Winter

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Shipka Pass in Bulgaria during winter Snow Scene at Shipka Pass 1.JPG
Shipka Pass in Bulgaria during winter
Snow in Sao Joaquim in the state of Santa Catarina in southern Brazil Neve na SC-438 em Sao Joaquim.JPG
Snow in São Joaquim in the state of Santa Catarina in southern Brazil

Winter is the coldest season of the year in polar and temperate zones (winter does not occur in most of the tropical zone). It occurs after autumn and before spring in each year. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun. Different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa. In many regions, winter is associated with snow and freezing temperatures. The moment of winter solstice is when the Sun's elevation with respect to the North or South Pole is at its most negative value (that is, the Sun is at its farthest below the horizon as measured from the pole). The day on which this occurs has the shortest day and the longest night, with day length increasing and night length decreasing as the season progresses after the solstice. The earliest sunset and latest sunrise dates outside the polar regions differ from the date of the winter solstice, however, and these depend on latitude, due to the variation in the solar day throughout the year caused by the Earth's elliptical orbit (see earliest and latest sunrise and sunset).

Contents

Etymology

The English word winter comes from the Proto-Germanic noun *wintru-, whose origin is unclear. Several proposals exist, a commonly mentioned one connecting it to the Proto-Indo-European root *wed- 'water' or a nasal infix variant *wend-. [1]

Cause

The tilt of the Earth's axis relative to its orbital plane plays a large role in the formation of weather. The Earth is tilted at an angle of 23.44° to the plane of its orbit, causing different latitudes to directly face the Sun as the Earth moves through its orbit. This variation brings about seasons. When it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. Conversely, winter in the Southern Hemisphere occurs when the Northern Hemisphere is tilted more toward the Sun. From the perspective of an observer on the Earth, the winter Sun has a lower maximum altitude in the sky than the summer Sun.

During winter in either hemisphere, the lower altitude of the Sun causes the sunlight to hit the Earth at an oblique angle. Thus a lower amount of solar radiation strikes the Earth per unit of surface area. Furthermore, the light must travel a longer distance through the atmosphere, allowing the atmosphere to dissipate more heat. Compared with these effects, the effect of the changes in the distance of the Earth from the Sun (due to the Earth's elliptical orbit) is negligible.

The manifestation of the meteorological winter (freezing temperatures) in the northerly snow–prone latitudes is highly variable depending on elevation, position versus marine winds and the amount of precipitation. For instance, within Canada (a country of cold winters), Winnipeg on the Great Plains, a long way from the ocean, has a January high of −11.3 °C (11.7 °F) and a low of −21.4 °C (−6.5 °F). [2] In comparison, Vancouver on the west coast with a marine influence from moderating Pacific winds has a January low of 1.4 °C (34.5 °F) with days well above freezing at 6.9 °C (44.4 °F). [3] Both places are at 49°N latitude, and in the same western half of the continent. A similar but less extreme effect is found in Europe: in spite of their northerly latitude, the British Isles have not a single non-mountain weather station with a below-freezing mean January temperature. [4]

Meteorological reckoning

Animation of snow cover changing with the seasons Earth-satellite-seasons.gif
Animation of snow cover changing with the seasons
Winter in the Southern Hemisphere in Tierra del Fuego, Argentina PN Tierra del Fuego (Hiver).jpg
Winter in the Southern Hemisphere in Tierra del Fuego, Argentina

Meteorological reckoning is the method of measuring the winter season used by meteorologists based on "sensible weather patterns" for record keeping purposes, [5] so the start of meteorological winter varies with latitude. [6] Winter is often defined by meteorologists to be the three calendar months with the lowest average temperatures. This corresponds to the months of December, January and February in the Northern Hemisphere, and June, July and August in the Southern Hemisphere. The coldest average temperatures of the season are typically experienced in January or February in the Northern Hemisphere and in June, July or August in the Southern Hemisphere. Nighttime predominates in the winter season, and in some regions winter has the highest rate of precipitation as well as prolonged dampness because of permanent snow cover or high precipitation rates coupled with low temperatures, precluding evaporation. Blizzards often develop and cause many transportation delays. Diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching −40 °C (−40 °F) due to air with slightly higher moisture from above mixing with colder, surface-based air. [7] They are made of simple hexagonal ice crystals. [8] The Swedish meteorological institute (SMHI) defines winter as when the daily mean temperatures are below 0 °C (32 °F) for five consecutive days. [9] According to the SMHI, winter in Scandinavia is more pronounced when Atlantic low-pressure systems take more southerly and northerly routes, leaving the path open for high-pressure systems to come in and cold temperatures to occur. As a result, the coldest January on record in Stockholm, in 1987, was also the sunniest. [10] [11]

Accumulations of snow and ice are commonly associated with winter in the Northern Hemisphere, due to the large land masses there. In the Southern Hemisphere, the more maritime climate and the relative lack of land south of 40°S makes the winters milder; thus, snow and ice are less common in inhabited regions of the Southern Hemisphere. In this region, snow occurs every year in elevated regions such as the Andes, the Great Dividing Range in Australia, and the mountains of New Zealand, and also occurs in the southerly Patagonia region of South Argentina. Snow occurs year-round in Antarctica.

Astronomical and other calendar-based reckoning

In the mid-latitudes and polar regions, winter is associated with snow and ice. KleinarlWinterwonderland.jpg
In the mid-latitudes and polar regions, winter is associated with snow and ice.
In the Southern Hemisphere winter extends from June to September, pictured in Caxias do Sul in the southern highlands of Brazil. Neve Caxias do Sul (2).jpg
In the Southern Hemisphere winter extends from June to September, pictured in Caxias do Sul in the southern highlands of Brazil.
Sea ice in the Port of Hamburg, Germany Hamburg Germany Jan 6.jpg
Sea ice in the Port of Hamburg, Germany

In the Northern Hemisphere, some authorities define the period of winter based on astronomical fixed points (i.e. based solely on the position of the Earth in its orbit around the Sun), regardless of weather conditions. In one version of this definition, winter begins at the winter solstice and ends at the March equinox. [12] These dates are somewhat later than those used to define the beginning and end of the meteorological winter – usually considered to span the entirety of December, January, and February in the Northern Hemisphere and June, July, and August in the Southern. [12]

Astronomically, the winter solstice, being the day of the year which has fewest hours of daylight, ought to be in the middle of the season, [13] [14] but seasonal lag means that the coldest period normally follows the solstice by a few weeks. In some cultures, the season is regarded as beginning at the solstice and ending on the following equinox [15] [16] – in the Northern Hemisphere, depending on the year, this corresponds to the period between 20, 21 or 22 December and 19, 20 or 21 March. [12]

In the United Kingdom, meteorologists consider winter to be the three coldest months of December, January and February. [17] In Scandinavia, winter in one tradition begins on 14 October and ends on the last day of February. [18] In Russia, calendar winter is widely regarded to start on 1 December [19] and end on 28 February. [20] In many countries in the Southern Hemisphere, including Australia, [21] [22] New Zealand and South Africa, winter begins on 1 June and ends on 31 August. In Celtic nations such as Ireland (using the Irish calendar) and in Scandinavia, the winter solstice is traditionally considered as midwinter, with the winter season beginning 1 November, on All Hallows, or Samhain. Winter ends and spring begins on Imbolc, or Candlemas, which is 1 or 2 February. This system of seasons is based on the length of days exclusively. (The three-month period of the shortest days and weakest solar radiation occurs during November, December and January in the Northern Hemisphere and May, June and July in the Southern Hemisphere.)

Also, many mainland European countries tended to recognize Martinmas or St. Martin's Day (11 November), as the first calendar day of winter. [23] The day falls at the midpoint between the old Julian equinox and solstice dates. Also, Valentine's Day (14 February) is recognized by some countries as heralding the first rites of spring, such as flowers blooming. [24]

In Chinese astronomy and other East Asian calendars, winter is taken to commence on or around 7 November, with the Jiéqì (known as 立冬 lì dōng – literally, "establishment of winter").

The three-month period associated with the coldest average temperatures typically begins somewhere in late November or early December in the Northern Hemisphere and lasts through late February or early March. This "thermological winter" is earlier than the solstice delimited definition, but later than the daylight (Celtic) definition. Depending on seasonal lag, this period will vary between climatic regions.

Cultural influences such as Christmas creep may have led to the winter season being perceived as beginning earlier in recent years, although high latitude countries like Canada are usually well into their real winters before the December solstice.

Since by almost all definitions valid for the Northern Hemisphere, winter spans 31 December and 1 January, the season is split across years, just like summer in the Southern Hemisphere. Each calendar year includes parts of two winters. This causes ambiguity in associating a winter with a particular year, e.g. "Winter 2018". Solutions for this problem include naming both years, e.g. "Winter 18/19", or settling on the year the season starts in or on the year most of its days belong to, which is the later year for most definitions.

Ecological reckoning and activity

The snowshoe hare, and some other animals, change color in winter. Snowshoe hare.jpg
The snowshoe hare, and some other animals, change color in winter.

Ecological reckoning of winter differs from calendar-based by avoiding the use of fixed dates. It is one of six seasons recognized by most ecologists who customarily use the term hibernal for this period of the year (the other ecological seasons being prevernal, vernal, estival, serotinal, and autumnal). [25] The hibernal season coincides with the main period of biological dormancy each year whose dates vary according to local and regional climates in temperate zones of the Earth. The appearance of flowering plants like the crocus can mark the change from ecological winter to the prevernal season as early as late January in mild temperate climates.

To survive the harshness of winter, many animals have developed different behavioral and morphological adaptations for overwintering:

Some annual plants never survive the winter. Other annual plants require winter cold to complete their life cycle; this is known as vernalization. As for perennials, many small ones profit from the insulating effects of snow by being buried in it. Larger plants, particularly deciduous trees, usually let their upper part go dormant, but their roots are still protected by the snow layer. Few plants bloom in the winter, one exception being the flowering plum, which flowers in time for Chinese New Year. The process by which plants become acclimated to cold weather is called hardening.

Exceptionally cold winters

River Thames frost fair, 1683 Frost Fair of 1683.JPG
River Thames frost fair, 1683

Other historically significant winters

Humans and winter

Humans are sensitive to cold, see hypothermia. Snowblindness, norovirus, seasonal depression. Slipping on black ice and falling icicles are other health concerns associated with cold and snowy weather. In the Northern Hemisphere, it is not unusual for homeless people to die from hypothermia in the winter.

One of the most common diseases associated with winter is influenza. [28]

Mythology

Allegory of Winter by Jerzy Siemiginowski-Eleuter with Aeolus' Kingdom of the Winds, 1683, Wilanow Palace Siemiginowski Allegory of Winter.jpg
Allegory of Winter by Jerzy Siemiginowski-Eleuter with Aeolus' Kingdom of the Winds, 1683, Wilanów Palace

In Persian culture, the winter solstice is called Yaldā (meaning: birth) and it has been celebrated for thousands of years. It is referred to as the eve of the birth of Mithra, who symbolised light, goodness and strength on earth.

In Greek mythology, Hades kidnapped Persephone to be his wife. Zeus ordered Hades to return her to Demeter, the goddess of the Earth and her mother. However, Hades tricked Persephone into eating the food of the dead, so Zeus decreed that Persephone would spend six months with Demeter and six months with Hades. During the time her daughter is with Hades, Demeter became depressed and caused winter.

In Welsh mythology, Gwyn ap Nudd abducted a maiden named Creiddylad. On May Day, her lover, Gwythr ap Greidawl, fought Gwyn to win her back. The battle between them represented the contest between summer and winter.

See also

Related Research Articles

Northern Hemisphere Half of Earth that is north of the equator

The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's North Pole.

Subarctic climate

The subarctic climate is a climate characterised by long, usually very cold winters, and short, cool to mild summers. It is found on large landmasses, away from the moderating effects of an ocean, generally at latitudes from 50° to 70°N poleward of the humid continental climates. Subarctic or boreal climates are the source regions for the cold air that affects temperate latitudes to the south in winter. These climates represent Köppen climate classification Dfc, Dwc, Dsc, Dfd, Dwd and Dsd.

Year Without a Summer 1816, a volcanic winter event during the Little Ice Age

The year 1816 is known as the Year Without a Summer because of severe climate abnormalities that caused average global temperatures to decrease by 0.4–0.7 °C (0.72–1.26 °F). Summer temperatures in Europe were the coldest on record between the years of 1766–2000. This resulted in major food shortages across the Northern Hemisphere.

Spring (season) One of the Earths four temperate seasons, occurring between winter and summer

Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of the term varies according to local climate, cultures and customs. When it is spring in the Northern Hemisphere, it is autumn in the Southern Hemisphere and vice versa. At the spring equinox, days and nights are approximately twelve hours long, with daytime length increasing and nighttime length decreasing as the season progresses.

Örebro Place in Närke, Sweden

Örebro is a city with 124,027 inhabitants, the seat of Örebro Municipality and the capital of Örebro County in Sweden. It is the sixth largest city in Sweden and one of the largest inland hubs of the country. It is located near the lake of Hjälmaren, although a few kilometres inland along the small river Svartån.

Ice Saints Weather lore named after a group of saints

The Ice Saints are St. Mamertus, St. Pancras, and St. Servatius. They are so named because their feast days fall on the days of May 11, May 12, and May 13 respectively, known as "the blackthorn winter" in Austrian, Belgian, Croatian, Czech, Dutch, French, German, Hungarian, North-Italian, Polish, Slovak, Slovene and Swiss folklore.

A cold wave is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in temperature within a 24-hour period requiring substantially increased protection to agriculture, industry, commerce, and social activities. The precise criterion for a cold wave is determined by the rate at which the temperature falls, and the minimum to which it falls. This minimum temperature is dependent on the geographical region and time of year.

Winter of 1962–63 in the United Kingdom Severe winter in the UK

The winter of 1962–63, known as the Big Freeze of 1963, was one of the coldest winters on record in the United Kingdom. Temperatures plummeted and lakes and rivers began to freeze over.

Winter solstice astronomical phenomenon that occurs in December in Northern Hemisphere and in June in Southern Hemisphere

The winter solstice, hiemal solstice or hibernal solstice, also known as midwinter, occurs when one of the Earth's poles has its maximum tilt away from the Sun. It happens twice yearly, once in each hemisphere. For that hemisphere, the winter solstice is the day with the shortest period of daylight and longest night of the year, when the Sun is at its lowest daily maximum elevation in the sky. At the pole, there is continuous darkness or twilight around the winter solstice. Its opposite is the summer solstice.

Geographical zone Major regions of the Earths surface demarcated by latitude

The five main latitude regions of the Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows:

  1. The North frigid zone, between the Arctic Circle 66.5° N and the North Pole 90° N. Covers 4.12% of Earth's surface.
  2. The North temperate zone, between the Tropic of Cancer 23.5° N and the Arctic Circle 66.5° N. Covers 25.99% of Earth's surface.
  3. The Torrid zone, between the Tropic of Cancer 23.5° N and the Tropic of Capricorn 23.5° S. Covers 39.78% of Earth's surface.
  4. The South temperate zone, between the Tropic of Capricorn 23.5° S and the Antarctic Circle 66.5° S. Covers 25.99% of Earth's surface.
  5. The South frigid zone, from Antarctic Circle 66.5° S and the South Pole 90° S. Covers 4.12% of Earth's surface.

The winter of 1894–95 was severe for the British Isles with a CET of 1.27 °C or 34.3 °F. Many climatologists have come to view this winter as the end of the Little Ice Age and the culmination of a decade of harsh winters in Britain. Whereas the average CET for the ten winters from 1885–86 to 1894–95 was 2.87 °C or 37.2 °F, no winter with a CET under 3.0 °C or 37.4 °F followed for twenty-two years and no month as cold as February or January 1895 until 1940. In contrast, between 1659 and 1894 no spell with every winter CET above 3.0 °C or 37.4 °F had lasted longer than twelve winters.

Summer solstice Astronomical phenomenon when Earths axial tilt toward the Sun is a maximum (currently 23.44°)

The summer solstice or estival solstice, also known as midsummer, occurs when one of the Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere. For that hemisphere, the summer solstice is when the Sun reaches its highest position in the sky and is the day with the longest period of daylight. Within the Arctic circle or Antarctic circle, there is continuous daylight around the summer solstice. On the summer solstice, Earth's maximum axial tilt toward the Sun is 23.44°. Likewise, the Sun's declination from the celestial equator is 23.44°.

Climate of the Arctic

The climate of the Arctic is characterized by long, cold winters and short, cool summers. There is a large amount of variability in climate across the Arctic, but all regions experience extremes of solar radiation in both summer and winter. Some parts of the Arctic are covered by ice year-round, and nearly all parts of the Arctic experience long periods with some form of ice on the surface.

December solstice Astronomical phenomenon; solstice that occurs each December, typically between the 20th and the 22nd day of the month according to the Gregorian calendar

The December solstice, is the solstice that occurs each December – typically on Dec 21, and can vary ± 1 day according to the Gregorian calendar. In the Northern Hemisphere, the December solstice is the winter solstice, whilst in the Southern Hemisphere it is the summer solstice. It is also known as the southern solstice.

A season is a division of the year marked by changes in weather, ecology, and the amount of daylight. On Earth, seasons are the result of Earth's orbit around the Sun and Earth's axial tilt relative to the ecliptic plane. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to undergo hibernation or to migrate, and plants to be dormant. Various cultures define the number and nature of seasons based on regional variations.

Ice cap climate polar climate in which no mean monthly temperature exceeds 0 °C (32 °F)

An ice cap climate is a polar climate where no mean monthly temperature exceeds 0 °C (32 °F). The climate covers areas in or near the high latitudes to polar regions, such as Antarctica and Greenland, that have vast deserts of snow and ice. In the coldest months, most ice cap climates have mean temperatures between -30 and -55 °C. Ice cap climates are normally covered by a permanent layer of ice and have no vegetation. There is limited animal life in most ice cap climates, usually found near the oceanic margins. Although ice cap climates are inhospitable to human life, there are some small research stations scattered in Antarctica and interior Greenland.

2014–15 North American winter

The 2014–15 North American winter refers to winter in North America as it occurred across the continent from late 2014 through early 2015. While both the meteorological and astronomical definitions of winter involve the onset of winter occurring in December, many places in North America experienced their first wintry weather during mid November. A period of below-average temperatures affected much of the contiguous United States, and several records were broken. An early trace of snowfall was recorded in Arkansas. There were greater accumulations of snow across parts of Oklahoma as well. A quasi-permanent phenomenon referred to as the polar vortex may have been partly responsible for the cold weather. Temperatures in much of the United States dropped 15 to 35 °F below average by November 19 following a southward "dip" of the polar vortex into the eastern two-thirds of the country. The effects of this dip were widespread, bringing about temperatures as low as 28 °F (−2 °C) in Pensacola, Florida. Following a significant snowstorm there, Buffalo, New York received several feet of snow from November 17–21. During the 2014–15 winter season, Boston broke its all-time official seasonal 107.6-inch (2.73-meter) snowfall record from the winter of 1995–96, with a total snowfall record of 108.6 inches (2.76 m) as of March 15, 2015.

Sweden had a very unusual start and finish to the year 2010, with two consecutive winter cold waves occurring in a single calendar year. Since both events were notable, both are covered in this article.

2017–18 North American winter

The 2017–18 North American winter refers to winter in North America as it occurred across the continent from late 2017 through early 2018. Similar to the previous winter, a La Niña was expected to influence the winter weather across North America. Winter weather patterns were very active, erratic, and protracted, especially near the end of the season. Significant events included rare snowfall in the South, a strong cold wave that affected the United States during the early weeks of January, and a series of strong nor'easters that affected the Northeastern U.S during the month of March. In addition, flooding also took place during the month of February in the Central United States. Finally the winter came to a conclusion with a powerful storm system that caused a tornado outbreak and flooding in mid-April. The most intense event, however, was an extremely powerful cyclonic blizzard that impacted the northeastern United States in the first week of 2018.

2018–19 European winter Winter

The 2018–19 European winter occurred from late 2018 to early 2019. Notable events included the early snows in Spain and intense flooding in Italy, in cities such as Venice, the intense snow storms which affected central Europe in January, the snow storms in Greece over the New Year period, as well as the end of February. As well as severe winter weather, there was also exceptional warmth across western Europe in the last week of February. Parts of France had their warmest February day on record, with temperatures up to 28.1 °C (82.6 °F) at Eus on the 27th. Many places in the United Kingdom also broke temperature records, including the national record in Kew Gardens, at 21.2 °C (70.2 °F) on the 26th. Unlike previous winters, a developing El Niño was expected to influence weather patterns across Europe, although the affect is not fully known.

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Further reading