Season is the division of the year marked by changes in weather, ecology, and the amount of daylight. On Earth, the seasonal results of Earth's orbit around the Sun and the slope of Earth's axis relative to the plane of the ecliptic. In temperate and polar regions, seasons are marked by changes in the intensity of sunlight reaching Earth's surface, variations that can cause animals to hibernate or migrate, and plants become dormant.
During May, June, and July, the Northern Hemisphere is exposed to direct sunlight because its cleft faces the Sun. The same applies to the southern hemisphere in November, December, and January. This is the axis of Earth's axis that causes the Sun to be higher in the sky during the summer months, which increases the solar flux. However, because seasonal slowness, June, July, and August are the warmest months in the Northern Hemisphere as December, January, and February are the warmest months in the Southern Hemisphere.
In temperate and subpolar areas, the four seasons based on the calendar are commonly known: spring, summer, fall, fall or , and winter . Ecologists often use the six-season model for temperate climates:
In some parts of the world, some other "seasons" capture time from important ecological events such as hurricane season, season tornado, and seasonal >. The most important historically are the three seasons - flood , growth and low water - previously defined by the former annual flood of the Nile River in Egypt.
Video Season
Causes and effects
The axis tilt
The seasonal results of the Earth's axis of rotation are tilted with respect to its orbital plane with an angle of about 23.5 degrees. (This slope is also known as "obliquity of the ecliptic".)
Despite the years, the northern and southern hemispheres are always experiencing the opposite season. This is because during the summer or winter, one part of the planet is more directly exposed to the Sun (see Figure 1 ) than others, and this exposure alternates when the Earth rotates in orbit. For approximately half a year (from around March 20 to September 22), tips of the Northern Hemisphere lead to the Sun, with the maximum number that takes place around June 21. For the other half year, the same thing happened, but in the Southern Hemisphere not the North, with a maximum of around 21 December. Two seconds when the Sun is just above the Equator is the equinox. Also at that point, the North Pole and the South Pole are only terminators, and therefore day and night are equally divided between two hemispheres. In the vicinity of the March equinox, the Northern Hemisphere will experience springtime as daylight hours, and the Southern Hemisphere falls during the fall of the day.
The influence of the axis of the axis can be observed as a change in the length of the day and the height of the Sun in the afternoon sun (the sun's peak) throughout the year. The low angle of the Sun during winter means that the incoming rays of radiation are scattered over a larger area of ​​the Earth's surface, so the light received is more indirect and the intensity lower. Among these effects and shorter day hours, the slope of the Earth's axis represents most of the seasonal variations in the climate in both hemispheres.
Elliptical Earth Orbit
Compared with axial slope, other factors contribute little to seasonal temperature changes. Season is not the result of variations of Earth's distance to the Sun because of its elliptical orbit. In fact, Earth reaches the perihelion (the point in its orbit closest to the Sun) in January, and reaches the aphelion (the furthest point from the Sun) in July, resulting in little eccentricity orbital contribution against the seasonal temperature trends in the Northern Hemisphere. In general, the eccentricity effect of orbital on Earth season is 7% variation in sunlight reception.
Orbital eccentricity can affect temperature, but on Earth, this effect is small and more than neutralize by other factors; research shows that the Earth as a whole is actually a little warmer when further away from the sun. This is because the Northern Hemisphere has more land than in the South, and the soil is warmer than the ocean. Intense intensification of winter and summer in the south due to Earth's elliptical orbit reduced by the abundance of water in the southern hemisphere.
Maritime and hemispheres
Seasonal weather fluctuations (change) also depend on factors such as proximity to oceans or other major bodies of water, currents in the oceans, El NiÃÆ' Â ± o/ENSO and other oceanic cycles, and prevailing winds.
In temperate and polar regions, seasons are characterized by changes in the amount of sunlight, which in turn often causes dormancy cycles in plants and hibernation in animals. This effect varies with latitude and close to the body of water. For example, the South Pole is in the middle of the Antarctic continent and therefore a considerable distance from the moderating influence of the southern oceans. The North Pole is in the Arctic Ocean, and thus its extreme temperatures are propped up by water. The result is that the South Pole is consistently cooler during the winter in the south than the North Pole during the northern winter.
Seasonal cycles in the polar and subtropical zones of one hemisphere are opposite to the other. When summer is in the Northern Hemisphere, winter in the South, and vice versa.
Tropics
The tropics and subtropics see little annual fluctuations in sunlight. However, a seasonal shift occurs along a low-pressure rain belt called the Intertropical Convergence Zone (ICZ). As a result, the amount of rainfall tends to vary more dramatically than the average temperature. When the Zone is the northern part of the Equator, the northern tropics experience their rainy season while the southern tropics have a dry season. This pattern flips when the Zone migrates to the south position of the Equator.
Disturbance of latitude latitude
In meteorological terms, solstices (maximum and minimum insertions) do not fall in the middle of summer and winter. The height of this season occurs up to 7 weeks later due to seasonal lag. The seasons, though, are not always defined in meteorological terms.
In astronomical counts by daylight hours alone, solstices and equinoxes are in the middle of their respective seasons. Due to seasonal delays due to thermal absorption and release by oceans, regions with continental climates, which predominate in the Northern Hemisphere, often regard these four dates as early in the season as in the diagram, with days of cross-quarter being considered seasonal midpoint. The length of the season is not uniform because of Earth's elliptical orbit and its different speeds along that orbit.
Maps Season
Calculation of the four calendar seasons
Calculations based on the calendar define the seasons in absolute terms rather than relative terms. Therefore, if interest activity is regularly observed during the coldest quarter of the year in certain areas, it is still considered winter despite the traditional association of flowers with spring and summer. In addition, seasons are considered to change on the same date everywhere using certain calendar methods regardless of variation in climate from one area to another. Most calendar-based methods use a four-season model to identify the hottest and coldest seasons, separated by two intermediate seasons.
Meteorology
The meteorological season is calculated by temperature, with summer being the hottest quarter of the year and the coldest winter of the year. In 1780 the Societas Meteorologica Palatina (which became dead in 1795), an early international organization for meteorology, seasons is defined as a full three-month grouping as identified by the Gregorian calendar. Since then, professional meteorologists around the world have used this definition. Therefore, for temperate regions of the northern hemisphere, spring begins on March 1, summer on June 1, autumn on September 1, and winter on 1 December. For the southern hemisphere southern zone, spring begins on September 1, summer on December 1, autumn on March 1, and winter on June 1st. In Australasia, the term meteorology for seasons applies to temperate zones that occupy all of New Zealand, New South Wales, Victoria, Tasmania, southeastern corner of South Australia and southwestern Western Australia, and southeast Queensland. south of Brisbane.
In Sweden and Finland, meteorologists use non-calendar-based definitions for seasons based on temperature. Spring begins when the daily average temperature rises permanently above 0 ° C, the summer starts when the temperature permanently rises above 10 ° C, the summer ends when the temperature permanently falls below 10 ° C and the season the cold starts when the temperature permanently falls below 0 ° C. "Permanently" here means that the average daily temperature remains above or below the limit for seven consecutive days. This implies two things: first, the season does not start on a definite date but must be determined by observation and only known after the fact; and secondly, the new season begins on different dates in different parts of the country. In the UK, early spring is used to be defined as when the maximum daily temperature reaches 50 ° F (10 ° C) in the order of the given day. This almost always happens in March. However, with global warming, this temperature is now unusual in winter. Astronomy
The time of astronomy as a basis for determining temperate seasons dates back at least to the Julian calendar used by the ancient Romans. It continues to be used on many modern Gregorian calendars around the world, although some countries like Australia, New Zealand, and Russia prefer to use meteorological calculations. The exact time of the season is determined by the sun transit time in the tropical regions of Cancer and Capricorn for solstices and sun transit times above the equator for the equinox, or the traditional date close to that time.
The following diagram shows the relationship between the solstice line and the line of the Earth's elliptical orbit apsides. The orbital ellipse (with excessive eccentricity to effect) passes through each of the six Earth images, which are perihelion sequentially (periapsis - the closest point to the sun) anywhere from January 2 to January 5, the equinox point of March at 19, 20 or 21 March , the solstice on June 20 or 21, aphelion (apoapsis - the furthest point from the sun) anywhere from 4 July to 7 July, the equinox September on September 22 or 23, and December solstice on December 21 or 22.
This "astronomical" season is not the same length, due to the elliptical nature of Earth's orbit, as found by Johannes Kepler. From the March equinox, it currently takes 92.75 days to the June solstice, then 93.65 days to the September equinox, 89.85 days to the December solstice and finally 88.99 days to the March equinox.
Variations due to calendar misalignment
The timing of the equinox and solstices are not fixed with respect to the modern Gregorian calendar, but fall about six hours later each year, for a full day in four years. They are reset by leap year. The Gregorian calendar is designed to keep the March equinox no later than March 21 as accurate as practical. See also: Gregorian seasonal error.
The calendar equinox (used in Easter calculations) is March 21, the same date as in the current Easter table at the Council of Nicaea in 325. Therefore the calendar is framed to prevent astronomical equinoxes from wandering to 22 March. From Nicea to the date of reform, 500, 600, 700, 900, 1000, 1100, 1300, 1400 and 1500, which will not be a leap year in the Gregorian calendar, the number up to nine days, but astronomers directing the ten days removed.
Currently, the most common equinox and solstice dates are March 20, June 21, September 22 or December 23 and 21; The four-year averages slowly shifted into the early ages as the century wore on. This shift is a full day in about 128 years (compensated mainly by the century "leap year" Gregorian calendar rules) and as the year 2000 is a leap year the current shift has grown since the beginning of the last century, when equinoxes and solstices are relatively late. This also means that in the last few years of the twentieth century, March 21, June 22, September 23 and December 22 are much more common, so older books teach (and older people may still remember) these dates.
Note that all the time is given in UTC (roughly speaking, time in Greenwich, ignoring Summer Time UK). People living further east (Asia and Australia), whose early local time, will see the astronomical season seem to begin later; for example, in Tonga (UTC 13), an equinox occurred on 24 September 1999, a date that will not reappear until 2103. On the other hand, people living far away in the west (United States) whose clock runs behind UTC may experience equinox as early as March 19th.
Change over time
For thousands of years, the axis of the Earth's axis and the eccentricity of the orbit vary (see Milankovitch cycle). The turning and turning points of the sun move westward relative to the star while the perihelion and aphelion move eastward. Thus, ten thousand years from now the northern winter of Earth will occur in the summer of aphelion and summer in perihelion. The severity of seasonal changes - the average temperature difference between summer and winter on site - will also change over time as the axial tilt of the earth fluctuates between 22.1 and 24.5 degrees.
Smaller deviations at times are caused by the disruption of the Moon and other planets.
Solar
Sun time is based on insolation where solstices and equinoxes are seen as the midpoint of the season. It was a method for counting seasons in medieval Europe, mainly by the Celts, and still ceremonially observed in some eastern Asian countries. Summer is defined as a quarter of the year with the greatest insolation and winter as the quarter with the fewest.
The solar season changes in the cross-quarter days, which are about 3-4 weeks earlier than the meteorological season and 6-7 weeks earlier than the season that starts at equinoxes and solstices. Thus, the largest insolation day is set "mid-summer" as recorded in William Shakespeare's drama A Midsummer Night's Dream, set at the summer solstice. On the Celtic calendar, the first day of traditional winter is November 1 (Samhain, of Celtic Halloween origin); spring begins February 1 (Imbolc, Celtic origin of Groundhog Day); summer starts May 1st (Beltane, Celtic origin from May Day); the first day of autumn is August 1 (Celtic Lughnasadh). The Celtic dates relate to four Pagan agricultural festivals.
Traditional calendars in China form the basis of other such systems in East Asia. The season is traditionally based on 24 periods known as the term sun. Four seasons ch? N (? ), xiÃÆ' (? ), qi? (? ), and d? ng (? ) is universally translated as "spring", "summer", "fall", and "winter "but actually start much earlier, with solstices and equinoxes forming the midpoint of each season rather than their initial. Astronomically, the season is said to begin in Lichun ( ?? , lit. Ã, "standing spring ") on about February 4th, Lixia ( ?? ) on about May 6th, Liqiu ( ?? ) on about August 8th, and Lidong ( ?? ) on about November 7th. This date is not part of the traditional lunar calendar, however, and movable vacations like the Chinese New Year and Mid-Autumn Festival are more closely tied to the season.
Six-season calendar calculation
Some calendars in South Asia use the six-seasons method where the number of seasons between summer and winter can be calculated from one to three. The date is set at even intervals of several months.
In the tropical and subtropical Hindu Indian calendar, there are six seasons or Ritu based calendars in the sense of having a fixed date: Vasanta (spring), Greeshma (summer), Varsha (rainy season), Sharad (autumn), Hemanta (early season cold), and Shishira (prevernal or late winter). Six seasons are thought to come from two months each of the twelve months in the Hindu calendar. Rough correspondence is:
The Bengali calendar is similar but different in start and end times. It has the following seasons or ritus:
The Tamil calendar follows the same pattern of six seasons
Polar day and night
Every point north of the Arctic Circle or south of the Antarctic Circle will have one period in summer when the sun does not set, and one period in winter when the sun does not rise. At higher latitudes, the maximum period of "midnight sun" and "polar night" is longer.
For example, in the military and Alert weather stations located at 82 Â ° 30? 05? N and 62 Â ° 20? 20? W, at the northern end of Ellesmere Island, Canada (about 450 nautical miles or 830 km from the North Pole), the sun begins to peek over the horizon for several minutes per day at the end of February and each day rises higher and stays longer; on March 21, sunrise for more than 12 hours. On April 6th the sun rose at 0522 UTC and remained above the horizon until it buried under the horizon again on September 6 at 0335 UTC. On October 13 the sun is above the horizon for only 1 hour 30 minutes and on October 14 it does not rise above the horizon at all and remains below the horizon until it rises again on 27 February.
The first light comes at the end of January because the sky has twilight, becomes light on the horizon, for an increase in hours every day, for more than a month before the sun first appears with its disc above the horizon. From mid November to mid January, there is no dusk.
In the weeks around June 21, in the Arctic region, the sun is at the highest altitude, visible circling the sky there without going down the horizon. Finally, it goes under the horizon, to progressively longer periods every day until around mid-October, when it disappears for the last time until next February. Over the next few weeks, the "day" is marked by the diminishing of the twilight period. Finally, from mid-November to mid-January, there is no dusk and keeps dark. In mid-January, the first faint faint twilight touched briefly the horizon (only a few minutes per day), and then dusk increased in duration with increasing brightness every day until sunrise at the end of February, then on April 6th the sun remained above the horizon until mid-October.
Non-calendar-based calculation
Ecologically, seasons are periods of the year in which only a few types of flower and animal events occur (eg: flowers bloom - spring, hibernation hedgehogs - winter). So, if we can observe changes in everyday flower/animal events, the seasons change. In this sense, the ecological season is defined in absolute terms, unlike the calendar-based method in which the season is relative. If certain conditions associated with a particular ecological season do not usually occur in a particular region, then the area can not be said to experience the season on a regular basis.
Economical modern latitude
Six distinguishable seasons that do not have date-based calendars such as meteorological and astronomical seasons. Marine regions tend to experience hibernation season beginning up to one month slower than continental climate. In contrast, prevernal and vernal seasons begin one month earlier near the sea and coastal areas. For example, crocus prevernal blooms usually occur in early February in the coastal areas of British Columbia, British Isles, but generally do not appear until March or April at sites such as Midwest USA or parts of eastern Europe. The actual dates for each season vary by climatic region and may change from one year to the next. The average dates listed here are for temperate and mild temperate zones in the Northern Hemisphere:
- Prevernal (early or spring): Start of February (temperate), until March (cool climate). The fallen tree shoots begin to swell. Some migratory bird species fly from winter to summer habitats.
- Vernal (spring): From mid March (temperate), until the end of April (cool climate). Tree tops explode into leaves. Birds make territory and start mating and nesting.
- Estival (high summer): Starts in June in most temperate regions. Trees with full leaves. Birds hatch and raise children.
- Serotinal (end of summer): Generally from mid to late August. The fall leaves begin to change color in higher latitudes (above 45 north). Young birds reach maturity and join other mature birds preparing for autumn migration. The traditional "harvest season" begins in early September.
- Autumn (autumn): Generally from mid to late September. The leaves of colorful trees then turn brown and fall to the ground. Birds migrate back to winter.
- Hibernal (winter): Starts in December (temperate), November (cold climates). The fall tree is a shaved and falling leaves begin to rot. Migratory birds settle in winter habitat.
Tropical ecology
In the tropics, where seasonal dates also vary, it is more common to talk about the rainy season (or rain, or the rainy season) versus the dry season. For example, in Nicaragua the dry season (November to April) is called 'summer' and the rainy season (May to October) is called 'winter', although it is located in the northern hemisphere. In some tropical regions three-way to summer, rain, and cool are used. There is no noticeable change in the amount of sunlight at different times throughout the year. However, many areas (such as northern Indian seas) are subject to rain and wind cycles.
Variations in flower and animal activity near the equator depend more on wet/dry cycles than seasonal temperature variations, with different species flowering (or emerging from cocoons) at certain times before, during, or after the wet season. Thus, the tropics are characterized by many "mini-seasons" in larger seasonal blocks.
In the tropical part of Australia in northern Queensland, Western Australia, and the Northern Territory, wet and dry seasons are observed alongside or in the name of the temperate seasons.
Original ecology
Indigenous peoples in the polar, temperate and tropical climates of northern Eurasia, the Americas, Africa, Oceania and Australia traditionally define ecologically sound seasons by observing the activities of plants, animals and the weather around them. Each of the different tribal groups has traditionally observed the various seasons that are determined according to local criteria that can vary from polar bears hibernation on the Arctic tundra to planting crops in tropical rainforests. In Australia, some tribes have up to eight seasons of the year, just like the Sami people in Scandinavia. Many indigenous peoples who no longer live directly from traditional, often sedentary land, are now observing modern methods of seasonal calculation according to what is prevalent in their country or territory.
"Official" title
As noted, dates are used in different countries to mark seasonal changes, especially those based on calendars. These observations are often declared "official" in their respective jurisdictions by local or national media, even when the weather or climate is conflicting. But they are primarily just customary issues, and have not been commonly proclaimed by the north or south governments of the equator for civilian purposes.
See also
- Equinox
- Planting season
- Indian Summer
- Persephone, the Greek mythological figure associated with the rebirth of vegetation in spring
- Solstice
- Sun path
- Vertumnus, the Roman god of the season
References
- Maris, Mihaela, St. Luchian School, Bacau, Romania, Seasonal Variations of Bird Species, ref. ecological season pp. 195-196 included. and pp.Ã, 207-209 included.
External links
- When's The Season Begins? (from Bad Astronomers)
- Southern Hemisphere Calendar
- Solstice does not signify the beginning of the season (from The Straight Dope)
- Why Earth has a season article on h2g2.
- Aboriginal Season of Kakadu
- Indigenous Season (Australian Meteorological Bureau)
- Mt Stirling Seasons
- The Lost Seasons
- Melbourne six seasons
- Season Length (numerical integration analysis)
- Distance of Earth vs slope
- Tutorials in Earth/Sun Relations and Seasons
- Sunpreview Season Forecast Project
- Satellite photos demonstrate seasonal changes in 2004 on the NASA website
- Video - how seasons change visible from space
Source of the article : Wikipedia
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