Snowflake

Complex shapes emerge as the flake moves through differing temperature and humidity zones in the atmosphere, and possibly combines with other snowflakes.

The main constituent shapes for ice crystals, from which combinations may occur, are needle, column, plate, and rime.

Snowflakes nucleate around mineral or organic particles in moisture-saturated, subfreezing air masses.

Artificial nuclei include particles of silver iodide and dry ice, and these are used to stimulate precipitation in cloud seeding.

[6] Experiments show that "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than −35 °C (−31 °F).

The droplet then grows by deposition of water molecules in the air (vapor) onto the ice crystal surface where they are collected.

These large crystals are an efficient source of precipitation, since they fall through the atmosphere due to their mass, and may collide and stick together in clusters, or aggregates.

Ukichiro Nakaya developed a crystal morphology diagram, relating crystal shape to the temperature and moisture conditions under which they formed, which is summarized in the following table:[21] The shape of a snowflake is determined primarily by the temperature and humidity at which it is formed.

Many more complex growth patterns also form such as side-planes, bullet-rosettes and also planar types depending on the conditions and ice nuclei.

[8] Magono and Lee devised a classification of freshly formed snow crystals that includes 80 distinct shapes.

[30][31] The Book of Isaiah refers to the atonement of sins causing them to appear "white as snow" before God (cf.

For example, snow tires which enhance traction during harsh winter driving conditions are labelled with a snowflake on the mountain symbol.

[33][34] A six pointed stylized hexagonal snowflake used for the Order of Canada (a national honor system) has come to symbolize Canadians' northern heritage and diversity.

In the Tang Dynasty, snowflakes in poetry sometimes served as a symbol of the cosmic energy of the Tao and the Milky Way galaxy.