Abstract
Embryos of graupel particles were studied by the thin section technique under a polarization microscope and direct observation by picking graupel particles apart under a microscope. Snow crystals and a frozen drop were picked out from graupel particles. They were considered as embryos morphologically. And it was confirmed by numerical calculations that they satisfy the condition for the graupel growth. According to the embryo and falling behavior of graupel, the formation of graupel was classified and a few formation mechanisms were presented.
