Impacts of aerosol-radiation and aerosol-cloud interactions on a short-Term heavy-rainfall event-a case study in the Guanzhong Basin, China

Atmospheric aerosols influence clouds and precipitation by aerosol-radiation interactions (ARIs) and aerosol-cloud interactions (ACIs). In this study, the synergetic effect of ARIs and ACIs on the development and precipitation of a mesoscale convective system (MCS) that occurred in the Guanzhong Basin (GZB) of central China have been examined using a cloud-resolving fully coupled weather research and forecasting model with chemistry (WRF-Chem). The model reasonably reproduces the temporal variation and spatial distribution of air pollutants, the hourly rain rate, and daily precipitation distribution against observations in the GZB. Sensitivity simulations are conducted under different aerosol scenarios by adjusting the anthropogenic emissions. When the ARI effect is not considered, the daily precipitation does not show an increasing trend with increasing aerosols in the GZB. This primarily reflects the effects of ACIs due to competition among convective clouds to available water vapor in the development of the MCS. ARIs exert two opposite effects on convection: A stabilizing effect to suppress convection and a lifting effect to foster convection, which counteract each other. When the lifting effect outweighs stabilizing effect, the updraft is enhanced, which increases precipitation in the GZB. However, the synergetic effect of ARIs and ACIs significantly suppress precipitation when the particulate-matter (PM) pollution is severe. Note that the synergetic effect consistently decreases the precipitation in the whole domain with increasing aerosols, but ARIs play a more important role in the decreasing trend of the precipitation with deterioration of PM pollution.