Winter

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Winter
Temperate season
Winter forest silver.jpg
Forest covered in snow during winter
Northern temperate zone
Astronomical season22 December – 21 March
Meteorological season1 December – 28/29 February
Solar (Celtic) season1 November – 31 January
Southern temperate zone
Astronomical season21 June – 23 September
Meteorological season1 June – 31 August
Solar (Celtic) season1 May – 31 July
Summer
Spring Seasons.svg Autumn
Winter

Winter is the coldest season of the year in polar and temperate climates. It occurs after autumn and before spring. The tilt of Earth's axis causes seasons; winter occurs when a hemisphere is oriented away from the Sun. Different cultures define different dates as the start of winter, and some use a definition based on weather.

Contents

When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa. In many regions, winter brings 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 and depend on latitude. They differ 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).

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

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 thermal 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] [13]

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, [14] [15] 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 [16] [17] – 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 an old Norwegian tradition winter begins on 14 October and ends on the last day of February. [18]

In many countries in the Southern Hemisphere, including Australia, [19] [20] New Zealand, [21] 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.[ citation needed ]

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. [22] 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. [23]

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").[ citation needed ]

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). [24] 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.

Examples

Exceptionally cold

River Thames frost fair, 1683, with Old London Bridge in the background Frost Fair of 1683.JPG
River Thames frost fair, 1683, with Old London Bridge in the background
Period of Ice Age on Earth IceAgeEarth.jpg
Period of Ice Age on Earth

Historically significant

Effect on humans

People enjoying the winter weather outdoors in Helsinki, Finland 2018 January in Helsinki (46315524324).jpg
People enjoying the winter weather outdoors in Helsinki, Finland

Humans are sensitive to winter cold, which compromises the body's ability to maintain both core and surface heat of the body. [27] Slipping on icy surfaces is a common cause of winter injury. [28] Other cold injuries include: [29]

Rates of influenza, COVID-19 and other respiratory diseases also increase during the winter. [30] [31]

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. Hades tricked Persephone into eating the food of the dead, so Zeus decreed that she 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

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<span class="mw-page-title-main">Subarctic climate</span> Climate characterised by long, usually very cold winters, and short, cool summers

The subarctic climate is a climate with long, cold winters, and short, warm to cool summers. It is found on large landmasses, often 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.

<span class="mw-page-title-main">Year Without a Summer</span> 1816 volcanic winter climate event

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 (0.7–1 °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.

<span class="mw-page-title-main">Spring (season)</span> One of the Earths four temperate seasons

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 until the Summer Solstice in June and December.

Seasonal lag is the phenomenon whereby the date of maximum average air temperature at a geographical location on a planet is delayed until some time after the date of maximum insolation. This also applies to the minimum temperature being delayed until some time after the date of minimum insolation.

<span class="mw-page-title-main">Cold wave</span> Weather phenomenon

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 criteria for a cold wave are 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.

<span class="mw-page-title-main">Winter of 1962–1963 in the United Kingdom</span> Severe winter in the UK

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<span class="mw-page-title-main">Climate of the Arctic</span> Overview of the climate of the Arctic

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<span class="mw-page-title-main">Season</span> Subdivision of the year based on orbit and axial tilt

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<span class="mw-page-title-main">Climate of Sweden</span> Overview of the climate of Sweden

Most of Sweden has a temperate climate, despite its northern latitude, with largely four distinct seasons and mild temperatures throughout the year. The winter in the far south is usually weak and is manifested only through some shorter periods with snow and sub-zero temperatures, autumn may well turn into spring there, without a distinct period of winter. The northern parts of the country have a subarctic climate while the central parts have a humid continental climate. The coastal south can be defined as having either a humid continental climate using the 0 °C isotherm, or an oceanic climate using the –3 °C isotherm.

<span class="mw-page-title-main">Ice cap climate</span> Polar climate where 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, some of the northernmost islands of Canada and Russia, Greenland, along with some regions and islands of Norway's Svalbard Archipelago that have vast deserts of snow and ice. Areas with 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.

<span class="mw-page-title-main">2013–14 North American winter</span>

The 2013–14 North American winter was one of the most significant for the United States, due in part to the breakdown of the polar vortex in November 2013, which allowed very cold air to travel down into the United States, leading to an extended period of very cold temperatures. The pattern continued mostly uninterrupted throughout the winter and numerous significant winter storms affected the Eastern United States, with the most notable one being a powerful winter storm that dumped ice and snow in the Southeastern United States and the Northeastern United States in mid-February. Most of the cold weather abated by the end of March, though a few winter storms did affect the Western United States towards the end of the winter.

<span class="mw-page-title-main">2014–15 North American winter</span> Winter season in North America

The 2014–15 North American winter was frigid and prolifically wintry, especially across the eastern half of North America in the months of January–March. The season began early, with many places in North America experiencing 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. In addition, significant winter weather occurred throughout the season, including a major blizzard that struck the Northeastern United States at the end of January, another blizzard that affected much of the Northern United States days later in early February, and several significant snow events paired with very frigid temperatures for much of February.

<span class="mw-page-title-main">2010–11 North American winter</span>

The 2010–11 North American winter was influenced by an ongoing La Niña, seeing winter storms and very cold temperatures affect a large portion of the Continental United States, even as far south as the Texas Panhandle. Notable events included a major blizzard that struck the Northeastern United States in late December with up to 2 feet (24 in) of snowfall and a significant tornado outbreak on New Year's Eve in the Southern United States. By far the most notable event was a historic blizzard that impacted areas from Oklahoma to Michigan in early February. The blizzard broke numerous snowfall records, and was one of the few winter storms to rank as a Category 5 on the Regional Snowfall Index. In addition, Oklahoma set a statewide low temperature record in February.

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.

<span class="mw-page-title-main">2018–19 European winter</span> 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 effect is not fully known.

<span class="mw-page-title-main">2019–20 North American winter</span>

The 2019–20 North American winter was unusually warm for many parts of the United States; in many areas, neutral ENSO conditions controlled the weather patterns, resulting in the sixth-warmest winter on record, and many areas in the Northeastern United States saw one of the least snowy winters in years. In fact, Baltimore and Islip saw no snow in February for the first time. Some notable events still occurred, such as a powerful blizzard that impacted the Western United States in late November, a series of cold shots in January and February, a snowstorm within the Texas Panhandle and a late-season blizzard in the High Plains.

References

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Further reading