Rainfall Hopes Dampened
The Sunday Age
Sunday May 4, 2008
LA NINA might have brought heavy rainfall to Australia over summer, but it is now undergoing unprecedented weakening because of climate change, according to the Bureau of Meteorology.
Hopes that La Nina would continue over winter, which would benefit Victoria above other states, have been dashed, although there is a chance it could revive later in the year.The head of climate analysis at the National Climate Centre, David Jones, said that, coupled with "astonishing" heat in March, the March-April period in Victoria had been the 12th-driest of the past 110 years."It's pretty unusual to see such poor rainfall at this time of year in the presence of La Nina, if not unprecedented," Dr Jones said."The impact of La Nina has, historically, been pronounced over Victoria. Over the past 10 years, things have just broken down. It seems our wet years are just average and our dry years are terrifically dry."According to the bureau's La Nina summary released during the week, "the 2007-08 La Nina event continued to fade during the past two weeks, with the majority of indicators returning to near-normal levels. The models indicate a low chance of either a stronger warming to El Nino levels or a reintensification of La Nina conditions during 2008."The La Nina-El Nino cycle is driven by the temperature of the equatorial Pacific Ocean. Water temperatures that are cooler than average, a La Nina, tend to bring more rain over Australia. Temperatures warmer than average, an El Nino, tend to bring less rainfall.There are also neutral years, when there is no effect either way.Dr Jones said that, initially, the La Nina had looked extremely promising."If you look at Victoria over summer, we did have reasonably above-average rainfall. In the past 110 years, it was ranked 71."Melbourne's water storages are 31.4% full, compared to 30% for the same time last year.
© 2008 The Sunday Age