| MORPHOLOGICAL CLASSIFICATION |
PROCESS-ORIENTED CLASSIFICATION |
ADDITIONAL INFORMATION ON PHYSICAL PROCESSES AND STRENGTH |
| Basic Classification |
Subclass |
Shape |
Place of Formation |
Classification |
Physical Processes |
Dependence on most important parameters |
Common effect on strength |
| Faceted crystals |
Solid faceted particles |
Solid faceted crystals; usually hexagonal prisms |
Dry snow
|
Solid kinetic growth form |
Strong grain-to-grain vapor diffusion driven by large temperature gradient; excess vapor density above critical value for kinetic growth |
Growth rate increases with temperature gradient and decreasing density; may
not occuring in high-density snow because of small pores |
Strength decreases with increasing growth rate and grain size
|
| |
Small faceted particles |
Small faceted crystals in surface layer; <0.5mm in size |
Near surface |
Kinetic growth form at early stage of development |
May develop directly from precipitation particles or partly decomposed precip. Particles due to large, near-surface temperature gradients |
Temperature gradient may periodically change sign but remains at a high absolute value |
Low strength snow |
| |
Mixed forms |
Faceted particles with recent rounding of facets |
Near surface |
Transitional form as temperature gradient decreases |
Faceted grains are rounding due to decrease in temp. gradient |
|
|
| Cup-shaped crystals; Depth hoar |
Cup crystals |
Cup-shaped striated crystal; usually hollow |
Dry Snow |
Hollow or partly solid cup-shaped kinetic growth crystals |
Very fast growth at large temperature gradient |
Formation increases with increasing vapor flux |
Usually fragile but strength increases with density |
| |
Columns of depth hoar |
Large, cup-shaped striated hollow crystals arranged in columns (<10mm) |
Dry Snow |
Large cup-shaped kinetic growth forms arranged in columns |
Intergranular arrangement in columns; most of the lateral bonds between columns have disappeared during crystal growth |
Snow has almost recrystalized; high recrystalization rate for long period at low snow density and high exterrnal temperature gradient facilitates formation |
Very fragile snow |
