Spring is one of the four conventional
temperate seasons, following 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 will be autumn in the Southern Hemisphere. At the spring
equinox, days are approximately 12 hours long with day length increasing as the
season progresses. Spring and "springtime" refer to the season, and
also to ideas of rebirth, rejuvenation, renewal, resurrection and regrowth.
Subtropical and tropical areas have climates better described in terms of other
seasons, e.g. dry or wet, monsoonal or cyclonic. Often the cultures have
locally defined names for seasons which have little equivalence to the terms
originating in
Natural events
During spring,
the axis of the Earth is increasing its tilt relative to the Sun, and the
length of daylight rapidly increases 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. In climates that have no snow and rare frosts,
the air and ground temperatures increase more rapidly. Many flowering plants
bloom this time of year, in a long succession sometimes beginning when snow is
still on the ground, continuing into early summer. In normally snowless areas
"spring" may begin as early as February (Northern Hemisphere)
heralded by the blooming of deciduous magnolias, cherries and quince, or August
(Southern Hemisphere) in the same way. 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.
While spring is a
result of the warmth caused by the changing orientation of the Earth's axis
relative to the Sun, the weather in many parts of the world is overlain by
events which appear very erratic taken on a year-to-year basis. The rainfall in
spring (or any season) follows trends more related to longer cycles or events
created by ocean currents and ocean temperatures. Good and well-researched
examples are the El Niño 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, 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 into direct conflict. 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 in winter, the jet streams play an important role in unstable
and severe weather in the springtime in the Northern Hemisphere.
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.
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 the Prague Spring.
Spring in the
Southern Hemisphere is different in several significant ways to that of the
Northern Hemisphere for several reasons: there is no land bridge between Southern
Hemisphere countries and the Antarctic zone capable of bringing in cold air
without the temperature-mitigating effects of extensive tracts of water; the
vastly greater amount of ocean in the Southern Hemisphere 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 40s and 50s) uninterrupted by large land
masses; no equivalent jet streams; and the peculiarities of the reversing ocean
currents in the Pacific.
Beginning of spring in the Netherlands
Spring begins in the northern hemisphere
(mostly) on 20 March and ends (mostly) on 21 June. The beginning of spring (20
or 21 March) has been determined on the basis of an agreement.
Astronomical spring starts as the day and
night are of equal length. During the spring the days are getting longer. The spring
evening occurs around 20 March in the northern hemisphere. The Sun then passes
through the vernal equinox and the day and night are approximately the same
length. Spring ends with the summer solstice (around June 21). That is the
moment that the Sun is the highest in the sky.
In 2015 the starting of the astronomical
spring in Netherlands 23:
45
During spring in the more northerly regions
of the northern hemisphere trees become much greener and many plants bloom;
gradually, it is warmer and the chance of Frost is smaller.
The Dutch word lente is an old derivation
of the Dutch word "lang" (long) and covers "lengen van de dagen"
For practical reasons, but also climatic
meteorological spring begins on March 1 and lasts until 1 June.
No comments:
Post a Comment