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This moves north-west and north-east with the seasons. The climate is variable, with frequent droughts lasting several seasons, thought to be caused in part by the El Niño-Southern Oscillation. Australia has a wide variety of climates due to its large geographical size. The largest part of Australia is desert or semi-arid.
By far the largest part of Australia is arid or semi-arid. A total of 18% of Australia's mainland consists of named deserts, [20] while additional areas are considered to have a desert climate based on low rainfall and high temperature. Only the south-east and south-west corners have a temperate climate and moderately fertile soil.
Visualization of the ice and snow covering Earth's northern and southern polar regions Northern Hemisphere permafrost (permanently frozen ground) in purple. The polar regions, also called the frigid zones or polar zones, of Earth are Earth's polar ice caps, the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles.
The air flows at the surface are called the polar easterlies, flowing from northeast to southwest near the north pole and from southeast to northwest near the south pole. The outflow of air mass from the cell creates harmonic waves in the atmosphere known as Rossby waves .
In winter, this relatively warm water, even though covered by the polar ice pack, keeps the North Pole from being the coldest place in the Northern Hemisphere, and it is also part of the reason that Antarctica is so much colder than the Arctic.
Australia is vulnerable to the effects of global warming projected for the next 50 to 100 years because of its extensive arid and semi-arid areas, and already warm climate, high annual rainfall variability. The continent's high fire risk increases this susceptibility to changes in temperature and climate.
The North Frigid Zone, between the North Pole at 90° N and the Arctic Circle at 66°33′50.3″ N, covers 4.12% of Earth's surface. The North Temperate Zone, between the Arctic Circle at 66°33′50.3″ N and the Tropic of Cancer at 23°26′09.7″ N, covers 25.99% of Earth's surface.
In winter it normally moves north, therefore permitting cold fronts and low pressure systems to relocate up from the Great Australian Bight and bring rainfall to most parts of southern Australia. [6] The high is part of the subtropical ridge system and it is the reason why a large part of Australia is arid to semi-arid. [7]