Observations and numerical simulations of precipitation development in seeded clouds over the Sierra Nevada

The particle growth model of Heymsfield embedded in a kinematic flow field representative of the Sierra barrier was used to study the ice particle growth by diffusion, accretion and subsequent fall trajectories. The particles observed by the aircraft were classified into habits. The key findings of this study were: i) aggregates (>1 mm) form in 4-8 minutes after seeding a convective cloud. ii) Riming is important close to the barrier in a stratiform cloud when large cloud droplets and liquid water up to 0.3 g m^-3 are present. iii) Diffusional growth is extremely important for temperatures near -15°C in these low liquid water content clouds. The particles grow to ~2 mm when released from just colder than -15°C, and to ~1 mm when falling from warmer than -15°C. -from Authors