Wikipedia

Search results

Monday, 11 October 2021

Why do natural disasters occur? Part 4


If you're lucky to be living in a place where environmental conditions are suitable to achieve snowfall, you would think snow is a wonderful sight to see and you might stick your tongue out to taste it. As more and more snow falls, there is enough snow for a snowball fight to last as long as your feet don't sink through the soft snow. You might think snow is harmless and soft, but once snow accumulates to substantial levels it can be disruptive to our daily lives, or increase our risk of serious injury, hypothermia, or worse, death. Don't believe me? Lets dig deep into the the coldest natural disasters. 


Where is the coldest place ever? 
https://en.wikipedia.org/wiki/Lowest_temperature_recorded_on_Earth





What is winter? 

  • Depending on where you live on Earth, the coldest season in the polar and temperate zones is known as winter. Note that winter doesn't occur in tropical zones. 
  • The word "winter" originates from the Proto-Germanic noun "wintru-", whose origin is unknown. A 2015 study suggested its origins associated with the Proto-Indo-European root *wed- 'water' or a nasal infix variant *wend-.

What causes winter? 
  • Since Earth is tilted 23.44° to the plane of its orbit, it leads to different latitudes directly facing the Sun as the Earth travels along its orbit. 
  • Winter in the Northern Hemisphere usually occurs between December and February, whereas winter in the Southern Hemisphere usually occurs between June and August. 
  • Winter in a certain hemisphere correlates with the lower altitude of the Sun allowing sunlight to shine on the Earth at an oblique angle. Since, the sun's rays travels longer distances through the atmosphere, it dissipates more the ray's heat in the atmosphere. 
  • The exacerbation of the meteorological winter in the northerly latitudes varies depending on elevation, position vs. marine winds and the amount of precipitation. 
  • e.g. Winnipeg on the Great Plains of Canada has a January high of -11.3 °C (11.7 °F) and a low of -21.43 °C (-6.5 °F). In comparison, Vancouver on the west coast has a January low of 1.4 °C (34.5 °F) with a few days above freezing temperatures at 6.9 °C (44.4 °F). Note both locations are at 49 °N latitude and in the same western half of the continent.  

Different types of winter reckoning 
i. Meteorological 
  • This method measures the winter season according to "sensible weather patterns" for record keeping purposes. 
  • In the Northern Hemisphere, winter season corresponds with the months of December, January and February. 
  • Whereas in the Southern Hemisphere, winter season corresponds with the months of June, July & August. 
  • During the winter season, the night sky lasts longer on average, the precipitation rate is the highest along with significant dampness due to permanent snow cover or precipitation combined with low temperatures, which precede evaporation. 
  • The Swedish Meteorological Institute (SMHI) defined 'thermal winter' as 'the daily mean temperature being below 0 °C (32 °F) for 5 consecutive days'. When Atlantic low-pressure systems move southerly or northerly, this clears the path for high-pressure systems to enter and temperatures to decrease in Scandinavian regions. e.g. Stockholm in January 1987. 

ii. Astronomical and other based on the calendar
  • In the Northern Hemisphere, winter can be defined according to the astronomical fixed points, regardless of weather conditions. This means winter starts at the winter solstice 


iii. Ecological 
  • Ecological reckoning of winter avoids the use of fixed periods of the year. Ecologists use the term "hibernal" (along with other terms such as prevernal, vernal, estival, serotinal and autumnal) to correspond with the main period of biological dormancy each year.
  • Those dates vary according to local and regional climates in temperate zones across Earth. 
  • For example, the sprouting of flowering plants such as the crocus indicates the change from ecological winter to prevernal season as early as January in mild temperate climates. 

Animals develops a number of behavioural and morphological adaptations for overwintering in order to survive the harsh winters. 
  • Migration = Populations of animals traversing across long distances to escape the harsh winters towards warmer climates where food sources are abundant. Examples include birds and butterflies. 
  • Hibernation = A state of decreased metabolism during the winter. Animals such as bats, gophers, frogs, and snakes sleep during winter and only leave their home during warmer climates. 
  • Animals such as beavers, badgers, squirrels, skunks and raccoons store food for the winter and feed themselves during cold climates. 
  • When an animal endures winter, their colour and musculature changes in order to adapt, known as resistance. For instance, the colour of their fur or plumage changes to white colour (in order to blend in with the snow) in order to retain its cryptic coloration. Examples of animals such as Arctic fox, weasel, mountain hare, white-tailed jackrabbit, and rock ptarmigan. 
  • Some animals survive wintry conditions by thickening their fur coats to increase the fur's body heat retention. 
  • Animals such as mice and voles typically burrow through and live under the snow layer to make use of the snow's insulating properties. 


When were the coldest winters? 


What is snow? 
https://en.wikipedia.org/wiki/Snow

The Science of Snowflakes (It's Okay to be Smart): 

Ted-Ed: 


  • Snow is a type of ice crystal that accumulate in the atmosphere, usually within clouds. Subsequently, it falls towards the ground where it blankets the surface in a thick layer. 
It comprises of frozen crystalline water throughout its life cycle: 
1. Ice crystals form in the atmosphere 
2. They increase to millimetre size. 
3. They precipitate and accumulate on surfaces. 
4. They metamorphose in place. 
5. They ultimately melt, slide or sublimate away. 


How does snow precipitate? 


This diagram illustrates the worldwide occurrence of snowfall. The coloured areas indicate annual snow levels at reference above sea levels (metres): 
Indigo = < 500 
Light blue = < 500, but not in all of its territory 
Navy blue = 500, above annually, below occasionally 
Light pink = > 500
Dark pink = > 2,000 
Grey = None at any elevation. 


How do snow clouds form? 

  • Depending on the context of larger weather systems, snow clouds usually form in low-pressure areas such as mid-latitude cyclones, as well as cold fronts. 
  • Mid-latitudes cyclones are capable of forming mild snow storms and severe blizzards, whereas cold fronts are capable of forming frontal snow squalls when conditions are suitable. 

i. Snow squalls 
  • A snow squall is a rapid heavy snow fall accompanied by blowing snow and gusty surface winds. It is occasionally referred to as a whiteout, or milky weather, which obscure and scatter sunlight to reduce the visibility of contours and landmarks in a snow-covered area. 

There are 2 types of snow squalls: 
a. Lake-effect snow 

A satellite image of cold northwesterly wind over Lakes Superior and Michigan produced the lake-effect snowfall in December 2000. 

  • When a cold air mass drifts across long stretches of warmer lake water, it produced lake-effect snow under cool atmospheric conditions. 
  • The areas affected by lake-effect snow known as snowbelts include: 
-- East of the Great Lakes in North America
-- West coasts of northern Japan
-- Kamchatka Peninsula in Russia
-- Areas near the Great Salt Lake, Black Sea, Caspian Sea, Baltic Sea, Adriatic Sea, and North Sea.


How does lake-effect snow form? 
Lake-effect snow forms as cold winds blow clouds over water waters. 

A number of factors are needed to produce lake-effect precipitation, which determine its characteristics: 
  • Instability = This occurs when there is a temperature difference of 13 °C (23 °F) between the lake temperature and the height in the atmosphere (about 1,500 m or 4,900 ft at which barometric pressure measures 850 mbar or 85 kPa). This leads to vertical movement of heat and moisture. 
  • Fetch = This is the distance that an air mass travels over a body of water. Normally, a fetch of at least 100 km (62 mi) is required to produce lake-effect precipitation. There is a directly proportional relationship between fetch and levels of precipitation. 
  • Wind shear = Environments with weaker wind shear associate with more intense squalls than those with higher shear levels. 
-- If directional shear between the surface and the height in the atmosphere at which the barometric pressure measures 700 mb (70 kPa) is greater than 60°, light snowfall is expected. 
-- If the directional shear between the body of water and the vertical height at which the pressure measures 700 mb (70 kPa) is between 30° and 60°, weak lake-effect snow may fall. 
-- In environments where the shear is less than 30°, intense and compact bands of lake-effect snow is forecast. 
-- To prevent upper portions of the snow band from shearing off, the wind-speed difference between the surface and vertical height at which the pressure reads 700 millibar (70 kPa) should be no greater than 40 knots (74 km/h). 
-- If we assume the surface to 700 mb (70 kPa) winds are uniform, moisture is transported more rapidly from the water, and the snow band subsequently travels much farther inland. 
  • Upstream moisture = If upstream moisture has a high relative humidity, lake-effect condensation, cloud, and precipitation can occur more easily and at higher levels. 
  • Upwind lakes = They impact lake-effect precipitation by enhancing moisture or pre-existing lake-effect bands, which can re-intensify over the downwind lake. 
  • Synoptic forces = A 2008 study found vorticity advection aloft and large upscale ascent augment fusion and the convective depth, while cold air advection decreases the temperature and increases instability. 
  • Orography & Topography = Topographic forcing extracts precipitation and dehumidifies the squall more rapidly, which increases the levels of lake-effect precipitation along with elevation to the lee of the lake. 
  • Snow and ice cover = Gradual ice cover over a lake decreases lake-effect precipitation because of diminishing open ice-free liquid surface area of the lake, which decreases fetch distances, as well as decreased overall available latent heat energy to create squalls. 


The location of lake-effect bands on the Great Lakes.



There is a direct relationship between the temperature difference and instability. As the temperature difference increases, instability increases and this influences the convection of the lake-effect precipitation.


Where does the lake-effect snow usually fall? 
United States of America
  • Michigan (Upper Peninsula & Western): Cities of Houghton, Marquette and Munising, Keweenaw Peninsula and Baraga
  • New York (Central & Western): Tug Hill plateau, Finger Lakes falls 
  • Pennsylvania (Northwestern)
  • Ohio (Northeastern)
  • Illinois (Northeastern)
  • Indiana (North central between Gary and Elkhart)
  • Wisconsin (Northern near Lake Superior)
  • Lake Erie: from Cleveland (Ohio), through Erie (Pennsylvania), to Buffalo & Geneva (New York), Garrett County (Maryland) 
  • Utah: Great Salt Lake - Wasatch Front 
  • Mississippi: Ross Barnett Reservoir 
  • Texas: Lake Texoma - Sherman and Denison 
  • Delaware Bay, Chesapeake Bay, Massachusetts Bay 
  • Oklahoma: Lake Hefner - Oklahoma City, Lake Oolagah - Owasso/Collinsville just outside of Tulsa 
  • Nevada: Lake Tahoe - Truckee Meadows 
  • Washington State: From Columbia River, Canada via Fraser Valley, Strait of Georgia and Strait of Juan de Fuca, over the northeastern slopes of the Olympic Mountains, before bringing snowfall between Port Angeles and Sequim, as well as areas in Kitsap County and the Puget Sound region. 
  • Florida: Northern coast of the Gulf of Mexico

Canada
  • Ontario (Southwestern and central): Port Stanley (West), Bruce Peninsula (North), Niagara-on-the-lake (East), Fort Erie (South) 
  • Snowbelt runs north-south from Grand Bend to Sarnia and London. Areas such as Lucan and Kincardine. 
  • Westerly winds can push the snowbelt from Tobermory, Owen Sound, and Grand Bend to as far south and east as Arthur, Orangeville and Caledon. This reaches Kitchener, as well as the Halton and Peel regions of the Greater Toronto Area. 
  • Northwesterly winds drives lake-effect snowbelts east from Owen Sound to Gravenhurst, Barrie, and Orillia. It may even approach as far south and east as York Region in the Greater Toronto Area.
  • Southwesterly winds pushes lake-effect snowbelts from Lake Huron and Georgian Bay, as well as Noelville to Sudbury, Gravenhurst, and Algonquin Provincial Park. 
  • Furthemore southwesterly squalls from Lake Ontario arrive ashore rom Cobourg through the Belleville area to Kingston and the Thousand Islands, reaching the Prince Edward County. 
  • Lake-effect snowbelts from Lake Superior impacts Wawa, Sault Ste. Marie, Marathon, the Keweenaw Peninsula in Upper Michigan, and Pukaskwa National Park.

Eurasia

IRIMO: Radar animation of lake effect snow in southern coast of Caspian Sea in the north of Iran


Regions in the:
  • Black Sea: Georgia, Romania, Bulgaria and northern Turkey
  • Caspian Sea: Iran (Gilan and Mazandaran provinces, Abkenar village near Anzali Lagoon)
  • Adriatic Sea: Italy, eastern Apennine Mountains 
  • North Sea
  • Irish Sea
  • Aegean Sea: Eastern Central Greece, eastern Thessaly, eastern Peloponnese, south-eastern Chalkidiki, the Cyclades, and Crete
  • Balearic Islands: 
  • Baltic Sea: Southern and eastern coasts of Sweden, Danish island of Bornholm, east coast of Jutland, northern coast of Poland.
  • Sea of Japan: Mountainous western Japanese prefectures of Niigata and Nagano. 

United Kingdom

This chart illustrates the sea-effect snow event of January 1987 in the UK: A continuous stream of showers deposited over 2 feet (24 in) of snow over SE coastal regions.


  • North-westerly winds across the Liverpool Bay through the Chesire Gap brings snowbelts to the West Midlands i.e. 2004 White Christmas
  • The city of Inverness in the Scottish Highlands, where north-east winds brings heavy snowfall in the Moray Firth. 
  • Northerly and north-westerly winds brings snow fall over the Irish Sea and Bristol Channel and into South West England and eastern Ireland. 
NetWeather: This radar image illustrates the "lake-effect" snow over Kent and northeast England.



b. Frontal snow squall 

  • Frontal snowsqualls are intense frontal convective lines that form in environments with near-freezing temperatures at the surface. It contains sufficient moisture to generate whiteout conditions in areas where the squall line travels over as the wind propels blowing snow. 
  • Snow squalls pose risks to motorists, airplanes or anyone unfortunate enough to be affected by. This is due to whiteouts diminishing visibility, slippery ground conditions and rapid change in weather conditions. This would lead to multiple-vehicle collisions, road closures, or shutting down cities. 

ii. Whiteout 

  • Sometimes called milky weather, a whiteout is a weather condition that obscures contours and landmarks in a snow-covered zone. 
  • Sir Vivian Fuchs & Sir Edmund Hillary (1958) defined it as "A condition of diffuse light when no shadows are cast, due to a continuous white cloud layer appearing to merge with the white snow surface. No surface irregularities of the snow are visible, but a dark object may be clearly seen. There is no visible horizon."
  • Whiteout conditions pose safety risks to mobile ground traffic, public transport, mountain climbers, skiers, and aviation, which can lead to multiple-vehicle collisions. 
  • In 1979, an Air New Zealand Flight 901 crashed on Mount Erebus, Antarctica in whiteout conditions. 

There are 3 different types of whiteout: 
1. In a blizzard, ground-level snow are blown by the wind that decreases visibility to near zero. 
2. The amount of snowfall determines how quickly visibility can be decreased to near zero e.g. lake-effect snow. 
3. Ground-level thick fog exists in a snow-covered environment, particularly in open areas that lack such features. 


iii. Mountain effects 
  • When moist air is pushed up the windward side of mountain ranges by a macroscopic wind flow, this produces orographic or relief snowfall. This results in adiabatic cooling, hence condensation and precipitation. 
  • A 2008 study found that this process causes the gradual disappeared of moisture in the air, which remains drier and warmer air on the descending side. When the resulting elevated snowfall combine with reduced temperature with elevation, it increases snow depth and seasonal persistence of snowpack in snow-prone areas.


How do snowflakes form? 



How does snow accumulate? 
  • Snow tends to accumulate in certain areas such as the Arctic and Antarctic, the Northern Hemisphere, and the alpine regions. Numerous snow events situate there because they are sufficiently cold to retain snow seasonally or perennially.
  • Examples of snow events that lead to snow accumulations include snow flurries, snow showers, snow storms and blizzards, which vary in terms of duration and intensity. The snow event's intensity is classified in terms of visibility and depth of accumulation: 
-- Light: Visibility > 1 km (0.6 mi) 
-- Moderate: Visibility restrictions 0.5 - 1 km (0.3 - 0.6 mi) 
-- Heavy: Visibility < 0.5 km (0.3 mi)

  • 10% of Earth's surface contains glaciers with permanent snowpacks, whereas 9% contain glaciers with seasonal snowpacks. A 1987 study estimated 40 million square km (15 million sq mi) of seasonal snow blankets the Northern Hemisphere. 
  • Lemke et al. (2007) estimated snow cover on the Northern Hemisphere to be between 2 million square km (770,000 square mi) every August and 45 million square km (17 million square km) every January. 
Records: 
  • Highest seasonal total snowfall = 2,896 cm (95.01 ft) of snow on Mount Baker Ski Area in the United States outside Bellingham, Washington during the 1998-1999 season. 
  • Highest seasonal average annual snowfall = 1,764 cm (57.87 ft) of snow fell on Sukayu Onsen, Japan between 1981 and 2010. 
  • Largest snowflake = 38 cm (15 in) in diameter discovered outside (formerly Fort Keogh) present-day Miles City, Montana in January 1887. 


Describe the metamorphosis of snow 
  • After snow is deposited, it either ablates (by melting) or transitions from firn into glacier ice. When a snowpack is close to its melting temperature, it continually transforms its properties of porousness and sintered structure in a process called "metamorphosis". That is, all three phases of water may coexist, including liquid water partially filling the pore space. 
  • David McClung & Peter Schaerer (2006) explained that deposited snow initially exists in a powdered form, before becoming more granular as it condenses under its own weight, being carried by the wind, its particles sintering together and the cycle of melting and refreezing commences. 
  • Snowpack = When layers of snow accumulate in geographic regions and high elevation, this leads to the formation of a snowpack. They are an integral water resource that supply streams and rivers upon melting, hence they are both the drinking water source for many communities and a potential source of flooding. Over time, it may settle under its own weight until its density is approximately 30% of water. 



  • Névé = This is a young, granular type of snow that is partially melted, refrozen and compacted, but precedes actual ice. It associates with the formation of glaciers through nivation, which is a set of geomorphic processes associated with snow patches. Its minimum density is roughly 500 kg/cm³ , which is roughly half of the density of liquid water at 1 atm. 



  • Firn = Derived from Swiss German word 'firn' meaning "last year's", cognate with before, it is a type of snow that has remained from previous seasons and  recrystallised into a substance that is denser than névé. It gives off the impression of wet sugar, and is sufficiently sturdy to resist shovelling. Its density can be between 0.4 g/cm³ to 0.83 g/cm³, and are found beneath the snow that accumulates at the glacier's head. 




How does deposited snow move? 
There are 4 main mechanisms for moving deposited snow: 
  • Drifting = Carried by the wind to possibly form snow slabs on steep slopes. 
  • Avalanche = Collections of snow that rapidly flow down a sloped surface, usually triggered by a mechanical failure in the snowpack. 
  • Snowmelt = Contributes to the formation of numerous rivers in mountainous or high-latitude regions. 
  • Glaciers = If snow and ice accumulation exceeds ablation, this leads to the formation of glaciers. An area in which an alpine glacier forms is called a cirque (corrie or cwm). 


Describe the science of snow 
Throughout history, the hexagonal shape of the snowflake, a crystalline formation of ice was a curious topic for researchers, artists and philosophers. Below is a timeline of the progress of research into the snowflake since the earliest records by the Chinese. 
  • 150 BC or 135 BCE = Han Ying (韓嬰) assembled the anthology Han shi waizhuan, which includes a passage that contrasts the pentagonal symmetry of flowers with the hexagonal symmetry of snow. This is explored further in the Imperial Readings of the Taiping Era.
  • 1250 = Albertus Magnus provided arguably the oldest detailed description of snow. 
  • 1555 =  Olaus Magnus published the earliest snowflake diagrams in Historia de gentibus septentrionalibus. He described snowflakes as having a peculiar assortment of shapes, including crescents, arrows, and even a human hand. 
  • 1591 = English astronomer Thomas Harriot accurately identified the snowflake’s six-fold symmetry. 
  • 1611 = In his work Strenaseu De Nive Sexangula, Johannes Kepler attempted to explain the reason for the snow crystal's hexagonal shape. 
  • 1637 =  René Descartes' Discourse on the Method includes hexagonal diagrams and an analysis of the crystallisation process and conditions for snowflakes.
  • 1660 = In his work De figura nivis dissertatio, Erasmus Bartholinus includes sketches of snow crystals. 
  • 1665 = Robert Hooke observed snow crystals under magnification in his work Micrographia.
  • 1675 = A German physician named Friedrich Martens catalogued 24 types of snow crystal. 
  • 1681 = Donato Rossetti categorised snow crystals in his work La figura della neve.
  • 1778 = Dutch theologian Johannes Florentius Martinet illustrated accurate sketches of snow crystals. 
  • 1796 = Shiba Kōkan published his sketches of ice crystals under a microscope.
  • 1820 = William Scoresby's An account of the Arteic Regions includes snow crystals by type. 
  • 1832 = In his work 雪華図説, Doi Toshitsura described and illustrated 86 types of snowflake. 
  • 1837 = Suzuki Bokushi (鈴木牧之) published his study called Hokuetsu Seppu.
  • 1840 = Doi Toshitsura expanded his list of snowflake categories to include 97 types.
  • 1855 = James Glaisher published his detailed sketches of snow crystals under a microscope.
  • 1865 = Frances E. Chickering published his work Cloud Crystals - a Snow-Flake Album. 
  • 1870 = Adolf Erik Nordenskiöld identified "cryoconite holes", which contain liquid water and therefore provide a niche for cold-adapted microorganisms like bacteria, algae and animals such as rotifers and tardigrades to thrive in the summer. 
  • 1872 = John Tyndall published his work The Forms of Water in Clouds and Rivers, Ice and Glaciers.
  • 1891 = Friedrich Umlauft published his work Das Luftmeer, which translates to "the sea of air". 
  • 1893 = Richard Neuhauss was the first to photograph a snowflake under a microscope, titled Schneekrystalle.
  • 1894 = A. A. Sigson photographed snowflakes under a microscope. 
  • 1901 = Wilson Bentley published a series of photographs of individual snowflakes in the Monthly Weather Review.
  • 1903 =  Svante Arrhenius described the crystallisation process in his work Lehrbuch der Kosmischen Physik.
  • 1904 = Helge von Koch discovered the fractal curves to be a mathematical description of snowflakes. 
  • 1931 = Wilson Bentley and William Jackson Humphreys published their work Snow Crystals. 
  • 1936 = Ukichiro Nakaya produced snow crystals and graphed the relationship between temperature and water vapour saturation, later called the Nakaya Diagram.
  • 1938 = Ukichiro Nakaya publishes another word called Snow (雪). 
  • 1949 = Ukichiro Nakaya published his work Research of snow (雪の研究, Yuki no kenkyu).
  • 1952 = Marcel R. de Quervain et al. defined 10 major types of snow crystals, including hail and graupel in IUGG for the Swiss Federal Institute for Snow and Avalanche Research.
  • 1954 = The Harvard University Press published Ukichiro Nakaya's work Snow Crystals: Natural and Artificial.
  • 1960 = Teisaku Kobayashi (小林禎作) verified and improved the Nakaya Diagram with the Kobayashi Diagram. 
  • 1962 = Cyoji Magono (孫野長治, Magono Cyōji) described meteorological sorting of snow crystal types in clouds. 
  • 1979 = Toshio Kuroda (黒田登志雄) and Rolf Lacmann, of the Braunschweig University of Technology, published their study titled Growth Mechanism of Ice from Vapour Phase and its Growth Forms.
  • 1982 = Toshio Kuroda and Rolf Lacmann published another work titled Growth Kinetics of Ice from the Vapour Phase and its Growth Forms. 
  • 1983 = Astronauts produced snow crystals in orbit on the Space Shuttle Challenger during mission STS-8. 
  • 1988 = Norihiko Fukuta (福田矩彦) et al. produced artificial snow crystals in an updraft, which confirmed the Nakaya Diagram.
  • 2002 = Kazuhiko Hiramatsu (平松和彦) designed a simple snow crystal growth observatory apparatus using a PET bottle cooled by dry ice in an expanded polystyrene box.
  • 2004 = Akio Murai (村井昭夫) invented the apparatus named (literally) Murai-method Artificial Snow Crystal producer (Murai式人工雪結晶生成装置). This apparatus created various shape of artificial snow crystals per pre-setting conditions meeting to Nakaya diagram by a vapour generator and its cooling Peltier effect element.
  • 2008 = Yoshinori Furukawa (吉川義純) demonstrated conditional snow crystal growth in space, in Solution Crystallisation Observation Facility (SCOF) on the JEM (Kibō), which was remotely controlled from Tsukuba Space Center of JAXA. 

First snowflake diagrams by Olaus Magnus in 16th century. 

Photographs of snowflakes by Wilson Bentley


The Nakaya Diagram illustrates different types of snow crystals that enlarge in the air at atmospheric pressure, as a function of temperature and water vapour supersaturation relative to ice. The water saturation line gives the supersaturation of supercooled water, as might be found within a dense cloud. Note that the morphology switches from plates ( T ≈ -2 °C) to columns ( T ≈ -5 °C) to plates ( T ≈ -15 °C) to predominantly columns ( T < -30 °C) as temperature is decreased. Temperature mainly determines whether snow crystals will develop into plates or columns, while higher supersaturations generally produce more complex structures. 



What properties of snow are measured? 
  • Height (H, cm) = Distance vertically from the ground surface.
  • Thickness (D, cm) = Snow depth measured at right angles to the slope on inclined snow covers. 
  • Height of snowpack (HS, cm) = Total depth of the snowpack, measured vertically from base to snow surface.
  • Height of new snow (HN, cm) = Depth of freshly fallen snow that accumulated on a snow board during a period of 24 hours or some other, specified period.
  • Snow water equivalent (SWE, m*kg/m³) = Depth of water that would result if the snow mass melted completely, whether over a given region or a confined snow plot, calculated as the product of the snow height multiplied by the vertically-integrated density. 
  • Water equivalent of snowfall (HNW) = Snow water equivalent of snowfall, measured for a standard observing period of 24 hours or other period.
  • Snow strength (Σ, Pascals per second squared) = Whether compressive, tensile, or shear, snow strength can be regarded as the maximum stress snow can withstand without failing or fracturing. 
  • Penetrability of snow surface (P, cm) = The depth an object penetrates into the snow from the surface, usually measured with a Swiss rammsonde, or more crudely by a person standing or on skis. 
  • Surface features (SF) = These describe the general appearance of the snow surface, influenced by deposition, redistribution and erosion by wind, melting and refreezing, sublimation and evaporation, and rain. The following processes have the corresponding results: (a) Smooth: Deposition without wind; (b) Wavy: Wind deposited snow; (c) Concave furrows: Melt and sublimation; (d) Convex furrows: Rain or melt; (e) Random furrows: Erosion.
  • Snow covered area (SCA) = This describes the extent of snow-covered ground, usually expressed as a fraction (%) of the total.
  • Slope angle (Φ) = The angle measured from the horizontal to the plane of a slope with a clinometer.
  • Aspect of slope (AS) = The compass direction towards which a slope faces, normal to the contours of elevation, given either degrees from true North N = 0° = 360° or as N, NE, E, SE, S, SW, W, NW.
  • Time (t, seconds) = A measurement duration or in longer units to describe the age of snow deposits and layers.

What are the main categories of deposited snow? 

  • Precipitation particles (PP) = All are formed in cloud, except for rime, which develops on objects exposed to supercooled moisture, and some plate, dendrites and stellars, which can generate in a temperature inversion under clear sky. 
  • Machine-made snow (MM) = Round polycrystalline particles produced by tiny water droplets from the surface inward being frozen or crushed and forced distribution of ice particles.
  • Decomposing and fragmented precipitation particles (DF) = Decomposition is caused by a decrease of surface area to reduce surface free energy initial break up by light winds. Wind causes fragmentation, packing and rounding of particles.
  • Rounded Grains (RG) = Varies from rounded, usually elongated and sintered particles of size around 0.25 mm. They may be wind packed or faceted rounded, as well.
  • Faceted Crystals (FC) = Develops with grain-to-grain vapour diffusion driven by a large temperature gradient 
  • Depth Hoar (DH) = Grain-to-grain vapour diffusion driven by large temperature gradient 
  • Surface Hoar (SH) = Rapid growth of crystals at the snow surface by transfer of water vapour from the atmosphere toward the snow surface, which is cooled by radiative cooling below ambient temperature.
  • Melt Forms (MF) = Ranges from clustered round grains of wet snow through melt-freeze rounded polycrystals when water in veins freezes to loosely bonded, fully rounded single crystals and polycrystals to polycrystals from a surface layer of wet snow that refroze after having been wetted by melt or rainfall.
  • Ice Formations (IF) = Incorporates the following features: 
-- Horizontal layers, resulting from rain or meltwater from the surface percolating into cold snow and refreezing along layer barriers. 
-- Vertical fingers of frozen drained water.
-- A basal crust resurgent from melt water ponding above a substrate and freezes. 
-- A glaze of ice on the snow surface, resulting from freezing rain on snow. 
-- A sun crust from melt water at the surface snow refreezes at the surface due to radiative cooling.


What are the physical properties of snow? 
  • Microstructure = Complex and hard to measure but understood to have an effect on the thermal, mechanical, and electromagnetic properties of snow.
  • Grain shape (F) = Includes both natural and artificial depositions
  • Grain size (E, mm) = Average size of grains, each measured at its greatest extension
  • Snow density (ρs, kg/m³) = Mass per unit volume of snow of a known volume, ranges from very fine at below 0.2 mm to very coarse (2.0–5.0 mm) and beyond. 
  • Snow hardness (R) = Resistance to penetration of an object into snow 
  • Liquid water content (LWC) = Sometimes called free water content, 
  • Snow temperature (Ts, °C) = Measured at various elevations in and above the snow column: at the ground, at the surface and a reported height above the surface
  • Impurities (J, %, ppm) = Examples include dust, sand, soot, acids, organic and soluble materials
  • Layer thickness (L, cm) = The stratum of a snowpack 
Platelets and needles forms of snowflakes 

Fresh, dry snow with newly formed bonds, showing a grain boundary (top centre).

Cluster of ice grains in wet snow at low liquid content—grain crystals diameter range from 0.5 to 1.0 mm.


Describe the models of snow science


Global climate change models (GCMs) incorporate snow as a factor in the mathematical equations. The following models compute snow water equivalent (SWE): 

SWE = [–ln( 1 – fc)] / D
-- fc = Fractional coverage of snow 
-- D = masking depth of vegetation (≈ 0.2 m worldwide)


Snowmelt models use a degree-day approach that highlights the temperature difference between the air and the snowpack to compute snow water equivalent (SWE) as:

SWE = M (Ta – Tm) when Ta ≥ Tm

= 0 when Ta < Tm

More recent models use an energy balance approach that take into account the following factors to compute the energy available for melt (Qm) as:
Qm = Q* + Qh + Qe + Qg + Qr – QΘ
-- Q* = Net radiation
-- Qh = Convective transfer of sensible heat between snowpack and airmass
-- Qe = Latent heat lost through evaporation from or condensation onto the snowpack
-- Qg = Conduction of heat from the ground into the snowpack
-- Qr = Advection of heat through rain
-- QΘ = Rate of change of internal energy per unit of surface area
Calculation of the various heat flow quantities (Q) requires measurement of a much greater range of snow and environmental factors than just temperatures.


How does snow affect human activity? 
i. Transportation 
  • Snow blocks the operation of highways, airfields, railroads, as well as decrease friction on the road and generate icing conditions on the road surface. 
  • This required a number of interventions to clear away snow and remove ice from the roadways, highways, railways and taxiways. 
Examples of interventions include: 
-- Snow tires 
-- Anti-icing Programs e.g. De-icing fluid 
-- Snow fences 
-- Mechanical brushes, Pulsing pneumatic boots, Electro-thermal areas, Fluid De-icers 
-- Snow plows e.g. Rotary or wedge snowplows 


ii. Agriculture 
  • Snow can function as a thermal insulator to agriculture, which protects crops from subfreezing weather and conserves the Earth's warmth. 
  • When snow on the ground melt in warmer months, it supports crops via runoff through streams and rivers that supply irrigation canals. 
  • e.g. Tributaries from the Ganges ascend in the Himalayas, distributing irrigation water to northeast India. 


iii. Structures 
  • According to the Minimum Design Loads for Buildings and Other Structures, the following factors into roof snow loads include ground snow loads, roof exposure, the roof's thermal properties, the roof's shape, drifting and the integrity of the building. 
  • Roofs are also specifically designed to prevent ice dams, which are caused by meltwater running under the snow on the roof and freezing at the eave. Ice dams lead to damaged building materials or in damage or injury upon falling from the roof. 
  • When heavy snow damage trees, those trees can damage adjacent utility distribution lines on poles. Farzaneh (2008) stated that removal of rime ice can be done manually or by a sufficient short circuit in the affected segment of power lines to melt the accretions. 


iv. Sports & Recreation 
  • Common winter sports played in the snow include skiing, sledding, cross-country skiing, Alpine skiing, snowboarding, snowshoeing, and snowmobiling. The winter sport equipment used such as skis or snowboards depend on the snow's bearing strength to cope with the snow's coefficient of friction in order to slide smoothly. 
  • Ski resorts use a snow cannon to produce snow by driving water and pressurised air through a snow gun on ski slopes. This improves the reliability of the ski resorts' snow cover and extend their ski seasons from late autumn to early spring.
  • Ski wax is a material applied to the bottom of ski runners such as skis, snowboards, and toboggans to enhance their coefficient of friction performance under varying snow conditions because it helps overcome both static and kinetic friction. 

v. Warfare 
  • The impacts of snow on war missions in winter, alpine environments or at regions of high latitudes include impaired visibility for acquiring targets in snowfall, improved visibility of targets against snowy backgrounds, and mobility for both mechanised and infantry troops. 
  • Further effects include inhibition of the logistics of supplying troops, as well as provision of cover and fortification against small-arms gunfire. 
Famous winter warfare campaigns impacted by snow include: 
  • French invasion of Russia: Deplorable traction conditions for ill-shod horses made supply of wagons to keep abreast with troops quite difficult. In December 1812, the retreating army approached the Neman River with only 10,000 of the 420,000 men that departed for Russia in June of the same year. 
  • Winter War: In late 1939, Soviet Union attempted to take territory in Finland by employing winter tactics of the Finnish Army, including over-snow mobility, camouflage, and the terrain. 
  • Battle of the Bulge: During WWII, on 16th December 1944, this German counteroffensive was impacted by snowstorms that hampered allied air support for ground troops, as well as spoiled German attempts to supply their front lines. In 1941, situated on the Eastern Front with the invasion of Russia by the Nazis, Operation Barbarossa, both Russian and German soldiers had to endure terrible conditions during the Russian winter.
  • Korean War (25th June 1950 - 27th July 1953): Most battles, such as the Battle of Chosin Reservoir, took place during winter conditions, which significantly impacted military operations. 
Army vehicles having difficulty with snow during the Battle of the Bulge of WWII.



Finnish troops using skis to traverse snow during the invasion of Finland by the Soviet Union 



Bivouac of Napoleon's Grande Armée, during the winter retreat from Moscow 



How does snow affect ecosystems? 
Both plant and animal life endemic to snow-bound areas adapt to the chilly conditions by developing survival mechanisms. Plants developed dormancy, seasonal dieback, seed survival, whereas animals developed hibernation, insulation, anti-freeze chemistry, food storage, energy expenditure from body resources, and clustering for mutual heat. 

i. Plant life 
  • Snow can impact the distribution and growth of vegetation, and conversely, the vegetation can affect the deposition and retention of snow. 
Effects include: 
-- Longer tree branches (e.g. conifers) intercept falling snow and prevent accumulation on the ground. 
-- Snow suspended in trees ablate more quickly than that on the ground because they are exposed to sun and air movement for a longer period. 
-- Stored water enhances plant growth. 
-- Avalanches and erosion from snowmelt clears terrain of vegetation. 


ii. Animal life 
  • Invertebrates such as spiders, wasps, beetles, snow scorpionflies and springtails are known to thrive in snowy environments. 
There are 2 categories of arthropods regarding survival in subfreezing temperatures: 
-- Freeze-resistant arthropods = They produce antifreeze agents in their body fluids that help them survive long periods in sub-freezing conditions.
-- Freeze-sensitive arthropods = They fast during the winter in order to release freezing-sensitive contents from their digestive tracts.

  • Small vertebrates such as alpine salamanders burrow to the surface during spring and lay their eggs in melt ponds. 
  • Omnivores tend to enter torpor to hibernate, whereas herbivores tend to maintain food caches beneath the snow. e.g. Voles store up to 3 kg (6.6 lb) of food and pikas store up to 20 kg (44 lb). 
  • Surface animals such as coyotes, foxes, lynx, wolves, and weasels heavily depend on subsurface dwellers for food, hence they dig into the snowpack to locate them. 


Can 2 snowflakes be alike? 




Can you spot any differences?


  • Given the complexity and the sheer number of possible snowflakes in terms of shape, size, and different types of water molecules, the answer is "probably, but hard to prove". 
  • There are number of studies and educational videos that argue for and against the likelihood of finding 2 identical snowflakes. From the naked eye, it may seem possible that at least 2 snowflakes share an identical appearance. However, if we observe these snowflakes at the microscopic level, they appear to be similar but not identical. 
  • Every winter, at least 1 septillion (1 x 1024) snowflakes fall from snow clouds and scavenging for at least 2 identical snowflakes would be taxing and ambitious. To put that in perspective, I would have a better chance of winning the lottery (1 in 300 million) than finding 2 identical snowflakes. 
  • According to physics, not all water molecules are created equally. A water molecule has 1 Hydrogen atom and 2 Oxygen atoms. Not every hydrogen atom created within our universe is identical. The common hydrogen atom we are all familiar with contains 1 Proton and 1 orbiting electron. The rare Hydrogen atoms contain a Neutron in its Nucleus, making it slightly heavier, which are labelled as Deuteriums. About 1 in 3,000 water molecules within a snowflake contain Deuteriums in various positions. 
  • Furthermore, the snowflake's nanoscopic structure is highly sensitive to unstable atmospheric conditions, which means its shape and design would change as soon as they descend from the snow cloud and become exposed to fluctuating temperatures. 
  • Therefore, finding 2 snowflakes with an identical structure that contains an identical number of water molecules, and identical composition deuteriums and normal hydrogen atoms in identical positions and orientation to form an identical arrangement would be close to impossible. 




Why are snowflakes hexagonal? 





  • The 2 Hydrogen atoms serve as the 2 positive poles, while the 2 localised orbital electrons on the oxygen atom directly opposite serve as the 2 negative poles. 
  • The positive poles of the water molecule are attracted to the negative poles of an adjacent water molecule to form an intermolecular Hydrogen bond. Each of the 3 remaining poles on the water molecule bond with 3 other adjacent water molecules. 


  • When the angle between the positive and negative poles of the water molecule is close to the interior angle of a perfect hexagon (i.e. 120 degrees), the water molecules bind to form a hexagonal ring. 
  • Microscopic analysis found the Hydrogen atoms in a snowflake adjust their orientation by shifting 5 degrees away from each other (104.5 degrees to 109.5 degrees) compared to a free Hydrogen atom. 
  • Because this larger internal angle is closer to but still less than 120 degrees, the sides of the hexagonal ring slightly scrunch up to form adequately strong Hydrogen bonds to the rings above, below and adjacent to the ring. Therefore, the tetragonal nature of the water molecules allows the formation of this hexagonal lattice. 





  • Water molecules on the snowflake's surface experience a number of unequal forces, depending on which sides of the rings are being interacted with by the free water molecules. 
  • When only a few water molecules exists at the surface of each hexagonal ring, the forces responsible for the growth of the surface gradually increases. These slow-growing faces expand along the surface, which effectively eliminates other faces. This means the remaining faces bind together at approximately angles of 120 degrees. 




ii. Blizzards 



  • Blizzards are severe snowstorms that feature powerful and persistent winds blowing large volumes of snow to decrease visibility and blanket affected areas with snowdrifts. 
  • Features that distinguish blizzards from snow storms include sustained winds or frequent gusts greater or equal to 56 km/h (35 mph) that blow snow, decreasing visibility to 400 m or 0.25 mi or less for an extended period of time (~ 3-4 hours). 
  • Blizzards commonly occur in regions of higher and mid-latitudes, particularly in Russia and central and northeastern Asia, northern Europe, Canada, the northern United States of America, and Antarctica. 

USA snow storm systems 
  • When the jet stream flows to the south, it brings cold, dry polar air from the north to collide with warm, humid air flowing up from the south.
In the case of USA, a blizzard forms due to the combination of air from 3 different sources: 
-- Cold, moist air from the Pacific Ocean drifts eastward to the Rocky Mountains and the Great Plains. 
-- Warmer, moist air from the Gulf of Mexico drifts northward.
-- Cold, polar air drifts southward. 
The potential blizzard conditions could extend from the Texas Panhandle to the Great Lakes and Midwest. 

Other potential areas where blizzards can form include: 
-- A cold core low situated over the Hudson Bay area in Canada is displaced southward over southeastern Canada, the Great Lakes, and New England.
-- Rapid, cold front colliding with warmer air drifting north from the Gulf of Mexico. 

  • A macro-scale storm situating off the New England and Atlantic Canada coastlines with winds blowing in the north-east direction is known as a nor'easter. 

a. North America 




Highest average blizzard activity occurs in the northern plains, particularly North and South Dakota and western Minnesota, as well as parts of eastern Minnesota, northwestern Iowa, northern Nebraska, and southeastern Wyoming. 



This figure shows the geographic distribution of blizzards by decade displayed distinct periods of concentrated blizzard events contrasted with phases of more widespread activity. 











When were the deadliest blizzards?


iii. Ice Storms 

https://en.wikipedia.org/wiki/Ice_storm 


  • Also known as a glaze event or silver thaw, an ice storm is a type of winter storm featuring freezing rain. 
  • The U.S. National Weather Service defines this weather event as "a storm that accumulates at least 0.25-inch (6.4 mm) of ice on exposed surfaces".

How do ice storms form?


  • When a layer of above-freezing air is above a layer of sub-freezing temperatures closer to the surface, ice begins to form. 
  • When frozen precipitation falls into the warm air layer, it melts to rain. Subsequently, it refreezes in the cold layer below the warm layer. 
  • If the precipitate refreezes whilst airborne, it reaches the ground as sleet or ice pellets, which are small, translucent balls of ice. 
  • Liquid droplets can continue to plummet without freezing through the cold air just above the surface, which then cools the rain to a temperature below freezing (0 °C; 32 °F). 
  • Since these raindrops don't become solid, this phenomenon is known as "supercooling". When the supercooled drops contacts the ground or any object below 0 °C (32 °F) (e.g. power lines, tree branches, aircraft), a layer of ice accumulates as the cold water drips off. This leads to the formation of thickening film of ice, known as freezing rain. 

What are the effects of ice storms? 
  • Ice storms blankets every object it interacts with heavy, smooth glaze ice. 
  • Hazardous driving or walking conditions
  • The weight of ice damages trees and its branches. 
  • Damage to infrastructure and facilities such as power lines, power / utility poles, and electricity pylons with steel frames, hence significant blackouts. 
  • Manifestation of illnesses and deaths due to unintentional carbon monoxide (CO) poisoning. Symptoms of low levels CO poisoning include nausea, dizziness, fatigue, and headache, whereas at high levels, symptoms include unconsciousness, cardiac arrest, and death. 
  • The increased CO levels are attributable to the use of alternative methods of heating and cooking during prolonged blackouts such as charcoal and propane barbecues, kerosene heaters and gas generators. 


iv. Hail 

https://en.wikipedia.org/wiki/Hail


  • A form of solid precipitation that resembles lumps of ice is called a hailstone, or hail. When a thunderstorm is capable of producing hail, it is known as a hailstorm. The diameter of hailstones ranges from 5 mm (0.20 in) to 15 cm (6 in), as well as weigh more than 0.5 kg (1.1 lb). 
  • In the USA, a number of hailstones known to have damaged car windscreens and home windows range from 2.5 cm (0.98 in) and 4.4 cm (1.75 in). Since January 2010, the US National Weather Service determined the threshold of a hailstone as having a diameter at least 2.5 cm (0.98 in). 


How does hail form? 
  • In cumulonimbus clouds, water droplets ascend and the temperature plummets below freezing to become supercooled water. Once it contacts with condensation nuclei, it freezes into hail stones. 
  • Hail stones develop layer by layer with varying transparency and thickness as it ascends into cloud regions of varying humidity and levels of supercooled water. 
  • Other factors of the hailstone size include the accretion rate of these water droplets, which are influenced by the relative velocities between these water droplets and the hailstone itself. 
  • Nelson (1983) states that larger hailstones develop a considerable distance from the stronger updraft where they spend more time increasing its size. 
  • Brimelow et al. (2002) found that hailstones release latent heat as it enlarges, which maintains the exterior in liquid form. Furthermore, one hailstone may collide with smaller hailstones to expand into a larger, irregular hailstone, known as "wet growth". 
  • If the latent heat released through freezing is insufficient to keep the outer layer in liquid form, hailstones would undergo "dry growth". This makes hailstones more opaque because of small air bubbles being trapped in the hailstone during the freezing phase. These bubbles coalesce and escape during the 'wet growth' phase, making the hailstone clearer. 
  • As the hailstone continues to ascend in the thunderstorm up to 10 km high, it begins descending when the updrafts can no longer support the hailstone's mass in the air. As hailstones fall through the cloud, it continues to enlarge until it reaches the cloud's bottom. 
  • It is suggested that hail tend to form within the continental interiors of the mid-latitudes where freezing level is under the altitude of 3,400 m (11,000 ft). 


Where does hail frequently fall?
  • Hail frequently form within the continental interiors at mid-latitudes, despite it having less thunderstorms situated there. A 2007 report stated hail is more common along mountain ranges due to orographic lifting along mountain surfaces, which intensify the updrafts within thunderstorms. 
  • Hail tends to be common across mountainous regions in northern India, where one of the highest hail-related death tolls on record was recorded in 1888, as well as China, Central Europe, southern Australia, southern & western Germany, northern and eastern France, southern and eastern Benelux, Croatia and Serbia and parts of North America. 
  • In North America, there is a region connecting Colorado, Nebraska and Wyoming known as "Hail Alley", where hail falls between March and October during the afternoon and evening hours. In Canada, Hailstorm Alley region is just downwind of the Rocky Mountains is Alberta. 


How fast do hail fall to the ground? 
  • The terminal velocity of hail varies depending on its shape, mass, its drag coefficient and size and, as well as external factors, wind direction and speed, collision with raindrops or other hailstones, and melting as they descend through a warmer atmosphere. 
  • The terminal velocity of a hailstone of 1 cm (0.39 in) diameter is estimated to be 9 m/s (20 mph), whereas the terminal velocity of a hailstone of 8 cm (3.1 in) in diameter is estimated to be 48 m/s (110 mph). Since hailstones aren't perfectly spherical and their drag coefficient is difficult to accurately calculate, their terminal velocity is difficult to estimate. 
  • The heaviest hailstone found in Gopalganj District, Bangladesh on 14th April 1986 was weighed at 1.02 kg (2.25 lb). 
  • The largest hailstone found in Vivian, South Dakota on 23rd July, 2010 was measured to be 20 cm (7.9 in) in diameter. 
  • The hailstone found in Aurora, Nebraska on 23rd July 2010 was measured to have a circumference of 47.6 cm (18.74 in). 
  • The greatest average precipitation occurred in Kericho, Kenya where it hailed for 132 days in a year. 

What are the effects of hail? 
  • Damage to automobiles, aircraft, crops, glass-roofed structures, roofs, livestock and skylights. 
  • Accumulation of hailstones can generate narrow zones. 
  • Concussions or fatal head trauma 
  • Damaging trees and causing power outages
Hail streaks in Sydney, Australia on April 2015


A large hailstone characterised by concentric rings


Largest recorded hailstone in the USA


When were the most notable hailstorms? 
  • On 13th April (Black Monday) 1360, a hailstorm killed an estimated 1,000 English soldiers during the Hundred Years War. 
  • Circa 9th century, hundreds of pilgrims were killed by a hailstorm in Roopkund, India. 
  • On 30th April, 1888, at least 230 people and over 1,600 sheep and goats were killed by hail in Moradabad (Uttar Pradesh) in northern India. This is due to larger than average size hailstones and a lack of a warning system at the time. 
  • An unknown number of people were killed during the 1490 Qingyang event in China due to a gigantic comet disintegrating the atmosphere, or a hailstorm. 
  • At least 92 people were killed in Gopalganj, Bangladesh by some of the heaviest hailstones recorded, which were as big as grapefruits. 
  • On 14th April, 1999, the costliest hailstorm in Australia that damaged an estimated 20,000 properties, 40,000 vehicles and 25 aircraft cost an estimated $AU1.5 billion ($AU3.3 billion adjusted in 2007). 
  • On 1st February, 1936, the most destructive hailstorm occurred in Settlers, Transvaal, South Africa, which killed 10 people and several cattle, as well as 9 people killed by floods. 
  • The costliest hailstorm in Germany occurred in Reutlingen and Pfortzheim, Baden-Württemberg, Wolfsburg and Hanover, Lower Saxony, which was estimated to be €3.6 billion. 
  • The costliest hailstorm in North America occurred in the I-70 corridor of eastern Kansas, across St. Louis, Missouri and into southwestern Illinois on 10th April, 2001. It lead to more than $US2.0 billion in damages. 

v. Cold Waves 



  • Sometimes called a cold snap or cold spell, a cold wave is defined by the U.S. National Weather Service as a sudden plummet in temperature within a 24-hour period that severely impacts agriculture, industry, commerce, and social activities.
  • In the USA, a cold spell is defined as the national average high temperature dropping below 20 °F (-7 °C). 


What are the effects of cold waves?
  • Mortality and injury to livestock and wildlife. 
  • Exposure to cold increases caloric intake for all animals, including humans. 
  • When a cold wave combines with heavy snow drifts, grazing animals can die of hypothermia and starvation. 
  • Freezing of poorly insulated water pipelines and mains. 
  • Burst indoor plumbing due to water expansion within them, leading to damaged property and costly insurance claims.
  • Increased demand for electrical power and fuels
  • Malfunction of motor vehicles due to antifreeze failure or gelling of motor oil 
  • Break down of water mains and unreliable water supply 
  • Impacts agriculture such as crop failure due to plants being killed during the early and most vulnerable stages of growth, leading to famines. 

When did the worst cold waves occur? 
  • Great Frost of 1683-84 (England) 
  • Great Frost of 1709 (England)
  • Eastern USA 1835
  • New England 1857
  • New England & Canada 1859
  • February 1899 Cold Wave 
  • USA 1912
  • Winter of 1917-18
  • North America 1936
  • United Kingdom Winter of 1962-63
  • South America July 1975
  • USA January 1977
  • Chile - White Earthquake August 1995
  • Greece 2004-2005
  • Europe 2005-06
  • Great Britain & Ireland February 2009-10 
  • New Zealand snowstorms 2011
  • United Kingdom March-April 2013
  • North America December 2013 & January 2014
  • North America November 2014 & February 2015
  • Europe & USA December 2017
  • Russia February 2019
  • North America, Greece and Middle East February 2021

I'll delve into the concepts of ice and cold in another post. 








Posted by at

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)