Snow

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Here is your Journalist Kevin !

This time our #takeover is about Weather and I'm going to discuss "Snow" with you guys :wink:

What is Snow ?

Snow refers to forms of ice crystals that precipitate from the atmosphere (usually from clouds) and undergo changes on the Earth's surface.

-Wikipedia

Snow, the solid form of water that crystallizes in the atmosphere and, falling to the Earth, covers, permanently or temporarily, about 23 percent of the Earth’s surface.

-www.britannica.com

How snow is formed ?

Snow is formed when the temperature in the atmosphere is cold enough to allow tiny ice crystals to form around bits of dirt that have been transported to the atmosphere by the wind. These tiny moisture particles then stick together when they collide, constantly increasing in size as well as mass.

Difference between Ice & Snow ?

Both are frozen water - the difference is how much air there is. Snow is a freeform crystal, with a lot of air in it. If it falls as snow, it can get compacted into solid ice (this is what glaciers are made of).

Ice is frozen water without air interspersed with it. Can for either from compacted snow as above, or when water freezes in a place where freeform crystals cannot form.

Another answer

Ice is the word for the solid form of water, regardless of how or where it formed or how the water molecules are stacked together. Frost is ice. Ice cubes are ice. Snow is a form of ice.

Snow is the word for precipitation that falls as frozen water. If the water forms crystals, you get "snowflakes".

Properties

Physical properties

Density (ρ) 0.1–0.8 g/cm3

Mechanical properties

Tensile strength (σt) 1.5–3.5 kPa

Compressive strength (σc) 3–7 MPa

Thermal properties

Melting temperature (Tm) 0 °C

Thermal conductivity (k) For densities 0.1 to 0.5 g/cm3

0.05–0.7 W/(K·m)

Electrical properties

Dielectric constant (εr) For dry snow density 0.1 to 0.9 g/cm3

Effects on human activity

Snow affects human activity in four major areas;

Transportation

Snow affects the rights of way of highways, airfields and railroads. They share a common tool for clearing snow, the snowplow. However, the application is different in each case—whereas roadways employ anti-icing chemicals to prevent bonding of ice, airfields may not; railroads rely on abrasives to enhance traction on tracks

Agriculture

Snowfall can be beneficial to agriculture by serving as a thermal insulator, conserving the heat of the Earth and protecting crops from subfreezing weather. Some agricultural areas depend on an accumulation of snow during winter that will melt gradually in spring, providing water for crop growth, both directly and via runoff through streams and rivers, which supply irrigation canals.

Structures

Snow is an important consideration for loads on structures. To address these, European countries employ Eurocode 1: Actions on structures - Part 1-3: General actions - Snow loads. In North America, ASCE Minimum Design Loads for Buildings and Other Structures gives guidance on snow loads. Both standards employ methods that translate maximum expected ground snow loads onto design loads for roofs.

Sports & Recreation

Snow figures into many winter sports and forms of recreation, including skiing and sledding. Common examples include cross-country skiing, Alpine skiing, snowboarding, snowshoeing, and snowmobiling. The design of the equipment used, typically relies on the bearing strength of snow, as with skis or snowboards and contends with the coefficient of friction of snow to allow sliding, often enhance by ski waves.

Effects on ecosystems

Plant Life

The presence of snow can affect the distribution and growth of vegetation. Tree branches, especially of conifers intercept falling snow and prevent accumulation on the ground. Snow suspended in trees ablates more rapidly than that on the ground, owing to its greater exposure to sun and air movement. Trees and other plants can also promote snow retention on the ground, which would otherwise be blown elsewhere or melted by the sun. Snow affects vegetation in several ways, the presence of stored water can promote growth, yet the annual onset of growth is dependent on the departure of the snowpack for those plants that are buried beneath it.

Animal Life

Many invertebrates thrive in snow, including spiders, wasps, beetles, snow scorpionflys and springtails. Such arthropods are typically active at temperatures down to −5 °C (23 °F). Invertebrates fall into two groups, regarding surviving subfreezing temperatures: freezing resistant and those that avoid freezing because they are freeze-sensitive. The first group may be cold hardy owing to the ability to produce antifreeze agents in their body fluids that allows survival of long exposure to sub-freezing conditions. Some organisms fast during the winter, which expels freezing-sensitive contents from their digestive tracts. The ability to survive the absence of oxygen in ice is an additional survival mechanism

Extraterrestrial snow

Extraterrestrial "snow" includes water-based precipitation, but also precipitation of other compounds prevalent on other planets and moons in the Solar System. Examples are:

On Mars, observations of the Phoenix Mars lander reveal that water-based snow crystals occur at high latitudes. Additionally,carbon dioxide precipitates from clouds during the Martian winters at the poles and contributes to a seasonal deposit of that compound, which is the principal component of that planet's ice caps.

On Venus, observations from the Magellan spacecraft reveal the presence a metallic substance, which precipitates as "Venus snow" and leaves a highly reflective substance at the tops of Venus's highest mountain peaks resembling terrestrial snow. Given the high temperatures on Venus, the leading candidates for the precipitate are lead sulfide and bismuth(III) sulfide.

On Titan(Moon of Saturn), Cassini–Huygens spacecraft observations suggest the presence of methane or some other form of hydrocarbon-based crystalline deposits.