Wetter years on the way?

April 13, 2008

Martin Babakhan addressed the "Landcare Adventure", held in Bingara last week. Mr Babakhan presented a great deal of information which reminded those listening that Australia is a very dry country, with prolonged periods of extreme dry in the past and a future that will see many more extremely dry years.

The audience listened to Mr Babakhan with great concentration, endeavouring to follow his enthusiastic presentation of what determines Australia’s weather patterns. The farmers in the group wanted to hear that a period of wet years is on the way, but such definitive information was not forthcoming.

Some interesting facts contained in Mr Babakhan’s speech included that Australia’s annual rainfall is the lowest of all the world’s continents and the amount of water discharged into the sea by Australia’s rivers is the lowest of any of the continents.

Australia is the driest populated continent and 87% of the rain that falls over Australia is lost to evaporation. Less than 5% of Australia has greater than 250mm average annual runoff and 26% of the land surface contributes almost 90% of total runoff.

The variability of Australia’s rainfall is the greatest in the world.

In a comparison of water storages around the world, Sydney has a water storage capacity of more than 900 kilolitres, while London has a storage capacity of 175 kilolitres and New York has a storage capacity of 250 kilolitres.

From 1900 to 1950 it was extremely dry over the Australian continent, while the period from 1950 to 1990 it was far wetter. In 1982 the Southern Oscillation Index plunged. It is a subject of continuing study to understand why this happened. The Murray-Darling River is experiencing its lowest inflow since the collection of data commenced. Why is the question, as yet unanswered.

Mr Babakhan reported that Professor Mike Young of the Wentworth Group of Concerned Scientists says that government action is needed urgently to "fix" the Murray River. The problems of the Murray Darling stem from the fact that since 1950 there has been a significant decrease of 55mm per decade in annual total rainfall on Australia’s eastern coast. In south eastern Australia there has been a significant reduction of 20mm of annual total rain over the past four decades. Up until 2005, there has been a decrease in summer rainfall on the east coast.

Mr Babakhan asserted that, in ground breaking research, ocean surface temperatures are compared with the ocean thermocline, which is a subsurface current, to create the Oceanic Nino Index (ONI) which is a very important predictive tool. Tropical Pacific oceanic and atmospheric conditions suggest that there is a La Nina of -1.1 for 2008.

According to Mr Babakhan, in the period from March to May this year there is an 88% probability of a la Nina which will continue until September, after which time we will return to a neutral prediction.

Mr Babakhan also talked about the Interdecadal Pacific Oscillation (IPO) as one of the most important elements of our weather here. He said that three phases of IPO have been identified in the twentieth century. The first positive phase was in the years 1922 to 1944, a negative phase was between 1946 and 1977 and a positive phase was between 1978 and 1998. Mr Babahkhan suggested that the last two years suggests that the region may be heading for another IPO swing in climate. Negative IPO years are generally, extremely wet years.


Mr Babakhan welcomes questions via email which he answers on his weather segment on Friday mornings on ABC radio.