogenic aerosols. Urban land cover and anthropogenic heat enhance, respectively, surface friction and exacerbate the heat island, driving low-level convergence and enhancing the warm-rain process. In contrast, aerosols primarily enhance the cloud-condensation nuclei concentration and strengthen ice-phase processes. This study underscores the critical importance of accounting for both urban land effects and human activities (anthropogenic heat and aerosol emissions) in understanding and predicting the impact of megacities on urban precipitation. Megacity effects in the Pearl River Delta significantly enhanced convection and precipitation during Typhoon Nida through urban land cover and anthropogenic heat impacts, according to high-resolution simulations and sensitivity experiments.