It is well understood that aerosol can impact the microphysics of clouds. What is less well understood is how much impact they have in various cloud types and what subsequent effects they have on cloud characteristics, such as cloud lifetime and precipitation efficiency. Some of the variability in how aerosol impacts cloud microphysics comes from whether the aerosol serves as cloud condensation nuclei (CCN) or ice nucleating particles (INPs). Tropospheric clouds are influenced and perturbed by aerosols in many ways, either sudden bursts of the natural aerosol abundance by, for example, fires or volcanoes, strong anthropogenic aerosol sources, or cloud seeding activities. In some places, especially more arid regions, clouds are seeded with specific aerosols to try to increase precipitation efficiency and to enhance precipitation reaching the ground. Silver iodide (AgI) is a common aerosol used in cloud seeding to act as INP; however, some cloud seeding methods may utilize other agents, such as hygroscopic aerosol particles to serve as giant CCN, or newly designed hygroscopic and ice nucleating particles.  Recent numerical modeling capabilities and field programs have advanced scientific research on the microphysical effects of seeding clouds with aerosol, especially with AgI. This session solicits papers discussing the microphysical impact of aerosol on clouds, including those perturbed by seeding activities.

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