The Microphysics of the Warm-Rain and Ice Crystal Processes of Precipitation in Simulated Continental Convective Storms

Precipitation in clouds can develop through warm-rain processes or ice crystal formation, referred to as warm and cold pathways, respectively. This study investigates the contributions of these pathways to surface precipitation in simulated continental convective storms. We analyze three distinct storm types: cold-based, slightly warm-based, and very warm-based convective storms. Using tracer-tagging techniques within our aerosol-cloud model, we trace the microphysical pathways leading to precipitation. Our results reveal that in cold- and slightly warm-based clouds, the cold components of graupel and rain mass outweigh the warm components. Conversely, in very warm-based clouds, nearly 80% of surface precipitation is generated through warm-rain processes. A reduction in cloud base altitude to levels approximately 10-20 K warmer shifts the predominant precipitation pathway to warm processes, driven by increased moisture in the planetary boundary layer and the growth of larger cloud droplets that enhance raindrop freezing. Our simulations demonstrate that both warm and cold processes coexist within any storm, with their balance dictated by cloud base temperature and solute aerosol conditions. Finally, we discuss the implications for secondary ice production (SIP) mechanisms in relation to the balance between warm and cold precipitation processes.