Australian experts find formula to predict rain

 (Release at 2100 GMT Wednesday, Nov 20)

     LONDON, Nov 20 (Reuter) - Australian climate experts said on 
Wednesday they had found a simple formula for predicting long-term 
rainfall around the world, based on the Pacific Ocean's El Nino current.
     The current, which appears in varying strengths and patterns off the
western coast of South America, has been blamed for causing weather 
disruptions from storms to droughts.
     Roger Stone and colleagues at the government's Agriculture 
Production Systems research Unit in Toowoomba, Queensland said they had 
devised a calculation using the current.
     "The system provides rainfall probability distributions three to six 
months in advance for regions worldwide, and is simple enough to be 
incorporated into management systems now," they wrote in a report in the 
science journal Nature.
     The El Nino/Southern Oscillation is the name given to a clear 
variation in rainfall and ocean currents in the southern hemisphere. 
Stone's group used it and the Southern Oscillation Index, a calculation 
based on the differences in atmospheric pressure between Tahiti and 
Darwin, Australia.
     They analyzed this index back over 120 years and compared it to 
rainfall records.
     "The maps show some remarkable features," they wrote in a report in 
the science journal Nature.
     For example, a certain "negative" phase of the index in June and 
July correlates with a low chance over the next three months of unusually 
high rainfall in many regions, including eastern Australia, Indonesia, 
the Caribbean, India, Vietnam, northern Russia and western Africa.
     "Conversely, many world regions such as southwestern and 
north-central United States, Iran, central Asia and parts of South 
America have relatively high probabilities of exceeding their respective 
climatological median rainfalls," they added.
     They said their formula could have wide uses.     
"These simple "forecast' maps may have direct relevance to many aspects 
of human endeavour such as food production and commodity marketing; they 
may be readily applied to agriculture," they wrote.
     They said it had already been used to help Australian wheat farmers 
plan their risks and had increased profits for some.