Microphysical Effects of Seeding Wintertime Stratiform Clouds Near the Sierra Nevada Mountains

Abstract

The microphysical consequences of seeding stratiform clouds near the Sierra Nevada Mountains are examined. Airborne seeding was conducted with droppable AgI flares released every 250 m and with dry ice pellets released at a rate of 0.1 g m?1 into the clouds having widespread liquid water contents ?0.1 g m?3. The Wyoming King Air penetrated the AgI curtains for ?1 h after seeding. The CO2 ice crystal curtain could not be determined beyond ?10 min because of natural cloud glaciation. Precipitation sized particles grew mainly by diffusion, and particle size spectra at particular levels below cloud top reached and maintained equilibrium shapes as a consequence of particles falling from higher levels.