El Niño
The science of predicting weather and drought has improved since the use of weather satellites began in the 1960s, but remains inexact.
Scientists use ocean and atmospheric observations to understand more about major influences on weather patterns including El Niño and La Niña.
El Niño - the extensive warming of the central and eastern Pacific Ocean that leads to a major shift in weather patterns across the Pacific - is often experienced as drought affecting large parts of eastern and northern Australia. The 1982/83 Ash Wednesday bushfires were largely due to drought conditions caused by the El Niño effect. The most recent strong El Niño event was 1997/98.
The El Niño phenomenon affects runoff in catchments serving all major water supply systems in eastern Australia. Weather researchers watch closely for signs of impending El Niño events to warn of impending drought. Not all droughts occur in El Niño years or can be predicted this way.
La Niña, the reverse of the El Niño effect, relates to changes in atmospheric conditions and ocean circulation. In Australia, especially the eastern part of Australia, La Niña events are associated with an increased probability of wetter conditions. The most recent strong La Niña was 1988/89. Not all La Niña events result in high rainfall over catchments.
The Southern Oscillation Index, which is a measure of atmospheric pressure differences between Darwin and Tahiti, is used to predict the likelihood of extended very wet or very dry periods.
For further information, see the Bureau of Meteorology website, www.bom.gov.au.
Source: Climate Variability and El Niņo, Bureau of Meteorology, 1994.
Links
- For more information on El Niņo, La Niņa and rainfall variability, see the Cooperative Research Centre for Water Quality and Treatment's consumer guide to drinking water, at: www.waterquality.crc.
org.au/consumers/
Consumersp18.htm#T1