In nature, no two complex snowflakes are believed to ever be alike. However, in a laboratory two identical complex snowflakes have been created. There are many recreational activities that require snow, like snowboarding, skiing and snowmobiling. Snows ability to reflect ultraviolet radiation can caused a condition called snow blindness.
These aggregates are snowflakes, and are usually the type of ice particle that falls to the ground. The exact details of the sticking mechanism remains controversial. Possibilities include mechanical interlocking, sintering, electrostatic attraction as well as the existence of a "sticky" liquid-like layer on the crystal surface.
The individual ice crystals often have hexagonal symmetry. Ice crystals formed in the appropriate conditions are often thin and flat. These planar crystals may be in the shape of simple hexagons, or if the supersaturation is high enough, develop branches and dendritic fern-like features and have six approximately identical arms.
The sixfold symmetry arises from the hexagonal crystal structure of ordinary ice, the branch formation is produced by unstable growth, with deposition occurring preferentially near the tips of branches.
The shape of the snowflake is determined broadly by the temperature and humidity at which it is formed. The most common snow particles are visibly irregular, although near-perfect snowflakes may be more common in pictures because they are more visually appealing.
No two snowflakes are alike. It is more likely that two snowflakes could become virtually identical if their environments were similar enough. The crystals were not flakes in the usual sense but rather hollow hexagonal prisms. Types of snow can be designated by the shape of its flakes, its rate of falling, and by how it collects on the ground.
Snowfall's intensity is determined by visibility. When the visibility is over 1 kilometre 0. Moderate snow describes snowfall with visibility restrictions between. Heavy snowfall describes conditions when visibility is restricted below. A blizzard and snowstorm indicate heavy snowfalls, with blizzards defined by having high winds during their heavy snowfall. Snow flurries are used to describe the lightest form of snow showers. Types which fall in the form of a ball due to melting and refreezing cycles, rather than a flake, are known as graupel, with sleet and snow pellets as types of graupel associated with wintry precipitation.
Once on the ground, snow can be categorized as powdery when fluffy, granular when it begins the cycle of melting and refreezing, and eventually ice once it packs down into a dense drift after multiple melting and refreezing cycles. When powdering, snow drifts with the wind , sometimes to the depth of several meters. After attaching to hillsides, blown snow can evolve into a snow slab, which is an avalanche hazard on steep slopes.
A frozen equivalent of dew known as hoar frost forms on a snow pack when winds are light and there is ample low-level moisture over the snow pack. Snow remains on the ground until it melts or sublimates. The water equivalent of a given amount of snow is the depth of a layer of water having the same mass and upper area. For example, if the snow covering a given area has a water equivalent of 50 centimetres 20 in , then it will melt into a pool of water 50 centimetres 20 in deep covering the same area.
This is a much more useful measurement to hydrologists than snow depth , as the density of cool freshly fallen snow widely varies. This means that 13 inches mm of snow melts down to 1 inch 25 mm of water.
Increases in density above this initial compression occur primarily by melting and refreezing, caused by temperatures above freezing or by direct solar radiation. In colder climates, snow lies on the ground all winter. Spring snow melt is a major source of water supply to areas in temperate zones near mountains that catch and hold winter snow, especially those with a prolonged dry summer. In such places, water equivalent is of great interest to water managers wishing to predict spring runoff and the water supply of cities downstream.
Measurements are made manually at marked locations known as snow courses , and remotely using special scales called snow pillows. When the snow does not all melt in the summer it evolves into firn, where individual granular elements become more spherical in nature, evolving into a glacier as the ice flows downhill. Since fresh snow reflects 90 percent or more of short-wave radiation, and radiates energy nearly completely further into the infrared spectrum, little energy from the sun is converted into heat from the new snow, and much heat is lost.
Many rivers originating in mountainous or high-latitude regions have a significant portion of their flow from snowmelt. This often makes the river's flow highly seasonal resulting in periodic flooding.
Question 1 : Can snow be dangerous? Answer 1 : Snow is lots of fun to play in, but it can be dangerous sometimes. Staying outdoors too long can cause frostbite.
Roads are usually very slick during snowstorms. Make sure you have some emergency supplies , like extra food, water and candles.
Play board games, drink warm drinks and make some soup. Once the storm is over, you can bundle up and play outside. Question 2: Can it be too cold for snow? This is not true, it can snow at extremely low temperatures providing that there is some moisture in the air.
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