Snow is a type of precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that is pulled down by gravity and deposited on the Earth's surface. The main forms of precipitation include rain, snow, ice pellets, and graupel. It occurs when the atmosphere, a large gaseous solution, becomes saturated with water vapour and the water within the Earth's atmosphere The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night. Dry air contains roughly (by volume) 78% nitrogen, 21% in the form of crystalline A crystal or crystalline solid is a solid material, whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is crystallography. The process of crystal formation via mechanisms of crystal growth is called water Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state, water vapor or steam ice Ice, technically, may be any one of the 15 known crystalline phases of water. In non-scientific contexts, the term usually means the phase known as ice Ih, which is the most abundant of these solid phases on the earth's surface. It can appear transparent or opaque bluish-white colour, depending on the presence of impurities or air inclusions. The, consisting of a multitude of snowflakes Snowflakes are conglomerations of frozen ice crystals which fall through the Earth's atmosphere. They begin as two snow crystals which develop when microscopic supercooled cloud droplets freeze. Snowflakes come in a variety of sizes and shapes. Complex shapes emerge as the flake moves through differing temperature and humidity regimes. Individual that fall from clouds A cloud is a visible mass of droplets of water or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. A cloud is also a visible mass attracted by gravity, such as masses of material in space called interstellar clouds and nebulae. Clouds are studied in the nephology or cloud physics branch of. Since snow is composed of small ice particles, it is a granular material A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact . The constituents that compose granular material must be large enough such that they are not subject to thermal motion fluctuations. Thus, the lower size limit for grains in granular material is about 1. It has an open and therefore soft structure, unless packed by external pressure Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. Snowflakes come in a variety of sizes and shapes. Types which fall in the form of a ball due to melting and refreezing, rather than a flake, are known as graupel Graupel refers to precipitation that forms when supercooled droplets of water condense on a snowflake, forming a 2–5 mm ball of rime; the snowflake acts as a nucleus of condensation in this process. Graupel is the German word for this meteorological phenomenon, with ice pellets Ice pellets are a form of precipitation consisting of small, translucent balls of ice. Ice pellets usually are smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with freezing rain. The METAR code for ice pellets is PL and snow grains as examples of graupel. Snowfall amount and its related liquid equivalent precipitation amount are determined using a variety of different rain gauges A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation (solid precipitation is measured by a snow gauge) over a set period of time.
The process of precipitating snow is called snowfall. Snowfall tends to form within regions of upward motion of air around a type of low-pressure system A low pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low pressure area is known as cyclogenesis. Within the field of atmospheric known as an extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and horizontal gradients in temperature and dew point. Snow can fall poleward of their associated warm fronts A warm front is defined as the leading edge of an advancing mass of warm air; it separates warm air from the colder air ahead and within their comma head precipitation patterns, which is called such due to its comma-like shape of the cloud and precipitation pattern around the poleward and west sides of extratropical cyclones. Where relatively warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall Lake-effect snow is produced in the winter when cold winds move across long expanses of warmer lake water, providing energy and picking up water vapor which freezes and is deposited on the leeward shores. The same effect over bodies of salt water is called ocean effect snow, sea effect snow, or even bay effect snow. The effect is enhanced when the becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow Thundersnow, also known as a winter thunderstorm or a thunder snowstorm, is a rare thunderstorm with snow falling as the primary precipitation instead of rain. It commonly falls in regions of strong upward motion within the cold sector of extratropical cyclone, where the precipitation consists of ice pellets rather than snow is possible within a cyclone's comma head and within lake effect precipitation bands. In mountainous areas, heavy snow is possible where upslope flow is maximized within windward The traditional nautical pronunciations are the elided forms /ˈljuːərd/ and /ˈwɪnərd/. However, nowadays these are sometimes regarded as old-fashioned, and the more literal /ˈliːwərd/ and /ˈwɪndwərd/ are common. The pronunciation for the Leeward and Windward Islands and the Leeward Antilles is normally the latter form sides of the terrain at elevation, if the atmosphere is cold enough.
Snow on trees, Germany A region named Germania, inhabited by several Germanic peoples, has been known and documented before AD 100. Beginning in the 10th century, German territories formed a central part of the Holy Roman Empire, which lasted until 1806. During the 16th century, northern Germany became the centre of the Protestant Reformation. As a modern nation-state,
Contents |
Forms
Photo of snow on the ground in the mountains A mountain is a large landform that stretches above the surrounding land in a limited area usually in the form of a peak. A mountain is generally steeper than a hill. The adjective montane is used to describe mountainous areas and things associated with them. The study of mountains is called Orography of Southern California Southern California is the southern area of the U.S. state of California. Though there is no official definition for the northern boundary of Southern California, most definitions in use include all the land south of the Tehachapi Mountains, located about 70 miles (113 km) north of Los Angeles. Southern California can be divided into Greater Los.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 Ice, technically, may be any one of the 15 known crystalline phases of water. In non-scientific contexts, the term usually means the phase known as ice Ih, which is the most abundant of these solid phases on the earth's surface. It can appear transparent or opaque bluish-white colour, depending on the presence of impurities or air inclusions. The once it packs down, after multiple melting and refreezing cycles, into a dense mass called snow pack Snowpack forms from layers of snow that accumulate in geographic regions and high altitudes where the climate includes cold weather for extended periods during the year. Snowpacks are an important water resource that feed streams and rivers as they melt. Snowpacks are the drinking water source for many communities. Sudden melting can cause. When powdery, snow moves with the wind Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space. Winds are commonly classified by their spatial from the location where it originally landed, forming deposits called snowdrifts A snowdrift is a deposit of snow created by wind into a mound during snowstorms. They resemble sand dunes and are formed in a similar manner, namely, by wind moving light snow and depositing it when the wind is slowed, usually against a stationary object. Snow normally crests and slopes off toward the surface on the windward side of a large object which may have a depth of several meters. After attaching to hillsides, blown snow can evolve into a snow slab, which is an avalanche An avalanche is a rapid flow of snow down a slope, from either natural triggers or human activity. Typically occurring in mountainous terrain, an avalanche can mix air and water with the descending snow. Powerful avalanches have the capability to entrain ice, rocks, trees, and other material on the slope. Avalanches are primarily composed of hazard on steep slopes. The existence of a snowpack keeps temperatures colder than they would be otherwise, as the whiteness of the snow reflects most sunlight, and the absorbed heat goes into melting the snow rather than increasing its temperature. The water equivalent of snowfall is measured to monitor how much liquid is available to flood rivers A river is a natural watercourse, usually freshwater, flowing toward an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and rill; there is no from meltwater Meltwater is the water released by the melting of snow or ice, including glacial ice and ice shelfs over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be produced during volcanic eruptions, in a similar way in which the more dangerous lahars form which will occur during the upcoming spring Spring is one of the four temperate seasons, the transition period between winter and summer. Spring and "springtime" refer to the season, and broadly to ideas of rebirth, renewal and regrowth. The specific definition of "spring" as a season differs, however, among scientific disciplines such as astronomy and meterorology, and. Snow cover can protect crops from extreme cold. If snowfall stays on the ground for a series of years uninterrupted, the snowpack develops into a mass of ice called glacier A glacier is a perennial mass of ice which moves over land. A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years. The word glacier comes from French via the Vulgar Latin glacia, and ultimately from Latin glacies meaning ice. The corresponding area of study is called glaciology. Fresh snow absorbs sound, lowering ambient noise over a landscape Landscape comprises the visible features of an area of land, including the physical elements of landforms, water bodies such as rivers, lakes and the sea, living elements of land cover including indigenous vegetation, human elements including land uses, buildings and structures, and transitory elements such as lighting and weather conditions because the trapped air between snowflakes attenuates vibration. These acoustic qualities quickly minimize, and reverse once a layer of freezing rain Freezing rain is the name given to rain that falls when surface temperatures are below freezing. The raindrops become supercooled while passing through a sub-freezing layer of air, many hundred feet , just above the surface, and then freeze upon impact with any object they encounter. The resulting ice, called glaze, can accumulate to a thickness falls on top of snow cover. Walking across snowfall produces a squeaking sound at low temperatures.
The energy balance of the snowpack itself is dictated by several heat exchange processes. The snowpack absorbs solar shortwave radiation that is partially blocked by cloud cover and reflected by snow surface. A long-wave heat exchange takes place between the snowpack and its surrounding environment that includes overlying air mass, tree cover and clouds. Heat exchange takes place by convection Convection is the movement of molecules within fluids . It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids between the snowpack and the overlaying air mass, and it is governed by the temperature gradient and wind speed. Moisture exchange between the snowpack and the overlying air mass is accompanied with latent heat transfer that is influenced by vapor pressure gradient and air wind. Rain on snow can add significant amounts of thermal energy to the snowpack. A generally insignificant heat exchange takes place by conduction In heat transfer, conduction is the transfer of thermal energy between neighboring molecules in a substance due to a temperature gradient. It always takes place from a region of higher temperature to a region of lower temperature, and acts to equalize temperature differences. Conduction takes place in all forms of matter, viz. solids, liquids, between the snowpack and the ground. The small temperature change from before to after a snowfall is a result of the heat transfer between the snowpack and the air.[1]
The term snow storm A winter storm is an event in which the dominant varieties of precipitation are forms that only occur at cold temperatures, such as snow or sleet, or a rainstorm where ground temperatures are cold enough to allow ice to form . In temperate continental climates, these storms are not necessarily restricted to the winter season, but may occur in the can describe a heavy snowfall while a blizzard A blizzard is a severe storm condition characterized by low temperatures, strong winds, and heavy snow. By definition, the difference between blizzard and a snowstorm is the strength of the wind. Ground blizzards are a variation on the traditional blizzard, in that ground blizzards require high winds to stir up snow that has already fallen, rather involves snow and wind, obscuring visibility. Snow shower is a term for an intermittent snowfall, while flurry is used for very light, brief snowfalls. Snow can fall more than a meter at a time during a single storm in flat areas, and meters at a time in rugged terrain, such as mountains A mountain is a large landform that stretches above the surrounding land in a limited area usually in the form of a peak. A mountain is generally steeper than a hill. The adjective montane is used to describe mountainous areas and things associated with them. The study of mountains is called Orography. When snow falls in significant quantities, travel by foot, car, airplane and other means becomes highly restricted, but other methods of mobility become possible: the use of snowmobiles A snowmobile, also known in some places as a snowmachine, sled, or skimobile , is a land vehicle for winter travel on snow. Designed to be operated on snow and ice, they require no road or trail. Design variations enable some machines to operate in deep snow or forests; most are used on open terrain, including lakes or driven on paths or trails, snowshoes A Snowshoe is footwear for walking over the snow. Snowshoes work by distributing the weight of the person over a larger area so that the person's foot does not sink completely into the snow, a quality called "flotation" and skis A ski is a long, flat device worn on the feet designed to help the wearer slide smoothly over snow. Originally intended as an aid to travel in snowy regions, they are now mainly used for recreational and sporting purposes. Also, a ski may denote a similar device used for other purposes than skiing, for example, for steering snowmobiles. When heavy snow occurs early in the fall Autumn is one of the four temperate seasons. Autumn marks the transition from summer into winter, usually in March (Southern Hemisphere) or September (Northern Hemisphere) when the arrival of night becomes noticeably earlier, significant damage occurs to trees still in leaf. Areas with significant snow each year can store the winter snow within an ice house Ice houses originally invented in Persia were buildings used to store ice throughout the year, prior to the invention of the refrigerator. The most common designs involved underground chambers, usually man-made, which were built close to natural sources of winter ice such as freshwater lakes, which can be used to cool structures during the following summer Summer is the warmest of the four temperate seasons, between spring and autumn. It is marked by the longest days and shortest nights. The seasons start on different dates in different cultures based on astronomy and regional meteorology. However, when it is summer in the southern hemisphere it is winter in the northern hemisphere, and vice versa. A variation on snow has been observed on Venus Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows. Because Venus is an inferior planet from Earth, it never, though composed of metallic compounds and occurring at a substantially higher temperature.
Cause
See also: Extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and horizontal gradients in temperature and dew point, Lake-effect snow Lake-effect snow is produced in the winter when cold winds move across long expanses of warmer lake water, providing energy and picking up water vapor which freezes and is deposited on the leeward shores. The same effect over bodies of salt water is called ocean effect snow, sea effect snow, or even bay effect snow. The effect is enhanced when the, and Rainband A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as banded structure. Rainbands within tropical cyclones Preferred region of heavy snowfall ("Banded Snowfall") around the comma head of a wintertime low pressure area, shaded in green Lake-effect snow bands near the Korean Peninsula The Korean Peninsula is a peninsula in East Asia. It extends southwards for about 684 miles from continental Asia into the Pacific Ocean and is surrounded by the Sea of Japan (also called East Sea) on the east, the East China Sea to the south, and the Yellow Sea to the west, the Korea Strait connecting the first two bodies of waterExtratropical cyclones Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and horizontal gradients in temperature and dew point can bring cold and dangerous conditions with heavy rain and snow with winds exceeding 119 km/h (74 mph),[2] (sometimes referred to as windstorms A European windstorm is a severe cyclonic windstorm associated with areas of low pressure that track across the North Atlantic towards northwestern Europe. They are most common in the winter months. Deep low pressure areas are relatively common over the North Atlantic and frequently track past the north coasts of Great Britain and Ireland onto the in Europe). The band of precipitation that is associated with their warm front is often extensive, forced by weak upward vertical motion of air over the frontal boundary which condenses as it cools and produces precipitation within an elongated band,[3] which is wide and stratiform, meaning falling out of nimbostratus clouds.[4] When moist air tries to dislodge an arctic air mass, overrunning snow can result within the poleward side of the elongated precipitation band. In the Northern Hemisphere, poleward is towards the North Pole, or north. Within the Southern Hemisphere, poleward is towards the South Pole, or south.
Within the cold sector, poleward and west of the cyclone center, small scale or mesoscale bands of heavy snow can occur within a cyclone's comma head pattern. The cyclone's comma head pattern is a comma-shaped area of clouds and precipitation found around mature extratropical cyclones. These snow bands typically have a width of 20 miles (32 km) to 50 miles (80 km).[5] These bands in the comma head are associated with areas of frontogenesis, or zones of strengthening temperature contrast.[6]
Southwest of extratropical cyclones, curved cyclonic flow bringing cold air across the relatively warm water bodies can lead to narrow lake-effect snow bands. Those bands bring strong localized snowfall which can be understood as follows: Large water bodies such as lakes efficiently store heat that results in significant temperature differences (larger than 13 °C or 23 °F) between the water surface and the air above.[7] Because of this temperature difference, warmth and moisture are transported upward, condensing into vertically oriented clouds (see satellite picture) which produce snow showers. The temperature decrease with height and cloud depth are directly affected by both the water temperature and the large-scale environment. The stronger the temperature decrease with height, the deeper the clouds get, and the greater the precipitation rate becomes.[8]
In mountainous areas, heavy snowfall accumulates when air is forced to ascend the mountains and squeeze out precipitation along their windward slopes, which in cold conditions, falls in the form of snow. Because of the ruggedness of terrain, forecasting the location of heavy snowfall remains a significant challenge.[9]
|
Sat, 04 Sep 2010 14:50:39 GMT+00:00
Leopard Mac Rumors You can use this same guide to perform a normal install of Snow Leopard, just skip the Disk Utility and Migration Assistant parts (steps 4, 5 and 12). ...
Mon, 29 Dec 2008 00:00:00 PST
Watch Evening News US Shivers From Snow Storm in the Online Video Guide. video.tvguide.com.
