Solid Precipitation

About Solid Precipitation

Solid precipitation originates in clouds where air temperatures are below freezing (0˚C, 32˚F), and generally where ground temperatures are less than 5˚C (41˚F). Solid precipitation has a variety of forms including snow, snow grains, snow pellets, diamond dust, hail, and ice pellets:

• Snow is an aggregate of ice crystals. See also About Snow.
• Ice Crystal Precipitation is made up of small ice crystals that float with the wind and fall very slowly. It is also called "diamond dust".
• Snow grains: Precipitation of very small opaque white particles of ice which fall from a cloud and which are fairly flat or elongated with diameters generally less than 1 mm.
• Snow Pellets: Precipitation of white and opaque ice particles, which falls from a cloud. These particles are generally conical or rounded. Their diameter may attain 5 mm. The term "graupel" is also used.
• Hail: Precipitation of either transparent, or partly or completely opaque particles of ice (hailstones), usually spheroidal, conical or irregular in form and of diameter very generally between 5 and 50 mm, which falls from a cloud either separately or agglomerated into irregular lumps.

The WMO intercomparisons of methods of measuring solid precipitation have focussed on falling snow and did not include hail.

---