Winter Flags

Winter is one of the four seasons of temperate zones. more...

Astronomically, it begins with the winter solstice (around December 21 in the Northern hemisphere and June 21 in the Southern hemisphere), and ends with the spring equinox (around March 21 in the Northern hemisphere and September 23 in the Southern hemisphere). In meteorology, it is by convention counted instead as the whole months of June, July and August in the Southern hemisphere and December, January and February in the Northern hemisphere.

However, in the United Kingdom and Ireland the winter solstice is traditionally considered as midwinter, the winter season beginning November 1 on All Hallows or Samhain. Elsewhere, in Chinese astronomy (and other East Asian calenders), winter is taken to commence on or around November 7, with the Jiéqì known as (立冬 lì dōng, i.e. "establishment of winter".

Meteorological aspects

Meteorological winter is the season having the shortest days (which vary greatly according to latitude) and the lowest temperatures. Nighttime predominates the winter season, and in some regions it has the highest rate of precipitation, as well as prolonged dampness due to permanent snow cover in such areas. Measured astronomically, winter begins on the shortest day of the year, and each day of winter has more sunlight than the previous one.

During winter, there is much snow and cold, especially in areas that are farther away from the Equator. Blizzards often develop and cause many delays. A rare meteorological phenomenon encountered during winter is ice fog, which is composed of ice crystals suspended in the air and happening only at very low temperatures (at least 10 degrees below zero).

What causes winter

The Earth revolves around the Sun once every year, and its distance from the Sun changes slightly as it does, affecting the amount of heat that the Earth receives from the Sun. At the same time, our planet remains tilted on its axis, and this has an even more dramatic effect on the weather. The popular belief that winter is caused by the Earth moving away from the Sun in its orbit is not necessarily true. For example, winter occurs in the northern hemisphere when the Earth is closest to the Sun.

The planet is tilted at an angle of 23°27' (23 degrees 27 minutes) to the plane of its orbit, and this causes different latitudes on the Earth to directly face the Sun as the Earth moves through its orbit. It is this variation that primarily brings about the seasons. When it is winter in the northern hemisphere, the southern hemisphere faces the Sun more directly and thus experiences warmer temperatures than the northern hemisphere.

During winter in either hemisphere, the radiation from the Sun hits that hemisphere at an oblique angle. Less energy is transferred to the Earth's surface as a result of the glancing nature of these rays. Basically, the same amount of light energy is spread out over a larger area. This effect is compounded by the larger distance that the light must travel through the atmosphere, allowing it to filter more of this already limited heat.

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