Winter is one of the most waited for seasons in a year. Beautiful icy patterns on your windows are such an art made by nature, and can only be seen in winter. Snow boarding, ice skating, winter is just a perfect time for having fun. How can winter be this fun? Of course by the precipitation that it produces. As the sun moves to another side of the earth, temperatures start to decrease. When it is cool enough and the temperature falls below zero degrees, solid precipitations – the snow – form and fall to the earth. Snow itself is actually composed by a multitude of smaller ice particles called snow crystals (the term of “Snow flakes” is also most likely used). If you see the lake start to freeze and water on the street turns into ice, you can tell that snow will fall from the clouds above in a moment. There are several different types of snow.
Mainly, they are classified by the shape of the flakes, description of how it is falling, and by how it collects on the ground.
1. By the Shape of Flakes
Snow crystals form when water vapor condenses directly into ice in clouds. As the crystals grow, the pattern emerges. The results are snow crystals with different shapes, depending on the temperature when it forms. In 1951, a classification system for solid precipitation was made by International Commission on Snow and Ice. It defined seven principal types of snow crystals, which are plates, stellar crystals, columns, needles, spatial dendrites, capped columns, and irregular forms. Some sources even classified shapes of flakes only into four. In fact, dividing different types of flake shapes is actually a matter of taste. While Ukichiro Nakaya, a physicist, divided snow crystal shapes into 41; C. Magono and C.W. Lee, meteorologist, divided snow crystal into 80 different types. Below are several examples of different snow flake shapes:
* Simple Prisms
It is the most basic of snow crystal shape – the hexagonal prism. They can appear as thin hexagonal prisms or slender hexagonal columns, depending on how fast the different facets grow.
* Stellar Plates
These common snowflakes are thin, plate-like crystals, with six arms that form star-like shape.
* Sectored Plates
Sometimes stellar plates show distinctive ridges that point to the corner between adjacent prism facets. When these ridges are prominent, they are called sectored plates.
* Stellar Dendrites
In Greek, Dendrite means “Tree”. A crystal dendrite is a crystal that develops with a typical multi branching tree-like form. They are plate-like snow crystals with branches and side branches. Forming under extremely cold conditions, -20 C to -25 C, Stellar dendrites are large crystals, usually 2-4 mm in size and can be easily seen by naked eye.
*Fern-like Stellar Dendrites
These are actually stellar dendrites with a lot of side branches, so that they look like ferns. This type of flakes has the largest diameter size, about 5 mm or more. The best snow powder is usually composed by stellar dendrites and fern-like dendrites, since these crystals are extremely thin and light, forming a low density snow pack.
* Needles
The length of these crystals is much longer than its diameter, just like needle. They are slender, columnar ice crystals which grow when the temperature is around -5 C (23 F)
* Rimed Snow
When snow flakes pass through a super cooled cloud, they will be coated, partially or completely, in tiny frozen water droplets called rime. The results are called rimed snow. All different types of snow crystals can be found decorated with rime.
There are other different types like 12-sided snowflakes, triangular crystals, bullet rosettes, radiating dendrites, and even
more. Click here for more information.
2. Description of How It Is Falling
There are several ways of how snow can fall to the earth:
* Thunder snow
It is just like a thunder storm, with snow as the main precipitation.
* Blizzard
This kind of snowfall usually occurs over a wide area. It is pretty intense and long lasting with high winds.
* Snow storm
This one is similar with blizzard, but without wind.
* Snow squall
It is a brief but very intense snow storm.
* Snow flurry
This term is used for the lightest snowfall. It is a period of light snow
with occasional moderate snowfall.
Snowfall intensity is usually determined by the visibility. A snowfall is considered as light, when the visibility is
over 1 km. It is considered as moderate, when the visibility is between 0.5 – 1 km. If the visibility constriction is below 0.5 km, we may consider it as a heavy snowfall.
3. By How It Collects on the Ground
Ranging from powdery to the hardest ice, snow can form many different types after it reaches the ground. For snowboarders and skiers, it is quite important to know all of these types. Some are nice to be landed on, while some others are not. These are types of snow after it collects on the ground:
* Snow Powder
Snow powder is untouched snow which is just fallen from the sky. It is composed by light crystals, such as stellar dendrites, forming a low density but thick layer of snow. The surface is smooth and soft. Snow powder has become the best choice for snow boarders to land on. But sometimes it can be a trap too, since the thick layer may cover hard
surfaces like rocks and tree stumps.
* Crud
When snow powder has been tracked out, an uneven surface with lumps of soft powder snow and slippery patches is formed. This is called crud. Crud is a next phase of snow powder after being tracked by snow boarders a!
nd skiers for many times.
* Crust
Just like its name, crust is basically snow powder with a layer of frozen crust on top. The crust is formed by direct sunlight and refreezing. Depending on its thickness, crust can be supportable or breakable. When the layer is thin enough, a skier usually consider breaking and skiing through it.
* Slush
Slush is formed when the snow starts to melt. Warmer temperature makes the water content in snow becomes pretty
high, forming grains of ice which mainly compose the slush. Very heavy and very wet, slush can be pretty hard to ski on.
* Ice
This one is the opposite of snow powder. It is hard and slippery, no wonder snow boarders and skiers hate it so much. The term “ice” here is not referred to pure ice. Actually it is snow that has melted and refrozen for several times, forming a solid icy surface of snow pack.
If you are an active snowboarder or skier, knowing the types of snow on the ground is important. Click here for further
information.
