02-10-2009, 01:02 AM
From The Times
February 9, 2009
Itââ¬â¢s been called the Big Dry and the Big Wet, and here The Times weatherman explains what's behind a nation's drought ... and floodsPaul Simons
Itââ¬â¢s been called the Big Dry and the Big Wet ââ¬â Australiaââ¬â¢s weather is split between floods in subtropical Queensland, while southeast Australia and Tasmania suffer heat and drought that have stoked up an inferno.
The heatwave in the south has lasted two weeks ââ¬â on Saturday the temperature in Melbourne reached 46.4C (115.5F), the hottest since records began 150 years ago.
The immediate cause of the heatwave is a vast high pressure system stuck over the Tasman Sea, blowing in searing hot air from the countryââ¬â¢s desert interior. With that heat have come intensely dry, gusting winds that have stoked the bushfires into vast infernos.
The heatwave was preceded by several weeks of punishing drought, leaving the ground parched and driving temperatures even higher. Hardly a drop of rain has fallen in southeast Australia this year ââ¬â Melbourne has recorded only 0.8mm rainfall ââ¬â and that follows 12 years of abnormally low rainfall. Officially it is the worst drought on record in southern Australia, and it has hit Melbourne hardest of all.
This long drought is partly being driven by a lurch in temperature in the seas around Australia. New findings reveal that, when the seas in the west of Australia are warm and cool to the northeast, dry winds sweep through southern Australia. When the sea temperatures reverse, the region turns wet.
The phenomenon is called the Indian Ocean Dipole (IOD) and scientists from the University of New South Wales have discovered that it explains all of Australiaââ¬â¢s long droughts, going back to 1885.
But this latest phase of the IOD is stuck in drought mode. ââ¬ÅThis is something new that in the historical record has never happened before,ââ¬Â said Caroline Ummenhofer at the University of New South Wales.
Researchers believe the severity of the drought is being exacerbated by higher general temperatures, a sign of global warming.
The drought is taking a heavy toll especially in the Murray-Darling Basin, where 40 per cent of Australiaââ¬â¢s agricultural produce is grown. Rivers there are drying up, hitting irrigated crops such as rice and fruit. Most eucalyptus trees have died and soil is turning to dust.
Farther north in Queensland, however, storms have submerged more than half the state. The blame lies in another ocean phenomenon known as La Niña. The eastern Pacific has cooled, driving storms over southeast Asia and tropical Australia. La Niña happens every few years, but this bout has been unusually severe and prolonged.
http://www.timesonline.co.uk/tol/news/we...688800.ece
February 9, 2009
Itââ¬â¢s been called the Big Dry and the Big Wet, and here The Times weatherman explains what's behind a nation's drought ... and floodsPaul Simons
Itââ¬â¢s been called the Big Dry and the Big Wet ââ¬â Australiaââ¬â¢s weather is split between floods in subtropical Queensland, while southeast Australia and Tasmania suffer heat and drought that have stoked up an inferno.
The heatwave in the south has lasted two weeks ââ¬â on Saturday the temperature in Melbourne reached 46.4C (115.5F), the hottest since records began 150 years ago.
The immediate cause of the heatwave is a vast high pressure system stuck over the Tasman Sea, blowing in searing hot air from the countryââ¬â¢s desert interior. With that heat have come intensely dry, gusting winds that have stoked the bushfires into vast infernos.
The heatwave was preceded by several weeks of punishing drought, leaving the ground parched and driving temperatures even higher. Hardly a drop of rain has fallen in southeast Australia this year ââ¬â Melbourne has recorded only 0.8mm rainfall ââ¬â and that follows 12 years of abnormally low rainfall. Officially it is the worst drought on record in southern Australia, and it has hit Melbourne hardest of all.
This long drought is partly being driven by a lurch in temperature in the seas around Australia. New findings reveal that, when the seas in the west of Australia are warm and cool to the northeast, dry winds sweep through southern Australia. When the sea temperatures reverse, the region turns wet.
The phenomenon is called the Indian Ocean Dipole (IOD) and scientists from the University of New South Wales have discovered that it explains all of Australiaââ¬â¢s long droughts, going back to 1885.
But this latest phase of the IOD is stuck in drought mode. ââ¬ÅThis is something new that in the historical record has never happened before,ââ¬Â said Caroline Ummenhofer at the University of New South Wales.
Researchers believe the severity of the drought is being exacerbated by higher general temperatures, a sign of global warming.
The drought is taking a heavy toll especially in the Murray-Darling Basin, where 40 per cent of Australiaââ¬â¢s agricultural produce is grown. Rivers there are drying up, hitting irrigated crops such as rice and fruit. Most eucalyptus trees have died and soil is turning to dust.
Farther north in Queensland, however, storms have submerged more than half the state. The blame lies in another ocean phenomenon known as La Niña. The eastern Pacific has cooled, driving storms over southeast Asia and tropical Australia. La Niña happens every few years, but this bout has been unusually severe and prolonged.
http://www.timesonline.co.uk/tol/news/we...688800.ece