Spring (season)

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Spring is one of the four temperate seasons. Spring marks the transition from winter into summer.

[edit] Overview

[edit] Definition of spring

According to an astronomical definition, spring begins on the vernal equinox (usually March 20 in the Northern Hemisphere, and September 21 in the Southern Hemisphere), and lasts until the summer solstice (usually June 21 in the Northern Hemisphere and December 21 in the Southern Hemisphere). According to this definition, therefore, the day called Midsummer's Day in some traditions, is close to the first day of Summer. An alternative tradition is to calculate Spring as starting on March 1 in the Northern Hemisphere and September 1 in the Southern Hemisphere. The lower (cooler) latitudes are more inclined to start with the later date, vernal equinox, while the higher (warmer) latitudes, where the biological indicators of spring arrive earlier, are more inclined to run with the 1st of the month. According to a less used solar term, spring begins on February 4 and ends on May 4, and calendars may give the first, but the second and third are more used with this tradition.

The phenological definition of spring relates to bioindicators, the blossoming of a range of plant species, and the activites of animals, or the special smell of soil that has reached the temperature for microflora to flourish. The first swallow to arrive or the flowering of lilac may be the indicator of spring. A number of meterological stations have planted Syringa rothamagensis, and the date of full flowering, as determined by defined means, is used as a more precise indicator of the date of start of spring for agricultural activities associated with spring and the passing of frosty weather. It therefore varies according to the climate (as in 'Spring comes late to the north-east'), and according the to specific weather of particular years (as in 'this was an unusually early spring for our area with all these extra days of warm winds, fewer frosts at this time of the year, and with the early flowering of the lilac, and early arrival of the swallows; we therefore planted longer season varieties to extend our growing season and get greater yields.')

[edit] Events that occur during spring

In recent decades season creep has been observed, which means that many phenological signs of spring are occurring earlier in many regions by a couple of days per decade.

In summer, the axis of the Earth is tilted toward the Sun and the length of daylight rapidly increases the for the relevant hemisphere. The hemisphere begins to warm significantly causing new plant growth to "spring forth," giving the season its name. Snow, if a normal part of winter, begins to melt and streams swell with runoff. Frosts, if a normal part of winter, become less severe. Many temperate climates have no snow and may have no frosts, and the air and ground temperature increase. Many flowering plants bloom this time of year, in a long succession sometimes beginning even if snow is still on the ground, continuing into early summer. In normally snowless areas "spring" may begin as early as August (Southern Hemisphere) heralded by the blooming of deciduous magnolias, cherries, and quince, or February (Northern Hemisphere) in the same way. Subtropical and tropical areas have climates better descibed in terms of other seasons, eg dry or wet, or monsoonal, or cyclonic. Often the cultures have locally defined names for seasons which have little equivalence to the terms originating in Europe. Many temperate areas have a dry spring, and wet autumn (fall), which brings about flowering in this season more consistent with the need for water as well as warmth. Subarctic areas may not experience "spring" at all until May or even June, or December in the outer Antarctic.

While spring is a result of the warmth of the turning of the earth's axis, the weather in many parts of the world is overlain by events which appear very eratic taken on a year to year basis, but the rainfall in spring, or any season, follow trends more related to longer cycles or events created by ocean currents and ocean temperatures which move to different complex effects. A good and well researched example being the El Nino effect and the Southern Oscillation Index.

Unstable weather may more often occur during spring, when warm air begins on occasions to invade from lower latitudes, while cold air is still pushing on occasions from the Polar Regions. Flooding is also most common in and near mountainous areas during this time of year because of snowmelt, many times accelerated by warm rains. In the United States, Tornado Alley is most active this time of year, especially since the Rocky Mountains prevent the surging hot and cold air masses from spreading eastward and instead force them directly at each other. Besides tornadoes, supercell thunderstorms can also produce dangerously large hail and very high winds, for which a severe thunderstorm warning or tornado warning is usually issued. Even more so than winter, the jet streams play an important role in unstable and severe weather in the springtime in the Northern Hemishere.

As mentioned, spring is a term for temperate climates, but the news of many countries covers large parts of continents and so we may hear of the hurricane season (Northern Hemisphere) and cyclone season Southern Hemisphere officially beginning in late spring. This is less to do with the relationship of spring to hurricanes / cyclones but more to do with the extent of media coverage and the use of seasonal terms from the one part of a continent to make reference to what is happening in other less temperate climates. The monsoon season is the monsoon season, and not some variation of spring or summer, except for those perceiving it from a temperate climate background.

Spring is seen as a time of growth, renewal, of new life (both plant and animal) being born. The term is also used more generally as a metaphor for the start of better times, as in Prague Spring.

Spring is the end of winter, and the culmination of lengthening days. The Christian season of birth and renewal has its origins in the prior religious traditions which gave celebratory value to the change to the lengthing of days which starts to be apparent in late December, the Winter Solstice. There is no evidence of Christ being born on December 25, but rituals for regeneration, the birth of the new year were well established at this time of the year in agriculture dominated economies and cultures, and available for being appropriated for this special celebration of birth.

Spring in the Southern Hemisphere is different in several significant ways to that of the Northern Hemisphere. This is because: there is no land bridge between Southern Hemisphere countries to the Artic zone capable of bringing in cold air without the temperture mitigating effects of extensive tracts of water; the vastly greater amount of ocean in the Southern Hemishere at all latitudes; at this time in Earth's geologic history the Earth has an orbit which brings it in closer to the Southern Hemisphere for its warmer seasons; there is a circumpolar flow of air (the roaring 40's and 50's) uninterupted by large land masses; no equivalent jet streams; and the peculiarities of the reversing ocean currents in the Pacific.

[edit] Nowruz

Main article: Nowruz

The first day of spring is the beginning of the new year, Nowruz, in the Iranian calendar. Nowruz (also Naw-Rúz, Norooz, Newroz, Navroj, and many other variants) marks an important traditional holiday festival celebrated in Iran as well as in many other countries with a significant population from one of various Iranian peoples, such as Azerbaijan, Afghanistan and Tajikistan, and by Kurdish communities in Turkey and Iraq and elsewhere. Several Turkic peoples also celebrate Nowruz.