320 
diagram given in Figure 3 can be used to repre- 
sent the various stages in the development of a 
hailstone. On the left the type of growth is 
given, whether by sublimation or accretion of 
drops, and on the right the main growth phase. 
This may consist either of an increase in volume 
or of an increase in particle density. Figure 3 also 
shows whether the accreted drops freeze slowly 
or quickly. 
While there is no need to give a definition of 
freezing nuclei and ice crystals, the other par- 
ticles may be characterized as follows: 
Graupel (soft 
are white opaque particles, resembling sectors 
of spheres, roundish or irregular in shape, and 
with a diameter rarely exceeding 7 mm. Origin: 
through the accretion of 
hail)—Appearance: Graupel 
Graupel originate 
cloud drops on an initial ice crystal which has 
grown by sublimation. Water caught up in this 
way freezes relatively quickly at the point of 
contact. 
ROLAND LIST 
Small Hail—Appearance: Small hail particles 
are particles having generally rounded surfaces, 
but of conical, spherical, or irregular shape. They 
appear white and opaque in parts; certain zones 
of their surface are glassy or wet. Their diameters 
rarely exceed 7 mm. Origin: Small hail originates 
through aceretion of water drops on graupel. 
Freezing takes place slowly, so that the floating 
water has time to spread out and penetrate the 
air capillaries on the original graupel. It may 
freeze entirely or in part. 
Hailstones—Appearance: Hailstones are trans- 
parent or partially opaque particles with a di- 
ameter of about 5 to 150 mm or more. The num- 
ber of shapes which are met with is extremely 
large; the structure is most frequently ‘onion- 
skin’ with alternating clear and opaque (white) 
layers. Larger hailstones often contain liquid 
water in a system of connected caverns. Origin: 
Hailstones originate from small hail through ac- 
Fia. 4 
Thin section of a graupel under translucent light; height, 4.5 mm 
