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A season is one of the major divisions of the year, generally based on yearly periodic changes in weather.

In temperate and polar regions generally four seasons are recognized: spring, summer, autumn (fall), and winter.

In some tropical and subtropical regions it is more common to speak of the rainy (or wet, or monsoon) season versus the dry season, as the amount of precipitation may vary more dramatically than the average temperature.

In other tropical areas a three-way division into hot, rainy and cool season is used. In some parts of the world, special "seasons" are loosely defined based upon important events such as a hurricane season, tornado season or a wildfire season.

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Illumination of the earth during various seasons
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Diagram of the Earth's seasons as seen from the north. Far right: December solstice
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Diagram of the Earth's seasons as seen from the south. Far left: June solstice
Fig. 1
This is a diagram of the seasons. Note that, regardless of the time of day (i.e. the Earth's rotation on its axis), the North Pole will be dark, and the South Pole will be illuminated; see also arctic winter. In addition to the density of incident light, the dissipation of light in the atmosphere is greater when it falls at a shallow angle.
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The four season mahjong tiles on the right and the four flower tiles on the other side. The flower tiles are arranged in accord to their growing seasons.
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Personifications of the Four Seasons are a frequent theme in Roman mosaics, like this from Complutum.

Causes and effects

The seasons result from the Earth's axis being tilted to its orbital plane; it deviates by an angle of about 23.44 degrees. Thus, at any given time during summer or winter, one part of the planet is more directly exposed to the rays of the Sun (see Fig. 1). This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the northern and southern hemispheres experience opposite seasons (see Fig. 2 and Month ranges of seasons (below) and Effect of sun angle on climate).

Seasonal weather fluctuations also depend on factors such as proximity to oceans or other large bodies of water, currents in those oceans, El Niño/ENSO and other oceanic cycles, and prevailing winds.

In the temperate and polar regions, seasons are marked by changes in the amount of sunlight, which in turn often causes cycles of dormancy in plants and hibernation in animals. These effects vary with latitude, and with proximity to bodies of water. For example, the South Pole is in the middle of the continent of Antarctica, and therefore a considerable distance from the moderating influence of the southern oceans. The North Pole is in the Arctic Ocean, and thus its temperature extremes are buffered by the presence of all that water. The result is that the South Pole is consistently colder during the southern winter than the North Pole during the northern winter.

The cycle of seasons in the polar and temperate zones of one hemisphere is opposite to that in the other. When it is summer in the Northern hemisphere, it is winter in the Southern hemisphere, and vice versa, and when it is spring in the Northern hemisphere it is autumn in the Southern hemisphere, and vice versa.

In the tropics, there is no noticeable change in the amount of sunlight. However, many regions (famously the northern Indian Ocean) are subject to monsoon rain and wind cycles. Curiously, a study of temperature records over the past 300 years (David Thomson, Science, April 1995) shows that the climatic seasons, and thus the seasonal year, are governed by the anomalistic year rather than the tropical year.

In meteorological terms, the winter solstice and summer solstice (or the date maximum/minimum insolation) do not fall in the middle of winter and summer respectively. The heights of these seasons occur up to a month later due to seasonal lag. Seasons though, are not always defined in meteorological terms; see reckoning

Compared to axial tilt, other factors contribute little to seasonal temperature changes. It's a common misconception that the seasons are the result of the variation in Earth’s distance to the sun due to its elliptical orbit.[1] Orbital eccentricity can influence temperatures, but on Earth, this effect is small and is more than counteracted by other factors; research shows that the Earth as a whole is actually a few degrees warmer when farther from the sun.[2] Mars however experiences wide temperature variations and violent dust storms every year at perihelion.[3] The sun, in its seasonal movement through the sky, passes directly over the equator each year on March and September.

Polar day and night

A common misconception is that, within the Arctic and Antarctic Circles, the sun rises once in the spring and sets once in the fall; thus, the day and night are erroneously thought to last uninterrupted for 183 calendar days each. This is true only in the immediate region of the poles themselves.

What does happen is that any point north of the Arctic Circle or south of the Antarctic Circle will have one period in the summer when the sun does not set, and one period in the winter when the sun does not rise. At progressively higher latitudes, the periods of "midnight sun" (or "midday dark" for the other side of the globe) are progressively longer. For example, at the military and weather station called Alert on the northern tip of Ellesmere Island, Canada (about 450 nautical miles or 830 km from the North Pole), the sun begins to peek above the horizon in mid-February and each day it climbs a bit higher, and stays up a bit longer; by 21 March, the sun is up for 12 hours. However, mid-February is not first light. The sky (as seen from Alert) has been showing twilight, or at least a pre-dawn glow on the horizon, for increasing hours each day, for more than a month before that first sliver of sun appears.

In the weeks surrounding 21 June, the sun is at its highest, and it appears to circle the sky without ever going below the horizon. Eventually, it does go below the horizon, for progressively longer and longer periods each day until, around the middle of October, it disappears for the last time. For a few more weeks, "day" is marked by decreasing periods of twilight. Eventually, for the weeks surrounding 21 December, nothing breaks the darkness. In later winter, the first faint wash of light briefly touches the horizon (for just minutes per day), and then increases in duration and pre-dawn brightness each day until sunrise in February.

Reckoning

Four Seasons

The date at which each of the four temperate season begins varies from culture to culture. In general there are three reckonings, "Astronomical", "Meteorological", and "Traditional".[4]

Meteorological

Meteorological seasons are reckoned by temperature, with summer being the hottest quarter of the year, and winter the coldest quarter of the year.

Using this reckoning, the Ancient Roman calendar began the year and the spring season on the first of March, with each season occupying three months. This reckoning is also used in Denmark, the former USSR, and Australia. In modern United Kingdom and Ireland there are no hard and fast rules about seasons, and informally many people use this reckoning.

So, in meteorology for the Northern hemisphere: Conversely, for the Southern hemisphere:

Astronomical

In astronomical reckoning, the seasons begin at the solstices and equinoxes. The cross-quarter days are considered seasonal midpoints. The length of these seasons is not uniform because of the elliptical orbit of the earth and its different speeds along that orbit (see Kepler's laws).

In the conventional United States calendar:
  • Winter (89 days) begins on 21-22 Dec, the winter solstice
  • Spring (92 days) on 20-21 Mar, the spring equinox
  • Summer (93 days) on 20-21 June, the summer solstice
  • Autumn (90 days) on 22-23 Sept, the autumn equinox
Because of the differences in the Northern and Southern Hemispheres (see Meteorological below), it is no longer considered appropriate to use the old northern-seasonal designations for the astronomical quarter days. The modern convention for them is:
  • The March Equinox
  • The June Solstice
  • The September Equinox
  • The December Solstice

Traditional

Traditional seasons are reckoned by insolation, with summer being the quarter of the year with the greatest insolation, and winter the quarter with the least. These seasons begin about 4 weeks earlier than the Meteorological seasons, and 7 weeks earlier than the Astronomical seasons.

In Traditional reckoning, the seasons begin at the cross-quarter days. The solstices and equinoxes are the midpoints of these seasons. For example, the days of greatest and least insolation are considered the "midsummer" and "midwinter" respectively.

This reckoning is used by various traditional cultures in the Northern Hemisphere, including East Asian and Irish cultures.

So, according to Traditional reckoning,
  • Winter begins on 5-10 Nov, Samhain, 立冬 (lìdōng),
  • Spring on 2-7 Feb, Imbolc, 立春 (lìchūn),
  • Summer on 4-10 May, Beltane, 立夏 (lìxià), and
  • Autumn on 3-10 Aug, Lughnasadh, 立秋 (lìqiū).
And, the middle of each season is considered,
Month Minang Arrernte Gadgerong Tasmania
JanuaryBerucUterneMayurrWegtellanyta
Feb/MarMeertilluc
April PournerAlhwerr-
rpeurle
Nguag/
Gagulong
May Tunna
Jun/JulMawkurAlhwerrpa
August Meerningal
SeptemberUlpulpePawenya
peena
Oct/NovUterne urleBandenyirrin
DecemberBerucUterneWegtellanyta

Australian Aboriginal

In Australia, the aboriginal people defined the seasons by what was happening to the plants, animals and weather around them. This led to each separate tribal group have different seasons, some with up to 8 seasons a year. However, most modern Aboriginal Australians follow the Meteorological Seasons, as is conventional amongst non-Aboriginal Australians.

Seasons in images

In hemiboreal and temperate climates:




In winter, the plant can't hold the leaves without Chloryphyll.

In spring, the plants produce Chloryphyll and start to grow again.

In summer, the plants grow. Usually at this time the plants completely mature.

In autumn, the trees stop making Chloryphyll and turn yellow or shades of orange and red then drop their leaves.


See also

External links

References

1. ^ "Fundamentals of physical geography", PhysicalGeography.net, Ch. 6: Energy and Matter:(h) Earth-Sun Geometry, [1]
2. ^ Phillips, Tony, "The Distant Sun (Strange but True: the Sun is far away on the 4th of July)," Science@NASA, downloaded 24 June 2006
3. ^ Christian Ho, Nasser Golshan, and Arvydas Kliore, Radio Wave Propagation Handbook for Communication on and Around Mars, JPL Publication 02-5, pp. 59-60, downloaded 23 June 2006
4. ^ The Straight Dope: Is it true summer in Ireland starts May 1?


Nature, in the broadest sense, is equivalent to the natural world, physical universe, material world or material universe. "Nature" refers to the phenomena of the physical world, and also to life in general.
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weather is the set of all extant phenomena in a given atmosphere at a given time. The term usually refers to the activity of these phenomena over short periods (hours or days), as opposed to the term climate, which refers to the average atmospheric conditions over longer periods of
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temperate latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather.
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Seasons

Temperate
Spring
Summer
Autumn
Winter
Tropical
Dry
season Cool
Hot
Wet season

Spring

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Summer is one of the four seasons of the year. In the West, the seasons are generally considered to start at the equies and solstices, based on astronomical reckoning. In English-language calendars, based on astronomy, summer begins on the day of the summer solstice and ends on the
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Autumn (also known as Fall in North American English) is one of the four temperate seasons. Autumn marks the transition from summer into winter. In the northern hemisphere, the start of autumn is generally considered to be around September and in the southern hemisphere, its
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Winter is one of the four seasons of temperate zones. Almost all English-language calendars, going by astronomy, state that winter begins on the winter solstice, and ends on the spring equinox.
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tropics are the geographic region of the Earth centered on the equator and limited in latitude by the Tropic of Cancer in the northern hemisphere, at approximately 23°30' (23.5°) N latitude, and the Tropic of Capricorn in the southern hemisphere at 23°30' (23.5°) S latitude.
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The Dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over
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A Wet season or rainy season is a season in which the average rainfall in a region is significantly increased. The term green season is also sometimes used as a euphemism by tourist authorities. These terms are commonly used describing the weather in the tropics.
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storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather. It may be marked by strong wind, thunder and lightning (a thunderstorm), heavy precipitation, such as ice (ice storm), or wind transporting
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thunderstorm, also called an electrical storm or lightning storm, is a form of weather characterized by the presence of lightning and its attendant thunder produced from a cumulonimbus cloud.
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tornado is a violently rotating column of air which is in contact with both a cumulonimbus cloud or, in rare cases, a cumulus cloud base and the surface of the earth. Tornadoes come in many sizes but are typically in the form of a visible condensation funnel, whose narrow end
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tropical cyclone is a meteorological term for a storm system characterized by a low pressure system center and thunderstorms that produces strong wind and flooding rain. A tropical cyclone feeds on the heat released when moist air rises and the water vapor it contains condenses.
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winter storm is a meteorological event in which the dominant varieties of precipitation are forms that only occur at cold temperatures, such as snow or sleet, or a rainstorm where ground temperatures are cold enough to allow ice to form (i.e. freezing rain).
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blizzard is a severe winter storm condition characterized by low temperatures, strong winds, and heavy blowing snow. Blizzards are formed when a high pressure system, also known as a ridge, interacts with a low pressure system; this results in the advection of air from the high
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precipitation (also known as hydrometeor) is any product of the condensation of atmospheric water vapor that is deposited on the earth's surface. It occurs when the atmosphere (being a large gaseous solution) becomes saturated with water vapour and the water condenses and
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FOG can be an acronym for...
  • the tool "Flexible Object Generator"
  • the tool "Fragmented-Object Generator"
  • Fiber Optic Gulf - a submarine telecommunications cable linking the United Arab Emirates, Qatar, Bahrain, and Kuwait
  • Fibre optic gyroscope

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Drizzle is light precipitation consisting of liquid water drops smaller than that of rain, and generally smaller than 0.5 mm (0.02 in.) in diameter.
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Rain is a type of precipitation, a product of the condensation of atmospheric water vapor that is deposited on the earth's surface. It forms when separate drops of water fall to the Earth's surface from clouds.
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Freezing Rain is a type of precipitation that begins as snow at higher altitude, falling from a cloud towards earth, melts completely on its way down while passing through a layer of air above freezing temperature, and then

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Sleet is a term used in a variety of ways to describe precipitation intermediate between rain and snow but distinct from hail.
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Hail is a form of precipitation which consists of balls or irregular lumps of ice (hailstones). Hailstones on Earth usually consist mostly of water ice and measure between 5 and 50 millimetres in diameter, with the larger stones coming from severe thunderstorms.
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SNOW 1.0 and 2.0 are two word-based synchronous stream ciphers developed by Thomas Johansson and Patrik Ekdahl at Lund University.

SNOW 1.0, originally simply SNOW, was submitted to the NESSIE project.
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Meteorology (from Greek: μετέωρον, meteoron, "high in the sky"; and λόγος, logos, "knowledge") is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and
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Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location.

Human beings have attempted to predict the weather since time immemorial.
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Climate is the average and variations of weather over long periods of time. Climate zones can be defined using parameters such as temperature and rainfall.
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temperate latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather.
..... Click the link for more information.
Seasons

Temperate
Spring
Summer
Autumn
Winter
Tropical
Dry
season Cool
Hot
Wet season

Spring

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