The Southern Hemisphere is the southern portion or half of the Earth (map). It begins at the equator at 0° and continues south into higher latitudes until it reaches 90°S or the South Pole in the middle of Antarctica. The word hemisphere itself specifically means half of a sphere, and because the earth is spherical (although it is considered an oblate sphere) a hemisphere is half.
Geography and Climate of the Southern Hemisphere
In comparison to the Northern Hemisphere, the Southern Hemisphere has fewer land masses and more water. The South Pacific, South Atlantic, Indian Oceans and various seas such as the Tasman Sea between Australia and New Zealand and the Weddell Sea near Antarctica make up around 80.9% of the Southern Hemisphere. Land comprises only 19.1%. In the Northern Hemisphere, the majority of area is composed of land masses instead of water.
The continents making up the Southern Hemisphere include all of Antarctica, around 1/3 of Africa, most of South America and nearly all of Australia.
Because of the large presence of water in the Southern Hemisphere, climate in the Earth's southern half is more mild overall than the Northern Hemisphere. In general, water heats and cools more slowly than land so water near any land area usually has a moderating effect on the land's climate. Since water surrounds land in much of the Southern Hemisphere, more of it is moderated than in the Northern Hemisphere.
The Southern Hemisphere, like the Northern Hemisphere is also divided into several different regions based on climate. The most prevalent is the southern temperate zone, which runs from the Tropic of Capricorn to the beginning of the Arctic Circle at 66.5°S. This area features a temperate climate which generally has large amounts of precipitation, cold winters and warm summers. Some countries included in the southern temperate zone include most of Chile, all of New Zealand and Uruguay. The area directly north of the southern temperate zone and lying between the equator and the Tropic of Capricorn is known as the tropics- an area which has warm temperatures and precipitation year round.
South of the southern temperate zone is the Antarctic Circle and the Antarctic continent. Antarctica, unlike the rest of the Southern Hemisphere is not moderated by the large presence of water because it is a very large land mass. In addition, it is considerably colder than the Arctic in the Northern Hemisphere for the same reason.
Summer in the Southern Hemisphere lasts from around December 21 to the vernal equinox around March 20. Winter lasts from around June 21 to the autumnal equinox around September 21. These dates are due to the Earth's axial tilt and from the period of December 21 to March 20, the southern hemisphere is tilted toward the sun, while during the June 21 to September 21 interval, it is tilted away from the sun.
The Coriolis Effect and the Southern Hemisphere
An important component of physical geography in the Southern Hemisphere is the Coriolis Effect and the specific direction that objects are deflected in Earth's southern half. In the southern hemisphere any object moving over the Earth's surface deflects to the left. Because of this, any large patterns in air or water turn counterclockwise south of the equator. For example, there are many large oceanic gyres in the North Atlantic and North Pacific- all of which turn counterclockwise. In the Northern Hemisphere these directions are reversed because objects are deflected to the right.
In addition, the left deflection of objects impacts the flows of air over the Earth. A high pressure system for example is an area where the atmospheric pressure is greater than that of the surrounding area. In the Southern Hemisphere, these move counterclockwise because of the Coriolis Effect. By contrast, low pressure systems or areas where atmospheric pressure is less than that of the surrounding area move clockwise because of the Coriolis Effect in the Southern Hemisphere.
Population and the Southern Hemisphere
Because the Southern Hemisphere has less land area than the Northern Hemisphere it should be noted that population is less in Earth's southern half than in the north. The majority of Earth's population and its largest cities are in the Northern Hemisphere, although there are large cities such as Lima, Peru, Cape Town, South Africa, Santiago, Chile, and Auckland, New Zealand.
Antarctica is the largest landmass in the Southern Hemisphere and it is the world's largest cold desert. Although it is the largest area of land in the Southern Hemisphere, it is not populated because of its extremely harsh climate and the difficulty of building permanent settlements there. Any human development that has taken place in Antarctica consists of scientific research stations- most of which are operated only during the summer.
In addition to people however, the Southern Hemisphere is incredibly biodiverse as the majority of the world's tropical rainforests are in this region. For example, the Amazon Rainforest is almost entirely within the Southern Hemisphere as are biodiverse places such as Madagascar and New Zealand. Antarctica also has a large variety of species adapted to its harsh climate such as emperor penguins, seals, whales and various types of plants and algae.
Wikipedia. (7 May 2010). Southern Hemisphere - Wikipedia, the Free Encyclopedia. Retrieved from: http://en.wikipedia.org/wiki/Southern_Hemisphere