Effect of Mutual Cloud–Aerosol Interaction on a Mesoscale Convective System

Cloud–aerosol interaction is a critical area of research in atmospheric science. Many numerical studies have primarily focused on one-way interactions, examining how aerosols influence the dynamics and microphysics of individual clouds and cloud systems. In this study, we simulate a mesoscale convective system using a mixed-phase spectral bin microphysics Weather Research and Forecasting (WRF) Model that explicitly incorporates two-way cloud–aerosol interactions. The model includes an aerosol budget that tracks aerosols as they are activated into cloud droplets, evolve through droplet collisions, and are incorporated into ice hydrometeors via immersion freezing. Aerosol mass increases in cloud droplets due to droplet–droplet collisions and in ice particles through drop–ice and ice–ice collisions. Eventually, aerosols are either released back into the environment through droplet evaporation and ice sublimation or removed from the atmosphere by precipitating to the surface. The results show that deep convective clouds efficiently transport aerosols to the upper atmosphere, shaping the vertical profiles of aerosol concentration. The release of aerosols significantly increases background aerosol concentrations across a broad area surrounding the mesoscale convective system both at the upper layer and in the boundary layer. Furthermore, the clouds are found to be efficient generators of giant cloud condensation nuclei (CCN). A portion of the released aerosols is reentrained into the cloud through lateral boundaries, leading to notable changes in cloud microphysics. These include increased droplet concentrations, enhanced hail mass content in the convective region, and increased snow mass content in the stratiform region. The rise in droplet concentration strengthens cloud dynamics and influences the precipitation rate. These findings highlight that feedbacks within cloud–aerosol interactions are a crucial component of the overall cloud–aerosol system and must be considered in future modeling and observational studies. SIGNIFICANCE STATEMENT: Cloud–aerosol interaction is a key area of research in atmospheric science, as aerosols influence cloud microphysics, dynamics, and radiative properties. Traditionally, many studies have focused on one-way interactions, where clouds evolve in the presence of a fixed background aerosol field. However, two-way cloud–aerosol interactions play a critical role in the evolution of both cloud systems and the atmospheric aerosol population. We consider three key findings of the study as primary results: 1) Deep convective clouds enhance both the concentration and mass of aerosols in their surrounding environment. These clouds play a critical role in shaping the vertical distribution of aerosol concentration and size. One key implication of this finding is that it is incorrect to assume that ambient aerosols remain unchanged in simulations involving convection. Furthermore, it is inaccurate to consider aerosol scavenging as the sole influence of clouds on aerosols; 2) clouds can generate large aerosol particles, which may impact the microphysical properties of subsequent cloud generations; and 3) the reentrainment of released aerosols can significantly influence the microphysics of the parent clouds and affect precipitation processes.