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61-645: Risnjak is a mountain in the Risnjak National Park , in Gorski Kotar , Croatia . It belongs to the Dinaric Alps mountain range. The name of the massif probably comes from ris , the Croatian word for lynx . Another interpretation suggests that it comes from the local word risje , which is a name for a type of grass. The vegetation is very diverse. Thirty different plant communities have been recorded, of which

122-401: 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

183-433: 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

244-649: 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

305-447: 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

366-589: 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

427-559: 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

488-485: 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

549-435: 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

610-530: 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

671-484: 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

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732-409: 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

793-419: 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

854-592: 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

915-416: 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

976-630: 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

1037-470: 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, a glacier may form. Otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater . Major snow-prone areas include

1098-550: A very cold temperature inversion present. Snow clouds usually occur in 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

1159-472: 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

1220-575: Is characterised by some especially interesting flora. The peak is home to a variety of rare and sometimes endangered species such as the edelweiss , black vanilla orchid , mountain milfoil , alpine yellow violet , livelong saxifrage , alpine snowbell , mountain avens and hairy alpine rose . The fauna is just as diverse as the flora. The park is home to mammals such as the brown bear , red deer , roe deer , chamois , wild boar , wolf , pine marten , stone marten , badger , weasel , squirrel and dormouse . The most important animal used to be

1281-429: 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

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1342-464: 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

1403-416: Is the site of an abandoned Yugoslav People's Army complex. Since the army left in 1991 the whole place was left to rot, giving it something of the appearance of a ghost town . There have been proposals to renovate the complex to create a mountain refuge, but these have not come to fruition. This path was created by the park administration 1993. It is a circular walk 4.5 km long, beginning and ending at

1464-619: 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

1525-637: The lynx , after which Risnjak got its name. The lynx was exterminated during the 19th century but returned to Risnjak three decades ago, after a successful reintroduction project in neighboring Slovenia. There are also numerous bird species living in Risnjak: capercaillie , hazel grouse , goshawk , eagle owl and several woodpecker species, amongst others. A number of amphibians and reptiles, as well as various insect and snail taxa can also be found. Due to its closeness to major road connections (motorway Zagreb - Rijeka) and vicinity of major tourist centers on

1586-411: 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

1647-790: 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 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

1708-516: The subalpine beech forest with lettuce grass, which grows in areas of the park at heights of between 1200 m and 1400 m above sea level. The upper border of this ecotone is marked by impenetrable underbrush in form of shrubs creating a unique ecosystem, which has been termed the Fagelatum croaticum subalpinum fruticosu . Above the subalpine beech forest there grows the last, highest forest ecosystem - crooked shrubby pine . The rocky peak of Risnjak

1769-629: 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

1830-476: The Croatian parliament voted to enlarge of the park to its current size. The areas of Snježnik and Kupa source were added to the park but also for the first time inhabited areas of villages of Razloge, Razloški okrug and Krašćevica. The park is entirely in Primorje-Gorski Kotar county , and is divided between the city of Čabar , the city of Delnice and the municipality of Jelenje . The highest point of

1891-460: 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

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1952-413: 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

2013-875: The area has once again been inhabited by the ris (lynx). The highest peak of Risnjak mountain is "Risnjak" or Veliki Risnjak at 1528 m.a.s.l. (the latter name means "Big Risnjak"), and it is also the highest peak in the Risnjak National Park, and the second in Gorski kotar next to Bjelolasica . On its southern slope is located the mountain lodge called Šloserov dom , built by Josip Schlosser . The peak can be reached only on foot, from Crni Lug (3 h) or from an unpaved road beginning in Gornje Jelenje (1 h). The highest peaks of Risnjak mountain are: Veliki Risnjak (1528 m), Sjeverni Mali Risnjak (1434 m) and Južni Mali Risnjak (1448 m). Risnjak National Park The name of

2074-458: 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

2135-467: The coastline it is most visited National Park in Croatia. Veliki Risnjak is the highest peak in the park and the second in Gorski kotar next to Bjelolasica. On its southern slope is located the mountain lodge called Šloserov dom, built by Josip Schlosser. The peak can be reached only on foot, from Crni Lug (3 h) or from an unpaved road beginning in Gornje Jelenje (1h). Snježnik is the second highest peak in

2196-462: The cold. Snow develops in clouds that themselves are part of 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

2257-448: 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

2318-544: 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

2379-450: 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

2440-446: 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

2501-483: 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

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2562-442: 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

2623-453: 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

2684-448: 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 the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on

2745-445: 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

2806-615: 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,

2867-471: The limestone is very porous there are few surface flows of water. Although Risnjak is of only a modest altitude, it is nevertheless a very significant climatic and vegetational barrier between coastal and continental parts of Croatia. Adriatic and continental weather patterns collide here and play a significant role in determining the park's climate. It has pleasantly warm summers and an average temperature of up to 22 °C; springs and autumns are rainy, and

2928-570: The massif probably comes from the Croatian word for the lynx , ris . Another interpretation suggests that it comes from the local word risje , which is a name for a type of grass. The first recorded scientific visit was made in 1825 by the Budapest botanist Joseph Standler . Many other botanists visited subsequently. The most prominent 19th century explorer of Risnjak was the botanist Josip Schlosser who wrote numerous publications about Risnjak and its flora . The first organized mountaineering visit

2989-563: 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

3050-429: The most common are beech and fir forests ( Fagetum illyricum abietotosum ) which go up to 1240 m and then are replaced by sub-alpine beeches ( Fagetum croaticum subalpinum ). The highest vegetation is a belt of mountain pine ( Pinetum mughi croaticum ). The fauna is also diverse, but has been less well researched. There are particularly many species of birds and mammals, including several types of chamois, while since 1974

3111-495: 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

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3172-521: The park at 1506 m. Its name comes from the word for snow - snijeg. The mountain should not be confused with Snežnik , a limestone plateau 20 km to the north-west in Slovenia. On its grassy peak is located a mountain lodge called Albaharijev dom. It is about 1.5 hours' walk from the ski resort of Platak ; this has made it the most common place for tour skiing in Croatia. Guslica is a peak about an hour's walk from Snježnik, with an altitude of 1490 m. It

3233-604: The park is Veliki Risnjak (1528 m) and the lowest is the area around the source of the Kupa (313 m). The massif is located on the northern part of the Dinaric Alps , and marks the divide between the Adriatic and Black Sea watersheds . Like most of the Dinaric Alps, the park is dominated by limestone and dolomite rocks and shows major karst features: ponikve, karren on bare rocks, rock falls, swallow holes, caves and so on. Because

3294-401: 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

3355-455: The visitor center in Crni Lug. The path passes through areas of different vegetation and through many different karstic features. The river Kupa has its source at the park's lowest point, in an oval pond some 50 m wide. Numerous expeditions have attempted to determine the pond's depth. Results thus far show that the water springs from two separate channels; the narrower channel is 86 m deep while

3416-406: 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

3477-426: The wider channel is 57 m. The source can be reached by half an hour's walk from the village of Razloge. Snow Snow comprises individual ice crystals that grow while suspended in the atmosphere —usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout its life cycle, starting when, under suitable conditions,

3538-492: The winter is long and snowy. The average year-round temperature at the Risnjak mountain lodge is 2.5 °C with an annual rainfall of 3600 mm, which is amongst the highest in the country, and an average snow depth of between 122 and 448 cm. Areas within the park called ponikvas experience a microclimate where, because of temperature inversions , the lower regions are colder than those at higher altitudes. In ponikvas

3599-783: The winter snow lasts much longer than elsewhere. Although the park occupies only a relatively small area, very diverse types of flora can be found. It marks the point where the coastal and continental vegetation zones meet, as well as combining the Dinaric and Alpine zones. This produces great floral variety across the multiple ecotones found in the park. Most of the park is covered by a mixture of beech and fir trees growing on limestone and dolomite. Numerous variations characterised by local microclimates and types of soil can also be found. Here one can find single trees of sycamore maple , elm , ash , and sometimes some yew . The beech and fir forest gradually gives way to another large forest zone -

3660-537: 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

3721-536: Was mounted by the Rijeka alpine club, and the first mountain refuge in the area was built in 1932. In 1949 botanist Ivo Horvat suggested for the first time that the area around Risnjak should be protected. On his advice, the parliament of the then Socialist Republic of Croatia declared 36.00 km around Risnjak to be a national park. In 1956 the area of the park was reduced to 30.14 km , of which 21.06 km were put under stricter protection. Finally, in 1997,

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