Large ice particles play a central role in the physics of clouds and precipitation, especially in deep convective clouds. Two processes are important for the formation of large ice particles, namely, the clumping and riming processes. The clumping processes produces snow aggregates which may serve as the embryos of graupel and hails. The graupel and hails then grow by riming and recycling through dry and wet growth stages. In the riming process, latent heat will be released which may influence the cloud dynamics. The impacts of these processes depend very much on the ice particle growth rates. Unfortunately, our previous understanding of the ice growth process is mostly qualitative. The main difficulty lies in the facts that ice particles have complicated shapes and thus complicated hudrodynamical behavior and that the motions are unsteady. Under this grant, Professor Wang will use the cloud tunnel at the University of California, Los Angles to conduct experiments of ice crystal aggregation, and also carry out theoretical computations of ice crystal motion in air. Professor Wang is competent and well qualified to carry out the work.
