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Northern Australia

Northern regions of Australia

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  • 4 chapters

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Through Australia, Coal and Natural gas

Although it comprises 53% of the total area of Australia, Northern Australia has only 5.2% of the Australian population (1.4 million). However, it includes several sources of Australian exports, being coal from the Great Dividing Range in Queensland/New South Wales and the natural gas and iron ore of the Pilbara region in Western Australia. It also includes major natural tourist attractions, such as Uluru (Ayers Rock), the Great Barrier Reef and the Kakadu National Park.

Geography and climate

Almost all of Northern Australia is a huge ancient craton that has not experienced geological upheaval since the end of the Precambrian. The only exception to this generalisation is the Wet Tropics of northern Queensland, where active volcanoes have been present as recently as the Pleistocene.

The vast craton in the north and west contains a number of quite rugged mountain ranges, of which the highest are the MacDonnell and Musgrave Ranges on the southern border of the Northern Territory. These rise to over 1,500 metres (4,900 ft), but the most spectacular features are the deep gorges of rivers such as the Finke. Most of the craton, however, is distinctly flat and generally low-lying with an average elevation of around 400 metres (1,300 ft), whilst in the Lake Eyre Basin most of the land is not far above sea level. Northern Australia is known for its abundance of pristine beaches. These beaches have seen an increase in marine debris floating in from Asia.

Major settlements in the region include Darwin, Cairns, Townsville, Mackay, Rockhampton, Gladstone and Mount Isa.

The climate of the north of Australia ranges from arid (Köppen BWh) in the south to monsoonal (Köppen Aw) in the Top End and Kimberley. On the eastern coast, however, the climate is much more humid and ranges from humid sub-tropical (Köppen Cfa around Brisbane and Cwa further north) to humid tropical (Köppen Am and Af) in the Wet Tropics. Except in the western part of the Pilbara and Gascoyne where the heaviest rain often occurs from May to July under northwest cloudbands, rainfall is heavily concentrated in the "summer" months from November to March. For instance, in Burketown, the months May to September are rainless in over fifty percent of years, with over eighty percent of Augusts having no rain.

Temperatures in summer are generally unpleasantly hot apart from the eastern coastal belt. Maximum temperatures elsewhere between October and April range from 30 °C (86 °F) in the south in April to around 40 °C (104 °F) in the inland Pilbara and Kimberley before the wet season breaks. Further north, maxima are consistently around 32 °C (90 °F) but extreme humidity makes conditions very unpleasant. On the coast, maxima in January range from 29 °C (84 °F) in the south to 32 °C (90 °F), with minima generally around 21 °C (70 °F).

In July, temperatures show a wider range, from 31 °C (88 °F) in the north to around 19 °C (66 °F) in the south, where minima can be as low as 5 °C (41 °F) in Alice Springs in June and July.

Climate variability

The above generalisations, however, mask the immense variability of the climate throughout the whole region. With the exception of the extreme north of the Northern Territory, rainfall variability throughout Northern Australia is quite markedly higher than most comparable climates in other continents. For example, at Charters Towers, the rainfall over the wet season can vary from less than 100 millimetres (3.9 in) in 1901/1902 to over 2,000 millimetres (79 in) in 1973/1974. The chief cause of this very high variability is erratic tropical cyclones, which occur from December to April and in many places can deliver as much as 350 millimetres (14 in) of rain over a day or two, causing extremely large floods in the region's rivers. For example, in April 1898, a tropical cyclone gave 740 millimetres (29 in) in one day at Whim Creek in the Pilbara, but for the whole of 1924 that same station recorded only 4 millimetres (0.16 in) for the whole year. Tropical cyclones may cross the coast anywhere in Northern Australia but are most frequent between Derby and Onslow on the west side and between Cooktown and Rockhampton on the east. Inland, variability of rainfall is related to the penetration of the summer monsoon, with high rainfall in seasons like 1973/1974, 1975/1976 and from 1998 to 2001 when the monsoon is most powerful.

Climate change has seen increases of up to fifty percent in annual rainfall since 1967 over the western half of Australia's tropics, but has not seen any increase over the east. The increase over the west is sometimes attributed to aerosol pollution over industrialising areas of China and India, but may be related to global warming.

Frosts are common in the southern inland during the winter, but in some years, such as 1998, they are much less frequent due to the recent incidence of warm pools in the Indian Ocean.

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