¥Hailstones are covered by a layer of
liquid water.
¥The thin layer of liquid is positively
charged.
¥When hailstones and ice crystals
collide, some of liquid
molecules stick to the ice crystals.
¥Along with the mass transfer, positive
ions transfer
from the hailstones to the ice crystals.
¥The heavier, negative hail falls to cloud
bottom.
¥The lighter, positive ice crystals drift to
cloud top.
¥Produces negative lower, positive upper
cloud.