Anthropogenic aerosol influence on a mixed-phase cloud precipitation in early Meiyu season over Yangtze River Delta: simulated microphysical and thermodynamic effects

Abstract. The influence of anthropogenic aerosols on cloud formation and precipitation, through their effects on cloud microphysics and thermodynamics, is crucial for understanding the environmental impacts of human activities. This study uses the WRF-Chem model to simulate a mixed-phase cloud precipitation event during the early Meiyu season over the Yangtze River Delta, China, focusing on how anthropogenic aerosols influence cloud and precipitation processes via microphysical and thermodynamic mechanisms. Model experiments indicate that anthropogenic emissions, ranging from very low to normal levels, lead to a 2 % increase in ice crystal mixing ratio and a 50 % increase in latent heat release (peak at 8 km with a rate of 1.2 K h^-1), thereby strengthening convection and enhancing precipitation by 6 %. In contrast, high emissions elevate cloud condensation nuclei (CCN) and cloud droplet number concentration, but decrease ice crystal production by 14 % and reduce the mean radius of cloud droplets by 37 %. These changes weaken the falling speed and collision efficiency of cloud droplets, leading to enhanced evaporative cooling and reduced vertical velocity, ultimately resulting in a 28 % decrease in precipitation. Process analysis reveals that cloud droplets below 5 km are transported downstream and subsequently uplifted to 12 km, where they contribute to the formation of additional ice crystals, releasing latent heat that strengthens convection and increases precipitation in the downstream region. This work provides insights into the impacts of anthropogenic aerosol emissions on precipitation, offering valuable reference data for future research on aerosol-cloud-precipitation interactions.