The Impact of Aerosol on Liquid‐Ice Phase Transition and Precipitation Formation in Mixed‐Phase Clouds: A Case Study

This study investigates how aerosol perturbations influence precipitation formation in supercooled stratiform clouds with different supercooled liquid water content (SLWC). Numerical experiments are performed using the WRF‐SBM model with different concentrations of cloud condensation nuclei (CCN) and ice‐nucleating particle (IN) within the same cloud field. Two cloud systems with contrasting SLWC are identified under similar large‐scale environmental conditions. The results show that the two systems exhibit distinctly different responses to aerosol perturbations. In the low‐SLWC cloud system, precipitation is more sensitive to increased CCN. The enhancement of CCN leads to an increase in the concentration of cloud droplets and a suppression of collision‐coalescence processes. This enables more supercooled liquid water to accumulate, which in turn promotes the growth of ice through vapor deposition and riming. Ultimately, this results in increased melting and precipitation. Conversely, the high‐SLWC system exhibits a more pronounced response to elevated IN concentrations. The abundance of supercooled liquid water facilitates efficient ice crystal nucleation and rapid depositional growth, thereby augmenting snow mass and overall precipitation. Further analysis indicates that SLWC regulates the efficiency of liquid‐to‐ice conversion processes. In the low‐SLWC system, increasing CCN mainly increases the supercooled liquid water reservoir, whereas increasing IN enhances the efficiency of the riming process in the high‐SLWC system. These results highlight that aerosol impacts on precipitation are strongly regime‐dependent and controlled by the availability of supercooled liquid water.