Meteorological Other Seasons Artic Extremes
Meteorological
Meteorological seasons are reckoned by temperature, with summer being the hottest quarter of the
year and winter the coldest quarter of the year. In 1780 the Societas Meteorologica Palatina
(which became defunct in 1795), an early international organization for meteorology, defined
seasons as groupings of three whole months as identified by the Gregorian calendar. Ever since,
professional meteorologists all over the world have used this definition.[12] Therefore, for
temperate areas in the northern hemisphere, spring begins on 1 March, summer on 1 June, autumn on
1 September, and winter on 1 December. For the southern hemisphere temperate zone, spring begins
on 1 September, summer on 1 December, autumn on 1 March, and winter on 1 June.[13][14] In Australasia
the meteorological terms for seasons apply to the temperate zone that occupies all of New Zealand,
New South Wales, Victoria, Tasmania, the south-eastern corner of South Australia and the south-west
of Western Australia, and the south east Queensland areas south of Brisbane.
Meteorological temperate seasons
| Northern Hemisphere | Southern Hemisphere | Start date | End date |
|---|---|---|---|
| Winter | Summer | 1 December/td> | 28 February |
| Spring | Autumn | 1 March | 31 May |
| Summer | Winter | 1 June | 31 August |
| Autumn | Spring | 1 September | 31 November |
In Sweden and Finland, meteorologists use a non-calendar based definition for the seasons based on the temperature. Spring begins when the daily averaged temperature permanently rises above 0 °C, summer begins when the temperature permanently rises above +10 °C, summer ends when the temperature permanently falls below +10 °C and winter begins when the temperature permanently falls below 0 °C. "Permanently" here means that the daily averaged temperature has remained above or below the limit for seven consecutive days. This implies two things: first, the seasons do not begin at fixed dates but must be determined by observation and are known only after the fact; and second, a new season begins at different dates in different parts of the country.
Winter, occurring from December to February. The year's coldest months are December and January, when temperatures average around 10–15 °C (50–59 °F) in the northwest; temperatures rise as one proceeds towards the equator, peaking around 20–25 °C (68–77 °F) in mainland India's southeast. Summer or pre-monsoon season, lasting from March to May. In western and southern regions, the hottest month is April; for northern regions of India, May is the hottest month. Temperatures average around 32–40 °C (90–104 °F) in most of the interior. Monsoon or rainy season, lasting from June to September. The season is dominated by the humid southwest summer monsoon, which slowly sweeps across the country beginning in late May or early June. Monsoon rains begin to recede from North India at the beginning of October. South India typically receives more rainfall. Post-monsoon or autumn season, lasting from October to November. In the northwest of India, October and November are usually cloudless. Tamil Nadu receives most of its annual precipitation in the northeast monsoon season.
Six Seasons
Some calendars in south Asia use a six-season method where the number of seasons between summer and winter can number
from one to three. The dates are fixed at even intervals of months.
In the Hindu calendar of tropical and subtropical India, there are six seasons or Ritu that are calendar-based in
the sense of having fixed dates: Vasanta (spring), Greeshma (summer), Varsha (monsoon), Sharad (autumn), Hemanta
(early winter), and Shishira (prevernal or late winter). The six seasons are ascribed to two months each of the
twelve months in the Hindu calendar. The rough correspondences are:
| Hindu season | Start | End | Hindu Months | Mapping to English Names |
|---|---|---|---|---|
| Vasanta | Mid-March | Mid-May | Chaitra, Vaishakha | spring |
| Greeshma | Mid-May | Mid-July | Jyeshtha, Ashadha | summer |
| Varsha | Mid-July | Mid-September | Shraavana, Bhadrapada | monsoon |
| Sharad | Mid-September | Mid-November | Ashvin, Kartika | autumn |
| Hemanta | Mid-November | Mid-January | Maargashirsha, Pushya/td> | early winter |
| Shishira | Mid-January | Mid-March | Magh, Phalguna | prevernal or late winter |
Three seasons
The most historically important of these are the three seasons—flood, growth, and low water—which were previously defined by the former annual flooding of the Nile in Egypt. In some tropical areas a three-way division into hot, rainy, and cool season is used. In Thailand three seasons are recognised [22]| Thai season | Months |
|---|---|
| Ruedu nao (cold season) | mid October to mid February |
| Ruedu ron (hot season) | mid February to mid May |
| Ruedu fon (rainy season) | mid May to mid October |
Twenty-four seasons
The traditional calendar in China has seasons traditionally based on 24 periods known as solar terms.[23] The four seasons chūn (春), xià (夏), qiū (秋), and dōng (冬) are universally translated as "spring", "summer", "autumn", and "winter" but actually begin much earlier, with the solstices and equinoxes forming the midpoint of each season rather than their start. Astronomically, the seasons are said to begin on Lichun (立春, lit. "standing spring") on about 4 February, Lixia (立夏) on about 6 May, Liqiu (立秋) on about 8 August, and Lidong (立冬) on about 7 November. These dates were not part of the traditional lunar calendar, however, and moveable holidays such as Chinese New Year and the Mid-Autumn Festival are more closely associated with the seasons. It forms the basis of other such systems in East Asian lunisolar calendars.Two seasons
In the tropical parts of Australia in the northern parts of Queensland, Western Australia, and the Northern Territory, wet and dry seasons are observed in addition to or in place of temperate season names.[24]Meteorological Tropical seasons
| Northern Hemisphere | Southern Hemisphere | Start date | End date |
|---|---|---|---|
| Dry season | Wet season | 1 November | 30 April |
| Wet season | Dry season | 1 May | 31 October |
Polar
Any point north of the Arctic Circle or south of the Antarctic Circle will have one period in the summer
called "polar day" when the sun does not set, and one period in the winter called 'polar night' when the
sun does not rise. At progressively higher latitudes, the maximum periods of "midnight sun" and "polar night"
are progressively longer.
For example, at the military and weather station Alert located at 82°30′05″N and 62°20′20″W, 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 for minutes per day at the end of February and each day it climbs higher and stays up
longer; by 21 March, the sun is up for over 12 hours. On 6 April the sun rises at 0522 UTC and remains above
the horizon until it sets below the horizon again on 6 September at 0335 UTC. By 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.[29]
First light comes in late January because the sky has twilight, being a glow on the horizon, for increasing
hours each 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 twilight.
In the weeks surrounding 21 June, in the northern polar region, the sun is at its highest elevation,
appearing to circle the sky there without going below the horizon. Eventually, it does go below the horizon,
for progressively longer periods each day until around the middle of October, when it disappears for the last
time until the following February. For a few more weeks, "day" is marked by decreasing periods of twilight.
Eventually, from mid-November to mid-January, there is no twilight and it is continuously dark. In mid
January the first faint wash of twilight briefly touches the horizon (for just minutes per day), and then
twilight increases in duration with increasing brightness each day until sunrise at end of February,
then on 6 April the sun remains above the horizon until mid October.