James Grubel PlanetArk 7 Jun 11;
Australia recorded its third-wettest year on record in 2010 due to a major La Nina weather pattern which is now causing record flooding and set to last another three months.
With summer floods swamping much of the northern Queensland state, the Bureau of Meteorology said the second half of 2010 was the wettest on record, with La Nina conditions firmly established by July. The switch to the intense La Nina occurred quickly, replacing the drought-causing El Nino pattern at the start of 2010.
But the bureau said while 2010 was also the coolest in nine years, the decade to the end of 2010 remained Australia's hottest on record.
"This underscored that the warming of Australia's climate continues, even though individual years may be cooler than other years," the bureau said in its annual climate statement for 2010 released on Wednesday.
La Nina conditions occur when tropical sea temperatures are cooler than average in the central and eastern Pacific Ocean, and warmer in the western Pacific resulting in higher rainfall in Australia and parts of Southeast Asia.
The El Nino pattern usually means less rainfall in the western Pacific, with warmer than average central and eastern Pacific sea temperatures.
The bureau said the severe floods in Queensland, which have affected 23 towns and cities, destroyed crops and disrupted coal mining, were fed by heavy rains over Christmas in areas already saturated by rainfall in the second half of 2010.
Separate modeling released by the bureau on Wednesday said long-range forecasts showed the current La Nina was set to persist into the southern hemisphere autumn.
The bureau also said the benchmark Southern Oscillation Index, which measures the intensity of La Nina and El Nino events, is its highest value since November 1973 and reached a record high for the month of December.
It said La Nina events usually produce lower daytime temperatures, higher rainfall and more tropical cyclones during the November-to-April cyclone season across northern Australia.
The drenching in 2010 ended drought conditions across parts of southeastern Australia and in the country's main agricultural region the Murray Darling Basin, where irrigators have had strict limits on their water allocations because of low river levels.
The bureau said the rains in 2010 had led to a dramatic recovery in water flows throughout the Murray-Darling Basin, with storages at 80 percent at the start of 2011 compared to 26 percent a year earlier.
However, the south-west of Western Australia state continued to suffer extremely dry conditions, a trend dating back to the late 1960s, with the lowest rainfall on record for that corner of the state.
Western Australia is usually the nation's largest producer of wheat. But the bureau said rainfall in the cropping season in the major wheat-growing area of the state's southwest was 310 mm (12.5 inches), compared to the previous low of 348 mm recorded in 1914.
(Editing by Michael Perry and David Fogarty)
