After a particularly cold winter, after getting frozen multiple times over…
I decided to do a post about the many different kinds of snow.
Most people perceive snow simply as frozen water. Delving in a little deeper, snow is actually a form of precipitation in the form of ice crystals. These ice crystals are hexagonal prisms that form when snow freezes up. Prisms are formed due to the molecular structure of water.
❄Snow in the atmosphere❄
Whether winter storms produce snow relies heavily on temperature, but not necessarily the temperature we feel here on the ground. Snow forms when the atmospheric temperature is at or below freezing and there is a minimum amount of moisture in the air. If the ground temperature is at or below freezing, the snow will reach the ground.
However, the snow can still reach the ground when the ground temperature is above freezing if the conditions are just right. In this case, snowflakes will begin to melt as they reach this higher temperature layer; the melting creates evaporative cooling which cools the air immediately around the snowflake. As a general rule, though, snow will not form if the ground temperature is at least 5°C.
While it can be too warm to snow, it cannot be too cold to snow. Snow can occur even at incredibly low temperatures as long as there is some source of moisture and some way to lift or cool the air. It is true, however, that most heavy snowfalls occur when there is relatively warm air near the ground—typically -9°C or warmer—since warmer air can hold more water vapor.
Types of snow crystals
Snowflakes are clusters of ice crystals that fall from a cloud.
Hoarfrost is the deposition of ice crystals on a surface when the temperature of the surface is lower than the frost point of the surrounding air. In this process, moisture goes directly from vapor to solid, skipping the liquid phase. Hoarfrost is usually composed of interlocking ice crystals, and tends to form on objects of small diameter that are freely exposed to air, such as wires, poles, tree branches, plant stems, and leaf edges.
Graupel consists of snowflakes that become rounded, opaque pellets ranging from 2 to 5 millimeters in diameter. They form as ice crystals fall through supercooled cloud droplets, which are below freezing but remain a liquid. The cloud droplets then freeze to the crystals, forming a lumpy mass. Graupel is sometimes mistaken for hail, but tends to have a texture that is softer and more crumbly. Graupel is sometimes also called snow pellets.
Polycrystals are snowflakes composed of many individual ice crystals.
❄How big can snowflakes get?❄
Snowflakes are accumulations of many snow crystals. Most snowflakes are less than 1.3 centimeters across. Under certain conditions, usually requiring near-freezing temperatures, light winds, and unstable atmospheric conditions, much larger and irregular flakes can form, nearing 5 centimeters across. No routine measure of snowflake dimensions are taken, so the exact size is not known.
Types of snow
Atmospheric conditions affect how snow crystals form and what happens to them as they fall to the ground. Snow may fall as symmetrical, six-sided snowflakes, or it may fall as larger clumps of flakes.
Similarly, once snow is on the ground, the snow may assume different qualities (depending on local
temperature changes, whether winds blow the snow around, or how long the snow has been on the ground).
For instance, a fresh snowfall may be loose and powdery, but snow that has been on the ground throughout the winter may have dense, crusted layers caused by melting and refreezing. Scientists and meteorologists have classified types of snowfall, snowpack, and snow formations.
Yup, that’s me right after a Snowstorm.
Types of snowfall
A Blizzard is a violent winter storm, lasting at least three hours, which combines subfreezing temperatures and very strong wind laden with blowing snow that reduces visibility to less than 0.40 kilometers (0.25 miles).
A snowstorm features large amounts of snowfall.
A Snow flurry is snow that falls for short durations and with varying intensity; flurries usually produce little accumulation.
A Snow squall is a brief, but intense snowfall that greatly reduces visibility and which is often accompanied by strong winds.
A Snowburst is a very intense shower of snow, often of short duration, that greatly restricts visibility and produces periods of rapid snow accumulation.
Blowing snow describes airborne snow particles raised by the wind to moderate or great heights above the ground; the horizontal visibility at eye level is generally very poor.
Drifting snow is snow on the ground that is blown by the wind to a height of less than 1.5 to 2 meters above the surface.
❄Snow on the ground❄
The character of the snow surface after a snowfall depends on the original form of the crystals and on the weather conditions present when the snow fell. For example, when a snowfall is accompanied by strong winds, the snow crystals are broken into smaller fragments that can become more densely packed. After a snowfall, snow may melt or evaporate, or it may persist for long periods. If snow persists on the ground, the texture, size, and shape of individual grains will change even while the snow temperature remains below freezing, or they may melt and refreeze over time, and will eventually become compressed by subsequent snowfalls.
Over the winter season, the snowpack typically accumulates and develops a complex layered structure made up of a variety of snow grains, reflecting the weather and climate conditions prevailing at the time of deposition as well as changes within the snow cover over time.
Types of snow cover
Snow cover, also called snowpack, is the total of all the snow and ice on the ground. It includes both new snow and previous snow and ice that have not melted.
New snow is a recent snow deposit in which the original form of the ice crystals can be recognized.
Firn is rounded, well-bonded snow that is older than one year and has a density greater than 550 kilograms per cubic meter, or 55 percent.
Névé is young, granular snow that has been partially melted, refrozen and compacted; névé that survives a full melt season is called firn. This type of snow is associated with glacier formation.
Old snow indicates deposited snow whose transformation is so far advanced that the original form of the new snow crystals can no longer be recognized.
Seasonal snow refers to snow that accumulates during one season or snow that lasts for only one season.
Perennial snow is snow that persists on the ground year after year.
Powder snow is dry new snow, freshly fallen, untouched, soft snow. Snowboarder’s paradise.
Powder, tiny flakes and crystals form the smooth and soft surface in mountains. It forms a soft smooth surface that will give you the feeling that you are floating in a weightless environment.
Powder is often packed in thick layers that form a natural pillow for any crashes. Most snowboarders and skiers find powder the ultimate surface especially since it is the best snow to land on because it does not hurt as much.
❄Snow and sound❄
The characteristics and age of snow can affect how sound waves travel, dampening them in some cases, or enhancing them in others. For instance, people often notice how sound changes after a fresh snowfall. When the ground has a thick layer of fresh, fluffy snow, sound waves are readily absorbed at the snow surface, dampening sound.
However, time and weather conditions may change the snow surface. If the surface melts and refreezes, the snow becomes smooth and hard. Then the surface will help reflect sound waves. Sounds may seem clearer and travel farther under these circumstances.
Snow may also crunch and creak. A layer of snow is made up of many tiny ice grains surrounded by air and when you step on it, you compress the grains. As the snow compresses, the ice grains rub against each other. This creates friction or resistance; the lower the temperature, the greater the friction between the grains of ice. The sudden squashing of the snow at lower temperatures produces the familiar creaking or crunching sound.
At higher temperatures, closer to melting, this friction is reduced to the point where the sliding of the grains against each other produces little or no noise. It is difficult to say at what temperature the snow starts to crunch, but the colder the snow, the louder the crunch.
Types of snow formations
Once on the ground, snow is subject to various weather conditions, including blowing wind, changing temperatures, and long periods of shade or sunshine. In certain instances, these elements can literally change the shape of the snow surface.
A Cornice is an overhanging accumulation of ice and wind-blown snow, characteristically found on the edge of a ridge or cliff face.
A Crust is a hard snow surface lying upon a softer layer, formed by sun, rain, or wind.
Megadunes are giant dunes of snow in Antarctica composed of large snow crystals measuring up to 2 centimeters (3/4 inch) across.
Penitents are tall, thin, closely-spaced pinnacles of hardened snow ranging in height from a few centimeters to a few meters (a few inches to a few feet). Fields of penitents can develop over glaciated and snow-covered areas, particularly in arid regions, such as the Dry Andes or in the mountains surrounding Death Valley in California.
Ripple marks refer to the corrugation on a snow surface caused by wind, similar to the ripples sometimes seen in sand.
Sastrugi occur when wind erodes or deposits snow in irregular grooves and ridges. Sastrugi sometimes result in delicate and fragile snow formations.
A Snow barchan is horseshoe-shaped snowdrift, with the ends pointing downwind. A snow bridge is an arch formed by snow that has drifted across a crevasse, forming first a cornice, and ultimately a covering which may completely obscure the crevasse.
A Snow bridge is an arch formed by snow that has drifted across a crevasse, forming first a cornice, and ultimately a covering which may completely obscure the crevasse.
A Snow roller is a rare formation that occurs during specific meteorological conditions. Wind blows a chunk of snow along the ground, and the resulting snowball accumulates material as it rolls along. Snow rollers are cylindrical rather than circular. Some are shaped like donuts because the weak inner layers collapse and blow away.
Sun cups refer to a pattern of shallow, bowl-shaped hollows that form during intense sunshine.
❄The colors of snow❄
Generally, snow and ice present us with a uniformly white appearance. This is because visible light is white. Most all of the visible light striking the snow or ice surface is reflected back without any particular preference for a single color. Most natural materials absorb some sunlight, which gives them their color. Snow, however, reflects most of the sunlight, creating a white appearance.
However, snow may also appear blue. As light waves travel into the snow or ice, the ice grains scatter a large amount of light. If light travels over any distance, it must survive many such scattering events. That is, it must keep scattering and not be absorbed. The observer sees the light coming back from the near surface layers after it has been scattered or bounced off other snow grains only a few times and it still appears white.
This absorption is preferential: More red light is absorbed than blue. The difference in absorption is small, but is enough that over a considerable distance, say a meter or more, photons emerging from the snow layer tend to be made up of more blue light than red light. For instance, if you were to poke a hole in the snow and look down into the hole, you may see a bluish color. In each case, the blue light is the product of a relatively long travel path through the snow or ice. Think of the ice or snow layer as a filter. If it is only a centimeter thick, all the light makes it through, but if it is about one meter thick, mostly blue light makes it through.
Particles or organisms within the snowpack may also affect the color of the snow. Watermelon snow, for instance, appears red or pink. This coloration is caused by a form of cryophilic, or cold-loving, fresh-water algae that contain a bright red pigment. Watermelon snow is most common during the summertime in high alpine areas as well as along coastal polar regions.
Although this snow may look candy-colored, it is not wise to eat it. Blood Falls, in Antarctica’s Taylor Glacier, also has red snow, but for a different reason. There, the deep red color is caused by saltwater leaking from an ancient reservoir under the glacier. This water is rich in a form of iron that oxidizes when it comes into contact with the atmosphere, producing a bright red waterfall.
Snow requires two specific weather conditions: low temperatures and moisture in the atmosphere. In warm, humid places, there is significant moisture in the air, but temperatures are rarely low enough to produce snow. And while many deserts get quite cold in the winter, there is often not enough moisture in the atmosphere to produce snow. Even Antarctica, the coldest and iciest continent, contains a region called the Dry Valleys, where it is extremely cold, but so dry that snow never falls.
Snow is most common in high altitudes and high latitudes, particularly among the mountainous regions of the Northern and Southern Hemispheres.