Climate of Australia
From Wikipedia, the free encyclopedia
The climate of Australia varies widely, but by far the largest part of Australia is desert or semi-arid – 40% of the landmass is covered by sand dunes. Only the south-east and south-west corners have a temperate climate and moderately fertile soil. The northern part of the country has a tropical climate: part is tropical rainforests, part grasslands, and part desert.
Rainfall is highly variable, with frequent droughts lasting several seasons thought to be caused in part by the El Niño-Southern Oscillation. Occasionally a duststorm will blanket a region or even several states and there are reports of the occasional large tornado. Rising levels of salinity and desertification in some areas is ravaging the landscape.
Australia's tropical/subtropical location and cold waters off the western coast make most of western Australia a hot desert with aridity, a marked feature of greater part of the continent. These cold waters produce precious little moisture needed on the mainland. A 2005 study by Australian and American researchers [2] investigated the desertification of the interior, and suggested that one explanation was related to human settlers who arrived about 50,000 years ago. Regular burning by these settlers could have prevented monsoons from reaching interior Australia.
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[edit] Moisture
Compared to the earths other continental landmasses, Australia is very dry. More than 80 per cent of the continent has an annual rainfall of less than 600 millimetres, only Antarctica receives less rainfall than Australia. There are four main factors that contribute to the dryness of the Australian landmass:
- Cold ocean currents off the west coast
- Flatness of the landmass
- Dominance of high-pressure systems
- Shape of the landmass
Low rate of evaporation from this very cool body of water result in little evaporation occurring. As a result, rain clouds are sparsely formed and very rarely do they form long enough for a continuous period of rain to be recorded. Australias arid/ semi-arid zone extends to this region. The absence of any significant mountain range or area of substantial height above sea level, results in very little rainfall caused by orographic uplift. This is when air rushes up the mountain side and follows it to its summit, where it cools, condenses and forms rain on the opposite side of the mountain. In the east, the Great Dividing Range limits rain moving into inland Australia. Australia has a compact shape and no significant bodies of water penetrate very far inland. This is important because it means that moist winds are prevented from penetrating to inland Australia, keeping rainfall low.
Because of Australia's mid latitude position its climate is generally dominated by high pressure systems. This correlates with increasingly often high levels recorded in the Southern Oscillation Index, and the increasing amounts of El Nino years in Australia. High Pressure Systems are generally associated with stable atmospheric conditions; clear skies, gentle winds and little rain.
[edit] Snow
In Australia snow can fall in the mountains of Victoria, Australian Capital Territory, New South Wales and Tasmania. Sometimes snow has even been reported in the mountains of South Australia, Western Australia and Queensland though this is very rare.
[edit] Predicted effects of global warming
Climate change is causing Global warming which is predicted by the CSIRO[1] to have significant effects on the climate of and extreme weather events in Australia. It is predicted that the Great Barrier Reef and reefs surrounding Lord Howe Island could be killed as a result of the rise in water temperature forecast by the IPCC Fourth Assessment Report. The Murray River, Darling River Coorong and Macquarie Marshes are all at risk from decreased rainfall from climate change.[citation needed]
Coastal communities face risks from sea level rise, albeit over a long period of time based on current estimates of the IPCC Fourth Assessment Report. The Gold Coast, being built on sand and with many canal developments, could be considered particularly at risk. Suburbs of Sydney like Drummoyne and Concord on rivers like the Parramatta River face risks of inundation of low lying areas such as parks (such as Timbrell Park and Majors Bay Reserve) reclaimed from mudflats at the heads of bays, or massive expenses in rebuilding seawalls to higher levels.
