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66-689: There are on the plateau many towns and several cities, including El Alto and Oruro in Bolivia, Juliaca and Puno in Peru. The northeastern part of the Altiplano is more humid than the southwestern part, which has several salares (salt flats), due to its aridity. At the Bolivia–Peru border lies Lake Titicaca , the largest lake in South America. Farther south, in Bolivia, there was until recently

132-633: A glacier may form. Otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater . Major snow-prone areas include the polar regions , the northernmost half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture and cold temperatures. In the Southern Hemisphere , snow is confined primarily to mountainous areas, apart from Antarctica . Snow affects such human activities as transportation : creating

198-401: A rainband ), when temperature is near freezing at the surface. The strong convection that develops has enough moisture to produce whiteout conditions at places which the line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path, but the motion of the line can cover large distances. Frontal squalls may form

264-476: A base for the new air force, which attracted additional settlement. In 1939, El Alto's first elementary school opened. El Alto started to grow tremendously in the 1950s when the settlement was connected to La Paz's water supply (before this, all water had to be transported from La Paz in tanker vehicles) and building land in the canyon became more and more scarce and expensive. In an administrative reform in March 1985,

330-433: A cirque (corrie or cwm), a typically armchair-shaped geological feature, which collects snow and where the snowpack compacts under the weight of successive layers of accumulating snow, forming névé. Further crushing of the individual snow crystals and reduction of entrapped air in the snow turns it into glacial ice. This glacial ice will fill the cirque until it overflows through a geological weakness or an escape route, such as

396-649: A crystal morphology diagram, relating crystal shapes to the temperature and moisture conditions under which they formed, which is summarized in the following table. Dendrites Hollow prisms Needles Solid plates Dendrites Solid plates Prisms Nakaya discovered that the shape is also a function of whether the prevalent moisture is above or below saturation. Forms below the saturation line tend more toward solid and compact while crystals formed in supersaturated air tend more toward lacy, delicate, and ornate. Many more complex growth patterns also form, which include side-planes, bullet-rosettes, and planar types, depending on

462-447: A droplet has frozen, it grows in the supersaturated environment—one where air is saturated with respect to ice when the temperature is below the freezing point. The droplet then grows by diffusion of water molecules in the air (vapor) onto the ice crystal surface where they are collected. Because water droplets are so much more numerous than the ice crystals, the crystals are able to grow to hundreds of micrometers or millimeters in size at

528-589: A few molecules in the droplet need to get together by chance to form an arrangement similar to that in an ice lattice. The droplet freezes around this "nucleus". In warmer clouds, an aerosol particle or "ice nucleus" must be present in (or in contact with) the droplet to act as a nucleus. Ice nuclei are very rare compared to cloud condensation nuclei on which liquid droplets form. Clays, desert dust, and biological particles can be nuclei. Artificial nuclei include particles of silver iodide and dry ice , and these are used to stimulate precipitation in cloud seeding . Once

594-568: A hemisphere's fall , winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall. In the Northern Hemisphere, the northern side of the low-pressure area produces the most snow. For the southern mid-latitudes , the side of a cyclone that produces the most snow is the southern side. A cold front , the leading edge of a cooler mass of air, can produce frontal snowsqualls —an intense frontal convective line (similar to

660-485: A highly porous, sintered material made up of a continuous ice structure and a continuously connected pore space, forming together the snow microstructure". Almost always near its melting temperature, a snowpack is continually transforming these properties wherein all three phases of water may coexist, including liquid water partially filling the pore space. After deposition, snow progresses on one of two paths that determine its fate, either by ablation (mostly by melting) from

726-514: A lake, Lake Poopó , but by December 2015 it had completely dried up, and was declared defunct. It is unclear whether that lake, which had been the second-largest in Bolivia, can be restored. The Altiplano was the site of several pre-Columbian cultures, including the Chiripa, Tiawanaku and the Inca Empire . Spain conquered the region in the 16th century. Today, major economic activities in

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792-470: A larger weather system. The physics of snow crystal development in clouds results from a complex set of variables that include moisture content and temperatures. The resulting shapes of the falling and fallen crystals can be classified into a number of basic shapes and combinations thereof. Occasionally, some plate-like, dendritic and stellar-shaped snowflakes can form under clear sky with a very cold temperature inversion present. Snow clouds usually occur in

858-435: A minimum extent of 2 million square kilometres (0.77 × 10 ^  sq mi) each August to a maximum extent of 45 million square kilometres (17 × 10 ^  sq mi) each January or nearly half of the land surface in that hemisphere. A study of Northern Hemisphere snow cover extent for the period 1972–2006 suggests a reduction of 0.5 million square kilometres (0.19 × 10 ^  sq mi) over

924-530: A mountain range results in adiabatic cooling, and ultimately condensation and precipitation. Moisture is gradually removed from the air by this process, leaving drier and warmer air on the descending, or leeward , side. The resulting enhanced snowfall, along with the decrease in temperature with elevation, combine to increase snow depth and seasonal persistence of snowpack in snow-prone areas. Mountain waves have also been found to help enhance precipitation amounts downwind of mountain ranges by enhancing

990-470: A population of about 2.2 million. The city is rapidly developing, although significant challenges with substandard infrastructure and utilities remain, especially in the outlying areas. The construction of an elaborate cable car system connected El Alto directly with central La Paz, dramatically easing transportation into the economic center of the metropolitan area. A locally indigenous Neo-Andean architectural style has developed alongside this growth, giving

1056-488: A series of snow events, punctuated by freezing and thawing, over areas that are cold enough to retain snow seasonally or perennially. Major snow-prone areas include the Arctic and Antarctic , the Northern Hemisphere, and alpine regions. The liquid equivalent of snowfall may be evaluated using a snow gauge or with a standard rain gauge , adjusted for winter by removal of a funnel and inner cylinder. Both types of gauges melt

1122-409: A short distance ahead of the surface cold front or behind the cold front where there may be a deepening low-pressure system or a series of trough lines which act similar to a traditional cold frontal passage. In situations where squalls develop post-frontally, it is not unusual to have two or three linear squall bands pass in rapid succession separated only by 25 miles (40 kilometers), with each passing

1188-419: A snow fall or seasonal snowpack, or by transitioning from firn (multi-year snow) into glacier ice . Over the course of time, a snowpack may settle under its own weight until its density is approximately 30% 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

1254-608: A snowpack can create flow fingers and ponding or flow along capillary barriers, which can refreeze into horizontal and vertical solid ice formations within the snowpack. Among the measurements of the properties of snowpacks that the International Classification for Seasonal Snow on the Ground includes are: snow height, snow water equivalent, snow strength, and extent of snow cover. Each has a designation with code and detailed description. The classification extends

1320-416: A snowslide or snowslip) is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack (slab avalanche) when the forces on the snow exceed its strength but sometimes only with gradually widening (loose snow avalanche). After initiation, avalanches usually accelerate rapidly and grow in mass and volume as they entrain more snow. If

1386-630: A substance denser than névé , yet less dense and hard than glacial ice . Firn resembles caked sugar and is very resistant to shovelling. Its density generally ranges from 550 to 830 kilograms per cubic metre (34 to 52 lb/cu ft), and it can often be found underneath the snow that accumulates at the head of a glacier . The minimum altitude that firn accumulates on a glacier is called the firn limit , firn line or snowline . There are four main mechanisms for movement of deposited snow: drifting of unsintered snow, avalanches of accumulated snow on steep slopes, snowmelt during thaw conditions, and

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1452-472: Is "the transformation that the snow undergoes in the period from deposition to either melting or passage to glacial ice". Starting as a powdery deposition, snow becomes more granular when it begins to compact under its own weight, be blown by the wind, sinter particles together and commence the cycle of melting and refreezing. Water vapor plays a role as it deposits ice crystals, known as hoar frost , during cold, still conditions. During this transition, snow "is

1518-429: Is not a requirement, as blowing snow can create a ground blizzard . Snowstorm intensity may be categorized by visibility and depth of accumulation. Snowfall's intensity is determined by visibility , as follows: Snowsqualls may deposit snow in bands that extend from bodies of water as lake-event weather or result from the passage of an upper-level front. The International Classification for Seasonal Snow on

1584-511: Is one of the highest major cities in the world, up to 4,300 meters (13,615 feet) above mean sea level. It has a cold climate, with the highest average monthly maximum temperature being 17 °C (63 °F) in November. It is one of the fastest-growing cities in Bolivia, due to immigration from Bolivia’s rural areas to the La Paz region which started with the rural reform of 1952 and increased in

1650-464: Is termed ocean-effect or bay-effect snow . The effect is enhanced when the moving air mass is uplifted by the orographic influence of higher elevations on the downwind shores. This uplifting can produce narrow but very intense bands of precipitation which may deposit at a rate of many inches of snow each hour, often resulting in a large amount of total snowfall. The areas affected by lake-effect snow are called snowbelts . These include areas east of

1716-399: Is very wide, with maximum temperatures in the order of 12 to 24 °C (54 to 75 °F) and the minimum in the order of −20 to 10 °C (−4 to 50 °F). The coldest temperatures occur in the southwestern portion of the Altiplano during the winter months of June and July. The seasonal cycle of rainfall is marked, with the rainy season concentrated between December and March. The rest of

1782-472: The Altiplano highlands. El Alto is today one of Bolivia's fastest-growing urban centers, with an estimated population of 943,558 in 2020. It is also the highest major city in the world , with an average elevation of 4,000 m (13,123 ft). The El Alto–La Paz metropolitan area, formed by La Paz, El Alto, Achocalla , Viacha , and Mecapaca , constitutes the most populous urban area of Bolivia, with

1848-645: The Great Lakes , the west coasts of northern Japan, the Kamchatka Peninsula in Russia, and areas near the Great Salt Lake , Black Sea , Caspian Sea , Baltic Sea , and parts of the northern Atlantic Ocean. Orographic or relief snowfall is created when moist air is forced up the windward side of mountain ranges by a large-scale wind flow. The lifting of moist air up the side of

1914-743: The Tibetan Plateau . Unlike conditions in Tibet , the Altiplano is dominated by massive active volcanoes of the Central Volcanic Zone to the west, such as Ampato (6288 m), Tutupaca (5,816 m), Parinacota (6348 m), Guallatiri (6071 m), Paruma (5,728 m), Uturunku (6,008 m) and Licancabur (5,916 m), and the Cordillera Real in the north east with Illampu (6,368 m), Huayna Potosí (6,088 m), Janq'u Uma (6,427 m) and Illimani (6,438 m). The Atacama Desert , one of

1980-464: The grassroots and highly successful Fejuve movement. El Alto is connected to La Paz by three lines of the Mi Teleférico system. The city is connected to domestic and international destinations by El Alto International Airport . Snow Snow comprises individual ice crystals that grow while suspended in the atmosphere —usually within clouds—and then fall, accumulating on

2046-411: The movement of glaciers after snow has persisted for multiple years and metamorphosed into glacier ice. When powdery snow drifts with the wind from the location where it originally fell, forming deposits with a depth of several meters in isolated locations. After attaching to hillsides, blown snow can evolve into a snow slab, which is an avalanche hazard on steep slopes. An avalanche (also called

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2112-648: The 35-year period. The following are world records regarding snowfall and snowflakes: The cities (more than 100,000 inhabitants) with the highest annual snowfall are Aomori (792 cm), Sapporo (485 cm) and Toyama (363 cm) in Japan , followed by St. John's (332 cm) and Quebec City (315 cm) in Canada , and Syracuse, NY (325 cm). According to the International Association of Cryospheric Sciences, snow metamorphism

2178-409: The Altiplano include mining, llama and vicuña herding, and services (in its cities). The area also attracts some international tourism. The Altiplano is an area of inland drainage ( endorheism ) lying in the central Andes , occupying parts of northern Chile , western Bolivia , southern Peru and northwest Argentina. Its height averages about 3,750 meters (12,300 feet), slightly less than that of

2244-468: The Altiplano paleolakes dried out. The term Altiplano is sometimes used to identify the altitude zone and the type of climate that prevails within it: it is colder than that of the tierra fría but not as cold as that of the tierra helada . Scientists classify the latter as commencing at an elevation of approximately 4,500 meters (or about 15,000 feet). Alternate names used in place of altiplano in this context include puna and páramos . In general

2310-460: The Ground defines "height of new snow" as the depth of freshly fallen snow, in centimeters as measured with a ruler, that accumulated on a snowboard during an observation period of 24 hours, or other observation interval. After the measurement, the snow is cleared from the board and the board is placed flush with the snow surface to provide an accurate measurement at the end of the next interval. Melting, compacting, blowing and drifting contribute to

2376-413: The accumulated snow and report the amount of water collected. At some automatic weather stations an ultrasonic snow depth sensor may be used to augment the precipitation gauge. Snow flurry , snow shower , snow storm and blizzard describe snow events of progressively greater duration and intensity. A blizzard is a weather condition involving snow and has varying definitions in different parts of

2442-425: The atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime . As snow accumulates into a snowpack , it may blow into drifts. Over time, accumulated snow metamorphoses, by sintering , sublimation and freeze-thaw . Where the climate is cold enough for year-to-year accumulation,

2508-458: The avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current . They occur in three major mechanisms: Many rivers originating in mountainous or high-latitude regions receive a significant portion of their flow from snowmelt. This often makes the river's flow highly seasonal resulting in periodic flooding during the spring months and at least in dry mountainous regions like

2574-405: The city a distinct appearance as it has modernized. The dry and inclement plain above La Paz was uninhabited until 1903 when the newly built railways from Lake Titicaca and Arica reached the rim of the canyon, where the La Paz terminus, railyards and depots were built along with a settlement of railway workers (a spur line down into the canyon opened in 1905). In 1925, the airfield was built as

2640-404: The climate is cool and humid to semi-arid and even arid , with mean annual temperatures that vary from 3 °C (37 °F) near the western mountain range to 12 °C (54 °F) near Lake Titicaca; and total annual rainfall that ranges between less than 200 mm (8 in) to the south west to more than 800 mm (31 in) near and over Lake Titicaca. The diurnal cycle of temperature

2706-448: The conditions and ice nuclei. If a crystal has started forming in a column growth regime at around −5 °C (23 °F) and then falls into the warmer plate-like regime, plate or dendritic crystals sprout at the end of the column, producing so called "capped columns". Magono and Lee devised a classification of freshly formed snow crystals that includes 80 distinct shapes. They documented each with micrographs. Snow accumulates from

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2772-475: The context of larger weather systems, the most important of which is the low-pressure area, which typically incorporate warm and cold fronts as part of their circulation. Two additional and locally productive sources of snow are lake-effect (also sea-effect) storms and elevation effects, especially in mountains. Mid-latitude cyclones are low-pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards . During

2838-544: The contribution of snowmelt to river hydraulics and ground hydrology . In doing so, they employ a variety of instruments to observe and measure the phenomena studied. Their findings contribute to knowledge applied by engineers , who adapt vehicles and structures to snow, by agronomists , who address the availability of snowmelt to agriculture , and those, who design equipment for sporting activities on snow. Scientists develop and others employ snow classification systems that describe its physical properties at scales ranging from

2904-450: The crystal facets and hollows/imperfections mean that the crystals often appear white in color due to diffuse reflection of the whole spectrum of light by the small ice particles. Micrography of thousands of snowflakes from 1885 onward, starting with Wilson Alwyn Bentley , revealed the wide diversity of snowflakes within a classifiable set of patterns. Closely matching snow crystals have been observed. Ukichiro Nakaya developed

2970-446: The difficulty of measuring snowfall. Glaciers with their permanent snowpacks cover about 10% of the earth's surface, while seasonal snow covers about nine percent, mostly in the Northern Hemisphere, where seasonal snow covers about 40 million square kilometres (15 × 10 ^  sq mi), according to a 1987 estimate. A 2007 estimate of snow cover over the Northern Hemisphere suggested that, on average, snow cover ranges from

3036-525: The district of El Alto and its surroundings were politically separated from the City of La Paz (this date is officially referred to and celebrated as the city's "founding day"). In 1987, El Alto was formally incorporated as a city. In 1994, the city became the seat of the Roman Catholic Diocese of El Alto . El Alto's autonomous government identifies 14 districts composing the city. El Alto

3102-402: The driest areas on the planet, lies to the southwest of the Altiplano; to the east lies the humid Amazon rainforest . The Altiplano is noted for hypoxic air caused by very high elevation . The communities that inhabit the Altiplano include Qulla , Uros , Quechua and Aymara . Several mechanisms have been put forth for the formation of the Altiplano plateau; hypotheses try to explain why

3168-483: The expense of the water droplets by the Wegener–Bergeron–Findeisen process . These large crystals are an efficient source of precipitation, since they fall through the atmosphere due to their mass, and may collide and stick together in clusters, or aggregates. These aggregates are snowflakes , and are usually the type of ice particle that falls to the ground. Although the ice is clear, scattering of light by

3234-442: The gap between two mountains. When the mass of snow and ice is sufficiently thick, it begins to move due to a combination of surface slope, gravity and pressure. On steeper slopes, this can occur with as little as 15 m (49 ft) of snow-ice. Scientists study snow at a wide variety of scales that include the physics of chemical bonds and clouds ; the distribution, accumulation, metamorphosis, and ablation of snowpacks; and

3300-453: The ground all winter. By late spring, snow densities typically reach a maximum of 50% of water. Snow that persists into summer evolves into névé , granular snow, which has been partially melted, refrozen and compacted. Névé has a minimum density of 500 kilograms per cubic metre (31 lb/cu ft), which is roughly half of the density of liquid water. Firn is snow that has persisted for multiple years and has been recrystallized into

3366-482: The ground where they undergo further changes. It consists of frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide or sublimate away. Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in

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3432-445: The individual crystal to the aggregated snowpack. A sub-specialty is avalanches , which are of concern to engineers and outdoors sports people, alike. Snow science addresses how snow forms, its distribution, and processes affecting how snowpacks change over time. Scientists improve storm forecasting, study global snow cover and its effect on climate, glaciers, and water supplies around the world. The study includes physical properties of

3498-552: The last 10 years. Some migrants say the difficulty of growing crops in the countryside drove them to move to the city. The Köppen climate classification system classifies El Alto's climate as a rare cold-summer variety of a subtropical highland climate ( Cwc ). Temperatures are typically cool during the day and crisp at night year-round. Snowfall is possible at any time during the year. The water supply in El Alto has been impacted by drought caused by shrinking glaciers. In 2016

3564-615: The lift needed for condensation and precipitation. A snowflake consists of roughly 10 water molecules which are added to its core at different rates and in different patterns depending on the changing temperature and humidity within the atmosphere that the snowflake falls through on its way to the ground. As a result, snowflakes differ from each other though they follow similar patterns. Snow crystals form when tiny supercooled cloud droplets (about 10  μm in diameter) freeze . These droplets are able to remain liquid at temperatures lower than −18 °C (0 °F), because to freeze,

3630-526: The major centers of the Bolivian gas conflict . El Alto is known for its Neo-Andean architecture, built from the mid-2000s onward. There is a large open-air market . El Alto is a municipality within the province of Murillo. The government of the city is divided into the executive and legislative branches. The mayor of El Alto is the head of the city government, elected for a term of five years by general election. The legislative branch consists of

3696-563: The material as it changes, bulk properties of in-place snow packs, and the aggregate properties of regions with snow cover. In doing so, they employ on-the-ground physical measurement techniques to establish ground truth and remote sensing techniques to develop understanding of snow-related processes over large areas. In the field snow scientists often excavate a snow pit within which to make basic measurements and observations. Observations can describe features caused by wind, water percolation, or snow unloading from trees. Water percolation into

3762-502: The mountain West of the US or most of Iran and Afghanistan , very low flow for the rest of the year. In contrast, if much of the melt is from glaciated or nearly glaciated areas, the melt continues through the warm season, with peak flows occurring in mid to late summer. Glaciers form where the accumulation of snow and ice exceeds ablation. The area in which an alpine glacier forms is called

3828-401: The municipal council, which elects a president, vice president, and secretary from a group of 11 members. The current mayor is Monica Eva Copa , who defeated MÁS candidate Zacarias Maquera in March 2021 after being ousted by the El Alto party. The previous election was held in March 2021. The Government of El Alto faces competition in providing public services, security and participation with

3894-409: The need for keeping roadways, wings, and windows clear; agriculture : providing water to crops and safeguarding livestock; sports such as skiing , snowboarding , and snowmachine travel; and warfare . Snow affects ecosystems , as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds that themselves are part of

3960-401: The same point roughly 30 minutes apart. In cases where there is a large amount of vertical growth and mixing, the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow . A warm front can produce snow for a period as warm, moist air overrides below-freezing air and creates precipitation at the boundary. Often, snow transitions to rain in

4026-402: The three main dams supplying water to the city were almost dry due to lack of glacial melt water. Museo de Arte Antonio Paredes Candia opened in 2002. From 2003, access from La Paz to the international airport, as well to oil and gas supplies, has been frequently blocked by protesting social leaders and some of the most powerful players in the politics of Bolivia . El Alto remains one of

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4092-678: The topography in the Andes incorporates this large area of low relief at high altitude (high plateau) within the orogen : At various times during the Pleistocene epoch, both the southern and northern Altiplano were covered by vast pluvial lakes . Remnants are Lake Titicaca , straddling the Peru–Bolivia border, and Poopó , a salt lake that extends south of Oruro, Bolivia . Salar de Uyuni , locally known as Salar de Tunupa , and Salar de Coipasa are two large dry salt flats formed after

4158-406: The warm sector behind the front. Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer lake water, warming the lower layer of air which picks up water vapor from the lake, rises up through the colder air above, freezes, and is deposited on the leeward (downwind) shores. The same effect occurring over bodies of salt water

4224-551: The world. In the United States , a blizzard occurs when two conditions are met for a period of three hours or more: a sustained wind or frequent gusts to 35 miles per hour (16 m/s), and sufficient snow in the air to reduce visibility to less than 0.4 kilometers (0.25 mi). In Canada and the United Kingdom , the criteria are similar. While heavy snowfall often occurs during blizzard conditions, falling snow

4290-624: The year tends to be very dry, cool, windy and sunny. Snowfall may happen between April and September, especially to the north, but it is not very common, occurring between one and five times a year. 16°00′13″S 69°39′12″W  /  16.00358°S 69.65332°W  / -16.00358; -69.65332 El Alto El Alto (Spanish for "The Heights" ) is the second-largest city in Bolivia , located adjacent to La Paz in Pedro Domingo Murillo Province on

4356-474: Was once known as La Paz's bedroom community, though recent growth of commerce and industry has led to concern about water pollution by businesses, including tanneries and slaughterhouses, for the city and communities downstream. Rapid population growth means the city struggles to bring potable water and sewer service to parts of the population, especially on the fringes of the expanding urban area. The city contains La Paz’s El Alto International Airport . El Alto

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